Method for recycling chemical waste salt

Abstract

The application relates to the field of chemical waste salt and discloses a method for recycling chemical waste salt resources. The method comprises the following steps: (1) mixing chemical waste salt and water to obtain high-salt wastewater, adjusting the pH value of the high-salt wastewater to 6-8.5 to obtain a mixture, and filtering the mixture through a composite membrane to obtain primary brine; (2) treating the primary brine obtained in step (1) by flowing through a cation exchange resin; wherein, in step (1), the composite membrane comprises a flexible membrane and a nano-aluminum oxide layer coated on the flexible membrane. The method for recycling chemical waste salt resources has a simple technological process, does not need to use multi-stage cation resins for ion exchange, and has a good effect of removing impurities.

Description

Technical Field

[0001] This invention relates to the field of chemical waste salt, and more specifically to a method for the resource utilization of chemical waste salt. Background Technology

[0002] Acid / base driven processes are a key characteristic of the chemical industry. Typical industries such as coal chemical engineering, textile printing and dyeing, pesticides, and fine chemicals largely rely on aqueous solutions of acids or bases as a medium to promote the bonding and dissociation of atoms. Large quantities of waste salts and sludge are generated during the reaction stages, acid-base reactions, salting out, and distillation. Chemical waste salts are the most common and complex type of industrial waste salt. The composition of chemical waste salts is usually complex and highly soluble, making them easily carried by rainwater into soil, groundwater, and even rivers. Without effective treatment, this not only wastes valuable elements but also easily leads to soil salinization.

[0003] Chemical waste salt is mainly composed of sodium salt. Therefore, achieving large-scale and efficient utilization of sodium salt in waste salt and recycling it as a bulk chemical in the production process is the main way to fundamentally solve the problem of sodium-based waste salt. However, due to the differences in production processes and salt production stages of industrial wastewater in different fields, the ion-exchange membrane used in the core electrolysis process of alkali production is sensitive to the concentration of heavy metals in the influent, and the content needs to be reduced to below ppb level. For the resource utilization of waste salt for alkali production, in addition to removing organic matter, the high-ratio removal of heavy metals is a key technical issue.

[0004] Because ion-exchange membrane electrolyzers have high requirements for brine quality, lower metal cation content during brine treatment is more beneficial for protecting the ion exchange membrane and better reflects the economic efficiency of ion-exchange membrane electrolyzer operation. In traditional processes, waste brine still contains a certain amount of calcium and magnesium ions after secondary purification. These ions can form slightly soluble or insoluble substances, such as MgCO3, CaCO3, or CaSO4, with specific anionic groups in the electrolyzer, thus contaminating the ion-exchange membrane. During electrolysis, Ca... 2+ Mg 2+ Fe3 + Fe 2+ Ba 2+ Ni 2+ and Sr 2+ It will react with OH in the cathode chamber - The reaction produces insoluble precipitates, which either deposit in the electrolytic cell or mix into the catholyte, reducing the purity of the NaOH product. Furthermore, impurity cations can induce competitive reversible contamination; that is, impurity cations occupy the active sites of the ion-exchange membrane, competing with sodium ions for mass transfer, thus reducing the sodium ion transfer rate and overall resulting in a decrease in the NaOH yield at the cathode.

[0005] Although Ca 2+ Mg2+ and Fe 2+ Metal cations can have their content reduced in brine during the brine purification process through filtration, sedimentation, and adsorption, thereby reducing their interaction with OH groups migrating from the cathode of the electrolytic cell on or within the ion exchange membrane. - Precipitation is generated, thereby reducing the impact on the performance of the ion exchange membrane; SO4 is reduced through membrane-based denitrification. 2- The content of SO4 in salt water is reduced. 2- For Cl - The effect of discharge ensures the normal operation of caustic soda production via the ion-exchange membrane process; another part of the ions, such as I... - 、Sr 2+ There is no effective removal method for these substances in the brine refining process, leading to their accumulation in the brine system and affecting the economical operation of the ion-exchange membrane electrolyzer. In one brine refining process, Sr... 2+ In the post-brine reaction tank stage, it reacts with the refining agent Na2CO3 to generate SrCO3 precipitate, thereby reducing its content. However, due to Ca... 2+ With CO3 2- Reaction ability is greater than Sr 2+ With CO3 2- The reaction has strong reactivity. Adding the refining agent Na2CO3 in the post-brine reaction tank stage is mainly to remove Ca. 2+ .

[0006] During the secondary purification of brine, the ease with which chelating resins replace various cations is as follows: Cu 2+ Pb 2+ >Zn 2+ >Ca 2+ Cd 2+ >Mg 2+ Ni 2+ >Sr 2+ >Ba 2+ Na + Therefore, to remove these cations, either a multi-stage resin exchange process must be used, or the chelated resin must undergo an acid-base regeneration reaction. Resin regeneration begins with a mixture of 31% hydrochloric acid and pure water at a flow rate of 5.5 m³ / h. 3 / h and 21.8m 3 After being mixed to a concentration of 7% by mass using a controlled-flow valve, the mixture is fed into a resin tower for acid regeneration, thereby regenerating Ca. 2+ Type, Mg 2+ Type I resin converted to H + Type-3 resin, thereby converting the resin back into Na + Reusing the resin is a complex process.

[0007] However, unlike the target pollutants in secondary brine in conventional chlor-alkali industry, industrial waste salt mainly comes from byproducts of industrial wastewater desalination and end-of-pipe zero-discharge systems. Its heavy metal impurity ions are complex, and the target pollutants are different from the heavy metal pollutants in secondary brine in conventional chlor-alkali industry. Industrial waste salt mainly includes metals such as Al, Cr, Mn, Cu, and Ni. Resin adsorption treatment has problems such as multi-stage treatment with anion and cation exchange resins and low Cr ion removal rate. Summary of the Invention

[0008] The purpose of this invention is to overcome the problems existing in the prior art and provide a method for the resource utilization of chemical waste salt. This method is simple and efficient, with a high impurity removal rate. The chemical waste salt treated by this method can be used as a raw material for the chlor-alkali industry system, converting waste salt into valuable products and realizing the resource utilization of chemical waste salt.

[0009] To achieve the above objectives, the present invention provides a method for the resource utilization of chemical waste salt, the method comprising the following steps:

[0010] (1) Chemical waste salt and water are mixed to obtain high-salt wastewater. The pH value of the high-salt wastewater is adjusted to 6-8.5 to obtain a mixture. The mixture is filtered through a composite membrane to obtain primary brine.

[0011] (2) The primary brine obtained in step (1) is processed through a cation exchange resin;

[0012] In step (1), the composite membrane includes a flexible membrane and a nano-alumina layer coated on the flexible membrane.

[0013] Preferably, in step (1), the average thickness of the nano-alumina layer coated on the flexible film is 100-10000 nm.

[0014] Preferably, in step (1), the chemical waste salt contains Na, Cr, Cu, Al, Ni and Mn elements.

[0015] Preferably, in step (1), the Na content in the chemical waste salt is 10-32 wt%.

[0016] Preferably, in step (1), the TDS of the high-salt wastewater is 120,000-320,000 mg / L.

[0017] Preferably, in step (1), the average pore size of the flexible membrane is 3-100 nm.

[0018] Preferably, in step (1), the particle size of nano-alumina is 5-100 nm.

[0019] Preferably, in step (2), the height-to-diameter ratio of the cation exchange resin is 2-5:1.

[0020] Preferably, in step (2), the adsorption flow rate of the cation exchange resin is 0.5-3 BV / h.

[0021] Preferably, in step (2), the adsorption capacity of the cation exchange resin is 8-15 BV.

[0022] Preferably, in step (2), the cation exchange resin is selected from strong acid cation exchange resin or weak acid macroporous cation exchange resin.

[0023] Preferably, step (2) further includes adjusting the pH of the primary brine flowing through the cation exchange resin to 5-7.

[0024] Compared with existing technical solutions, the technical solution of the present invention has the following advantages:

[0025] (1) The method of the present invention is used to treat chemical waste salt. In step (1), the Cr in the primary brine is reduced. 3+ and Cu 2+ <0.1ppm, Al 3+ It can meet the effluent quality requirements, Ni 2+ The adsorption removal rate can reach 70%-96%, Mn 2+ The adsorption removal rate can reach 40%-75%;

[0026] (2) The method of the present invention is used to treat chemical waste salt. In step (2), the filtrate obtained after treatment with cation exchange resin contains Ni. 2+ Cr 3+ and Cu 2+ <0.05ppm, Al 3+ and Mn 2+ The removal rate is as high as 98%;

[0027] (3) The method for resource utilization of chemical waste salt described in this invention has a simple process flow, does not require multi-stage cation exchange resin, and has a good effect on removing impurities.

[0028] (4) The chemical waste salt is treated by the method described in this invention. The product obtained after treatment can be used as raw material for the chlor-alkali process system, which can effectively promote the transformation of waste salt into valuable products, realize the resource utilization of chemical waste salt, reduce the enterprise's dependence on external resources, reduce raw material costs, create new sources of income for the enterprise, promote local economic development, extend the industrial chain, increase the added value of products and the scope of market application, which is in line with the concept of circular economy and helps to promote the efficient use of resources and sustainable development. Detailed Implementation

[0029] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0030] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0031] This invention provides a method for the resource utilization of chemical waste salt, the method comprising the following steps:

[0032] (1) Chemical waste salt and water are mixed to obtain high-salt wastewater. The pH value of the high-salt wastewater is adjusted to 6-8.5 to obtain a mixture. The mixture is filtered through a composite membrane to obtain primary brine.

[0033] (2) The primary brine obtained in step (1) is processed through a cation exchange resin;

[0034] In step (1), the composite membrane includes a flexible membrane and a nano-alumina layer coated on the flexible membrane.

[0035] In this invention, there are no special requirements for the substance used to adjust the pH value of high-salinity wastewater to 6-8.5. As long as it can adjust the pH value of high-salinity wastewater to 6-8.5, it is acceptable. Preferably, hydrochloric acid or sodium hydroxide is used to adjust the pH value of high-salinity wastewater to 6-8.5.

[0036] In a preferred embodiment, in step (1), the pH value of the high-salt wastewater is adjusted to 7-8.5; specifically, the pH value of the high-salt wastewater can be adjusted to 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2 or 8.5.

[0037] In a preferred embodiment, in order to improve the removal rate of Cr, Cu, Al, Ni and Mn elements, in step (1), the average thickness of the nano-alumina layer coated on the flexible film is 100-10000 nm; preferably 200-5000 nm.

[0038] In a preferred embodiment, in step (1), the chemical waste salt contains Na, Cr, Cu, Al, Ni and Mn elements.

[0039] In a preferred embodiment, in step (1), the Na content in the chemical waste salt is 10-32 wt%.

[0040] In a preferred embodiment, in step (1), the TDS of the high-salt wastewater is 120,000-320,000 mg / L.

[0041] In this invention, "TDS" is also known as total dissolved solids, which indicates how many milligrams of dissolved solids are dissolved in 1 liter of water. The higher the TDS value, the more dissolved substances are contained in the water.

[0042] In a preferred embodiment, in order to improve the removal rate of Cr, Cu, Al, Ni and Mn elements, the flexible membrane in step (1) is made of nylon.

[0043] In a more preferred embodiment, in order to further improve the removal rate of Cr, Cu, Al, Ni and Mn elements, in step (1), the average pore size of the flexible membrane is 3-100 nm; preferably 4-10 nm; specifically, the average pore size of the flexible membrane can be 4 nm, 6 nm, 8 nm or 10 nm.

[0044] In a preferred embodiment, in order to improve the removal rate of Cr, Cu, Al, Ni and Mn elements, in step (1), the particle size of nano-alumina is 5-100 nm; preferably 20-80 nm.

[0045] In this invention, the particle size of nano-alumina is larger than the average pore size of the flexible membrane, thereby enabling nano-alumina to be coated onto the flexible membrane.

[0046] In a preferred embodiment, in step (1), when the nano-alumina reaches adsorption saturation, the nano-alumina adsorbed with heavy metal elements can be washed away.

[0047] In a specific implementation, the cleaning process includes: rinsing from the outside to the inside of the composite membrane to separate the nano-alumina adsorbed with heavy metal elements from the flexible membrane; then rinsing the inside of the composite membrane with water and optional air to completely separate the nano-alumina adsorbed with heavy metal elements from the flexible membrane and carry the pollutants out with the water flow.

[0048] In a preferred embodiment, in order to increase the adsorption flow rate of the cation exchange resin, in step (2), the height-to-diameter ratio of the cation exchange resin is 2-5:1; preferably 2-4:1; specifically, the height-to-diameter ratio of the cation exchange resin can be 2:1, 2.5:1, 3:1, 3.5:1 or 4:1.

[0049] In a preferred embodiment, in step (2), the adsorption flow rate of the cation exchange resin is 0.5-3 BV / h; preferably 1-3 BV / h.

[0050] In a preferred embodiment, in step (2), the adsorption capacity of the cation exchange resin is 8-15 BV; preferably 8-12 BV.

[0051] In a preferred embodiment, in order to further improve the adsorption flow rate of the cation exchange resin, in step (2), the cation exchange resin is selected from strong acid cation exchange resin or weak acid macroporous cation exchange resin.

[0052] In a preferred embodiment, step (2) further includes adjusting the pH of the primary brine flowing through the cation exchange resin to 5-7.

[0053] In this invention, there are no special requirements for the substance used to adjust the pH of the primary brine to 5-7, as long as it can adjust the pH of the primary brine to 5-7. Preferably, hydrochloric acid or sulfuric acid is used to adjust the pH of the primary brine to 5-7.

[0054] In a more preferred embodiment, to further improve the impurity removal effect, the pH of the primary brine is adjusted to 5.5-6.5.

[0055] In a preferred embodiment, in step (2), after the cation resin used reaches adsorption saturation, the cation resin can be regenerated to restore its adsorption performance.

[0056] In a specific implementation, the regeneration process includes: first, backwashing the cation exchange resin with clean water until the pH of the discharged solution is 6.5-7, and then performing acid washing, water washing, alkali washing, and water washing again.

[0057] In this invention, the chemical waste salt refers to the waste salt sludge generated during the preparation of chemical products in the coal chemical, textile printing and dyeing, pesticide, and fine chemical industries. The main component of the waste salt sludge is sodium salt, with a sodium content of 10-32 wt%. It also contains complex heavy metal impurities, mainly including Al, Cr, Mn, Cu, and Ni. If the waste salt sludge is used as a raw material for alkali production, these heavy metal elements will have a significant damaging effect on the ion-exchange membrane used in the alkali electrolysis process and affect the yield of sodium hydroxide. Therefore, it is necessary to treat the chemical waste salt to achieve resource utilization.

[0058] In this invention, chemical waste salt is treated using the method described herein. In step (1), under pH conditions of 6-8.5, nano-alumina can chemically adsorb heavy metal elements from impurities. Simultaneously, due to the small particle size of nano-alumina, it can also act as a physical filter. Furthermore, after secondary physical filtration through a flexible membrane, the Cr content in the primary brine is reduced. 3+ and Cu 2+ <0.1ppm, Al 3+ It can meet the effluent quality requirements, Ni 2+ The adsorption removal rate can reach 70%-96%, Mn 2+ The adsorption removal rate can reach 40%-75%; after the treatment in step (1), the obtained primary brine only needs to be exchanged once with cation exchange resin to obtain the raw material of the chlor-alkali process system that meets the requirements. The Ni in the filtrate obtained after one cation exchange resin exchange is... 2+ Cr 3+ and Cu 2+ <0.05ppm, Al 3+ and Mn 2+ The removal rate is as high as 98%, achieving zero discharge of wastewater. Therefore, by using the method described in this invention to treat chemical waste salt, the resulting product can be used as a raw material for the chlor-alkali process system, effectively promoting the conversion of waste salt into valuable products and realizing the resource utilization of chemical waste salt. Furthermore, the method described in this invention does not require the use of multi-stage cation exchange resins, making the process simple and efficient.

[0059] The following examples further illustrate the method for resource utilization of chemical waste salt according to the present invention. These examples are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures; however, the scope of protection of the present invention is not limited to the following examples.

[0060] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods in the art. Unless otherwise specified, the experimental materials used in the following embodiments are commercially available; the chemical waste salt is derived from the chemical waste salt of Ningdong Coal Chemical Plant.

[0061] The water quality parameters of the high-salinity wastewater in the examples and comparative examples are shown in Table 1.

[0062] Table 1

[0063] name pH Na Al (ppm) Ni (ppm) Mn (ppm) Cu (ppm) Cr (ppm) High-salinity wastewater 6～7 30％ 1.86 0.37 0.08 0.6 0.51

[0064] Example 1

[0065] (1) Chemical waste salt and water are mixed to obtain high-salt wastewater with a TDS of 315000 mg / L. The pH of the high-salt wastewater is adjusted to 8.5 to obtain a mixture. The mixture is filtered through a composite membrane to obtain primary brine. The composite membrane is a flexible membrane and a nano-alumina layer coated on the flexible membrane. The flexible membrane is a nylon membrane with an average pore size of 4 nm, the nano-alumina layer has an average thickness of 1000 nm, and the nano-alumina has a particle size of 30 nm.

[0066] (2) Adjust the pH of the primary brine obtained in step (1) to 6, and then pass it through a strong acid cation exchange resin for treatment; wherein the height-to-diameter ratio of the strong acid cation exchange resin is 3:1, the adsorption flow rate is 3BV / h, and the adsorption capacity is 10BV.

[0067] Example 2

[0068] (1) Chemical waste salt and water are mixed to obtain high-salt wastewater with a TDS of 315000 mg / L. The pH of the high-salt wastewater is adjusted to 7 to obtain a mixture. The mixture is filtered through a composite membrane to obtain primary brine. The composite membrane is a flexible membrane and a nano-alumina layer coated on the flexible membrane. The flexible membrane is a nylon membrane with an average pore size of 4 nm, the nano-alumina layer has an average thickness of 1000 nm, and the nano-alumina has a particle size of 30 nm.

[0069] (2) Adjust the pH of the primary brine obtained in step (1) to 6, and then pass it through a strong acid cation exchange resin for treatment; wherein the height-to-diameter ratio of the strong acid cation exchange resin is 3:1, the adsorption flow rate is 3BV / h, and the adsorption capacity is 10BV.

[0070] Example 3

[0071] (1) Chemical waste salt and water are mixed to obtain high-salt wastewater with a TDS of 315000 mg / L. The pH of the high-salt wastewater is adjusted to 6 to obtain a mixture. The mixture is filtered through a composite membrane to obtain primary brine. The composite membrane is a flexible membrane and a nano-alumina layer coated on the flexible membrane. The flexible membrane is a nylon membrane with an average pore size of 4 nm, the nano-alumina layer has an average thickness of 1000 nm, and the nano-alumina has a particle size of 30 nm.

[0072] (2) Adjust the pH of the primary brine obtained in step (1) to 6, and then pass it through a strong acid cation exchange resin for treatment; wherein the height-to-diameter ratio of the strong acid cation exchange resin is 3:1, the adsorption flow rate is 3BV / h, and the adsorption capacity is 10BV.

[0073] Example 4

[0074] (1) Chemical waste salt and water are mixed to obtain high-salt wastewater with a TDS of 315000 mg / L. The pH of the high-salt wastewater is adjusted to 7 to obtain a mixture. The mixture is filtered through a composite membrane to obtain primary brine. The composite membrane is a flexible membrane and a nano-alumina layer coated on the flexible membrane. The flexible membrane is a nylon membrane with an average pore size of 4 nm, the nano-alumina layer has an average thickness of 1000 nm, and the nano-alumina has a particle size of 150 nm.

[0075] (2) Adjust the pH of the primary brine obtained in step (1) to 6, and then pass it through a strong acid cation exchange resin for treatment; wherein the height-to-diameter ratio of the strong acid cation exchange resin is 3:1, the adsorption flow rate is 3BV / h, and the adsorption capacity is 10BV.

[0076] Comparative Example 1

[0077] (1) Chemical waste salt and water are mixed to obtain high-salt wastewater with a TDS of 315000 mg / L. The pH of the high-salt wastewater is adjusted to 5.5 to obtain a mixture. The mixture is filtered through a composite membrane to obtain primary brine. The composite membrane is a flexible membrane and a nano-alumina layer coated on the flexible membrane. The flexible membrane is a nylon membrane with an average pore size of 4 nm, the nano-alumina layer has an average thickness of 1000 nm, and the nano-alumina has a particle size of 30 nm.

[0078] (2) Adjust the pH of the primary brine obtained in step (1) to 6, and then pass it through a strong acid cation exchange resin for treatment; wherein the height-to-diameter ratio of the strong acid cation exchange resin is 3:1, the adsorption flow rate is 3BV / h, and the adsorption capacity is 10BV.

[0079] Comparative Example 2

[0080] (1) Chemical waste salt and water are mixed to obtain high-salt wastewater with a TDS of 315000 mg / L. The pH of the high-salt wastewater is adjusted to 8.5 to obtain a mixture. The mixture is filtered through a composite membrane to obtain primary brine. The composite membrane is a flexible membrane and a nano-magnesium oxide layer coated on the flexible membrane. The flexible membrane is a nylon membrane with an average pore size of 4 nm, the nano-magnesium oxide layer has an average thickness of 1000 nm, and the nano-magnesium oxide has a particle size of 30 nm.

[0081] (2) Adjust the pH of the primary brine obtained in step (1) to 6, and then pass it through a strong acid cation exchange resin for treatment; wherein the height-to-diameter ratio of the strong acid cation exchange resin is 3:1, the adsorption flow rate is 3BV / h, and the adsorption capacity is 10BV.

[0082] Comparative Example 3

[0083] (1) Chemical waste salt and water are mixed to obtain high-salt wastewater with a TDS of 315000 mg / L. The pH of the high-salt wastewater is adjusted to 6, and then it is treated by passing it through a strong acid cation exchange resin to obtain primary brine. The height-to-diameter ratio of the strong acid cation exchange resin is 3:1, the adsorption flow rate is 3 BV / h, and the adsorption capacity is 10 BV.

[0084] (2) Adjust the pH value of the primary brine obtained in step (1) to 8.5 to obtain a mixture, and filter the mixture through a composite membrane; the composite membrane is a flexible membrane and a nano-alumina layer coated on the flexible membrane, wherein the flexible membrane is a nylon membrane with an average pore size of 4nm, the average thickness of the nano-alumina layer is 1000nm, and the particle size of the nano-alumina is 30nm.

[0085] Test case

[0086] Water quality tests were performed on the products of the examples and comparative examples after step (1), and the results are shown in Table 1; water quality tests were performed on the products of the examples and comparative examples after step (2), and the results are shown in Table 2; the removal rates of each element in the examples and comparative examples are shown in Table 3.

[0087] Table 1

[0088]

[0089]

[0090] Table 2

[0091] serial number Al (ppm) Ni (ppm) Mn (ppm) Cu (ppm) Cr (ppm) Example 1 0.03 Not detected Not detected <0.05 <0.05 Example 2 0.02 Not detected 0.001 <0.05 <0.05 Example 3 0.025 Not detected Not detected <0.05 <0.05 Example 4 0.023 Not detected 0.001 <0.05 <0.05 Comparative Example 1 0.027 Not detected 0.001 >0.1 >0.1 Comparative Example 2 0.55 0.15 0.02 >0.1 >0.1 Comparative Example 3 0.35 0.06 0.025 >0.1 >0.1

[0092] Table 3

[0093] serial number Al(％) Ni (%) Mn(%) Cu (%) Cr(％) Example 1 98 100 100 >91.6 >90 Example 2 99 100 98.75 >91.6 >90 Example 3 98.6 100 100 >91.6 >90 Example 4 98.8 100 98.75 >91.6 >90 Comparative Example 1 98.5 100 98.75 <83.3 <80 Comparative Example 2 70 59.5 75 <83.3 <80 Comparative Example 3 81.2 83.8 68.75 <83.3 <80

[0094] As can be seen from the results in Tables 1-3, the method described in this invention for treating chemical waste salt has high impurity removal efficiency and can achieve zero wastewater discharge. The product after treatment by the method described in this invention contains almost no heavy metal elements Cr, Cu, Al, Ni and Mn, and has good application prospects in the raw materials of alkali production process.

[0095] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for the resource utilization of chemical waste salt, characterized in that, The method includes the following steps: (1) Chemical waste salt and water are mixed to obtain high-salt wastewater. The pH value of the high-salt wastewater is adjusted to 6-8.5 to obtain a mixture. The mixture is filtered through a composite membrane to obtain primary brine. (2) The primary brine obtained in step (1) is processed through a cation exchange resin; In step (1), the composite film includes a flexible film and a nano-alumina layer coated on the flexible film. In step (1), the average thickness of the nano-alumina layer coated on the flexible film is 100-10000 nm; In step (1), the particle size of nano-alumina is 5-100 nm.

2. The method for resource utilization of chemical waste salt according to claim 1, characterized in that, In step (1), the chemical waste salt contains Na, Cr, Cu, Al, Ni and Mn elements.

3. The method for resource utilization of chemical waste salt according to claim 2, characterized in that, In step (1), the Na content in the chemical waste salt is 10-32 wt%.

4. The method for resource utilization of chemical waste salt according to any one of claims 1-3, characterized in that, In step (1), the TDS of the high-salt wastewater is 120,000-320,000 mg / L.

5. The method for resource utilization of chemical waste salt according to claim 4, characterized in that, In step (1), the average pore size of the flexible membrane is 3-100 nm.

6. The method for resource utilization of chemical waste salt according to any one of claims 1-3, characterized in that, In step (2), the height-to-diameter ratio of the cation exchange resin is 2-5:

1.

7. The method for resource utilization of chemical waste salt according to claim 6, characterized in that, In step (2), the adsorption flow rate of the cation exchange resin is 0.5-3 BV / h.

8. The method for resource utilization of chemical waste salt according to claim 6, characterized in that, In step (2), the adsorption capacity of the cation exchange resin is 8-15 BV.

9. The method for resource utilization of chemical waste salt according to claim 7 or 8, characterized in that, In step (2), the cation exchange resin is selected from strong acid cation exchange resin or weak acid macroporous cation exchange resin.

10. The method for resource utilization of chemical waste salt according to claim 9, characterized in that, Step (2) also includes adjusting the pH of the primary brine flowing through the cation exchange resin to 5-7.

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