Preparation method of a sulfur-urea functional group-containing separation membrane and its application in selectively adsorbing gold ions

Abstract

The present invention discloses a preparation method of a separation membrane containing thiourea functional groups and its application in selectively adsorbing gold ions. The method uses a polymer porous membrane as a carrier, coats it with a dopamine solution at room temperature, and then transfers it to a solution containing carbon disulfide for reaction, finally forming a separation membrane modified with thiourea groups. The thiourea functional groups introduced on the separation membrane are stable and have good selective adsorption for gold ions. The preparation process of this method is simple, the reaction conditions are mild, and it is easy to combine with the industrial production process of porous membranes. The thiourea-modified material prepared by the above method has good application potential in the field of efficient adsorption separation and recovery of precious metals.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrometallurgical precious metal recovery, and in particular relates to a method for preparing a thiourea-modified separation membrane for selectively adsorbing gold. Background Art

[0002] Precious metals, due to their unique properties of high-temperature oxidation resistance, corrosion resistance, catalytic activity, and strong coordination capacity, as well as their limited availability, high quality, and widespread use, have found widespread applications in the pharmaceutical, aviation, laser, automation, and energy industries. Faced with the increasing depletion of mineral resources and the severe challenges of environmental protection, the rapid and efficient recovery of precious metal ions has been a hot topic of research in the industrial and environmental fields in recent years.

[0003] Currently, the main methods used to recover and extract gold ions from water include chemical precipitation, redox, electrolysis, and ion exchange. While each has its advantages, these technologies still have numerous drawbacks. Precipitation and reduction methods are subject to secondary pollution, while ion exchange suffers from low strength, high temperature resistance, susceptibility to oxidation failure, frequent regeneration, and high operating costs. Furthermore, all of these methods exhibit low removal efficiency for low-concentration wastewater.

[0004] Membrane adsorption technology, a combination of membrane and adsorption technologies, is a purely physical process characterized by energy efficiency, economy, convenience, excellent separation performance, stable operation, and zero secondary pollution. It combines the dual functions of membrane filtration and membrane adsorption, exhibiting high metal removal rates and being widely used in the treatment of various types of wastewater. Furthermore, it eliminates the need for adsorbent separation processes. After adsorption, desorption allows for the recovery of heavy metal ions, demonstrating excellent reusability. The main membrane materials used in polymer separation membrane research include polyvinyl chloride, polyvinylidene fluoride, polysulfone, and polyethersulfone. Polysulfone, due to its heat resistance, acid and alkali resistance, and high mechanical properties, is widely used in membrane separation, particularly in water treatment. However, research on the adsorption capacity of polysulfone membranes has primarily focused on protein adsorption and the retention of suspended solids, colloids, and large bacteria, limiting its application in the treatment of wastewater containing gold and precious metals.

[0005] In recent years, research on thiourea adsorption modification materials has focused more on fibers, resins, activated carbon, and gels, with less research on the modification of polymer membrane materials. However, the demand for the recovery and treatment of precious metals in wastewater in industrial production is increasing. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a method for preparing a thiourea-modified separation membrane and its application in selectively adsorbing gold ions. On a polymer matrix, by coating dopamine and amine monomers and then reacting with carbon disulfide, thiourea functional groups are formed to complex with metals, achieving efficient and selective adsorption of gold ions in gold-containing wastewater at low concentrations. The method for preparing a separation membrane modified to carry thiourea groups provided by the present invention combines adsorption and membrane separation, uses the adsorption method to remove trace metal ions, has no secondary pollution, can filter and adsorb wastewater containing metal ions simultaneously, and has the advantages of simple operation, low pressure, large water output, no phase change, and small floor area.

[0007] The object of the present invention is achieved by the following technical solutions:

[0008] A method for a thiourea-modified separation membrane for selectively adsorbing gold, the method comprising the following steps:

[0009] (1) Immerse the polymer porous membrane in an aqueous solution composed of dopamine and polyamine monomers, and at room temperature, evenly coat dopamine or polyamine on the polymer porous membrane through an air bath shaker;

[0010] (2) Transfer the polymer porous membrane coated with dopamine and polyamine to a solution containing carbon disulfide, and react to obtain a separation membrane containing thiourea functional groups; after the reaction, take out the separation membrane containing thiourea functional groups, wash to remove unreacted substances, and obtain a pure separation membrane containing thiourea functional groups.

[0011] Dopamine has strong adhesion and a wide range of choices for the modified matrix. Among them, catechol is the key to the adhesion effect. On the surface of hydrophobic polymers, the adhesion of dopamine mainly occurs through van der Waals forces and hydrophobic interactions (between the benzene ring and the hydrophobic surface).

[0012] Typical reaction equations for forming thiourea functional groups in the present invention are as follows:

[0013] 1. Reaction equation for dopamine reacting with CS2 to form thiourea

[0014]

[0015] 2. Reaction equation for the intermediate and final products of the self-polymerization after the oxidation of dopamine reacting with CS2 to form thiourea

[0016]

[0017] 3. Reaction equation for the products of the oxidation of dopamine and the self-polymerization of polyamine monomers reacting with CS2 to form thiourea

[0018]

[0019] Further, the polymer porous membrane is made of any one selected from polysulfone, polyethersulfone, polyacrylonitrile, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and polyvinylidene fluoride. The polysulfone membrane has the best effect. Polymers are one of the most commonly used materials for preparing commercial porous separation membranes. Polymers have good antioxidant properties, thermal stability, mechanical properties, and processability.

[0020] Further, in the aqueous solution composed of dopamine hydrochloride, the polyamine monomer, and the combination of dopamine hydrochloride and the polyamine monomer, the concentration of the dopamine monomer or dopamine hydrochloride is 1-20 mg / ml.

[0021] Further, the polyamine monomer is ethylenediamine, polyethyleneimine, propylenediamine, or m-phenylenediamine; in the aqueous solution composed of dopamine and the polyamine monomer, the molar ratio of the polyamine monomer / dopamine is (0-3):1.

[0022] Further, in step (2), the concentration of the carbon disulfide solution is 2-200 mg / ml.

[0023] Further, the solvent of the carbon disulfide solution is methanol, ethanol, isopropanol, or a mixed solution composed of methanol, ethanol, isopropanol, and dimethylformamide respectively. It is better that carbon disulfide is dissolved in ethanol, and the ratio is 1-200 mg of carbon disulfide dissolved in each milliliter of ethanol. Preferably, 20-50 mg of carbon disulfide is dissolved in each milliliter of ethanol. If the solution concentration is too low, too few thiourea groups are generated. If the concentration is too high, the solution is supersaturated and it is difficult to maintain the structure of the base membrane.

[0024] Further, in step (2), the reaction time for obtaining the separation membrane containing thiourea functional groups is 8-24 h, and the reaction temperature is 20-60 °C.

[0025] A separation membrane containing thiourea functional groups obtained by the above method.

[0026] An application of a separation membrane containing thiourea functional groups in selectively adsorbing gold ions. The separation membrane containing thiourea functional groups is placed in a gold ion solution with a pH value of 1-6 and a temperature of 20-25 °C, and the separation membrane containing thiourea functional groups forms a cationic complex with gold ions. Thiourea is unstable in alkaline solutions and is easily decomposed into sulfide ions and cyanamide and consumed. Moreover, in an alkaline medium, the S2- generated by the decomposition of thiourea forms a sulfide precipitate with the Au+ metal cations in the solution. If the system is overheated, thiourea will hydrolyze to generate ammonia, carbon dioxide, and liquid hydrogen disulfide. Although an increase in temperature can accelerate the initial rate of gold dissolution by thiourea, it will seriously affect the stability of thiourea, causing the gold dissolution rate to continuously decrease over time and even become ineffective.

[0027] Further, the solvent in the gold ion solution is an aqueous solution, and the concentrations of copper, iron, silver, mercury, platinum, palladium, nickel, zinc, sodium, and calcium ions are all lower than 100 ppm.

[0028] The beneficial effects of the present invention are as follows:

[0029] (1) Compared with most current gold extraction methods, the thiourea method purification process is simple, non-toxic, renewable, and green and pollution-free. The membrane has the characteristics of being operable at low temperature, having a short diffusion path, and being easy to operate continuously. The separation membrane carried with the thiourea gold extraction method prepared by the method of the present invention has the advantages of fast gold absorption speed, low toxicity during leaching, low price, high efficiency, environmental protection, and few interfering ions, and can become a green gold leaching method to replace cyanide gold extraction.

[0030] (2) This method can modify the most commonly used polymer membranes at present, providing the possibility for the application of polysulfone separation membranes in the adsorption and recovery of precious metals.

[0031] ((3) The polymer membrane carried with thiourea groups prepared by the method of the present invention can separate and recover precious metal ions such as gold ions.

[0032] (4) The preparation method of the separation membrane of the present invention uses mild reaction conditions, simple steps, and strong versatility, which is conducive to large-scale production. Description of the Drawings

[0033] Figure 1 It is the infrared spectrogram of the polysulfone membrane prepared in Example 1 and after thiourea modification;

[0034] Figure 2 It is the contact angle diagram of the modified membrane prepared in Example 1;

[0035] Figure 3 It is the physical diagram of the polysulfone membrane carried with thiourea groups prepared in Example 1 after adsorbing gold ions;

[0036] Figure 4 It is the change curve of the gold adsorption rate of the modified membranes prepared in Example 1 and Example 3;

[0037] Figure 5 It is the change curve of the gold adsorption amount of the modified membranes prepared in Example 1 and Example 3; Detailed Embodiments

[0038] The present invention will be described in detail below according to the drawings and preferred embodiments. The purpose and effect of the present invention will become more apparent. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0039] Example 1

[0040] (1) Dissolve commercial polysulfone at a concentration of 15 wt% in N-methylpyrrolidone solvent, stir evenly to obtain a casting solution, let it stand for a period of time until the bubbles completely disappear, then coat it on a clean glass plate with a 150-μm-thick doctor blade, and then immerse it in water for phase inversion to form a membrane. After the solvent exchange is complete, take out the formed film and dry it to obtain a polymer porous membrane. Test the membrane with an infrared spectrometer to obtain its infrared spectrum, as Figure 1 shown. Then use a contact angle tester to measure the contact angle of the prepared pure polymer porous membrane, and the contact angle is 106.9°.

[0041] (2) Immerse the polymer porous membrane in an aqueous solution containing 1 mg / ml of dopamine hydrochloride, and at room temperature of 25 °C, coat dopamine evenly on the polymer porous membrane through an air bath shaker.

[0042] (3) Transfer the polymer porous membrane coated with dopamine to an ethanol solution containing 1 mg / ml of carbon disulfide, and obtain a modified separation membrane containing thiourea groups through reaction. After the reaction, take out the membrane, rinse it 3 times with ethanol and 2 times with deionized water to obtain a pure separation membrane containing thiourea functional groups.

[0043] The reaction equations are as follows:

[0044] (1) The reaction equation for the reaction of dopamine with CS2 to form thiourea

[0045]

[0046] (2) The reaction equations for the reaction of the intermediate and final products of the self-polymerization of dopamine after oxidation with CS2 to form thiourea:

[0047]

[0048] (3) The reaction equations for the reaction of the products of the oxidation of dopamine and the self-polymerization of polyamine monomers with CS2 to form thiourea:

[0049] [[ID=?]]

[0050] Perform infrared spectrum analysis and testing on the prepared pure separation membrane containing thiourea functional groups to obtain the corresponding infrared spectrum, as Figure 1 shown. Compared with before modification, the characteristic peaks corresponding to the thiourea functional groups change, proving that the reaction has occurred successfully.

[0051] Use a contact angle tester to measure the contact angle of the prepared pure separation membrane containing thiourea functional groups, as Figure 2 shown. The contact angle is 67.3°, and the contact angle becomes smaller compared with before modification, indicating that the hydrophilicity of the modified polysulfone membrane is enhanced, further indicating that the polysulfone membrane containing thiourea functional groups is successfully prepared.

[0052] Adsorption performance test:

[0053] The prepared polysulfone membranes containing thiourea functional groups were cut into 5 pieces of 2×2 cm in size and were respectively immersed in 10 ml of chloroauric acid solutions with different concentrations. They were placed in an air bath oscillator, with the internal temperature of the oscillator set at 20 °C, the frequency at 170 r / min, and the adsorption time at 24 h. After the adsorption was completed, the membrane pieces were taken out. At this time, the surface of the membrane pieces changed from gray before adsorption to light red. Then, the concentration of Au + in the solution before and after adsorption was measured, and the adsorption capacity q (mg / g) and adsorption rate D (%) of the membrane for heavy metal ions were calculated.

[0054]

[0055] q is the adsorption capacity of the separation membrane for gold ions, mg / g; C0 is the initial concentration of gold ions, mg / L; C e is the concentration of gold ions at adsorption equilibrium, mg / L; V is the volume of the gold ion solution, L; m is the mass of the separation membrane, g;

[0056]

[0057] q is the adsorption rate of the separation membrane for gold ions, %; C0 is the initial concentration of gold ions, mg / L; C e is the concentration of gold ions at adsorption equilibrium, mg / L.

[0058] Figure 3 Schematic diagrams of the original polysulfone membrane, the modified membrane, and the membrane after adsorbing gold ions are given. In addition, the results of the adsorption rate of the separation membrane for gold ions are as Figure 4 shown, and the results of the adsorption capacity of the separation membrane for gold ions are as Figure 5 shown. It can be seen from the figure that as the concentration of the chloroauric acid solution increases, both the adsorption rate and adsorption capacity of the separation membrane for gold ions increase, indicating that the separation membrane has strong adsorption performance for gold ions.

[0059] Example 2

[0060] (1) Commercial polysulfone was dissolved in N-methylpyrrolidone solvent at a concentration of 15 wt%, and stirred evenly to obtain a casting solution. After standing for a period of time until all the bubbles disappeared, it was coated on a clean glass plate with a 150-μm-thick scraper, and then immersed in water for phase inversion to form a membrane. After the solvent exchange was complete, the formed thin film was taken out and dried to obtain a polymer porous membrane.

[0061] (2) The porous membrane was immersed in an aqueous solution containing 1 mg / ml of dopamine hydrochloride and ethylenediamine. At room temperature of 25 °C, dopamine and ethylenediamine were uniformly coated on the membrane through an air bath shaker.

[0062] (3) Transfer the membrane coated with dopamine to a 1 mg / ml solution containing carbon disulfide. Through a chemical reaction, a modified separation membrane containing thiourea groups is obtained. After the reaction, take out the membrane and rinse it 3 times with ethanol and 2 times with deionized water.

[0063] Example 3

[0064] (1) Dissolve commercial polysulfone at a concentration of 15 wt% in N-methylpyrrolidone solvent, stir evenly to obtain a casting solution. After standing for a period of time until all bubbles disappear, coat it onto a clean glass plate with a 150-μm-thick doctor blade, and then immerse it in water for phase inversion to form a membrane. After the solvent exchange is complete, take out the formed thin film and dry it to obtain a polymer porous membrane.

[0065] (2) Immerse the porous membrane in an aqueous solution containing 1 mg / ml of hydrochloric acid dopamine and polyethyleneimine. At room temperature of 25 °C, evenly coat dopamine and polyethyleneimine on the membrane through an air bath shaker.

[0066] (3) Transfer the membrane coated with dopamine to a 1 mg / ml solution containing carbon disulfide. Through a chemical reaction, a modified separation membrane containing thiourea groups is obtained. After the reaction, take out the membrane and rinse it 3 times with ethanol and 2 times with deionized water.

[0067] Example 4

[0068] (1) Dissolve commercial polysulfone at a concentration of 15 wt% in N-methylpyrrolidone solvent, stir evenly to obtain a casting solution. After standing for a period of time until all bubbles disappear, coat it onto a clean glass plate with a 150-μm-thick doctor blade, and then immerse it in water for phase inversion to form a membrane. After the solvent exchange is complete, take out the formed thin film and dry it to obtain a polymer porous membrane.

[0069] (2) Immerse the porous membrane in an aqueous solution containing 1 mg / ml of hydrochloric acid dopamine and propylenediamine. At room temperature of 25 °C, evenly coat dopamine and propylenediamine on the membrane through an air bath shaker.

[0070] (3) Transfer the membrane coated with dopamine to a 1 mg / ml solution containing carbon disulfide. Through a chemical reaction, a modified separation membrane containing thiourea groups is obtained. After the reaction, take out the membrane and rinse it 3 times with ethanol and 2 times with deionized water.

[0071] Example 5

[0072] (1) Dissolve commercial polysulfone at a concentration of 15 wt% in N-methylpyrrolidone solvent, stir evenly to obtain a casting solution. After standing for a period of time until all bubbles disappear, coat it onto a clean glass plate with a 150-μm-thick doctor blade, and then immerse it in water for phase inversion to form a membrane. After the solvent exchange is complete, take out the formed thin film and dry it to obtain a polymer porous membrane.

[0073] (2) Immerse the porous membrane in an aqueous solution containing 1 mg / ml of dopamine hydrochloride and m-phenylenediamine. At room temperature of 25 °C, uniformly coat dopamine and m-phenylenediamine on the membrane through an air bath shaker.

[0074] (3) Transfer the membrane coated with dopamine to a solution containing 1 mg / ml of carbon disulfide, and obtain a modified separation membrane containing thiourea groups through a chemical reaction. After the reaction, take out the membrane and rinse it 3 times with ethanol and 2 times with deionized water.

[0075] The trends of the experimental results obtained in Examples 2 to 5 are the same as those in Example 1. The reason is that the groups capable of reacting have commonalities in structure, and the reaction conditions are similar. The advantages and disadvantages of the adsorption performance only have slight deviations in terms of the dosage of the reactants, and the impact on the quality of adsorption is not significant.

[0076] Those of ordinary skill in the art can understand that the above are only preferred examples of the invention and are not used to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, for those skilled in the art, they can still modify the technical solutions described in the foregoing examples, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, etc. made within the spirit and principle of the invention shall be included within the protection scope of the invention.

Claims

1. A preparation method of a separation membrane containing a thiourea functional group, characterized in that, The method comprises the following steps: (1) Immerse the polymer porous membrane in an aqueous solution composed of dopamine and polyamine monomer, and at room temperature, uniformly coat dopamine and polyamine on the polymer porous membrane by an air bath shaker; (2) Transfer the polymer porous membrane coated with dopamine and polyamine to a solution containing carbon disulfide, and react to obtain a thiourea-functionalized separation membrane; after the reaction, take out the thiourea-functionalized separation membrane and wash to remove unreacted substances to obtain a pure thiourea-functionalized separation membrane.

2. The preparation method of the separation membrane containing thiourea functional groups according to claim 1, characterized in that, The polymer porous membrane is selected from any one of polysulfone, polyethersulfone, polyacrylonitrile, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, and polyvinylidene fluoride.

3. The preparation method of the separation membrane containing thiourea functional groups according to claim 1, characterized in that, In the aqueous solution composed of dopamine and polyamine monomer, the concentration of dopamine is 1-20 mg / ml.

4. The preparation method of the separation membrane containing thiourea functional groups according to claim 1, characterized in that, The polyamine monomer is ethylenediamine, polyethyleneimine, propylenediamine or m-phenylenediamine; in the aqueous solution composed of dopamine and polyamine monomer, the molar ratio of polyamine monomer / dopamine is (0-3):

1.

5. The preparation method of the separation membrane containing thiourea functional groups according to claim 1, characterized in that, In step (2), the concentration of the carbon disulfide solution is 2-200 mg / ml.

6. The preparation method of the separation membrane containing thiourea functional groups according to claim 5, characterized in that, The solvent of the carbon disulfide solution is methanol, ethanol, isopropanol, or a mixed solution composed of methanol, ethanol, isopropanol and dimethylformamide respectively.

7. The preparation method of the separation membrane containing thiourea functional groups according to claim 1, wherein In step (2), the reaction time for obtaining the thiourea-functionalized separation membrane is 8-24 h, and the reaction temperature is 20-60 °C.

8. A thiourea-functionalized separation membrane obtained by any one of the preparation methods in claims 1 to 7.

9. Use of a separation membrane containing a thiourea functional group as described in claim 8 in the selective adsorption of gold ions, characterized in that, Place the thiourea-functionalized separation membrane in a gold ion solution with a pH value of 1-6, and the thiourea-functionalized separation membrane forms a complex with gold ions.

10. Use of the separation membrane containing thiourea functional groups according to claim 9 in selective adsorption of gold ions, characterized in that, The solvent in the gold ion solution is an aqueous solution, and the concentrations of copper, iron, silver, mercury, platinum, palladium, nickel, zinc, sodium, and calcium ions are all lower than 100 ppm.

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