Treatment method of hydrometallurgy wastewater

Abstract

The invention discloses a hydrometallurgy wastewater treatment method, which comprises: S1, adding a toluene and ethyl acetate mixture into hydrometallurgy wastewater, extracting to remove organic matters, and carrying out phase splitting to obtain pretreated wastewater; s2, steam is introduced into the pretreated wastewater in the S1 for steam stripping, and residual methylbenzene, ethyl acetate and volatile organic compounds in the wastewater are removed; s3, hydrogen peroxide and sodium hypochlorite are added into the steam stripping produced water in the step S2 for oxidation. The hydrometallurgy wastewater produced in the hydrometallurgy industry can be treated to reach the sea discharge standard, and the problems that the wastewater treatment cost is high, pollutants are difficult to treat and the like are solved.

Description

Technical Field

[0001] The invention relates to a method for treating organic matter in hydrometallurgical wastewater, in particular to a method for deep treatment of organic matter in hydrometallurgical wastewater, and belongs to the field of environmental protection of industrial wastewater treatment. Background Art

[0002] Hydrometallurgy is a method of bringing ores, concentrates enriched by beneficiation or other raw materials into contact with aqueous solutions or other liquids, and then transferring the useful metals contained in the raw materials into the liquid phase through chemical reactions, and then separating and enriching the various useful metals contained in the liquid phase, and finally recovering them in the form of metals or other compounds. It mainly includes unit operations such as leaching, liquid-solid separation, solution purification, metal extraction from solution and wastewater treatment.

[0003] Hydrometallurgy mainly produces metal sulfates such as nickel sulfate, cobalt sulfate, and manganese sulfate, which are mainly used in the electroplating industry and the battery industry. In recent years, with the surge in demand for ternary cathode materials for power batteries, the demand for materials such as nickel sulfate in the battery industry has exploded. However, the production process will generate a large amount of wastewater, waste gas, and waste residue, which contain a large amount of harmful substances, such as heavy metals such as nickel, cadmium, and lead. If not handled properly, it will cause serious pollution to the environment.

[0004] At present, there are few treatment methods for hydrometallurgical wastewater in the industry, most of which are dilution treatment after adsorption or evaporation crystallization salt treatment. CN109987742B discloses a treatment method for hydrometallurgical wastewater, firstly using special resin for adsorption and oil removal, then preliminarily adjusting the wastewater pH, removing heavy metal ions mainly nickel in the wastewater by heavy metal scavenger, adjusting the wastewater pH to acidic after removing precipitation, so that carbonate in the wastewater is completely converted into sulfate, and then removing insoluble fine particles in the wastewater by precision filtration to obtain a relatively pure sodium sulfate solution, and finally concentrating the wastewater by high-pressure reverse osmosis, and the membrane water is reused for production, and the obtained concentrated brine is recovered by MVR or multi-effect evaporation to recover anhydrous sodium sulfate. The equipment construction and operation costs of this scheme are high, and the final wastewater can only be treated by evaporation and crystallization. The salt evaporated has high pollutants and is difficult to sell. Most of them are outsourced for hazardous waste treatment, which further increases the cost. CN116495938A discloses a method for treating nickel sulfate extraction wastewater. The method adopts advanced reagent sedimentation + combined ion exchange resin process to deeply remove various heavy metal ions, heavy metal complexes, oils, calcium, magnesium and other pollutants in the extraction wastewater, and can achieve high-standard stable discharge of wastewater. The wastewater treated with the combined ion exchange process is filtered with a filter paper filter to deeply remove SS, COD and other pollutants in the wastewater. This process has limited effect on the removal of pollutants, which is equivalent to pre-treating the pollutants, and the deep treatment effect is low. In addition, the wastewater is diluted and discharged after treatment, and strictly speaking, it fails to meet the wastewater treatment acceptance standard.

[0005] Therefore, the treatment of hydrometallurgical wastewater is difficult, the treatment cost is high, and the disposal method is single. There is little research on the treatment of this wastewater, and the treatment method needs to be adapted to local conditions. This is an urgent problem to be solved in this field. Summary of the invention

[0006] The purpose of the present invention is to provide a method for treating hydrometallurgical wastewater, which removes organic pollutants in the wastewater through simple and efficient treatment methods such as extraction, stripping and combined oxidation treatment with hydrogen peroxide and sodium hypochlorite. The treatment method successfully solves the current problem of treatment and disposal of wastewater from the plant.

[0007] In the present invention, the hydrometallurgical wastewater refers to wastewater obtained by leaching reaction and extraction reaction using mineral materials containing nickel, cobalt and the like as raw materials, wherein the organic matter is an extractant such as P204, P507, C272 kerosene and its decomposition products, which are divided into oil, small molecule, medium molecule and macromolecular organic matter, and the TOC content is 100-300ppm. This article mainly removes organic matter from hydrometallurgical wastewater. This article mainly removes different substances in a targeted manner, such as removing oil macromolecules by extraction, but if the oxidation process is performed first, some macromolecules will be degraded into small and medium molecules that are more difficult to degrade, and the extraction process capacity will be lost, which will increase the cost of wastewater treatment by nearly 10 times. Therefore, the significance of treating wastewater according to the appropriate process sequence is very significant and necessary.

[0008] To achieve the above object, the present invention provides a method for treating hydrometallurgical wastewater, and the technical scheme adopted is as follows:

[0009] S1. Adding a mixture of toluene and ethyl acetate to the hydrometallurgical wastewater to extract and remove organic matter, and obtaining pretreated wastewater after phase separation;

[0010] S2. introducing steam into the pretreated wastewater in S1 for stripping to remove residual toluene, ethyl acetate and volatile organic matter in the wastewater;

[0011] S3. Add hydrogen peroxide and sodium hypochlorite to the stripping water in S2 for oxidation.

[0012] In the method of the present invention, the composition of the hydrometallurgical wastewater is 40-70 ppm of kerosene; 100-200 ppm of P204, P507 and C272 extractants, 100-200 ppm of organic matter formed by degraded carboxylic acid, 3-7% of sodium sulfate and 1-5% of inorganic salts of sodium chloride, and the balance is water.

[0013] In the method of the present invention, in S1, the pH value of the wastewater is controlled to be less than 3, the volume ratio of the mixture of toluene and ethyl acetate is 0.1-10:1, the ratio of the mixture of toluene and ethyl acetate to the wastewater is 1:1-1:10, the extraction time is 5-30 minutes, the extraction temperature is 20-50°C, and after the extraction is completed, the phase separation is completed by standing for 10-60 minutes, and the aqueous phase enters the next stage of treatment.

[0014] In the method of the present invention, in S2, the steam is water vapor with a pressure of 0.2-0.4 MPaG, the stripping time is 30-180 min, the stripping is carried out in a stripping tower, the temperature of the stripping tower kettle is controlled at 70-110° C., and the temperature of the tower top is controlled at 60-100° C. Toluene, ethyl acetate and volatile organic matter can be removed by stripping.

[0015] In the method of the present invention, in S3, the concentration of hydrogen peroxide is 27.5-30wt%, and the amount added is 0.2%-1% of the mass of the wastewater; the concentration of sodium hypochlorite is 5-15wt%, and the amount added is 2%-10% of the mass of the wastewater.

[0016] In the method of the present invention, the oxidation temperature of the hydrogen peroxide and sodium hypochlorite is 20-90°C, hydrogen peroxide is first added to react for 30-120 minutes, and then sodium hypochlorite is added to react for 30-120 minutes to complete the removal of C1-C3 carboxylic acid substances (such as formic acid and acetic acid), and finally the TOC of the wastewater is reduced to below 15 ppm, meeting the sea discharge standard.

[0017] The beneficial effects of the present invention are as follows: the method of the present invention is simple, has good treatment effects on light components and heavy components of organic matter, and has low wastewater treatment costs; the mixed extraction process of toluene and ethyl acetate has a strong removal effect on macromolecular substances of hydrometallurgical extractants, and then toluene, ethyl acetate and volatile substances are removed by steam stripping, and finally the organic matter in wastewater is deeply removed by a combined oxidation process of hydrogen peroxide and sodium hypochlorite. The above processes are combined in sequence, and the TOC removal efficiency can reach 99.7%. The wastewater of the treatment method can meet the requirements whether it is treated by salt distillation or sea discharge (national standard GB 31571-2015), and is suitable for the treatment of hydrometallurgical wastewater. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is described in detail below in conjunction with specific embodiments. The embodiments of the present invention are only used to illustrate the present invention, but the protection scope of the present invention is not limited to the following.

[0019] Hydrometallurgical wastewater: produced by the hydrometallurgical process of Wanhua Chemical Group Co., Ltd. This process uses ore to leach through reaction, dissolves metals in sulfuric acid, and then enriches and purifies the metals through P204, P507 and C272 extractants to obtain a sulfate metal solution. In this process, metal replacement reactions will occur in the water phase and the oil phase, producing hydrometallurgical wastewater containing about 5wt% sodium sulfate, 3wt% sodium chloride and about 100-200ppm of P204, P507 and C272 extractants, about 50ppm kerosene, and about 100-200ppm of degraded carboxylic acid substances.

[0020] Test method: TOC analysis was performed using TOC analysis tester multiN / C2100S (Jena Analytical Instruments AG, Germany).

[0021] Example 1

[0022] S1. Take 10 parts of hydrometallurgical wastewater produced by Wanhua Chemical Group Co., Ltd., with a TOC of 233 ppm;

[0023] Adjust the wastewater pH to <3, add toluene and ethyl acetate mixed extractant (volume ratio of 1:1) to the wastewater, and heat to 50°C, extract and stir for 30 minutes, and stand for 60 minutes to complete phase separation. The TOC of the water phase is 143ppm, and enter the S2 step. The oil phase extractant returns to the front end for recycling;

[0024] S2. 0.4MPaG steam is introduced into the water phase in S1, and the stripping lasts for 60min. The temperature of the stripping tower is controlled at 110℃, and the temperature of the tower top is controlled at 100℃. The TOC of the stripping water is reduced to 35ppm and enters S3;

[0025] S3. The temperature of the stripping water was adjusted to 60°C, and 27.5wt% hydrogen peroxide was directly added in an amount of 1% of the mass of the stripping water. The reaction was stirred for 120 minutes, and the TOC of the obtained water was 22.2ppm. Sodium hypochlorite with a concentration of 15wt% was added in an amount of 2% of the mass of the wastewater. The reaction was stirred for 60 minutes, and the TOC of the obtained water was 8.2ppm. The removal efficiency of TOC in hydrometallurgical wastewater in this example reached 96.5%, meeting the standards in Table 2 of the national standard GB 31571-2015.

[0026] Example 2

[0027] S1. Take 10 parts of hydrometallurgical wastewater produced by Wanhua Chemical Group Co., Ltd., with a TOC of 233 ppm;

[0028] Adjust the wastewater pH to <3, add toluene and ethyl acetate mixed extractant (volume ratio of 1:1) to the wastewater, and heat to 32°C at a ratio of 1:10 between extractant and wastewater. After stirring for 30 minutes, stand for 20 minutes to complete phase separation. The TOC of the water phase is 162ppm, and enter the S2 step. The oil phase extractant returns to the front end for recycling.

[0029] S2. 0.2MPaG steam is introduced into the water phase in S1, and the stripping lasts for 60 minutes. The temperature of the stripping tower is controlled at 70°C, and the temperature of the tower top is controlled at 60°C. The TOC of the stripping water is reduced to 48ppm and enters S3;

[0030] S3. The temperature of the stripping water was adjusted to 20°C, and 27.5wt% hydrogen peroxide was directly added in an amount of 0.5% of the mass of the stripping water. The reaction was stirred for 30 minutes, and the TOC of the produced water was 28.4ppm. Then, 5wt% sodium hypochlorite was added in an amount of 10% of the mass of the wastewater. The reaction was stirred for 120 minutes, and the TOC of the produced water was 6.2ppm. The removal efficiency of TOC in hydrometallurgical wastewater in this example reached 97.4%, meeting the standards in Table 2 of the national standard GB 31571-2015.

[0031] Example 3

[0032] S1. Take 10 parts of hydrometallurgical wastewater produced by Wanhua Chemical Group Co., Ltd., with a TOC of 233 ppm;

[0033] Adjust the wastewater pH to <3, add toluene and ethyl acetate mixed extractant (volume ratio of 1:1) to the wastewater, and heat to 20°C, extract and stir for 10 minutes, and stand for 45 minutes to complete phase separation. The TOC of the water phase is 151ppm, and enter the S2 step. The oil phase extractant returns to the front end for recycling;

[0034] S2. 0.4MPaG steam is introduced into the water phase in S1, and the stripping lasts for 60min. The temperature of the stripping tower is controlled at 90℃, and the temperature of the tower top is controlled at 80℃. The TOC of the stripping water is reduced to 31ppm and enters S3;

[0035] S3. The temperature of the stripping water was adjusted to 90°C, and 27.5wt% hydrogen peroxide was directly added in an amount of 0.8% of the mass of the stripping water. The reaction was stirred for 60 minutes, and the TOC of the obtained water was 17.3ppm. Then, 5wt% sodium hypochlorite was added in an amount of 5% of the mass of the wastewater. The reaction was stirred for 30 minutes, and the TOC of the obtained water was 4.9ppm. The removal efficiency of TOC in hydrometallurgical wastewater in this example reached 97.9%, meeting the standards in Table 2 of the national standard GB 31571-2015.

[0036] Example 4

[0037] S1. Take 10 parts of hydrometallurgical wastewater produced by Wanhua Chemical Group Co., Ltd., with a TOC of 233 ppm;

[0038] Adjust the wastewater pH to <3, add toluene and ethyl acetate mixed extractant (volume ratio of 1:1) to the wastewater, and heat to 50°C, stir for 5 minutes, and stand for 10 minutes to complete phase separation. The TOC of the water phase is 143ppm, and enter the S2 step. The oil phase extractant returns to the front end for recycling;

[0039] S2. 0.2MPaG steam is introduced into the water phase in S1, and the stripping lasts for 30 minutes. The temperature of the stripping tower is controlled at 90°C, and the temperature of the tower top is controlled at 80°C. The TOC of the stripping water is reduced to 64ppm and enters S3;

[0040] S3. The temperature of the stripping water was adjusted to 60°C, and 30wt% hydrogen peroxide was directly added, the amount of which was 0.2% of the mass of the stripping water. The reaction was stirred for 30 minutes, and the TOC of the produced water was 28.4ppm. Then, 10wt% sodium hypochlorite was added, the amount of which was 5% of the mass of the wastewater. The reaction was stirred for 60 minutes, and the TOC of the produced water was 12.3ppm. The removal efficiency of TOC in hydrometallurgical wastewater in this example reached 94.7%, meeting the standards in Table 2 of the national standard GB 31571-2015.

[0041] Comparative Example 1: No extraction with extractant (Compared with Example 1)

[0042] S1. Take 10 parts of hydrometallurgical wastewater produced by Wanhua Chemical Group Co., Ltd., with a TOC of 233 ppm;

[0043] S2. 0.4MPaG steam is introduced into the wastewater of S1, and the stripping lasts for 1h60min. The temperature of the stripping tower is controlled at 100℃, and the temperature of the tower top is controlled at 90℃. The TOC of the stripping water is reduced to 197ppm and enters S3;

[0044] S3. The temperature of the stripping water was adjusted to 60°C, and hydrogen peroxide with a concentration of 27.5wt% was directly added in an amount of 0.3% of the mass of the stripping water. The reaction was stirred for 60 minutes, and the TOC of the obtained water was 96.3ppm. Sodium hypochlorite with a concentration of 5wt% was added in an amount of 2% of the mass of the wastewater. The reaction was stirred for 30 minutes, and the TOC of the obtained water was 62.4ppm. The removal efficiency of TOC of hydrometallurgical wastewater in this example was 73.3%, which did not meet the standards of Table 2 in the national standard GB 31571-2015, and the effect was worse than that of the example.

[0045] Comparative Example 2: No hydrogen peroxide oxidation process (Compared with Example 1)

[0046] S1. Take 10 parts of hydrometallurgical wastewater produced by Wanhua Chemical Group Co., Ltd., with a TOC of 233 ppm;

[0047] Adjust the wastewater pH to <3, add toluene and ethyl acetate mixed extractant (volume ratio of 1:1) to the wastewater, and heat to 45°C, extract and stir for 15 minutes, and stand for 30 minutes to complete phase separation. The TOC of the water phase is 143ppm, enter the S2 step, and the oil phase extractant returns to the front end for recycling;

[0048] S2. 0.4MPaG steam is introduced into the water phase in S1, and the stripping lasts for 60min. The temperature of the stripping tower is controlled at 100℃, and the temperature of the tower top is controlled at 90℃. The TOC of the stripping water is reduced to 35ppm and enters S3;

[0049] S3. The temperature of the stripping water was adjusted to 60°C, and sodium hypochlorite with a concentration of 10wt% was directly added in an amount of 2% of the mass of the stripping water. The reaction was stirred for 60 minutes, and the TOC of the obtained water was 29.4ppm. The removal efficiency of TOC in hydrometallurgical wastewater in this example was 87.4%, which did not meet the standards in Table 2 of the national standard GB 31571-2015, and the effect was worse than that of the example.

[0050] Comparative Example 3 Comparison of treatment effects of different process sequences (oxidation followed by extraction and stripping) (Compared with Example 1)

[0051] S1. Take 10 parts of hydrometallurgical wastewater produced by Wanhua Chemical Group Co., Ltd., with a TOC of 233 ppm;

[0052] Adjust the wastewater temperature to 60°C, directly add 27.5wt% hydrogen peroxide, the amount added is 0.3% of the wastewater mass, stir and react for 60 minutes, the obtained water TOC is 193.4ppm, then add 10wt% sodium hypochlorite, the amount added is 2% of the wastewater mass, stir and react for 60 minutes, the obtained water TOC is 141.7ppm,

[0053] S2. Add toluene and ethyl acetate mixed extractant (volume ratio of 1:1) to the S1 aqueous phase, and the ratio of extractant to wastewater is 1:5. After heating to 45°C, extract and stir for 15 minutes, and then stand for 30 minutes to complete phase separation. The TOC of the aqueous phase is 102ppm, and then enter the S2 step. The oil phase extractant is returned to the front end for recycling;

[0054] S3. 0.4 MPaG of steam was introduced into the water phase in S1, and the stripping was continued for 60 min. The temperature of the bottom of the stripping tower was controlled at 100°C, and the temperature of the top of the tower was controlled at 90°C. The TOC of the stripping water was reduced to 77 ppm. The removal efficiency of TOC in hydrometallurgical wastewater in this example was only 66.9%, which did not meet the standards in Table 2 of the national standard GB 31571-2015.

[0055] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various materials, environments and combinations, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge in the relevant field. The changes and supplements made by those skilled in the art do not deviate from the main purpose and concept of the present invention, and these improvements and supplements should also be regarded as the protection scope of the present invention.

Claims

1. A method for treating hydrometallurgical wastewater, the technical scheme adopted is as follows: S1. Adding a mixture of toluene and ethyl acetate to the hydrometallurgical wastewater to extract and remove organic matter, and obtaining pretreated wastewater after phase separation; S2. introducing steam into the pretreated wastewater in S1 for stripping to remove residual toluene, ethyl acetate and volatile organic matter in the wastewater; S3. Add hydrogen peroxide and sodium hypochlorite to the stripping water in S2 for oxidation.

2. The processing method according to claim 1, characterized in that The pH of the hydrometallurgical wastewater is less than 3; and / or the volume ratio of the mixture of toluene and ethyl acetate is 0.1-10:1; and / or the ratio of the mixture of toluene and ethyl acetate to the wastewater is 1:1-1:

10.

3. The processing method according to claim 1 or 2, characterized in that: The extraction time is 5-30 minutes, the extraction temperature is 20-50° C., and after the extraction is completed, the extraction is allowed to stand for 10-60 minutes to complete phase separation.

4. The processing method according to any one of claims 1 to 3, characterized in that: In the S2, the steam is water vapor with a pressure of 0.2-0.4 MPaG, and the stripping time is 30-180 min.

5. The processing method according to any one of claims 1 to 4, characterized in that: The stripping is carried out in a stripping tower, the temperature of the bottom of the stripping tower is controlled at 70-110°C, and the temperature of the top of the tower is controlled at 60-100°C.

6. The processing method according to any one of claims 1 to 5, characterized in that: In S3, the concentration of hydrogen peroxide is 27.5-30wt%, and the amount added is 0.2%-1% of the mass of the wastewater; the concentration of sodium hypochlorite is 5-15wt%, and the amount added is 2%-10% of the mass of the wastewater.

7. The processing method according to any one of claims 1 to 6, characterized in that: The temperature of the hydrogen peroxide and sodium hypochlorite oxidation is 20-90° C. The hydrogen peroxide is first added to react for 30-120 minutes, and then the sodium hypochlorite is added to react for 30-120 minutes.