CN107008231A - Composite particles for remediating heavy metal pollutants and method thereof - Google Patents

Abstract

The invention discloses a composite particle for remedying heavy metal pollutants and a method thereof. The composite particle comprises a nano metal core and a modified surface layer surrounding the nano metal core. The modified surface layer has at least one coordination functional group which can form a metal complex with a heavy metal ion, so that the heavy metal ion is easy to contact with the composite particle. The nano metal core takes iron nano particles as a main component and is used for rapidly and continuously reducing the heavy metal ions, and in addition, the nano metal core contains aluminum nano particles and nickel nano particles and is used for improving the corrosion resistance and the stability of the composite particles.

Description

Composite particles and methods for remediation of heavy metal pollutants

technical field

The present invention relates to a composite particle for remediating heavy metal pollutants and a method thereof, in particular to a composite particle for remediating heavy metal pollutants capable of absorbing and further reducing heavy metal ions and a method for using the same.

Background technique

With the rapid development of industry and the excessive use of heavy metals, the seepage water of industrial waste liquid and unidentified waste dump sites contains heavy metals that cannot be loaded by the environment. Different raw materials and power are used in various industrial methods, and the amount and quality of the wastewater produced are extremely complex, especially the wastewater containing heavy metals, which will affect the ecology of the water body after being discharged into the river, and further affect agricultural irrigation. Water and water for people's livelihood. If people drink water containing heavy metals for a long time, it will cause cumulative poisoning. If the wastewater infiltrates into the soil surface, it may be leached and the wastewater may enter the underground aquifer, causing pollution of the groundwater source. Among the sources of heavy metal wastewater, electroplating wastewater is a well-known major source. In other industrial production such as fertilizer factories, the catalysts used in the production of nitrogen fertilizers contain zinc, copper, cobalt, nickel, chromium, molybdenum and other metal substances. If not properly recovered Or discarded, it will pollute the environment.

There are many kinds of heavy metals, some of which are necessary for the growth and physiological functions of organisms, called essential elements, such as zinc, iron, copper, manganese and cobalt. In addition, those not required by biological life are called non-essential elements, such as cadmium, lead, and mercury. The characteristic of heavy metals is that once they enter the environment, they will persist in the environment without being naturally decomposed. In addition, heavy metals in the environment can enter the human body in various ways. For example, heavy metals in the atmosphere can enter the body directly through the respiratory tract, or they may indirectly pollute food and then enter the human body through diet. Excessive heavy metals can cause toxic reactions and even death in organisms.

Taking chromium as an example, it is a common heavy metal pollutant in groundwater. For example, chromium is often used in the livelihood industrial processes such as paint, alloy, electroplating, photography, alkali chlorine, petrochemical, paper making, textile and leather, so the process control Negligence or improper disposal of waste may cause leakage, and have serious impacts and impacts on the health of the people and the ecological environment in the vicinity of the leakage through multiple exposure routes such as drinking water. The main existence forms of chromium in the water environment include trivalent chromium and hexavalent chromium, among which trivalent chromium has relatively stable chemical properties, weak penetration ability to biological cell membranes and is easy to fix in tissues; hexavalent chromium has a strong Strong oxidizing ability will have a greater toxic effect on organisms, and hexavalent chromium species are often listed as control items in relevant regulations on safety, health and environmental protection.

Although there have been many studies on the remediation of groundwater or soil polluted by heavy metals, green remediation technologies have the most potential for development under the rising awareness of environmental protection. However, there is still a need for a better solution in terms of maintaining the composition of the environment such as soil and groundwater, using the stability of the substrate itself, controlling the length of remediation time, the diffusion of pollutants, or simplifying the remediation steps.

Therefore, it is necessary to provide a composite particle and its method for remediating heavy metal pollutants, so as to solve the problems existing in conventional technologies.

Contents of the invention

The main purpose of the present invention is to provide a composite particle for remediation of heavy metal pollutants, which has a multi-layer structure, wherein the inner layer structure is composed of various metal nanoparticles contained in the earth's crust, and iron nanoparticles are the main particles. The components are used to reduce the heavy metal ions, and at the same time, the stability of the iron nanoparticles is enhanced and the consumption speed is reduced by the assistance of other metal nanoparticles, so that the service life of the composite particles can be extended.

The secondary purpose of the present invention is to provide a kind of composite particles for remediation of heavy metal pollutants, the outer structure of which contains functional groups that can be combined with heavy metal ions, so the chance of contact between heavy metal ions and composite particles can be improved, and the remediation efficiency can be improved. And the heavy metal ions can settle with the weight of the composite particles, thereby reducing the re-release of the heavy metal ions and limiting their diffusion range. In addition, its outer structure also has bioavailable components, which can promote the growth of microorganisms on the spot, and can also strengthen and connect with the bioremediation projects of other pollutants.

Another object of the present invention is to provide a method for remediating heavy metal pollutants, which can simplify the remediation process by mixing or contacting the above-mentioned composite particles with heavy metal pollutants, and will not change the site during and after remediation. The composition of soil and groundwater is extremely environmentally friendly.

To achieve the above-mentioned purpose, an embodiment of the present invention provides a composite particle for remediating heavy metal pollutants, which includes a nano-metal core, which includes iron nanoparticles, aluminum nanoparticles and nickel nanoparticles; and a modification The surface layer surrounds the nano-metal core, and the modified surface layer has at least one coordination functional group for forming a metal complex with a heavy metal ion, so that the heavy metal ion is adsorbed on the modified surface layer.

In an embodiment of the present invention, in the nano-metal core, the weight of the nickel nanoparticles is less than the weight of the aluminum nanoparticles, and the weight of the aluminum nanoparticles is less than the weight of the aluminum nanoparticles The weight occupied by iron nanoparticles.

In one embodiment of the present invention, the iron nanoparticles account for at least 65% by weight of the nano-metal core.

In an embodiment of the present invention, the aluminum nanoparticles account for at most 25% by weight of the nanometal core.

In an embodiment of the present invention, the nickel nanoparticles account for at most 10% by weight of the nano-metal core.

In one embodiment of the present invention, the coordination functional groups are hydroxyl (-OH), ether (-O-), aldehyde (-CHO), ketone (-CO-), carboxyl (-COOH) , ester group (-COO-), amine group (-NH ₂ ) or amide group (-CO-NH ₂ ).

In one embodiment of the present invention, the heavy metal ion is hexavalent chromium ion.

In an embodiment of the present invention, the modified surface layer includes citric acid, amino acids, multivitamins, a biodegradable surfactant, and an organic solvent.

In one embodiment of the present invention, the weight ratio of the citric acid, the amino acid, the multivitamin, the biodegradable surfactant and the solvent is 10:5:5:30:50 .

In one embodiment of the present invention, the biodegradable surfactant comprises lecithin, and the lecithin is at least 15 to 30% by weight of the modified skin.

Moreover, another embodiment of the present invention provides a method for remediating heavy metal pollutants, which includes the following steps: (1) providing the above-mentioned composite particles for remediating heavy metal pollutants; and (2) making the Composite particles come into contact with a heavy metal pollutant.

In one embodiment of the present invention, the heavy metal pollutants are heavy metal-containing soil or heavy metal-containing water.

In one embodiment of the present invention, the heavy metal ions contained in the heavy metal pollutants are hexavalent chromium ions.

In an embodiment of the present invention, the modified surface layer reacts with water to form an emulsified colloid layer.

In order to allow the above content of the present invention to be more obvious and understandable, the following preferred embodiments are described in detail as follows:

Description of drawings

Figure 1: Schematic diagram of the structure of composite particles according to an embodiment of the present invention.

Fig. 2: A bar graph of iron/aluminum/nickel metal composition ratios in composite particles according to an embodiment of the present invention.

FIG. 3 : shows the total reduction efficiency of hexavalent chromium ions under the condition of continuous injection of hexavalent chromium ions by composite particles according to an embodiment of the present invention.

Fig. 4: Spectrogram analyzed by X-ray photoelectron spectrometer (XPS) after the composite particle of an embodiment of the present invention reduces hexavalent chromium ions.

Fig. 5: The regulation mechanism of hexavalent chromium ions by composite particles according to an embodiment of the present invention.

detailed description

The direction terms mentioned in the present invention, such as up, down, top, bottom, front, back, left, right, inside, outside, side, around, center, horizontal, transverse, vertical, longitudinal, axial, radial, The uppermost layer, the lowermost layer, and the like are merely directions referring to the attached drawings. In addition, the singular forms "a", "an" and "the" mentioned in the present invention include plural references, unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include multiple compounds, including mixtures thereof; "%" mentioned in the present invention refers to "weight percent (wt%)" unless otherwise specified; numerical range (such as 10% to 11% of A) if there is no specific description, both upper and lower limits are included (ie 10%≦A≦11%); if the value range does not define the lower limit (such as B below 0.2%, or B) below 0.2% means that the lower limit may be 0 (that is, 0%≦B≦0.2%); the proportional relationship of "weight percentage" of each component can also be replaced by the proportional relationship of "weight parts". The above terms are used to illustrate and understand the present invention, but not to limit the present invention.

Referring to FIG. 1 , an embodiment of the present invention provides a composite particle 10 for remediating heavy metal pollutants, which mainly includes a nano-metal core 11 and a modified surface layer 12 . The particle size of the composite particle 10 is about 80 to 100 nm.

The nano-metal core 11 can be composed of various metal nanoparticles, including iron nanoparticles, aluminum nanoparticles and nickel nanoparticles. In the nano-metal core 11 , the nickel nanoparticles occupy less weight than the aluminum nanoparticles, and the aluminum nanoparticles occupy less weight than the iron nanoparticles. The iron nanoparticles account for at least 65% by weight of the nanometal core 11 . The aluminum nanoparticles account for at most 25% by weight of the nanometal core 11 . The nickel nanoparticles account for at most 10% by weight of the nanometal core 11 . Preferably, relative to the weight of the nano-metal core 11, the iron nanoparticles are 65 to 80wt% (ie 65%≦Fe≦100%), and the aluminum nanoparticles are 15 to 25wt% (ie 15%≦ Al≦25%), and the nickel nanoparticles are 5 to 10wt% (ie 5%≦Ni≦10%), and the sum of the above-mentioned iron, aluminum, nickel nanoparticles is 100wt%.

Furthermore, the modified surface layer 12 is formed on the outer layer of the nano-metal core 11 and surrounds the nano-metal core 11 . The modified surface layer 12 contains at least one coordination functional group, which can form a metal complex with a heavy metal ion, so that the heavy metal ion is adsorbed on the modified surface layer 12, increasing the interaction between the heavy metal ion and the The contact opportunities of the composite particles 10 are improved, and the reduction reaction with the nano-metal cores 11 is easy. The coordinating functional group can be selected from, for example, hydroxyl group (-OH), ether group (-O-), aldehyde group (-CHO), ketone group (-CO-), carboxyl group (-COOH), ester group (-COO -), amine group (-NH ₂ ) and amido group (-CO-NH ₂ ). The heavy metal ion may be, for example, hexavalent chromium ion (Cr ⁶⁺ ), but is not limited thereto.

Furthermore, the modified surface layer 12 includes components that allow microorganisms to grow, such as citric acid, amino acids, multivitamins, biodegradable surfactants, and an organic solvent. Preferably, the weight ratio of the citric acid, the amino acid, the multivitamin, the biodegradable surfactant and the solvent may be 10:5:5:30:50, but it is not limited thereto . The multivitamin includes, for example, at least one of vitamin B group, vitamin A, C, D, E and K or any combination thereof, which can promote the growth of microorganisms. The biodegradable surfactant can improve the miscibility of oil and water, and can be decomposed naturally in the environment without leaving harmful substances in the environment, meeting the requirements of environmental protection. The biodegradable surfactant can be, for example, lecithin, natural vegetable oil derivatives (such as coconut oil, palm oil derivatives) or natural sapindus extract saponin, but is not limited thereto. Preferably, said biodegradable surfactant comprises lecithin, and said lecithin is at least 15 to 30% by weight of said modified skin, may for example be 15, 16, 17, 18 or 20% , but not limited to this. The organic solvent is preferably a water-miscible solvent, such as ethanol.

Another embodiment of the present invention provides a method for remediating heavy metal pollutants, which includes the following steps: (1) providing the composite particles 10 for remediating heavy metal pollutants as described above; and (2) making the Composite particles 10 are in contact with a heavy metal contaminant.

The method for remediating heavy metal pollutants according to an embodiment of the present invention firstly includes: (1) providing the above-mentioned composite particles 10 for remediating heavy metal pollutants. In this step, for example, the nano-metal core 11 can be synthesized by wet deposition method, and then immersed in 50% ethanol, 15% lecithin, 10% citric acid, 5% comprehensive amino acid, 5% comprehensive vitamin, In a 15% mixed solution of natural derived surfactants (such as coconut oil and palm oil derivatives), a suspension is made after sufficient shaking. Then the product powder was obtained after freeze-drying to remove excess water, and its surface microscopic state could be analyzed by scanning electron microscope with energy dispersive spectrometer (SEM-EDS), and the material was completely dissolved into a solution state by inductively coupled plasma-atomic radiation Spectroscopic (ICP-AES) analysis of its metal composition. As shown in Table 1, the analysis results of the iron/aluminum/nickel metal composition of the composite particles obtained from 4 groups of different weights are shown in Fig. 2 .

Table 1

group 1 2 3 4 5 Sampling weight (g) 0.0364 0.0640 0.1195 Average weight theoretical value

The theoretical value of the fifth group is the weight percentage of iron/aluminum/nickel in the current crust, which is set as iron:aluminum:nickel=76.6:13.4:10. The other four groups are analyzed by ICP-AES, as shown in Figure 2 It shows that the average value of the actual composition of iron/aluminum/nickel metal can be obtained is about iron:aluminum:nickel=70:20.8:9.2, so it can be confirmed that the composite particle composition is indeed iron/aluminum/nickel, and its actual The ratio of the value to the theoretical value is close, which also proves that the composite particle of the present invention can indeed adjust the ratio of the metal contained in the nano-metal core according to the composition of the earth's crust.

The method of an embodiment of the present invention is followed by: (2) contacting the composite particles 10 with a heavy metal pollutant. In this step, for example, water can be used as a carrier to form a suspension of the composite particles 10 and water, and then inject or mix the suspension into the heavy metal pollutants; or, the The heavy metal pollutants, water, and the composite particles 10 are mixed; or, the composite particles can be filled in a suitable container, which can be used as a filter material for the heavy metal pollutants to pass through. The above method can be adjusted depending on the type of heavy metal pollutants, the scope of remediation, or the need to combine with other types of remediation, and is not particularly limited. The heavy metal pollutants can be heavy metal-containing soil or heavy metal-containing water. The heavy metal pollutants include at least one heavy metal ion, such as hexavalent chromium ion (Cr ⁶⁺ ), but it is not limited thereto, as long as it can form a metal complex with the above-mentioned coordination functional group, and can be absorbed by the nanometer The heavy metal ions reduced by the metal core 11 can be treated by using the composite particle 10 of the present invention. The modified surface layer 12 of the composite particles 10 can react with water to form an emulsified colloid layer, and the emulsified colloid layer has a porous structure, so the heavy metal ions can pass through to reach the nano-metal core 11 . Furthermore, the modified surface layer 12 contains the biodegradable surfactant, so it is very beneficial to the dispersion in water (underground water, waste water, etc.).

In order to verify the effectiveness of the method for remediating heavy metal pollutants of the present invention, the present invention carried out a laboratory simulation test and the results are as follows.

Experiment 1: Treatment of hexavalent chromium pollutants in water

The composite particles 10 (with an iron content of about 56.0mg) were injected into a water sample containing hexavalent chromium, and potassium dichromate solution was replenished at regular intervals to provide hexavalent chromium ions (Cr ⁶⁺ ) to simulate the current The state of the continuous injection of hexavalent chromium pollutants in the ground environment is used to evaluate the continuous decontamination ability of the composite particles 10 after being injected into the water body. The number and time of replenishment are shown in Table 2 below.

Table 2

frequency 0 1 2 3 4 5 6 time (hours) 0 6 twenty four 48 72 96 144

After the composite particle was injected into the hexavalent chromium water sample at the beginning (0 hour), the analysis result found that the Cr ⁶⁺ concentration in the solution tended to 0 mg/liter (mg/L), showing that the Cr ⁶⁺ in the solution was in the Composite particles are reduced to Cr ³⁺ immediately after being charged. After 6 hours, the same solution was supplemented with Cr ⁶⁺ for the first time, so that the estimated concentration of Cr ⁶⁺ in the solution was 100mg/L, and the analysis of hexavalent chromium was carried out again, and it was found that the concentration of Cr ⁶⁺ also tended to 0mg /L, it shows that the composite particles can still rapidly reduce Cr ⁶⁺ after re-injection of hexavalent chromium pollutants. When the Cr ^{6+ reinjection was carried out for the fifth time (96 hours), the measured Cr 6+ concentration} was about 50 mg/L, and then the sixth Cr ^{6+ reinjection} was carried out at the 144th hour (sixth day) of the experiment. The residual concentration of hexavalent chromium in the water sample was measured to be about 57mg/L. On the 216th hour (ninth day) of the continuation of the experiment, it can be measured that the Cr ⁶⁺ concentration in the water sample tends to 0 mg/L, which shows that the composite particles can still continuously reduce hexavalent chromium under sufficient reaction time. The total amount of hexavalent chromium that can be continuously and rapidly removed by the composite particles is about 49.0 mg (only calculated until the fifth replenishment), and the calculated weight of continuously removed hexavalent chromium per gram of the composite particles is about 0.875 grams. Figure 3 shows the total reduction efficiency of the composite particles to hexavalent chromium during the test process. It was confirmed that the reduction efficiency of the composite particles was still as high as 100% under six continuous injections of the pollutant Cr ⁶⁺ , which showed that the composite particles could not only reduce the pollutants rapidly, but also continuously reduce the newly added pollutants.

Experiment 2: After treating hexavalent chromium pollutants, observe the type of sediment on the surface

As shown in FIG. 4 , the results of X-ray photoelectron spectroscopy (XPS) can confirm that the composite particles can effectively adsorb chromium ions in water and reduce hexavalent chromium to trivalent chromium. After the reaction, the hydroxide and oxygen functional groups on the surface of the composite particles increase, and it can be seen from the bond energy that there is no absorption peak of hexavalent chromium, and only the bond of _trivalent chromium such as _Cr2O3 or Cr(OH) ₃ energy (9.8eV). The analysis results confirmed that the hexavalent chromium pollutants in the water phase were reduced to trivalent chromium to form solids and adsorbed on the surface of the composite particles, so the hexavalent chromium pollutants in the water phase were removed, and it was also confirmed by the elemental form analysis results Hexavalent chromium in water is effectively reduced to trivalent chromium, and the formation and adsorption mechanism of chromium hydroxide (Cr(OH) ₃ ) is shown in Figure 5.

Referring to FIG. 5 , the regulation mechanism of the composite particles 10 for the hexavalent chromium ions is shown in FIG. 4 . Firstly, the aluminum nanoparticles contained in the nano-metal core 11 can cover and protect the nano-metal core 11, slow down the corrosion rate and provide electrons to the iron nanoparticles. The nickel nanoparticles are inert metal ends, which are not easily oxidized and can form a DC battery structure with the iron nanoparticles, so that electrons are continuously and stably released to the surface of the nano-metal core 11 . The coordination functional groups of the modified surface layer 12 can hold hexavalent chromium ions, and the hexavalent chromium ions (Cr ⁶⁺ ) are reduced to trivalent chromium ions (Cr ³⁺ ) by iron nanoparticles through the modified surface layer 12. ⁺ ), and then form chromium hydroxide (Cr(OH) ₃ ) solid to deposit on the nano-metal core 11, meanwhile, the iron nanoparticles are oxidized to ferrous ions (Fe ²⁺ ), and the hexavalent chromium ions are continuously reduced. The on-site microorganisms 20 can utilize the biodegradable surfactants, vitamins and minerals contained in the modified surface layer 12 to promote growth. The main component of the fully oxidized nano-metal core 11 is similar to that of the earth's crust, which is highly bioacceptable and has extremely low impact on the environment.

Compared with the prior art, according to the composite particles and method for remediating heavy metal pollutants provided by the present invention, the green physical and chemical remediation technology combined with the biological restoration method can quickly and continuously reduce heavy metal pollutants, and improve the current production efficiency. The activity and quantity of microorganisms in the soil can be used to degrade other pollutants. The composite particles of the present invention have the following advantages: (1) the crustal elements that do not change the environmental composition of soil, groundwater, etc. after adding are a localized remediation technology; (2) nanotechnology combined with surface modification technology, zero-valent iron due to aluminum The presence of nickel and nickel can slow down its corrosion rate and improve the effective time, stability and transmission of the material; (3) nanoscale and microporosity can increase the specific surface area of the material and accelerate the heavy metal ions in the unsaturated layer and saturated layer. Anaerobic reduction reaction; (4) Provide substrates available to microorganisms to enhance local biodegradability; (5) Can quickly create an anaerobic environment to promote the reduction reaction of pollutants, and continuously release electrons in the later stage of the reaction, strengthening Degrade residual target pollutants; (6) Avoid soil acidification and destruction.

The present invention has been described by the above-mentioned related embodiments, however, the above-mentioned embodiments are only examples for implementing the present invention. It must be pointed out that the disclosed embodiments do not limit the scope of the invention. On the contrary, modifications and equivalent arrangements included in the spirit and scope of the claims are included in the scope of the present invention.

Claims (14)

1. A composite particle for remediation of heavy metal pollutants, characterized in that: the composite particle comprises: a nano-metal core, which includes iron nanoparticles, aluminum nanoparticles and nickel nanoparticles; and a modified surface layer, surrounded by The nano-metal core, the modified surface layer has at least one coordination functional group, which is used to form a metal complex with a heavy metal ion, so that the heavy metal ion is adsorbed on the modified surface layer. 2. The composite particle according to claim 1, characterized in that: in the nano-metal core, the weight of the nickel nanoparticles is less than the weight of the aluminum nanoparticles, and the aluminum nanoparticles The weight occupied is less than the weight occupied by the iron nanoparticles. 3. The composite particle of claim 1, wherein the iron nanoparticles account for at least 65% by weight of the nanometal core. 4. The composite particle according to claim 1, wherein the aluminum nanoparticles account for at most 25% by weight of the nano-metal core. 5. The composite particle according to claim 1, wherein the nickel nanoparticles account for at most 10% by weight of the nano-metal core. 6. The composite particle according to claim 1, wherein the heavy metal ion is hexavalent chromium ion. 7. The composite particle according to claim 1, characterized in that: the coordination functional group is a hydroxyl group, an ether group, an aldehyde group, a ketone group, a carboxyl group, an ester group, an amine group or an amide group. 8. The composite particle according to claim 1, wherein the modified surface layer comprises citric acid, amino acid, multivitamin, a biodegradable surfactant and an organic solvent. 9. The composite particle according to claim 8, characterized in that: the weight ratio of the citric acid, the amino acid, the multivitamin, the biodegradable surfactant and the solvent is 10: 5:5:30:50. 10. The composite particle according to claim 8, wherein the biodegradable surfactant comprises lecithin, and the lecithin is 15 to 30% by weight of the weight of the modified surface layer. 11. A method for remediating heavy metal pollutants, characterized in that: the method comprises steps: (1) providing the composite particles for remediating heavy metal pollutants as claimed in claim 1; and (2) Contacting the composite particles with a heavy metal pollutant. 12. The method for remediating heavy metal pollutants according to claim 11, characterized in that: the heavy metal pollutants are heavy metal-containing soil or heavy metal-containing water. 13. The method for remediating heavy metal pollutants according to claim 11, characterized in that: the heavy metal ions contained in the heavy metal pollutants are hexavalent chromium ions. 14. The method for remediating heavy metal pollutants according to claim 11, characterized in that: the modified surface layer reacts with water to form an emulsified colloid layer.