HK1184100B - Amine-aldehyde resins and uses thereof in separation processes - Google Patents

Description

Amine-aldehyde resins and their use in separation processes

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of chinese patent application 200580044828.6. This application claims priority from U.S. provisional patent application No.60/638,143 filed on 23/12/2004 and U.S. provisional patent application No.60/713,340 filed on 2/9/2005, which are incorporated herein by reference in their entirety.

Technical Field

The present invention relates to resins for use in separation processes, particularly selective separation processes for separating solids and/or ionic species such as metal ions from aqueous media. Such processes include froth flotation (e.g., for the purification of clay-containing ores), separation of drill cuttings from oil drilling fluids, clay and coal slurry dewatering, sewage treatment, pulp and paper mill wastewater treatment, removal of sand from bitumen, and purification of water to make it potable. The resin includes the reaction product of a primary or secondary amine and an aldehyde (e.g., urea formaldehyde resin).

Background

Froth flotation

The industry is quite common with processes for purifying liquid suspensions or dispersions, especially aqueous suspensions or dispersions, to remove solid particles. For example, froth flotation is a separation process based on the difference in the binding tendencies of various materials to rising bubbles. Additives are typically introduced into the froth flotation liquor to enhance the selectivity of the separation process. For example, the "collectors" may be used to chemically and/or physically adsorb onto the minerals to be floated, making them more hydrophobic. On the other hand, "depressants" commonly used in conjunction with collectors make other materials (e.g., gangue minerals) less likely to bind to the bubbles and, therefore, are less likely to be carried into the foam condensate.

In this manner, some materials (e.g., valuable minerals) exhibit a preferential affinity for air bubbles relative to other materials (e.g., gangue minerals), causing them to rise to the surface of the aqueous slurry where they can be collected into the foam condensate. The degree of separation is thereby affected. In the less common so-called reverse froth flotation, it is gangue that is preferentially floated and accumulated at the surface, and the desired material is moved to the bottom. Gangue materials typically refer to quartz, sand and siliceous clays, and calcite, although other minerals (e.g., fluorite, barite, etc.) may be included. In some cases, the material to be purified (i.e., the desired material) actually comprises primarily such material, while the lesser amount of impurities are preferentially floated. For example, in the beneficiation of kaolin clay, a material that has found a great deal of industrial use-oxides of iron and titanium can be separated from impure clay-containing ores by flotation, leaving a purified kaolin clay bottoms product.

The manner in which known collectors and inhibitors achieve their efficacy is not fully understood, but several theories have been proposed to date. The inhibitors may, for example, prevent the gangue minerals from adhering to the valuable minerals to be separated, or they may even prevent the collectors from adsorbing on the gangue minerals. Whatever the mechanism, the ability of a depressant to increase selectivity in a froth flotation process can very favorably impact its economics.

Froth flotation, in general, is commonly used in the beneficiation process of a variety of valuable materials (e.g., minerals and metal ores, and even high molecular weight hydrocarbons such as bitumen) to separate them from unwanted impurities that are inevitably simultaneously extracted from natural deposits. A particular froth flotation process of commercial importance involves the separation of bitumen from sand and/or clay, which is ubiquitous in oil sands deposits such as those found in Athabasca river (Athabasca) in the wider of Alberta, canada. Bitumen is considered a valuable source of "semi-solid" petroleum or heavy hydrocarbon-containing crude oil that can be upgraded into many valuable end products including transportation fuels such as gasoline or even petrochemicals. Oil sands deposits in alberta province are estimated to contain 1.7 trillion barrels of bituminous crude oil, exceeding the reserves of the entire saudi arabia. For this reason, significant efforts have recently been made to develop economically viable operations for the recovery of bitumen, primarily based on subjecting an aqueous slurry of extracted oil sands to froth flotation. For example, the "Clark Process" involves the recovery of bitumen in the foam condensate while suppressing sand and other solid impurities.

Various gangue depressants for improving froth flotation separation are known in the art and include sodium silicate, starch, tannic acid, dextrin, lignosulfonic acid, carboxymethyl cellulose, cyanide salts, and many others. Recently, certain synthetic polymers have been favored in particular beneficiation processes. For example, U.S. Pat. No. re.32,875 describes a separation process for separating gangue from phosphate minerals (e.g., apatite) using phenol-formaldehyde copolymers (e.g., phenolic resins, novolaks) or modified phenol polymers (e.g., melamine modified novolaks) as inhibitors.

U.S. patent No.3,990,965 describes a separation process for separating iron oxide from bauxite using a water-soluble, low chain length prepolymer as an inhibitor, which selectively adheres to the gangue and can be further polymerized to obtain a crosslinked insoluble resin.

U.S. patent No.4,078,993 describes the separation of sulphide ores or oxidised sulphide ores (e.g. pyrite, pyrrhotite or sphalerite) from metal ores (e.g. copper, zinc, lead, nickel) using low molecular weight condensation products of aldehydes with compounds containing 2-6 amine or amide groups as inhibitors.

U.S. patent nos. 4,128,475 and 4,208,487 describe the separation of gangue materials from mineral ores using conventional blowing agents (e.g., pine oil) in combination with (preferably alkylated) amine-aldehyde resins that may have free methylol groups.

U.S. patent No.4,139,455 describes the use of amine compounds (e.g., polyamines) in which at least 20% of the total amount of amine groups are tertiary amine groups and the number of quaternary ammonium groups is from 0 to no more than 1/3 of the number of tertiary amine groups as inhibitors for the separation of sulfide or oxidized sulfide ores (e.g., pyrite, pyrrhotite or sphalerite) from metal ore (e.g., copper, zinc, lead, nickel).

U.S. patent No.5,047,144 describes the separation of siliceous materials (e.g., feldspar) from minerals (e.g., kaolinite) using as inhibitors a cationically active condensation product of an aminoplast template with formaldehyde in combination with an active cationic surfactant (e.g., an organic alkylamine) or an anionic active surfactant (e.g., a long chain alkyl sulfonate).

Russian patent nos. 427,737 and 276,845 describe the use of carboxymethyl cellulose and urea formaldehyde resins, optionally in combination with methacrylic acid-methacrylamide copolymers or starch (' 845 patent), to inhibit clay slimes.

Russian patent nos. 2,169,740, 2,165,798 and 724,203 describe the inhibition of clay carbonate slimes from ores including sylvite (KCl-NaCl) ores in the potassium industry. The inhibitors used are urea/formaldehyde condensation products modified with polyethylene polyamines. In addition, guanidine-formaldehyde resins were used (the' 203 patent).

Markin, a.d. et al describe the use of urea formaldehyde resins as carbonate clay inhibitors in potassium ore flotation. Study of the hydrophilic effect of Urea-Formaldehyde resins on Carbonate Clay impurities in Potassium ore (Study of the hydrophilizing Action of Urea-Formaldehyde resin resins on Carbonate Clay Impuritizisin Potasaium Ores, Inst.Obshch.Neorg.Khim, USSR, Vestsi Akademii NavBSSR, Seryya Khimicinkh Navuk (1980)); the effect of Urea-Formaldehyde resins on Potassium ore Flotation (effect of Urea-Formaldehyde resins on the Flotation of Potassium Ores, Khimicheshaya promyelenest, Moscow, Russian Federation (1980)); and the absorption of the Clay Minerals of potash Ores by Urea-Formaldehyde resins (Adsorption of Urea-Formaldehyde resins on Clay Minerals of potassium Ores, inst. obshch new. khim., Minsk, US SR, doklademi nauk BSSR (1974)).

As recognized in the art, a wide variety of materials can be beneficiated/refined by froth flotation. Likewise, the properties of the desired and undesired components vary widely. This is due to the different chemical compositions of these materials, as well as the variety of previous chemical treatments and the processing steps used. Thus, the number and type of froth flotation depressants is relatively broad.

Furthermore, the use of a particular inhibitor in a process (e.g. beneficiation of green potassium ore) does not predict that it will be equally effective in applications involving significantly different feedstock feeds (e.g. bituminous oil sands). The same applies to the expectation that an effective inhibitor in connection with froth flotation is used for any of the following separation of solid impurities from an aqueous suspension (and vice versa). The theoretical mechanisms by which froth flotation and aqueous liquid/solid separation occur are clearly different, with the former process relying on differences in hydrophobicity and the latter process relying on several other possibilities (charge instability/neutralization, agglomeration, host-guest theory (including podium compounds), hard-soft acid-base theory, dipole-dipole interactions, highest molecular orbital-lowest molecular orbital (HOMO-LUMO) interactions, hydrogen bonding, gibbs free energy of bonding, etc.). Depressants used in froth flotation for metal ore flotation such as guar gum cannot be used as dewatering agents or even as depressants for bitumen separation. Moreover, in both applications described below (dewatering of waste clay and coal), there is currently no reagent for improving the solid/liquid separation thereof. Overall, despite the large amounts of flotation depressants and dewatering agents in the art, it is difficult in many cases to achieve a sufficient degree of beneficiation. There is therefore a need in the art for an agent that can be effectively used in a wide range of separation processes, including froth flotation and separation processes for separating solid impurities from liquid suspensions.

Other separations

Other processes for separating solid impurities from liquid suspensions besides froth flotation may include the use of additives that destabilize these suspensions or coagulate the impurities into larger agglomerates. Coagulation, for example, refers to destabilizing suspended solid particles by neutralizing the charge of the separated suspended solid particles. Flocculation refers to bridging or agglomerating together solid particles into clumps or floes, thereby facilitating their separation by sedimentation or flotation, depending on the density of the floe relative to the liquid. In addition, filtration can be used as a means of separating larger floes.

The above additives, especially flocculants, are often used, for example, to separate the solid particles of rock or drill cuttings from oil and gas well drilling fluids. These drilling fluids (often referred to as "drilling muds") are important in the drilling process for several reasons, including cooling and lubricating the drill bit, creating a fluid back pressure that prevents fluids formed of high pressure oil, gas, and/or water from entering the well prematurely, and preventing the exposed wellbore from collapsing. Drilling mud, whether water-based or oil-based, also removes cuttings from the drilling area and transports them to the surface. Flocculants such as acrylic acid polymers are commonly used to agglomerate these drill cuttings at the surface of the circulating drilling mud where they can be separated from the drilling mud.

Other uses of flocculants in solid/liquid separation include agglomerating clay suspended in the bulk waste slurry effluent from phosphate production plants. Flocculants, such as anionic natural or synthetic polymers, which may be mixed with fibrous materials such as recycled newspapers, are often used for this purpose. The aqueous clay slurry formed in the phosphate purification unit typically has a flow rate of greater than 100,000 gallons per minute, typically containing less than 5% solids by weight. Dehydration of such waste clays (e.g. by precipitation or filtration) is one of the most difficult problems associated with recovery, given the recycling of water. The settling ponds used for this dewatering typically constitute about half a mine area, and dewatering times can be on the order of months to years.

Other specific applications of industrial importance in the separation of solids from aqueous liquids include filtration of coal from aqueous slurries (i.e., slurry dewatering), treatment of wastewater by settling to remove contaminants (e.g., sludge), and treatment of pulp and paper mill wastewater to remove suspended cellulosic solids. Coal dewatering is a significant industrial problem because the BTU value of coal decreases with increasing water content. Industrial and municipal untreated sewage requires significant treatment capacity, for example, foam generated by the U.S. population is collected in sewer systems and carried away by about 140 billion gallons of water per day. Paper industry effluent also produces large quantities of solids-containing aqueous liquids, and typical paper mills often produce waste waters in excess of 2500 gallons per day. As mentioned above, the removal of sand from the aqueous bitumen-containing slurry produced in the extraction and subsequent treatment of oil sands presents another major challenge in the purification of aqueous suspensions on a large scale. Furthermore, the removal of suspended solid particles is often an important consideration in the purification of water, for example in the preparation of drinking (i.e. potable) water. In this process, synthetic polyacrylamide and naturally occurring hydrocolloid polysaccharides such as alginates (copolymers of D-mannuronic acid and L-gulonic acid) and guar gum are flocculants.

Thus, the above applications provide several specific examples relating to the treatment of aqueous suspensions to remove solid particulates. However, such separations are common in a wide variety of other processes in the mining industry, chemical industry, industrial and municipal waste, sewage treatment and paper industry, and in a wide variety of other water consuming industries. Thus, there is a need in the art for additives that can effectively facilitate the selective separation of a variety of solid contaminants from liquid suspensions. Advantageously, such additives should be selective in chemical interaction with solid contaminants, facilitating removal of such contaminants by coagulation, flocculation or other mechanisms. Particularly desirable are additives that are also capable of complexing unwanted ionic species such as metal cations to also facilitate their removal.

Disclosure of Invention

The present invention relates to amine-aldehyde resins for removing a variety of solid and/or ionic species, typically in a selective manner, from a liquid in which the variety of solid and/or ionic species is suspended and/or dissolved. These resins are highly versatile, but they are particularly useful as froth flotation depressants in the separation of bitumen from sand and/or clay or in the purification of clay (e.g. kaolin) from clay-containing ores. Amine-aldehyde resins can also be used to treat aqueous suspensions (e.g., aqueous suspensions containing sand, clay, coal, and/or other solids, such as spent drill cuttings fluids and process waters and wastewaters of phosphate and coal production, sewage treatment, paper or asphalt recovery facilities), to remove solid particles, and potential metal cations (e.g., in the purification of drinking water).

Froth flotation

Without being bound by theory, the amine-aldehyde resins of the present invention are highly selective in (1) froth flotation processes in combination with sand and/or clay to purify bitumen and (2) refining clay-containing ores. Furthermore, because these resins are indeed hydrophilic to water, sand and/or clay particles that have acted upon or bound to the resin are effectively isolated in the aqueous phase during froth flotation. Thus, sand and/or clay can be separated from impurities such as iron oxide in bitumen or clay-containing ores.

Accordingly, in one embodiment, the present invention is a process for purifying bitumen from a bitumen-containing slurry comprising sand or clay. The method includes treating the slurry with an inhibitor containing a resin that is the reaction product of a primary or secondary amine and an aldehyde, and recovering a purified bitumen having a reduced amount of sand or clay by froth flotation after or during the treating step. In another embodiment, the resin is a urea-formaldehyde resin, which is typically the reaction product of formaldehyde and urea at a formaldehyde to urea (F: U) molar ratio of about 1.75: 1 to about 3: 1. In another embodiment, the inhibitor comprises the resin in a solution or dispersion having a resin solids content of from about 30% to about 90% by weight.

In another embodiment, the invention is a process for purifying clay from clay-containing ores containing impurities selected from the group consisting of metals, metal oxides, minerals, and mixtures thereof. The method includes treating a clay-containing ore with a resin-containing depressant and recovering a purified clay having a reduced amount of at least one impurity by froth flotation after or during the treating step. The resin is the reaction product of a primary or secondary amine and an aldehyde. In another embodiment, the clay-containing ore comprises kaolin. In another embodiment, the impurities comprise a mixture of iron oxide and titanium dioxide. In another embodiment, the impurities comprise coal.

Other separations

In another embodiment, the invention is a method for purifying an aqueous liquid containing solid contaminants. The method includes treating the liquid suspension with the resin described above and removing (1) at least a portion of the solid contaminants in the contaminant-enriched fraction and/or (2) the purified liquid after or during the treating step. In another embodiment, the treating step comprises flocculating the solid contaminant (e.g., sand or clay). In another embodiment, the removing step is performed by sedimentation, flotation or filtration. In another embodiment, the liquid suspension is an oil well drilling fluid and the method includes removing the cleaned drilling fluid for reuse in oil well drilling. In another embodiment, the aqueous suspension is a clay-containing effluent slurry from a phosphate production facility, and the method includes removing purified water for reuse in phosphate production. In another embodiment, the aqueous suspension is an aqueous suspension comprising coal, and the method comprises removing the coal-rich fraction by filtration. In another embodiment, the aqueous suspension comprises contaminated water and the method comprises removing purified water by sedimentation. In another embodiment, the aqueous suspension comprises pulp or paper mill wastewater and the solid contaminants comprise cellulosic material, the method comprising removing purified water. In another embodiment, the aqueous suspension is an intermediate or effluent slurry comprising sand or clay in a bitumen production process. In another embodiment, the purified liquid is potable water.

In another embodiment, the invention is a method for purifying water containing metal cations. The method comprises treating the water with the resin and removing at least a portion of the metal cations by filtration to produce purified water (e.g., potable water). In another embodiment, the removing step comprises membrane filtration. In another embodiment, the metal cation is selected from As⁵⁺、Pb²⁺、Cd²⁺、Cu²⁺、Mn²⁺、Hg²⁺And mixtures thereof. In another embodiment, the resin is modified with anionic functional groups.

These and other embodiments will become apparent from the following detailed description.

Drawings

Figure 1 is a picture of four jars containing graphite (two jars on the left) and bentonite (two jars on the right) after being vigorously shaken to suspend these solids in water and left to stand for 24 hours. The leftmost jar and the third from the left were treated with urea formaldehyde resin prior to shaking.

Detailed Description

The resin used in the separation process of the present invention is the reaction product of a primary or secondary amine and an aldehyde. Having nitrogen atoms that are not fully substituted (i.e., not part of a tertiary or quaternary amine), primary or secondary amines can react with aldehydes to form addition compounds. If formaldehyde is used as the aldehyde, for example, the addition compound is a hydroxymethylated addition compound having reactive methylol functionality. Typical primary and secondary amines used to form the resin include compounds having at least two functional amine or amide groups, or amidine-type compounds having at least one of each of these groups. Such compounds include ureas, guanidines, and melamines that may be substituted at their respective amine nitrogen positions with aliphatic or aromatic groups, wherein at least two of the nitrogen atoms are not fully substituted. Primary amines are generally used. Urea is representative of these primary amines since it is inexpensive and readily available. In the case of urea, if desired, at least a portion thereof may be replaced with ammonia, primary alkylamines, alkanolamines, polyamines (e.g., alkyl primary diamines such as ethylenediamine and alkyl primary triamines such as diethylenetriamine), polyalkanolamines, melamines, or other amine-substituted triazines, dicyandiamide, substituted ureas or cyclic ureas (e.g., ethylene urea), primary, secondary and alkylamine, quaternary and alkylamine, guanidine, and guanidine derivatives (e.g., cyanoguanidine and acetoguanidine). Aluminum sulfate, cyclic phosphates and phosphates, formic acid or other organic acids may also be used with urea. If incorporated into the resin in place of a portion of the urea, the amount of any of these components (or their combined amount if used in combination) will typically vary from about 0.05% to about 20% by weight of resin solids. These types of agents help to improve hydrolysis resistance, flexibility, reduced aldehyde volatility, and other properties, as will be appreciated by those skilled in the art.

The aldehyde used to react with the above primary or secondary amines to form the resin may be formaldehyde or other aliphatic aldehydes such as acetaldehyde and propionaldehyde. Aldehydes also include aromatic aldehydes (e.g., benzaldehyde and furfural) and other aldehydes such as alditols, glyoxal, and crotonaldehyde. Mixtures of aldehydes may also be used. Formaldehyde is commonly used because it is readily available and relatively inexpensive.

The initial formation of addition compounds between amines and aldehydes during resin formation is well known in the art. The rate of aldehyde addition reaction is generally highly dependent on the pH and the degree of substitution obtained. For example, the addition rate of formaldehyde to urea to form one, two, and three methylol groups in sequence has been estimated to be 9: 3: 1, whereas quaternary methylol aldehydes are not typically produced in significant quantities. The addition compound formation reaction typically proceeds under basic conditions and at a favorable rate, and therefore proceeds in the presence of a basic catalyst (e.g., ammonia, an alkali metal hydroxide, or an alkaline earth metal hydroxide) and at a favorable rate. Sodium hydroxide is the most widely used.

At sufficiently high pH values, it is possible for the addition compound formation reaction to proceed substantially without condensation reactions, which increase the molecular weight of the resin by polymerization (i.e., improve the resin). However, in order to form the low molecular weight condensation resin from further reaction of the amine-aldehyde adduct, the reaction mixture is generally maintained at a pH typically in the range of from about 5 to about 9. If desired, an acid such as acetic acid may be added to help control the pH and thus the rate of condensation and the molecular weight of the final condensation resin. The reaction temperature is generally in the range of from about 30 ℃ to about 120 ℃, typically less than about 85 ℃, often with reflux temperature. In the preparation of the low molecular weight amine-aldehyde condensation resin from the starting primary or secondary amine and aldehyde, a reaction time of from about 15 minutes to about 3 hours, typically from about 30 minutes to about 2 hours, is employed. Various additives may be added prior to or during the condensation reaction to impart desired properties to the amine-aldehyde resin. Such as guar gum; carboxymethyl cellulose or other polysaccharides such as alginate; or for example polyvinyl alcohol, pentaerythritol or Jeffol^TMPolyols (huntman Corporation, salt lake city, utah, usa) can be used to modify the viscosity and consistency of the final amine-aldehyde resin and improve its performance in froth flotation and other applications. In addition, quaternary ammonium salts including diallyldimethylammonium chloride (or the like such as diallyldiethylammonium chloride) or alkylating agents including epichlorohydrin (or the like such as epibromohydrin) can be used to increase the cationic charge of the amine-aldehyde resin, thereby improving its performance in certain solid/liquid separations (e.g., clay dehydration) discussed below. In this manner, such additives can be more efficiently reacted into the amine-aldehyde resin than they can be mixed with the resin only after it has been prepared.

The condensation reaction products of the above amine-aldehyde, amide-aldehyde and/or amidine-aldehyde adducts include, for example, those resulting from (i) formation of a methylene bridge between the amido nitrogens by reaction between an alkanol and an amino group; (ii) formation of methylene ether linkages by reaction between two alkanol groups; (iii) subsequent removal of formaldehyde from the methylene ether linkage to form a methylene linkage; and (iv) those resulting from the subsequent removal of water and formaldehyde from the alkanol to form methylene linkages.

Generally, in preparing the resin, the molar ratio of aldehyde to primary or secondary amine is from about 1.5: 1 to about 4: 1, which represents the ratio of the molar amount of all aldehydes to the molar amount of all amines, amides and amidines participating in the reaction in preparing the resin during the above adduct formation and condensation reactions (whether conducted separately or simultaneously). The resin is typically prepared at atmospheric pressure. The viscosity of the reaction mixture is often used as a suitable representative of the molecular weight of the resin. Thus, the condensation reaction can be stopped after a sufficiently long time and at a sufficiently high temperature to obtain the desired viscosity. At this point, the reaction mixture may be cooled and neutralized. Water can be removed by vacuum filtration to give the resin the desired solids content. Any of a variety of conventional methods for reacting primary and secondary amines with the aldehyde component may be employed, such as staged addition of monomers, staged addition of catalysts, control of pH, amine modification, and the like, although the invention is not limited to any particular method.

A representative amine-aldehyde resin for use in the separation process of the present invention is urea-formaldehyde resin. As noted above, other reactive amines and/or amides can be substituted for a portion of the urea and other aldehydes can be substituted for a portion of the formaldehyde to provide various desired properties without departing from the resin characteristics as a urea-formaldehyde resin. Urea-formaldehyde resins can be prepared from urea and formaldehyde monomers or precondensates in a manner well known to those skilled in the art. Typically, urea is reacted with formaldehyde in a molar ratio of formaldehyde to urea (F: U) in the range of about 1.75: 1 to about 3: 1, usually about 2: 1 to 3: 1, in order to provide sufficient methylolated species (e.g., dimethylol urea or trimethylol urea) for resin crosslinking. In general, urea-formaldehyde resins are very water-dilutable dispersions, which otherwise should be aqueous.

In one embodiment, the condensation is carried out to an extent such that the urea-formaldehyde resin has a number average molecular weight (M) of greater than about 300 grams/mole_n) And typically from about 400 to about 1200 g/mole. M of Polymer samples having molecular weight distribution, as known in the art_nThe value defines:

wherein N is_iIs the number of polymeric species having i repeating units, and M_iIs the molecular weight of a polymeric species having i repeating units. Typically using Gel Permeation Chromatography (GPC), withSolvents, standard samples and procedures well known to those skilled in the art to determine average molecular weight.

Cyclic urea-formaldehyde resins are utilized and prepared, for example, according to the method described in U.S. patent No.6,114,491. The urea, formaldehyde and ammonia reactants are used in a molar ratio of urea to formaldehyde to ammonia of about 0.1-1.0: about 0.1-3.0: about 0.1-1.0. These reactants are charged to the reaction vessel while maintaining a temperature below about 70 ℃ (160 ° F), often about 60 ℃ (140 ° F). The order of addition is not critical, but it is important that care be taken in adding the ammonia to the formaldehyde because it is an exothermic reaction. In fact, due to the intense exotherm, it is preferred to add formaldehyde and urea first, followed by ammonia. This sequence of addition allows one to take advantage of the endotherm caused by the addition of urea to water, thereby increasing the rate of ammonia addition. Alkali may be required to maintain alkaline conditions throughout the cooking process.

Once all reactants are in the reaction vessel, the resulting solution is heated under basic pH conditions to between about 60-105 ℃ (about 140-220 ° F), typically about 85-95 ℃ (about 185-205 ° F), depending on molar ratios and temperature, for 30 minutes to 3 hours, or until the reaction is complete. Once the reaction was complete, the solution was cooled to room temperature for storage. The resulting solution is stable to storage for several months at room temperature. The pH value is between 5 and 11.

The yield is typically about 100%. The cyclic urea resins often contain at least 20% of triazinone and substituted triazinone compounds. The ratio of cyclic ureas to di-and tri-substituted ureas and mono-substituted ureas varies with the molar ratio of reactants. For example, the cyclic urea resin obtained in solution with a molar ratio of U: F: A of 1.0: 2.0: 0.5 is passed through C¹³NMR, containing approximately 42.1% cyclic urea, 28.5% di/tri-substituted urea, 24.5% mono-substituted urea and 4.9% free urea. The resulting cyclic urea resin in solution having a molar ratio of U: F: A of 1.0: 1.2: 0.5 was passed through C¹³NMR, containing approximately 25.7% of cyclic urea, 7.2% of bis/trisubstituted urea, 31.9% of monosubstituted urea and 35.2% of monosubstituted ureaFree urea.

In addition, cyclic urea-formaldehyde resins can be prepared by methods such as those described in U.S. Pat. No.5,674,971. The cyclic urea resins are prepared by reacting urea with formaldehyde in at least two, optionally three, steps. In a first step, urea is reacted with dimethyl ether in the presence of ammonia in a molar F/U ratio of between about 1.2: 1 and 1.8: 1 by addition under basic reaction conditions. The ammonia is supplied in an amount sufficient to produce an ammonia/urea molar ratio of between about 0.05: 1 and 1.2: 1. The mixture is reacted to form a cyclic triazinone/triazine or a cyclic urea resin.

Water-soluble triazinone compounds can also be prepared by reacting urea, formaldehyde and primary amines, as described in U.S. Pat. Nos. 2,641,584 and 4,778,510. These patents also describe suitable primary amines, such as, but not limited to, alkylamines such as methylamine, ethylamine, and propylamine; lower hydroxyl amines such as ethanolamine, cycloalkyl monoamines such as cyclopentylamine, ethylenediamine, hexamethylenediamine, and linear polyamines. The primary amine may be substituted or unsubstituted.

In the case of cyclic urea-formaldehyde resins or urea-formaldehyde resins, the skilled practitioner will recognize that many forms of urea and formaldehyde are available. In preparing the urea-formaldehyde resin for use in the present invention, any form can be used which has sufficient reactivity and does not introduce extraneous moieties which are detrimental to the desired reaction and reaction product. For example, common forms of use for formaldehyde include polyoxymethylene (solid, polymerized formaldehyde) and formalin solutions (aqueous formaldehyde solutions at 37%, 44% or 50% formaldehyde concentration, sometimes containing methanol). Formaldehyde can also be obtained in gaseous form. Any of these forms is suitable for use in the preparation of urea formaldehyde resins. Typically, formalin solutions are used as the formaldehyde source. To prepare the resins of the present invention, any of the above aldehydes (e.g., glyoxal) may be used in place of, in whole or in part, methanol.

Similarly, urea is generally available in a variety of forms. Such as granular solid urea and urea solutions, typically aqueous solutions, are commercially available. Any form of urea is suitable for use in the practice of the present invention. For example, a number of commercially prepared urea-formaldehyde solutions can be used, including urea-formaldehyde combination products such as urea-formaldehyde condensates (e.g., UFC 85), as disclosed in U.S. Pat. nos. 5,362,842 and 5,389,716.

Furthermore, urea-formaldehyde Resins such as the types sold by Georgia Pacific Resins, Borden Chemical and Neste Resins may be used. These resins are made as low molecular weight condensates or adducts containing reactive methylol groups as described above which can undergo condensation to form resinous polymers and are generally within the aforementioned average molecular weight ranges. The resins typically contain small amounts of unreacted (i.e., free) urea and formaldehyde, as well as cyclic ureas, mono-methylolated ureas, and bis-and tris-methylolated ureas. The relative amounts of these materials may vary depending on the preparation conditions (e.g., the molar ratio of formaldehyde to urea used). The balance of these resins are typically water, ammonia and formaldehyde. Various additives known in the art, including stabilizers, cure accelerators, fillers, extenders, and the like, may also be added to the resin.

The amine-aldehyde resins described above are highly selective for binding to unwanted solid materials (e.g., sand or clay) and/or ionic species such as metal cations that are separated in the separation/purification process of the present invention. Without being bound by theory, in one embodiment, the amine-aldehyde resins of the present invention are generally cationic (i.e., generally more positively than negatively charged) to attract a majority of the clay surfaces, which are generally anionic (i.e., generally more negatively than positively charged). These differences in electrical properties between the resin and the clay can create mutual attraction at multiple locations, and may even share electrons to form covalent bonds. It is possible to explain the positive-negative charge interactions that cause clay particles to be attracted to resins by several theories, such as host-guest theory (including the british ether compounds), hard-soft acid-base theory, dipole-dipole interactions, highest molecular orbital-lowest molecular orbital (HOMO-LUMO) interactions, hydrogen bonding, gibbs free energy of bonds, and the like.

Silica, silicates and/or polysiloxanes may be used in combination with the amine-aldehyde resins of the present invention, possibly increasing their affinity for various materials, especially siliceous materials containing sand and clay, whether such materials are desirable or undesirable in any particular application. Other agents that may be used to enhance resin properties in the separation process of the present invention include polysaccharides, polyvinyl alcohol, polyacrylamide, and known flocculants (e.g., alginates). These agents may also be used with modified urea-formaldehyde resins wherein, as described above, at least a portion of the urea is replaced with ammonia or an amine as described above (e.g., primary alkyl amines, alkanolamines, polyamines, etc.). In addition, such a reagent may also be used with a resin modified with an anionic functional group (e.g., a sulfonic acid group) or stabilized by etherification with an alcohol (e.g., methanol) as described below.

Silicon dioxide in the form of a silica hydrosol is available, for example, from Akzo Nobel under the registered trademark "Bindzil" or from DuPont under the registered trademark "Ludox". Other grades of colloidal silica having various particle sizes and containing various stabilizers are available. The sols can be stabilized with alkali metal hydroxides such as sodium, potassium or lithium or quaternary ammonium hydroxide bases, or with water-soluble organic amines such as alkanolamines.

In the preparation of the resin, silicates, such as alkali metal silicates and alkaline earth metal silicates (e.g., lithium silicate, sodium silicate, potassium silicate, magnesium silicate and calcium silicate) and ammonium silicate or quaternary ammonium silicate may also be used. In addition, stable colloidal silica-silicate mixtures or blends are useful as described in U.S. patent No.4,902,442.

Particularly good performance is obtained when the resin is prepared in a solution or dispersion having a solids content of from about 30% to about 90%, typically from about 45% to about 70%, in the separation process of the present invention. In addition, the resin may be used in "neat" form with little or no added solvent or dispersant (e.g., water). In any event, the amine and aldehyde components used to form the resin are typically at least about 90% by weight, and typically at least about 95% by weight, reacted in order to reduce the amount of free (unreacted) amine and aldehyde. This operation more efficiently utilizes the amine and aldehyde components in the preparation of the resin polymer while minimizing any deleterious effects associated with these components in free form (e.g., vaporization into the environment). In summary, the amine-aldehyde resins used in the separation process of the present invention typically comprise from about 40% to about 100% resin solids or non-volatiles, often from 55% to 75% non-volatiles. The non-volatile content is measured in terms of weight loss by heating a small sample (e.g., 1-5 grams) of the composition at about 105 ℃ for about 3 hours. When an amine-aldehyde resin is used in substantially "neat" form with little or no volatile components, the neat resin (e.g., as a viscous liquid, gel, or solid form such as a powder) can be added to the froth flotation slurry or liquid dispersion to be purified to form an aqueous resin solution or dispersion in situ. The amine-aldehyde resins can be obtained in pure form from solutions or dispersions of these resins using conventional drying techniques such as spray drying.

The aqueous solution or dispersion of the resin of the present invention is generally a clear liquid or a liquid having a white or yellow appearance. They typically have a brookfield viscosity of about 75 to about 500cps, and a pH of about 6.5 to about 9.5. Urea-formaldehyde resins typically have a free formaldehyde content and a free urea content of less than 5%, usually less than 3%, and often less than 1%. Low levels of formaldehyde are generally obtained due to concerns about exposure to formaldehyde volatilization which is detrimental to health. If desired, conventional "formaldehyde scavengers" known to react with free formaldehyde may be added to reduce the formaldehyde level in the solution. However, small amounts of free formaldehyde are also desirable for different reasons. Without being bound by theory, (1) in froth flotation separation, free urea is not believed to have the necessary molecular weight to "block" the gangue or desired material (e.g., clay) from interacting with the rising bubbles; (2) in the purification of liquid dispersions, free urea is not considered to have the necessary molecular weight to agglomerate a sufficient amount of solid contaminants into flocs; or (3) in removing ionic species from aqueous solutions, the free urea is not believed to have the necessary molecular weight to bind these species to molecules of sufficient size to be retained by filtration. In particular, it has been found that resinous polymers having an average molecular weight greater than about 300 grams/mole exhibit the mass required to facilitate effective separation.

Froth flotation

Due to the high selectivity of the resins of the invention, they provide good results in terms of saving of the addition amount when used as depressants in froth flotation separations. For example, the resin may be added in an amount of about 100g to about 1000 g, typically about 400 to about 600 g, per ton of material (e.g., clay-containing ore) to be purified by froth flotation, based on the weight of the resin solution or dispersion. In general, the optimum amount to be added for a particular separation can be readily determined by one skilled in the art based on a number of factors, including the type and amount of impurities.

The resins of the present invention can be applied to froth flotation of a variety of materials containing sand and/or clay (e.g., high molecular weight hydrocarbons such as bitumen) for which the resins are particularly selective. Although clay is often considered an impurity in the beneficiation of conventional metal or mineral ores, it may also be present in relatively large amounts, to be recovered as a major component. Some clays, such as kaolin, are valuable minerals in many applications, for example as mineral fillers in paper making and rubber manufacturing. Thus, one froth flotation process that may use the resin of the present invention involves separating clay from clay-containing ore. The impurities in such ores are typically metals and their oxides, such as iron oxide and titanium dioxide, which are preferentially floated by froth flotation. Other impurities of clay-containing ores include coal. Impurities originally present in most Georgia kaolins that are preferentially floated in the purification process of the present invention include iron-containing titanium dioxide and other minerals that are also typically iron-containing, such as mica, ilmenite or tourmaline.

Thus, the clay selectively bound to the amine-aldehyde resin of the present invention can be separated and recovered from metals, metal oxides and coal. In the clarification of clays, it is often advantageous to use anionic collectors such as oleic acid, flocculants such as polyacrylamines, clay dispersants such as fatty or rosin acids and/or rosin oils in combination with the resins of the invention as inhibitors to control foaming. As described in more detail below, one method involves modifying the resin with anionic functional groups, particularly in the refining of clay-containing ores.

The resins of the present invention are also advantageously used for the separation of bitumen from sand and/or clay simultaneously extracted from natural oil sands deposits. Bitumen/sand mixtures removed from oil sands or tar sand deposits, often within hundreds of feet of the surface, are typically first mixed with warm or hot water to form an oil sand aqueous slurry of reduced viscosity for convenient transport (e.g., through a pipeline) to a processing facility. Steam and/or caustic solution may also be injected to improve the slurry for froth flotation, as well as many other purification steps described below. Bitumen-containing slurries comprising sand or clay are aerated in view of the recovery of bitumen as a purified product, resulting in selective flotation of bitumen. This aeration step can be accomplished by merely agitating the slurry to release bubbles and/or introducing a source of air into the bottom of the separation chamber. One skilled in the art can readily determine the optimum amount of air required to float the desired bitumen without entraining excessive solid contaminants.

Thus, the use of the resin inhibitor of the present invention advantageously facilitates retention of sand and/or clay impurities in the aqueous portion removed from the bottom of the froth flotation vessel. The bottom is enriched (i.e., has a higher concentration) with sand and/or clay impurities relative to the original bitumen slurry. The total purification of bitumen may rely on two or more flotation separation stages. For example, the middle section of the primary flotation separation vessel may contain a large amount of bitumen that can ultimately be recovered in the secondary flotation of this "middle" section.

Typically, in any froth flotation process of the present invention, at least 70% of the valuable material (e.g. bitumen or kaolin) having a purity of at least 85 wt% is recovered from the raw material (e.g. clay-containing ore). Furthermore, when the resin of the present invention is used as an inhibitor, a commonly known collector may be used in combination. These collectors include, for example, fatty acids (e.g., oleic acid, sodium oleate, hydrocarbon oils), amines (e.g., dodecylamine, octadecylamine, alpha amino aryl phosphonic acids, and sodium sarcosinate), and xanthan gum salts. Likewise, conventional inhibitors known in the art may also be combined with the resin inhibitor. Conventional inhibitors include guar gum and other hydrocolloid polysaccharides, sodium hexametaphosphate, and the like. Conventional blowing agents that aid in trapping (e.g., methyl isobutyl carbinol, pine oil, and polypropylene oxide) may also be used in conjunction with the resin inhibitor of the present invention, depending on normal flotation operations.

The pH of the slurry added when the resin of the present invention is used as an inhibitor in a froth flotation separation will vary depending on the particular material to be treated, as will be appreciated by those skilled in the art. Typically, the pH varies from neutral (pH 7) to strongly basic (e.g., pH 12). It is generally believed that in some flotation systems, high pH values (e.g., about 8 to about 12.5) produce the best results.

Typically, in froth flotation for the beneficiation of solid materials, the raw ore to be beneficiated is usually first ground to a "lift mesh" size. Prior to introducing the solid material into the brine solution to produce an aqueous slurry, the material may be ground to produce, for example, particles having an average diameter of one-eighth inch. After the material is crushed and slurried, the slurry may be stirred or agitated in a "washing" process that breaks some of the solids into very fine particles that remain in the brine as a cloudy suspension. Some of these particles may be washed out of the ore particles prior to froth flotation. Furthermore, as is known in the art, any conventional pre-treatment steps including further comminution/screening, cyclone separation and/or water splitting steps may be used separately prior to froth flotation to further reduce/classify the raw material particle size and/or recover smaller solid particles.

The resin of the present invention used as a depressant is typically added to the aqueous slurry before or during froth flotation in such a way that the depressant is readily dispersed throughout. As mentioned above, conventional collectors may also be used to assist in the flotation of certain materials. In a froth flotation process, a slurry, typically having a solids content of about 10 to about 50 weight percent, is passed to one or more flotation cells. Air is passed into the bottom of these tanks and into the relatively hydrophobic portion of the material, which has a selective affinity for the rising bubbles, floats to the surface (i.e., froth), where the material is extracted and recovered. A bottoms product that is hydrophilic relative to the foam concentrate can also be recovered. The process may be accompanied by stirring. Commercially acceptable products can be produced from the separated fractions recovered in this manner, often after using further conventional steps including separation (e.g. by centrifugal precipitation), drying (e.g. in a gas kiln), size classification (e.g. screening) and refining (e.g. crystallization).

Although not always the case, froth flotation according to the invention may include flotation in a "rougher cell" followed by "concentration" of one or more roughers. Two or more flotation steps may also be employed, first recovering a bulk material comprising more than one component, followed by selective flotation to separate the components. The amine-aldehyde resins of the present invention, when used as depressants, can be advantageously used in any of these steps to improve the selective recovery of the desired material subjected to froth flotation. When multi-stage froth flotation is used, the resins may be added at once prior to multi-stage flotation, or they may be added separately at each flotation stage.

Other separations

Due to their affinity for solid contaminants in liquid suspensions or slurries, the amine-aldehyde resins of the present invention are applicable to a wide variety of separation processes, particularly those involving the removal of silicate contaminants, such as sand and/or clay, from aqueous suspensions or slurries thereof. Such an aqueous suspension or slurry may be treated with the amine-aldehyde resin of the present invention in view of separating at least a portion of the contaminants from the purified liquid in the contaminant-enriched portion. The "contaminant-enriched" fraction refers to the fraction of the liquid suspension or slurry that is enriched in solid contaminants (i.e., contains a higher percentage of solid contaminants than the solid contaminants originally present in the liquid suspension or slurry). Conversely, the purified liquid contains a lower percentage of solid contaminants than the solid contaminants originally present in the liquid suspension or slurry.

The separation process described herein is applicable to both "suspensions" and "slurries" of solid particles. These terms are sometimes defined identically, but in the case of "slurry" there is sometimes a distinction based on the addition of at least some agitation or energy to maintain homogenization. Because the inventive process described herein is broadly applicable to the separation of solid particles from an aqueous medium, the term "suspension" is used interchangeably with "slurry" (and vice versa) in the present specification and appended claims.

The treating step may include adding a sufficient amount of amine-aldehyde resin to cause charge interaction and to cause agglomeration or flocculation of the solid contaminants into larger agglomerates. The necessary amount is readily determined based on a number of variables, such as the type and concentration of the contaminant, as will be appreciated by those skilled in the art. In other embodiments, the treatment may include continuously contacting the liquid suspension with a fixed bed of solid resin.

During or after treatment of the liquid suspension with the amine-aldehyde resin, agglomerated or flocculated solid contaminants (which may now be in the form of larger agglomerated particles or floes, for example) are removed. Removal can be accomplished by flotation (with or without the use of ascending bubbles, as described above with respect to froth flotation) or sedimentation. The optimal method of removal will depend on the relative density of the floe or other factors. Filtration or leaching (straining) can also be an effective means of removing agglomerated flocs of solid particles, whether they are on the surface or in the precipitate.

Examples of liquid suspensions that may be purified in accordance with the present invention include drilling fluids of oil and gas wells that accumulate rock (or drill cuttings) solids during normal use. These drilling fluids (often referred to as "drilling muds") are important in the drilling process for several reasons, including the transport of these drill cuttings from the drilling zone to the surface, the removal of which allows the drilling mud to be recycled. The addition of the amine-aldehyde resins of the present invention to oil well drilling fluids, particularly water-based (i.e., aqueous) drilling fluids, effectively agglomerates or flocculates the solid particle contaminants into larger clumps (or flocs) thereby facilitating their separation by sedimentation or flotation. The resins of the present invention may be used in combination with known flocculants such as polyacrylamide or hydrocolloid polysaccharides for this application. Typically, in the case of water-based oil or gas well drilling fluids, the separation of solid contaminants is sufficient to provide a purified drilling fluid for reuse in drilling operations.

Other aqueous suspensions of practical interest include clay-containing aqueous suspensions or brines accompanying those ore refining processes described above. For example, the production of purified phosphate from mined calcium phosphate rock generally relies on multiple separations of solid particulates from an aqueous medium, whereby such separations can be improved using the resins of the present invention. Calcium phosphate is produced throughout the process from a mineral reserve about 25 feet in the ground at an average depth. Phosphate rock is initially recovered in parent rock containing sand and clay impurities. The parent rock is first mixed with water to form a slurry, typically after mechanical agitation, the slurry is screened to retain the phosphate gravel and to pass the fine clay particles with a large amount of water as a clay slurry effluent.

These clay-containing effluents generally have high flow rates, typically with less than 10 wt% solids, often times containing only about 1% to 5% solids. Dewatering of waste clay (e.g., by settling or filtration) presents significant challenges to recovery in view of water recycling. However, treatment of the clay slurry effluent obtained in the production of phosphate with the amine-aldehyde resin of the present invention can reduce the time required to dehydrate the clay. The reduction in clay settling time allows for efficient reuse of purified water resulting from clay dehydration in phosphate production. In an embodiment of the purification process, wherein the liquid suspension is a clay-containing discharge slurry from a phosphate production facility, the purified liquid contains less than about 1 wt% solids after a settling or dewatering time of less than about 1 month.

In addition to the phosphate gravel and clay slurry effluents retained by screening as described above, a mixture of sand and finer phosphate particles is also obtained in the initial treatment of the mined phosphate matrix. The sand and phosphate in this fluid are separated by froth flotation, which can be improved by using the amine-aldehyde resin of the present invention as an inhibitor of sand as described above.

Another specific application of the resin in the slurry dewatering zone is the filtration of coal from an aqueous slurry. Dewatering of coal is commercially important because as the moisture content increases, the BTU value decreases, and thus the quality of the coal decreases. Thus, in one embodiment of the invention, the aqueous coal-containing suspension or slurry is treated with an amine-aldehyde resin prior to dewatering the coal by filtration.

Another important application of the amine-aldehyde resins of the invention is in the field of sewage treatment, which refers to various processes responsible for the removal of pollutants from industrial and municipal wastewater. These processes purify wastewater, providing purified water suitable for discharge into the environment (e.g., rivers, streams, and oceans), as well as sludge. Sewage refers to any type of aqueous foam that is typically collected in a sewer system and then transported to a treatment facility. Thus, sewage includes municipal wastewater from toilets (sometimes referred to as "foul waste") and hand basins, bathrooms, showers, and kitchens (sometimes referred to as "sewage"). Sewage also includes industrial and commercial wastewater (sometimes referred to as "industrial wastewater") as well as storm water runoff from hard surface areas such as roofs and streets.

Conventional treatment of wastewater often involves primary, primary and secondary treatment steps. Primary treatment refers to the filtration or screening of large solids such as wood, paper, debris, etc. and grit that often damage the pump. The majority of the remaining solids are then separated by settling in large water tanks with subsequent primary treatment, and the solids-enriched sludge is recovered from the bottom of these tanks and further processed. The purified water is also recovered and typically subjected to secondary treatment by biological means.

Thus, in one embodiment of the present invention, precipitation or settling of the wastewater may comprise treating the wastewater with the amine-aldehyde resin of the present invention. For example, the treatment may be used to improve the settling operation (batch or continuous) by reducing the residence time required to complete a given operation (e.g., based on the purity of the purified water and/or the percent recovery of solids in the sludge). In addition, for a given settling time, the improvement in producing a higher purity of purified water and/or a higher recovery of solids in the sludge is evident.

After treatment of sewage with the amine-aldehyde resins of the present invention and removal of the purified water stream by settling, it is also possible to use or introduce the amine-aldehyde resins into a secondary treatment process to further purify the water. Secondary treatment often relies on the destructive action of naturally occurring microorganisms on organic matter. In particular, the aerobic biological process substantially reduces the biological content of the purified water recovered from the primary treatment. Microorganisms (e.g., bacteria and protozoa) consume biodegradable soluble organic contaminants (e.g., sugars, fats, and other organic molecules) and bind many of the scarcely soluble fractions into flocs, thereby further facilitating the removal of organic materials.

Secondary treatment relies on "supplying" oxygen and other nutrients to aerobic microorganisms to make them viable and consume organic pollutants. Advantageously, the nitrogen-containing amine-aldehyde resins of the present invention can serve as a "food" source for microorganisms in the secondary treatment, and potentially also as an additional flocculant for organic materials. Thus, in one embodiment of the invention, the wastewater purification process further comprises, after removing the purified water by settling (in the primary treatment step), further treating the purified water in the presence of microorganisms and an amine-aldehyde resin, optionally with an additional amount of amine-aldehyde resin, to reduce the Biochemical Oxygen Demand (BOD) of the purified water. As is understood in the art, BOD is an important indicator of water quality and represents the amount of oxygen in mg/L (or ppm by weight) required by microorganisms to oxidize organic impurities for more than 5 days. The BOD of the purified water after treatment with the microorganisms and the amine-aldehyde resin is generally less than 10ppm, typically less than 5ppm, often less than 1 ppm.

The amine-aldehyde resins of the present invention may also be used in the purification of effluent waste waters from pulp and paper mills. These waste water streams typically contain solid contaminants in the form of cellulosic materials (e.g., waste paper; bark or other wood components such as wood chips, wood strands, wood fibers, or wood particles; or plant fibers such as wheat straw fibers, rice fibers, switchgrass fibers, soybean fibers, bagasse fibers, or corn stalk fibers; and mixtures of such contaminants). According to the method of the present invention, an effluent stream comprising cellulosic solid contaminants is treated with the amine-aldehyde resin of the present invention such that purified water is removed by settling, flotation or filtration.

In the separation of bitumen from sand and/or clay impurities (as described above), various separation steps may be employed before or after froth flotation of the bitumen-containing slurry. These steps may include screening, filtration, and settling, any of which may benefit from treating the oil sands with the amine-aldehyde resins of the present invention, followed by removal of a portion of the sand and/or clay contaminants in a contaminant-enriched portion (e.g., bottom), or removal of a cleaned bitumen portion. As discussed above with respect to phosphate ore treatment wastewater, which typically contains solid clay particles, the treatment step may include flocculating these contaminants to facilitate their removal (e.g., by filtration). The wastewater effluent from bitumen treatment facilities also contains sand and/or clay impurities and therefore benefits from treatment with the amine-aldehyde resins of the present invention to dehydrate them and/or remove at least a portion of these solid impurities in a contaminant-enriched fraction. An important specific process fluid produced during bitumen extraction is known as "mature fine tailings," which is an aqueous suspension of fine solid particles that can benefit from dewatering. Often, in the case of sand-and/or clay-containing suspensions from bitumen production facilities, the separation of solid contaminants is sufficient to allow recovery or removal of a clean liquid or water stream that can be recycled back to the bitumen process.

The resins of the present invention are used to treat various intermediate fluids and effluents in bitumen production processes, and are not limited to those processes that rely at least in part on froth flotation of a bitumen-containing aqueous slurry. As will be readily appreciated by those skilled in the art, other techniques for bitumen purification (e.g., centrifugal filtration through a "syncrude process") will produce an aqueous intermediate fluid from which it is desirable to remove solid contaminants, as well as a by-product fluid.

In the purification of water, in particular for purposes of rendering it potable, the amine-aldehyde resins of the present invention may be used to remove suspended solid particles such as sand and clay. Moreover, the resins of the present invention also have the additional ability to complex metal cations (e.g., lead and mercury cations) so that these unwanted impurities are bound to the solid particles to be removed. Thus, the resin of the present invention can be used to effectively treat impure water containing solid particulate impurities and metal cation impurities. Without being bound by theory, it is believed that negatively charged moieties, such as carbonyl oxygen atoms on the urea-formaldehyde polymer backbone, complex with the undesirable cations to facilitate their removal. Generally, this complexation occurs in water having a pH greater than about 5, typically in the range of about 7 to about 9.

Another possible mechanism for removing metal cations is based on their binding to negatively charged solid particles. Flocculation and removal of these particles will also result in removal of metal cations, at least to some extent. Regardless of the mechanism, in one embodiment, the treatment and removal of these impurities can be accomplished in accordance with the present invention to produce potable water.

For example, when the water to be purified contains little or no solid particulates, the removal of metal cations may represent the primary or even the only means of water purification achieved by amine-aldehyde resins. Impure water containing metal cations is passed continuously through a fixed bed of a resin in solid form, which can be used to remove cations in a continuous process. Alternatively, a soluble form of the resin, typically having a lower molecular weight, may be added to the impure water in order to treat the impure water. In this case, the complex cations can be removed by, for example, ultrafiltration through a porous membrane (e.g., polysulfone) having a molecular weight cut-off less than the molecular weight of the resin. The water purification methods described herein may also be used in combination with known methods including reverse osmosis, UV irradiation, and the like.

In order to increase the efficiency of resin complexation with metal cations, it is desirable to modify the amine-aldehyde resin with one or more anionic functional groups. Such modifications are known in the art and may include resin reactions that introduce the desired functional groups (e.g., by sulfonation with sodium metabisulfite). Alternatively, modification is achieved during the preparation of the resin (e.g. during condensation) by incorporating an anionic comonomer such as sodium acrylate into the urea-aldehyde resin. Representative functional groups that may be used to modify resins, including urea-formaldehyde resins, include anionic functional groups such as bisulfites, acrylates, acetates, carbonates, azides, amides, and the like. Methods of modifying resins with additional functional groups are known to those skilled in the art. Anionic functional groups may also be introduced into the resin in separations involving the purification of slurries containing solid clay particles (e.g., by froth flotation, flocculation, etc.), including the purification of kaolin ores. Without being bound by theory, sulfonation of the resin or the introduction of other anionic functional groups may also enhance hydrogen bonding between the resin and the surrounding aqueous phase to inhibit condensation of the resin or to enhance its stability.

Thus, as noted above, in one embodiment, the present invention is a method for purifying water containing metal cations by treating the water with an amine-aldehyde resin as described herein and possibly modified with anionic groups. Removal of at least a portion of the metal cations can be accomplished by holding the metal cations in a fixed bed of resin or filtering them out. In the latter case, the removal may be carried out by filtration, for example membrane filtration, by binding the metal cations to the resin either directly or indirectly through solid particles to which the resin has affinity. In the case of indirect bonding, as mentioned above, flocculation of the solid particles also entails agglomeration of a portion of the metal ions, and thus removal of the metal ions by flotation or sedimentation of these particles is possible.

The amine-aldehyde resins of the invention can therefore be used advantageouslyIn treating water, metal cations such as arsenic, lead, cadmium, copper and mercury, which are known to pose health risks when ingested, are removed. These cations thus include As⁵⁺、Pb²⁺、Cd²⁺、Cu²⁺、Hg²⁺And mixtures thereof. Typically, the removal is to such an extent that the purified water is substantially free of one or more of the above-mentioned metal cations after treatment. By "substantially free" is meant that the concentration of the relevant metal cation or cations is reduced to or below a concentration considered safe (e.g., as determined by an Agency such as the Environmental Protection Agency). Thus, in various embodiments, the purified water will contain up to about 10ppb of As⁵⁺Up to about 15ppb of Pb²⁺Up to about 5ppb of Cd²⁺Up to about 1.3ppm Cu²⁺And/or up to about 2ppb of Hg²⁺. That is, in purified water, generally at least one, typically at least two, and often all of the above cations are at or below these threshold concentrations.

In any of the applications described herein, the resins of the present invention may be stabilized by reaction with an alcohol (i.e., etherification). Without being bound by theory, it is believed that etherification of the branched hydroxyl functionality may inhibit further condensation of the amine-aldehyde resin (e.g., condensation of the urea-formaldehyde resin with itself). This may ultimately hinder or prevent the resin from precipitating during long term storage, so that the etherified resin may have an increased molecular weight relative to its corresponding non-etherified resin without a corresponding loss in its stability.

Etherification thus includes the reaction of amine-aldehyde adducts or condensates even to resins with alcohols as described above. In one embodiment, the urea-formaldehyde resin is etherified with an alcohol containing 1 to 8 carbon atoms. Representative alcohols for etherification include methanol (e.g., for methylation), ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. In an exemplary preparation of the etherified resin, the amine-aldehyde adduct or condensation reaction product is heated to a temperature of about 70 ℃ to about 120 ℃ in the presence of an alcohol until fully etherified. An acid such as sulfuric acid, phosphoric acid, formic acid, acetic acid, nitric acid, alum, ferric chloride, or other acids may be added before or during the reaction with the alcohol. Sulfuric acid or phosphoric acid is commonly used.

All documents cited in this specification, including but not limited to all U.S. patents, international and foreign patent applications, and all abstracts and documents (e.g., journal articles, periodicals, etc.), are hereby incorporated by reference in their entirety. The discussion of the references herein is intended merely to summarize the assertions made by their authors and no admission is made that any reference constitutes prior art. Applicants reserve the right to challenge the accuracy and pertinency of the cited documents. In view of the above, it will be seen that the several advantages of the invention are achieved and other advantageous results attained.

As various changes could be made in the above methods and compositions without departing from the scope of the invention, it is intended that all matter contained in this application, including the above-described theoretical mechanisms and/or modes of interaction, shall be interpreted as illustrative only and not limiting in any way the scope of the appended claims.

The following examples are presented as representative of the invention. These examples should not be construed as limiting the scope of the invention thereto, other equivalent embodiments will be apparent with reference to the specification and the appended claims.

Examples

Example 1

Various urea-formaldehyde resins were prepared as low molecular weight condensation resins by first forming methylolated urea adducts under basic conditions and then forming the condensates under acidic conditions. The condensation reaction is stopped by raising the pH of the condensation reaction mixture. Other preparation conditions were as described above. The relevant parameters for these resins are determined in table 1 below: molecular weight in grams/mole (mol.wt.); and approximately normalized weight percentages of free urea, cyclic urea species (cyclic ureas), Mono-methylolated ureas (Mono), and combined bis/tris-methylolated ureas (Di/Tri). In all cases, the resin is in a solution having a solids content of 45-70% resin, a viscosity of 500cps or less, and a free formaldehyde content of less than 5% by weight.

TABLE 1 Urea-formaldehyde resins

^*Resin B is a very stable urea-formaldehyde resin with a high cyclic urea content. The resin is described in U.S. patent No.6,114,491.

^**Resin C' was formed by adding 2 wt% diethylenetriamine and 2 wt% dicyanodiamine to a mixture of urea and formaldehyde during the resin preparation.

^***Resin D' was formed by adding 0.75 wt% of a cyclic phosphate ester to a mixture of urea and formaldehyde during resin preparation. The resin has a low molecular weight formulation, has a high content of free urea, is substantially free of free formaldehyde, and has a high content of non-volatiles (about 70% solids).

^aWith PLgel of suitable size^TMGel Permeation Chromatography (GPC) of the column (polymer laboratories, inc., Amherst, MA, USA) determined the average molecular weight, 0.5% glacial acetic acid/tetrahydrofuran as mobile phase at 1500psi, polystyrene, phenol and bisphenol-a as measurement standards.

Example 2

Samples of urea-formaldehyde (UF) resin similar to that described in example 1 were tested for their ability to precipitate graphite and bentonite suspended in an aqueous medium. In four separate experiments, 4.4 grams of graphite microparticles (two experiments) and bentonite microparticles (two experiments) samples were suspended in 220 grams of water in jars and the jars in each example were shaken vigorously for 2 minutes to suspend the solid particles. However, 22 grams of UF resin was added to one jar containing graphite prior to shaking, and also to one jar containing bentonite. The four jars were allowed to stand for 24 hours and the effect of solid-liquid separation by precipitation with UF resin addition was observed. Four jars were photographed and are shown in figure 1.

As is apparent from fig. 1, in the leftmost jar to which UF resin was added, graphite precipitated at the bottom of the jar. No graphite was visible at the air-water interface or on the jar surface. In this case, the UF resin used also precipitates with the graphite. In contrast, the second jar from left without added resin had a large amount of graphite adhered to its surface. There are also many graphites that stay at the air-water interface. Thus, the use of UF resin greatly facilitates the separation of graphite from water via precipitation.

Similarly, bentonite precipitated at the bottom of the third jar from left to right where UF resin was added. In this example, the use of a water-dispersed UF resin resulted in the liquid phase being opaque. In contrast, the rightmost jar to which no resin was added had a large amount of bentonite adhered to its surface and stayed at the air-water interface. The use of UF resin again significantly improves the separation process for bentonite via precipitation.

Example 3

Urea-formaldehyde (UF) resins similar to that described in example 1 were tested for their ability to reduce the dewatering time of various solid contaminants suspended in an aqueous slurry by filtration. In each experiment, a 25 gram sample of solid impurities was mixed with 100 grams of 0.01 mole KNO₃And mixing the mixture into slurry. The pH of the slurry was measured. The slurry was then vacuum filtered using a standard 12.7cm diameter buchner funnel device and 11.0cm diameter Whatman qualitative #1 filter paper. Except for the first experiment using montmorillonite, the dewatering time was in all cases the time required to recover 100ml of filtrate through the filter paper. In the dehydration of montmorilloniteIn the case of the solid used, it is so fine that about 100ml of filtrate is removed for more than 5 minutes. Thus, the relative dewatering time is based on the amount of filtrate removed in 5 minutes.

For each solid impurity tested, a control experiment was performed, followed by the same experiment except that (1) 0.5-1 grams of silane modified UF resin was added to the slurry, and (2) after obtaining a uniform slurry under agitation, the slurry was mixed for a while more. The results are shown in Table 2 below.

TABLE 2 dehydration time of the slurry (at 100g 0.01M KNO)₃With 25 g solid impurities in it)

^*Amount of water removed over 5 minutes

^**Average of two experiments (139 seconds/137 seconds)

^***Average of two experiments (35 sec/38 sec)

Average of two experiments (9.3 sec/9.5 sec)

Average of two experiments (5.9 sec/6.2 sec)

The above results show that UF resins, even when used in small amounts, are capable of significantly reducing the dewatering time for many solid particles.

Claims (25)

1. A froth flotation process for removing solid impurities from an aqueous slurry comprising:

dispersing a urea-formaldehyde resin in the aqueous slurry to provide a dispersed mixture, wherein the urea-formaldehyde resin has a number average molecular weight of 400 to 1200 g/mole and wherein the dispersed mixture comprises 400 to 1000 g urea-formaldehyde resin per metric ton of ore;

passing the dispersed mixture to one or more froth flotation cells;

forcing air through the dispersed mixture to provide a relatively hydrophobic fraction and a relatively hydrophilic fraction, wherein the air is forced through the bottom of the one or more froth flotation cells and the relatively hydrophobic fraction of the material, having a selective affinity for rising froth, to float to the surface; and

commercially available products were collected from either fraction.

2. The method of claim 1, wherein the urea formaldehyde resin has a free formaldehyde concentration of less than 1% based on the total weight of the urea formaldehyde resin.

3. The method of claim 1, wherein the urea-formaldehyde resin comprises a cyclic urea-formaldehyde resin, wherein urea, formaldehyde, and ammonia reactants are added to a reaction vessel and reacted while maintaining a temperature below 70 ℃, wherein the reactants are used in a molar ratio of 0.1 to 1 mole urea, 0.1 to 3 moles formaldehyde, and 0.1 to 1 mole ammonia, wherein the urea-formaldehyde resin is stabilized by etherification with an alcohol, and wherein the alcohol comprises methanol, ethanol, n-propanol, isopropanol, n-butanol, or isobutanol.

4. The method of claim 1, wherein the aqueous slurry has a solids content of 10% to 50% by weight, wherein the urea-formaldehyde resin is prepared using an alkaline catalyst.

5. The method of claim 1, wherein a commercially available product is recovered from the hydrophilic fraction.

6. The method of claim 1, wherein a commercially available product is recovered from the hydrophobic fraction.

7. The method of claim 1, wherein a marketable product is recovered from the hydrophilic fraction and a second marketable product is recovered from the hydrophobic fraction.

8. A froth flotation process for removing solid impurities from an aqueous slurry comprising:

treating an aqueous slurry comprising ore and one or more impurities with a urea-formaldehyde resin and with at least one of a collector and an inhibitor to provide a treated mixture, wherein the urea-formaldehyde resin has a number average molecular weight of 400 to 1200 grams/mole and wherein the treated mixture comprises 400 to 1000 grams of urea-formaldehyde resin per metric ton of ore;

recovering a purified product from the treated mixture, the purified product having a reduced concentration of at least one impurity relative to the aqueous slurry.

9. The method of claim 8, wherein the collector comprises a fatty acid, an amine, a xanthate, or any combination thereof.

10. The method of claim 8, wherein the inhibitor comprises sodium hexametaphosphate, guar gum, other hydrocolloid polysaccharides, or any combination thereof.

11. The method of claim 8, wherein the urea formaldehyde resin has a free formaldehyde concentration of less than 1% based on the total weight of the urea formaldehyde resin.

12. The method of claim 11, wherein the urea-formaldehyde resin comprises a cyclic urea-formaldehyde resin, wherein urea, formaldehyde, and ammonia reactants are added to a reaction vessel and reacted while maintaining a temperature below 70 ℃, wherein the reactants are used in a molar ratio of 0.1 to 1 mole urea, 0.1 to 3 moles formaldehyde, and 0.1 to 1 mole ammonia, wherein the urea-formaldehyde resin is stabilized by etherification with an alcohol, and wherein the alcohol comprises methanol, ethanol, n-propanol, isopropanol, n-butanol, or isobutanol.

13. The method of claim 8, wherein recovering the purified product comprises passing the dispersed mixture to one or more froth flotation cells; and forcing air through the treated mixture to provide a relatively hydrophobic fraction and a relatively hydrophilic fraction, wherein the air is forced through the bottom of the one or more froth flotation cells and the relatively hydrophobic fraction of the material, has a selective affinity for rising froth, floats to the surface, and wherein a purified product is recovered from either fraction.

14. The method of claim 8, wherein the urea-formaldehyde resin is prepared using a basic catalyst.

15. The method of claim 8, wherein the urea-formaldehyde resin comprises a cyclic urea-formaldehyde resin, wherein urea, formaldehyde, and ammonia reactants are added to a reaction vessel and reacted while maintaining a temperature below 70 ℃, wherein the reactants are used in a molar ratio of 0.1 to 1 mole urea, 0.1 to 3 moles formaldehyde, and 0.1 to 1 mole ammonia, wherein the urea-formaldehyde resin is stabilized by etherification with an alcohol, and wherein the alcohol comprises methanol, ethanol, n-propanol, isopropanol, n-butanol, or isobutanol.

16. The method of claim 13, wherein the aqueous slurry has a solids content of 10% to 50% by weight.

17. The method of claim 13, wherein the purified product is recovered from the hydrophilic fraction.

18. The method of claim 13, wherein the purified product is recovered from the hydrophobic fraction.

19. The method of claim 13, wherein a purified product is recovered from the hydrophilic fraction and a second purified product is recovered from the hydrophobic fraction.

20. A froth flotation process for removing solid impurities from an aqueous slurry comprising:

treating an aqueous slurry comprising ore and one or more solid impurities by dispersing urea-formaldehyde resin in the aqueous slurry to provide a treated mixture, wherein the urea-formaldehyde resin has a number average molecular weight of 400 to 1200 g/mole and wherein the dispersed mixture comprises 400 to 1000 g urea-formaldehyde resin per metric ton of ore;

recovering a bottoms product comprising a marketable product by froth flotation, wherein the concentration of at least one solid impurity in the bottoms product is reduced relative to the aqueous slurry.

21. The method of claim 20, wherein the urea-formaldehyde resin is prepared using a basic catalyst.

22. The method of claim 20, wherein the urea-formaldehyde resin comprises a urea-formaldehyde resin having a free formaldehyde concentration of less than 1% based on the total weight of the urea-formaldehyde resin.

23. The method of claim 20, wherein the urea formaldehyde resin is added to the aqueous slurry during froth flotation.

24. The method of claim 20, wherein the urea formaldehyde resin is added to the mixture prior to froth flotation.

25. The method of claim 20, wherein froth flotation produces a relatively hydrophobic fraction and a relatively hydrophilic fraction, and wherein the hydrophilic fraction is recovered as a bottoms product.