MXPA99008927A - Process for removing selenium from selenium-containing waste streams - Google Patents

Abstract

A process for removing contaminating levels of selenium from a contaminated aqueous solution is disclosed. That process includes providing a vessel or flow-permissive container containing a water-insoluble polymeric adsorption medium having a plurality of polymerized C1-C4 N-alkylated pyridinium-containing adsorption sites. An influent of an aqueous solution having a total selenium concentration of about 10 to about 1000 parts per billion is introduced to the vessel or flow-permissive container to contact the insoluble polymeric adsorption medium. The solution is maintained in contact with the insoluble adsorption medium for a time period sufficient for the medium to bind the selenium in the contacting solution. The resulting aqueous solution is discharged from the vessel as an effluent having a total selenium concentration whose ratio to the total selenium concentration of the influent is about zero to about 10-3.

Description

PROCESS TO SEPARATE SELECTION TO PftRTTR OF RESIDUAL CURRENTS CONTAINING SELENIO Field of the invention This invention pertains to a process for separating an environmentally hazardous pollutant from industrial waste solutions. More specifically, the present invention relates to an efficient affinity process for the selective separation of selenium from waste streams containing selenium.

BACKGROUND OF THE INVENTION Selenium is commonly found in copper and molybdenum ores, and in fossil fuels. Selenium compounds are normally present in waste streams from oil refineries, agricultural and irrigation waste streams, waste streams from carbon-fueled power plants, waste streams from carbon processing and waste streams from copper ore refining . The main industrial source of selenium is anodic slime from electrolytic copper refineries. Selenium is useful for the production of photovoltaic cells, among other things. u £ u Cui-iuii, ia Cu? n-, cu? a? -. ??? -. -c; oc- < -? -.--. v- > ^ - ^ "- • - '-'y" residual of the sources mentioned above is low, that is, in the range of 50-1000 parts per billion (50-1000 micrograms per liter, 0.6-12 micromolar.) However, even at these levels, it has been found that selenium from sewage is toxic and teratogenic to certain wildlife species, and even at the analytically small levels described above, the selenium compounds present in the Industrial waste streams have a particularly bad foul odor that contributes to poor air quality and popular nonconformity directed towards the industrial operations responsible for the waste Selenium has been found in different oxidation states: two negative (gaseous hydrogen selenide, H2Se; and polyselenide chains, See2") / zero (elemental selenium, Se0), plus two (selenium halide, Se2X), plus four (selenium dioxide, Se02; and selenious acid, H2Se03) and plus six (trioxide enio, Se? 3, * and selenic acid H2Se0). The aforementioned selenium compounds are only examples commonly associated with this oxidation state of selenium. An ion exchange type wastewater treatment designed to reduce toxic levels of selenide is the method described in US Pat. No. 4,915,928 which includes the treatment of a solution contaminated with selenide with a strong base anion exchange resin. , carry out the selenide drag from the resin, followed by the oxidation of the selenide and the recovery of elemental selenium from the eluate containing selenium. After passage of the anion exchange resin, the level of selenium in the treated wastewater may still be as high as about 50 parts per 1000 million (ppb). For example, in Figure 2 of this patent, when a waste stream containing selenium at about 244-393 ppb was treated with a hot-swelling resin based on DOWEX® 11, the selenium-depleted wastewater effluent (consisting of approximately 700-1000 bed volumes) still contained approximately 45-20 ppb of selenium, an impermissible level. The anionic exchangers with strong base described in this patent generally contain tetraalkyl quaternary ammonium functional groups which are aliphatic and acyclic, usually attached to crosslinked polystyrene beads. Examples that are available commercially are DOWEX® 11 (Dow Chemical Co., Midland, Michigan) and AMBERLITE® IRA 458 (Rhom &Hass, Philadelphia, Pennsylvania). Typically, the ammonia exchange capacity of these reams is milliequivalent per gram (dry basis), or 1.0-1.4 milliequivalents per milliliter of resin bed volume (meq / mL). A resin of 1.5 meq / ml has an anionic binding capacity 1.25 times greater than a resin of 1.2 meq / ml. The common ion exchange includes the pre-equilibrium of an anion exchange column with a low ion concentration buffer, followed by loading the solution containing the anion. The anions in this solution bind to the column due to the ion-ion interactions between the anion and the quaternary ammonium cation of the resin. The anions are then eluted from the column with a buffer of higher ionic strength that breaks the anion-resin interaction. Contrary to the ion exchange that includes the ion-ion interaction, an affinity technique is specific to a certain objective and includes a combination of several types of interactions. The types of chemical interactions known approximately in the order of the strongest to the weakest are interactions of the covalent bond, coordinated bond, ion-ion (ionic union), hydrogen bond, dipole-ion, and dipole-dipole. Selenium is a chalcogenic element, considered "soft" due to the marked polarization capacity of its electronic cloud, especially in the selenide state due to the low ionic charge and the large ionic radius. Selenium has a slight propensity to form coordination compounds 6. Therefore, there remains a need for an adequate and practical process for the separation of toxic selenium in any form from waste streams containing selenium that is efficient and effective. The following description describes a solution to the selenium separation problems.

BRIEF SUMMARY OF THE INVENTION In accordance with the present invention, selenium can be efficiently and economically separated from an aqueous solution that also contains other ions at levels less than five parts per billion. Furthermore, as described herein, the separation resin can be easily regenerated in the column by providing an equally effective regenerated selenium separation medium. The present invention utilizes satisfactorily the binding of selenium to an adsorption medium containing a plurality of N (C) -C4 pyridinium (N) alkyl portions (groups), and in fact, shows that the adsorption medium has an unexpectedly high affinity for selenium.

One method contemplated for reducing selenium in an aqueous solution includes providing a flow permissive vessel or reservoir containing a water-insoluble adsorption medium with a plurality of pyridyl-containing portions present as 2- or 4--portions. polymerized C? -C-pyridinium N-alkyl, and preferably N-methylpyridinium portions as adsorption sites. An influent of an aqueous solution of waste water having an initial, total concentration of selenium of about 10 parts per billion to about 1000 parts per billion is introduced into the container to make contact with the insoluble adsorption medium. The solution is kept in contact with the insoluble adsorption medium for a period sufficient for the adsorption sites to bind selenium in the effluent solution and form selenium bound to the medium and an aqueous composition. This aqueous composition is subsequently discharged from the vessel as an effluent with a total selenium concentration whose ratio to the total selenium concentration of the influent is from about 0 to about 10"3. It is an advantage that the selenium-contaminated wastewater is subjected to a selenium. Process such as that described herein is within acceptable parameters for environmental safety with respect to the selenium content.

Specific to the invention you demonstrated? * 3 n unexpected and surprising that a polymer resin containing polymerized C? -C-pyridinium N-alkyl, insoluble in water used as a selenium adsorption medium can remove selenium from the waste water. The present invention has various benefits and advantages. A benefit of the invention is that aqueous solutions contaminated with selenium can be economically treated to provide a solution with acceptable environmental safety limits. An advantage of the invention is that the selenium can be practically completely separated from the aqueous solution containing selenium and recovered for another use. Another advantage of the invention is that selenium can be separated more efficiently than previously obtainable. Another benefit of the invention is that the above benefits and advantages can be obtained with readily available materials. Another advantage of the invention is that its process is very direct to be carried out and does not require highly specialized equipment. Still another benefit of the invention is that the water-insoluble adsorption medium can be re-used numerous times without loss of capacity or effectiveness.

Still other benefits and advantages and invention will be apparent to skilled workers from the following description.

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a process for separating pollutant levels of selenium from an aqueous solution that also contains other ions. This process is used to reduce the total selenium level of an aqueous solution so that the solution can be disposed of safely or used. Selenium can be recovered from it as elemental selenium. Those skilled in the art will recognize that the recovery of these commercially useful chemicals is an economically and environmentally sound approach compared to the removal of the chemicals as a waste product. Unless the term is used for a specific oxidation state or selenium compound, the use of the term "selenium" herein is intended to comprise any of the forms of selenium present in the residual solution, including all compounds containing selenium and the oxidation states of selenium, that is, minus 2, zero, plus 4, and more 6. As is known in the art, many unidentified selenium compounds are present in the residual currents my coni i n n selenium, and the selenium compounds may change during the treatment and handling of the waste. Usually, in order to reduce selenium to environmentally acceptable levels, the total selenium concentration must be at or below five parts per 1000 million (ppmm). This is approximately the lowest concentration detectable in practice for selenium. A process for reducing the concentration of selenium in a residual stream containing selenium is thus contemplated. According to this process, there is provided a container or a reservoir that allows the flow and that contains a polymeric adsorption medium, insoluble in water with a plurality of adsorption sites that are pyridyl-containing portions present as 2-p portions. 4-vinyl N-C 1 -C 4 -pyridinium polymerized pyridinium, and preferably as N-methyl pyridinium portions. An influent of an aqueous solution having an initial total concentration of selenium of about 10 parts per 1000 million to about 1000 parts per 1000 million is introduced into the container or flows into the reservoir to make contact with the insoluble adsorption medium. The aqueous solution is kept in contact with the insoluble adsorption medium for a period sufficient for the adsorption sites to bind to the selenium in the influent solution to form seienium bound to the medium and a "-. This aqueous composition is subsequently discharged from the container or flows out of the container as an effluent having a total selenium concentration whose ratio to the total selenium concentration of the influent is from about 0 to about 10 ~ 3. Selenium containing, usually, comes from a waste stream of production.In a preferred process, the aqueous solution has an initial selenium concentration of about 10 parts per 1000 million to about 1000 parts per 1000 million. effluent discharged from the container or flowing out of the container has a total selenium concentration of approximately 0 to approximately 5 parts per 1000 million. A contemplated polymeric adsorption medium contains a plurality of adsorption sites which are polymerized pyridyl-containing portions present with polymerized C-C4-pyridinium 2-or 4-vinyl N-alkyl portions. The use of polymerized C-C4 pyridinium 4-vinyl N-alkyl portions (groups) is preferred. Although the C_-C4 alkyl groups such as methyl, ethyl, isopropyl, n-butyl, sec-butyl and the like may be present attached to the nitrogen of the polymerized pyridinium moiety, the N-methyl is an N-alkyl portion of C.- C- particularly preferred. Typically, a polymeric adsorption medium contains at least about 50 mol% of the polymerized monomers present as N-alkylated pyridinium portions of C? -C4. Up to about 80% of the pyridyl groups can be alkylated, with the use of an adsorption medium having about 60 to about 80% alkylated pyridyl nitrogens being preferred. In this manner, the amount of N-alkylated pyridinium portions of C 1 -C 4 may be about 50 to about 80% of the polymeric [sic] adsorption medium. A contemplated adsorption medium is also insoluble in water. This insolubility in water can be achieved by copolymerizing the pyridyl-containing monomer with a cross-linking agent, and also by the use of another comonomer such as styrene or ethyl styrene, as are well known. Divinyl benzene is a preferred crosslinking agent, but other crosslinking agents can also be used as is also well known. The copolymer can then be N-alkylated for use herein. The water-insoluble, water-insoluble copolymer adsorption medium of 4-vinyl pyridine, divinyl benzene and ethyl styrene are available commercially from Reilly Industries, Inc. of Indianapolis, Indiana (Reilly). These media are marketed as REILLEX® 402 (powder, 4-vinyl pyridine, ethyl-styrene, divinyl benzene), REILLEX® 402-1 (granules, components as above), REILLEX® HP (beads, components like the above) ) and REILLEX® 425 (pearls); components such as the above) each of which may be N-alkylated for use herein. The medium also differs in exchange capacity [approximately 8.8 equivalents / kilogram (eq / kg) to approximately 4.4 eq / kg] and in particle size. The water-insoluble, water-insoluble copolymers of 4-vinyl pyridine, divinyl benzene and ethyl styrene with a preponderance of N-methylated pyridinium residues are available commercially from Reilly as REILLEX® HPQ (an N-methylated version of REILLEX® 425, total exchange capacity of approximately 4.6 meq / g dry, ie strong and weak ion exchange capacity) and available from NTEC Solutions, Inc. (Mount Prospect, Illinois, USA ) as a PERFIX® adsorption medium. In these media, about 70% of the pyridyl residues are N-methylated (about 1-2 molar equivalents of N-methylpyridinium ion per liter of medium). The PERFIX® adsorption medium is especially preferred for use herein. The manufacture of a preferred resin (adsorption medium) for use in carrying out the present pre-process is described in U.S. Patent Nos. 4,221,871, No. , - ---. ^, 4-13, WO. ^ / uy -or descriptions are incorporated herein by reference. In the preferred practice, it is contemplated that the contact between the aqueous solution containing selenium and the adsorption medium is carried out in a chromatographic column or container with fluid passage, such as a perforated plastic bag or mesh containing adsorption particles. , for example, a "tea bag". As such, the adsorption medium is preferably in the form of beads or particles. However, it will be noted that it is also possible to use another physical form such as a liquid, dust membrane, sheet or other network. It should be apparent to those skilled in the recovery of metal ions that a polymeric adsorption medium, insoluble in water, can be solid or liquid, as noted above. It should also be understood that the portions containing N-C 1 -C 4 alkyl pyridinium do not need to be part of a polymer backbone, but can also be grafted onto a previously worked polymer, and then preferably N-alkylated to form a adsorption medium having the adsorption sites in the N-alkyl portion of C? -C4 pyridinium. Thus, for example, a thiol-containing polymer can be reacted with 2 or 4-vinyl pyridine to form polymerized thioethylpyridine groups which can then be N-alkylated with methyl chloride or methyl iodide or the like to form the adsorption medium favorite. Although other polymerized monomers may be present in a polymerized adsorption medium, other monomers and the adsorption medium are free of other ion-charged functional groups. The polymerized, non-alkylated 2- or 4-vinyl pyridine can be present, however, as is the case with a preferred polymerized adsorption medium. The contact between the adsorption medium and the aqueous solution containing selenium is maintained for a sufficient time for the selenium to be bound by the adsorption sites containing N-alkyl pyridinium from the medium. This union is usually very fast, with contact times of a few seconds to a few minutes. Much larger contact times as hours can be used without being observed any detrimental effects. In an example of the present process, an aqueous solution containing contaminant levels of selenium is introduced into a vessel or reservoir that allows flow, such as by pumping or gravity feed onto a chromatographic column containing a preferred adsorption medium [poly ( 4-vinyl pyridinium) -methylated] also known as PERFIX® available from NTEC Solutions, Inc., described above. The time of stay of the solution, that is, the time - U.C S? lucLi _L C ±± ß j- 3 SO adsorption must be long enough so that the adsorption sites containing N-alkyl pyridinium from the adsorption medium bind to the selenium. In the present examples, the solution was kept in contact with the adsorption medium in the column for about 10 seconds. The restrictions of flow, temperature and pressure of the process are dictated mainly by the limitations of the equipment used and the resin used in carrying out the invention. Temperature and ambient pressure are normally used. The resin-treated effluent is practically depleted of selenium haßta, which exceeds the adsorption capacity of the medium. The moment in which the capacity of adsorption of the medium is exceeded is indicated by the visual observation of the color of the resin that changes from a whitish to a reddish brown color in the presence of selenium-containing waste or by analytical testing of the effluent. That is to say, the preferred PERFIX® adsorption medium changes the color from whitish to reddish brown with selenium binding, so that a column can be charged until the resin changes color at the opposite end to the inlet, or the load can continue until the selenium assays indicate that selenium is discharged from the column. Another indication of selenium discharged from the column is a foul odor of the effluent.

When the selenium separation system is operated at or below its capacity, the amount of selenium remaining in the effluent under load (selenium saturation) was very low (less than 5 ppb). The results of selenium binding capacity were surprising for PERFIX® (1.5 meq / ml) compared to the selenium binding capacity of DOWEX® 11 (1.2 meq / ml). It is expected that the 1.25 fold improvement in selenium binding would be 1.2 meq / g of medium to 1.5 meq / g of medium, while a double improvement in selenium binding capacity was observed. It was also surprising that the binding efficiency of a resin with selenium affinity of the invention is much better than the selenium binding efficiency of the ion exchange resins of the art. PERFIX® exhibited selenium binding efficiency greater than 99-, while US Patent No. 4,915,928 described only 80-95% selenium binding efficacy with the DOWEX® 11 ion exchange resin. It is noted that this observed improvement in selenium binding capacity and effectiveness was very unexpected. It is considered that this surprising improvement in selenium binding capacity is a result of the ion-dipole or dipole-dipole interactions between the polarizable selenium species and the polarizable N-alkyl-pyridinium groups which, together with --- .--. i OJ- V. ion exchange give rise to a better binding interaction by affinity with selenium. The identity of the reddish-brown species observed in the union by the resin is currently unknown, but its elution corresponds to the analytical observation of the selenium elution and the characteristic unpleasant odor. The fact is that there was no detectable selenium in the effluent, until the selenium was specifically eluted or until it exceeded the selenium binding capacity. The total amount of residual water contaminated with selenium that can be processed per cubic foot of an adsorption medium containing the N-alkylated pyridinium ion of C; -C4, contemplated, such as PERFIX® resin is controlled by the level of Selenium contamination in the influent (feed stream) of the wastewater. Unexpectedly, the treated wastewater effluent presented selenium levels that were not detectable by sensitive analytical means such as atomic adsorption spectroscopy (less than about 5 ppb). Also unexpectedly, as already described herein, it was observed that the adsorption medium can be regenerated repeatedly (for example, by entrainment), rinsed and reused without noticeable physical or chemical degradation of the selenium binding capacity of the resin. The PERFIX® resin that was used can withstand operational pressures of 100 psi and temperatures of 100 degrees Celsius. A contemplated process successfully separates selenium from aqueous residual solutions contaminated with selenium at temperatures between approximately 15 ° C and 90 ° C. Preferably, the process operates at temperatures between about 20 ° C and 70 ° C. The process of the present successfully separates the selenium from an aqueous solution in a pH range from acid to approximately neutral (approximately pH 1 to approximately pH 7). Preferably, the process is operated with a solution having a pH value between about 4 and 7, and more preferably between about 6 and 7. At pH values above about 7, the process begins to lose efficiency and a value of pH of about 14 (for example, the addition of 2.0 N NaOH), the binding of selenium to the adsorption medium is much less efficient. The process effectively reduces selenium contaminants from waste streams having selenium initial concentrations from about 10 to about 1000 ppb, and has been found to reduce selenium concentrations thereof to approximately less than 5 ppb and more particularly down to concentrations between approximately zero and 5 pptr? tn. It was also observed that the adsorption medium can be regenerated and reused several times. The regeneration of the adsorption medium preferably takes place without separating the adsorption medium from the column or the container that allows the flow. The adsorption medium (resin) can be regenerated by methods well known in the art. For example, the affinity interaction can be broken by mass action treatment of the base resin as is well known in the art, for example a normal aqueous sodium hydroxide 1-2 (N) or other strong base solution. The ion-dipole or dipole-dipole interaction can be broken by treating the resin with a moderately non-polar organic aqueous solution, such as acetone, together with a strong acid solution such as an aqueous solution of hydrochloric acid 1-2. N. The resin is then washed with water to remove excess acid and counter-ions, completing the regeneration. The resin can be used, purified and regenerated and can be used in multiple cycles without measurable loss in the binding capacity or increase in backpressures during operation. In general, the increase in back pressure indicates physical degradation of the adsorption medium.

Best way to carry out the invention Example 1: Separation of selenium from waste water using an N-alkylated pyridinium adsorption medium of C3.-C4 Preparation of the resin Approximately 300 ml of N-methylated poly (4-vinyl pyridyl) bead resin with approximately 70 * n-methylation, marketed under the name PERFIX®, marketed by NTEC Solutions, Inc., of Mount Prospect, IL EU, were suspended with approximately 600 ml of deionized water. This resin has a particle size in the 18-50 mesh size, and has an exchange capacity of approximately 3.4 meq / g dry as a strong base and a total exchange capacity of approximately 4.6 meq / g dry as a base strong and a weak base. The spherical beads were left at rest. After about 1 minute, the colorful supernatant was decanted and discarded together with small particles of resin, or fines, which did not settle out during the first minute. This operation was repeated until the supernatant had no color and was free of fines (from 5 to 6 cycles of suspension and decantation). This operation was also repeated using 0.1 N sodium hydroxide instead of deionized sm-i, dried by washing with 10% acetic acid in water and 4 to 5 additional cycles of suspension and decantation with deionized water. The resin slurry was then loaded onto a 25 x 500 nm glass column with a fritted, porous glass support and a stopper on the bottom until the column contained 200 ml of the packed bed volume filled with resin.

Introduction of residual water with a selenium content in the resin bed Thirty (30) liters of the "sulphurous water" wastewater solution from an oil refinery, contaminated with approximately 600 parts per billion selenium had a pH value of approximately 2. The wastewater solution was used as a supply , without additional treatment. The solution was continuously added to the column until the complete sample of the solution was introduced and brought into contact with the resin bed. As the solution was introduced into the resin bed, the color of the resin at the top of the column changed to a dark reddish brown of its original whitish color. As the additional wastewater solution flowed down the column, the color band slowly extended down the column ia.S i-.ci ue c-pr? Xl ± --aG.c--. ? -er- l_e U? QCI ici-Il? u-c j-. C --.--- 1 -. ÍIUJJÍ U -----i- ^ - -. used, while the unused resin in the lower part of the column remained practically whitish. It was observed that washing the column with deionized water did not result in migration of the dark reddish-brown band. It was also observed that selenium was not detected in the effluent of the column using atomic absorption analysis, nor by its characteristic odor, so that less than about 5 ppb were present. The capacity of the resin was determined by measuring the length of the dark reddish-brown band that formed on the column with the selenium bonding to the resin and comparing the length of the color with the total length of the resin bed. The capacity of the resin was determined to be approximately 25 grams of selenium (as metal) per cubic foot - (ft3) of resin, while US Patent No. 4,915,928 which used DOWEX® 11 strong base anion exchange resin, reported a selenium capacity in the effluent of purified sulphurous water of approximately 13 grams / ft3 of resin. In addition, the use of the DOWEX® 11 resin provided an average selenium concentration of about 26 ppb in the effluent, while the use of a resin contemplated herein resulted in undetectable selenium (less than about 5 ppb) in the effluent.

Regeneration of the resin bed The resin column was regenerated using a 1.0 N NaOH solution. The solution was prepared and two column volumes thereof were passed through the column containing the bound selenium. After treatment of the column with an NaOH solution the column was rinsed with two column volumes of deionized water. A solution of 1: 9 acid: acetone was separated using a 1.0 solution of N H2S04, and was run through the column, followed by two more volumes of deionized water column. The combination of the solutions completely separated the bound selenium from the resin. It was unexpected that the adsorption medium will exhibit highly effective binding capacity for selenium representing an affinity interaction with selenium. The use of N-methylated poly (4-vinyl pyridine) adsorption media (PERFIX®) to separate selenium from wastewater showed that virtually all of the selenium could be separated from the wastewater solution with an unexpected improvement in selenium binding capacity relative to strong base anion exchange resins, suggesting another interaction in addition to the anion exchange interaction of the strong base between the resin and the selenium.

The observation of the best affinity for selenium by the anion exchange resin was unexpected. The observed column capacity was higher for the resin containing N-alkyl pyridinium functional groups than that expected for DOWEX® 11, a strong base anion exchange resin that does not contain an aromatic functional group.

While the selenium sorption in the known processes was expected better than 1.25 times over a strong base anion exchange resin such as DOWEX® 11, the present process presented a double improvement in the selenium binding capacity from the current of residual water. In fact, since the levels of selenium contamination of the wastewater (effluent) treated from the present process are between about 0 ppb and 5 ppb, the ratio here of the total selenium concentration of the effluent to that of the influent is about 0 to about 0.008 (0 ppb / 600 ppb at 5 ppb / 600 ppb, respectively). Without the desire to stick to this mechanism, it is considered that the highly polarizable selenium is interacting with the Pi electrons cloud of the highly polarizable C? -C4 pyridinium N-alkyl, resulting in a dipole-dipole interaction in addition to the ion interaction. expected between the anion and the anion exchange resin. This hypothesis is supported by the observed reddish-brown color, which can be a result of im- | ---- £ -. "--_- ~, - ~ '"? At-. orif ro 1 electron cloud of selenium and a cloud of pi electrons of pyridinium. Those skilled in the art will recognize that the present process can be carried out in a batch mode and a steady state mode. In the steady state mode, the contact or stay time of the solution with the adsorption medium must be sufficiently long to allow adsorption sites containing N-alkyl pyridinium from the adsorption medium to bind selenium. It will also be recognized by those skilled in the art that the various methods of regenerating the resin can be used, and that the regeneration method presented herein is illustrative only and should not be considered to limit the scope of the invention to the method of regeneration of the present.

Example 2: Separation of selenium from wastewater using a non-pyridyl N-alkylated resin A resin in beads with approximately 5.5 meq / 1 of polymerized 4-vinyl pyridine incorporated as an integrated component of its polymer backbone was evaluated for its effectiveness in separating selenium from wastewater streams of petroleum. Unlike the resin in beads of Example 1, lc ---. pyridilc poi.clones of this resin are not alkylated. This resin in pearls with a content of non-alkylated pyridyl groups is available commercially from Reilly Industries (Indianapolis, IN, USA) under the tradename REILLEX® HP Polymer. Approximately 100 ml of REILLEX® HP Polymer beads were washed and the fines were removed by sequential suspension and decanting from 500 ml volumes of water, IN NaOH, water, H; SO-; 1N, water, NaOH IN, water, 10% acetic acid and finally water. The resulting resin beads (50 ml) were added to a chromatographic column (2.2 cm x 120 cm) equipped with a bottom porous frit and a shut-off valve valve. The prepared resin occupies the lower 13 cm of the bed of the column. The water was allowed to flow through the column until the water level was about 1 cm above the resin bed. The residual water with a content of 790 ppb of selenium was added to the top of the column and the flow through the column was allowed until 5 column volumes (250 ml) had been collected to displace the initial volume of the water originally present. The eluted volumes of 5 initial columns were discarded. 20 additional column volumes (1000 ml) passed through the column, they were combined and collected. As in the 3 eir-.pl or earlier with the res to ptpf-_r -Ha H <; - oc-t ";." i nvpp c i on. The reddish brown band formed on the upper part of the resin bed as wastewater was applied. Analysis of 5-25 column volumes combined revealed a 25- (approximately 200 ppb) reduction in selenium content compared to untreated wastewater. This example demonstrates that the level of selenium binding efficiency for REILLEX® HP Polymer is too low that there was a measurable contribution to selenium binding defined by the non-alkylated pyridyl residues of REILLEX® HP Polymer. Therefore, it is considered that the improved binding (affinity) between the selenium species found in the wastewater and the N-alkylated pyridinium containing resin of C? -C4 is probably partly the result of the pi electrons of the pyridinium interacting with the species of selenium. From the foregoing, it will be noted that numerous modifications and variations may be made without departing from the real spirit and scope of the novel concepts of the present invention. It should be understood that no limitations with respect to the specific example presented are intended and should be inferred. The description is proposed to cover, through the appended claims, all such modifications falling within the scope of the claims.

Claims (6)

1. A process for separating selenium in an aqueous solution comprising the steps of: (a) providing a vessel or a reservoir that permits flow, containing a water-insoluble polymeric adsorption medium with a plurality of adsorption sites that are portions that contain pyridyl, present as N-alkyl portions of C: -; polymerized pyridinium; (b) introducing an influential aqueous solution with a total initial selenium concentration of from about 10 to about 1000 parts per 1000 million into the vessel or reservoir allowing flow to make contact with the insoluble adsorption medium; (c) keeping the solution in contact with the insoluble medium for a sufficient time for the selenium in the influent to bind to the adsorption sites to form selenium bound to the medium and an aqueous composition; and (d) discharging the aqueous composition of the vessel or reservoir that allows flow as an effluent having a total selenium concentration whose ratio to the total selenium concentration of the influent is from about 0 to about 103.

2. The process according to the claim 1, wherein the effluent has a total selenium concentration of about 0 to 5 parts per 1000 million.

3. The process according to claim 1, wherein the portions of 2- or 4-vinyl N-alkyl of C; -C; Polymerized pyridinium constitute about 50 to about 80 mol% of the polymeric adsorption medium.

4. A process for separating selenium in an aqueous wastewater solution, comprising the steps of: (a) providing a vessel or a reservoir allowing flow, containing a polymeric adsorption medium insoluble in water with about 50 to about 80 mol% of C-C4 pyridinium N-alkyl portions polymerized as adsorption sites; (b) introducing an influent of an aqueous selenium-contaminated waste water solution with a total initial selenium concentration of about 10 to about 1000 parts per 1000 million into the vessel or reservoir allowing flow to make contact with the adsorption sites; (c) keeping the solution in contact with the adsorption medium for a sufficient time for the adsorption sites to bind the selenium in influent to form selenium bound to the medium and an aqueous composition; and (d) discharging the aqueous composition of the container or reservoir that permits flow as an effluent having a total selenium concentration of from about 0 to about 5 parts per 1000 million.

5. The process according to claim 4, wherein the N-alkyl-C4-pyridinium portions of the polymeric [sic] absorption medium are N-methyl pyridinium portions. The process according to claim 4, further includes the steps of separating selenium from the polymeric adsorption medium by contacting the medium with an aqueous solution of a strong base, maintaining the contact for a sufficient time to form an aqueous solution that contain selenium and recovery of the aqueous solution containing selenium.