A method for resource recovery of waste liquid from lithium compound production in the lithium battery new energy field

Abstract

This invention relates to the field of lithium compound production wastewater treatment technology in the lithium battery new energy industry, specifically a method for the resource recovery of lithium compound production wastewater in the lithium battery new energy field. The method includes the following steps: S1: pretreatment; S2: EDTA oxidation removal; S3: removal of calcium and other high-valence metal ions; S4: UV / O3 treatment; S5: lithium extraction from the wastewater. After treatment by this method for the resource recovery of lithium compound production wastewater in the lithium battery new energy field, the lithium extraction wastewater achieves complete degradation of EDTA in the saturated sodium sulfate solution, reducing the COD value by more than 80%. Due to the complete degradation of EDTA, subsequent lithium precipitation treatment can achieve lithium resource recovery. Furthermore, the iron sludge formed by the ferrous sulfate catalyst added in the EDTA oxidation step after its first use can dissolve in EDTA. Therefore, the catalyst in the UV / Fenton reaction can be recycled. This method avoids lithium loss due to iron sludge entrainment.

Description

Technical Field

[0001] This invention relates to the field of lithium compound production wastewater treatment technology in the lithium battery new energy industry, specifically a method for the resource utilization of lithium compound production wastewater in the lithium battery new energy field. Background Technology

[0002] The traditional production method of lithium compounds in the field of lithium battery new energy is to remove high-valence metal ions such as calcium and magnesium from the brine after raw material treatment, and then carry out a series of other treatments. Then, under certain temperature conditions, an excess of sodium carbonate and other substances are added to convert them into corresponding substances. After washing and evaporation, the finished product is obtained.

[0003] Currently, some domestic manufacturers have developed a better production process: adding EDTA (Ethylene Diamine Tetraacetic Acid) to the lithium extraction brine to shield it from high-valence metal ions, followed by direct lithium precipitation after concentration. The main advantages of this method compared to traditional methods are lower impurity content, whiter color, and better appearance. After lithium extraction, the EDTA-containing mother liquor is treated by evaporation, and the evaporated salts are disposed of as hazardous waste. The EDTA mother liquor after lithium extraction typically contains a high content of impurity metal ions, such as Ca... 2+ Mg 2+ Ni 2+ Co 3+ / Co 2+ and Fe 2+ Due to the poor quality of domestically produced stainless steel in China, corrosion during pipeline use leads to the introduction of impurities such as nickel and iron. Simultaneously, the chelating effect of EDTA, while preventing the precipitation of impurity ions during lithium deposition, also results in a significant amount of lithium ions failing to precipitate. Therefore, the final discarded lithium extraction mother liquor, after 8-10 times evaporation and concentration (including EDTA), mainly contains sodium. + SO4 2- In addition, the lithium content exceeds 5 g / L, which is close to or even higher than the lithium content in the leachate of many roasted ores. Furthermore, the concentrated lithium extraction mother liquor also has a very high COD (chemical oxygen demand) value. Although the concentrate contains a high concentration of CO3... 2- The process conditions exceed those for lithium precipitation. However, due to the influence of EDTA and other factors, the lithium in the sample will not be converted into Li2CO3 (or Li3PO4, LiF) and will not be precipitated.

[0004] The EDTA lithium extraction mother liquor after evaporation and concentration contains a lot of impurities, and therefore usually has a very dark color. Due to the chelating effect of EDTA, it is impossible to treat it for lithium precipitation by conventional methods. Based on this, this application proposes a method for the resource utilization of lithium compound production waste liquid in the field of lithium battery new energy to solve the above problems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for the resource recovery of lithium compound production waste liquid in the field of lithium battery new energy. This method achieves complete degradation of EDTA in saturated sodium sulfate solution, reducing the COD value by more than 80%. Due to the complete degradation of EDTA, subsequent lithium precipitation treatment can achieve the resource recovery of lithium.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for resource recovery of waste liquid from lithium compound production in the field of lithium battery new energy, comprising the following steps:

[0007] S1: Collect the EDTA mother liquor after lithium extraction, determine the content of each substance, and perform pretreatment;

[0008] S2: The liquid obtained after pretreatment in step S1 is subjected to EDTA oxidation removal;

[0009] S3: Remove calcium and other high-valence metal ions from the liquid obtained by EDTA oxidation in step S2;

[0010] S4: The liquid obtained in step S3 after removing calcium and other high-valence metal ions is treated with UV / O3. The solution after UV / O3 treatment is filtered again. The sludge filtered after UV / O3 treatment is dewatered and then processed separately. The water after UV / O3 treatment is dewatered and then mixed with the filtrate after UV / O3 treatment.

[0011] S5: After the UV / O3 treatment in step S4, the filtrate is analyzed and measured for various parameters. After the UV / O3 treatment in step S4 is measured for various parameters, lithium precipitation is carried out according to the traditional or original lithium precipitation process for producing lithium compounds (lithium products).

[0012] Furthermore, the preprocessing procedure in step S1 is as follows:

[0013] 1) After the content of various substances in the EDTA mother liquor after lithium extraction is determined, acid is added for acidification. The pH value of the acidified EDTA lithium extraction mother liquor is between 1 and 5.

[0014] 2) After the acidification is completed, the acidified mother liquor is allowed to stand for 5-24 hours. After the standing time is completed, the supernatant is taken for subsequent processing.

[0015] 3) After the acidified mother liquor has been left to stand for a certain period of time, the lower sediment is dehydrated. The clear water obtained from the dehydration of the lower sediment is collected together with the supernatant. The sludge obtained from the dehydration of the lower sediment is treated as solid waste and disposed of separately.

[0016] 4) Measure the COD value (COD1) parameter of the clear liquid.

[0017] Furthermore, the preferred pH value for acidification is below 4.

[0018] Furthermore, the oxidative removal process of EDTA in step S2 is as follows:

[0019] 1) Add ferrous sulfate catalyst to the clear liquid obtained in step S1. After the ferrous sulfate is added, add hydrogen peroxide to the clear liquid. After the hydrogen peroxide is added, a reaction solution is obtained.

[0020] 2) The reaction solution is subjected to a first-stage UV / Fenton (ultraviolet) treatment; during the first-stage UV / Fenton treatment, acid is added to the reaction solution, and the addition of acid can maintain the pH value of the reaction solution at no higher than 4;

[0021] 3) After the first-stage UV / Fenton treatment is completed, alkali is added to the solution to adjust the pH value. After the alkali addition is completed to adjust the pH value, the pH value of the reaction solution is not higher than 6. After the pH value is adjusted, the reaction solution is filtered.

[0022] 4) The filtrate obtained after filtering the reaction solution is further processed. The water obtained after dewatering the filtered sludge is mixed with the filtrate to obtain filtrate A. The dewatered sludge is returned to step 1) and reused as a catalyst.

[0023] Furthermore, the calculation formula for the dosage of ferrous sulfate (FeSO4·7H2O) is as follows:

[0024] m=n×COD1 (1)

[0025] In formula (1), m is the amount of ferrous sulfate (FeSO4·7H2O) to be added, in kg / m. 3 Or kg / t, COD1 value is the parameter of the clear liquid described in step S1, the unit is g / L, n is a coefficient, and the value of n is between 0.1 and 10;

[0026] The formula for calculating the amount of hydrogen peroxide added is as follows:

[0027] V1=p1×COD1 (2)

[0028] In formula (2), V1 is the volume of hydrogen peroxide to be added, and the mass percentage concentration of the hydrogen peroxide is 27%-27.5%, with units of L / m³. 3 Or L / t, the meaning or unit of COD1 is the same as in formula (1), p1 is a coefficient, and the value of p1 is between 10 and 40.

[0029] Furthermore, the preferred value of n is between 0.1 and 1, and the preferred value of p1 is between 20 and 30.

[0030] Furthermore, the process of removing calcium and other high-valence metal ions in step S3 is as follows:

[0031] 1) Add oxalic acid or sodium oxalate to the filtrate A obtained in step S2. After the oxalic acid or sodium oxalate is added, add alkali to the filtrate to adjust the pH value of the filtrate to above 10.

[0032] 2) After the pH value of the filtrate is adjusted, let it stand for more than 1 hour. After the standing time is reached, filter the filtrate A. The sludge filtered from the filtrate is further processed by pressure filtration. The clear liquid from the sludge pressure filtration is mixed with the filtrate filtered from filtrate A to obtain filtrate B.

[0033] 3) Analyze and determine the COD value (COD2) and the contents of calcium (c), magnesium, etc. in the filtrate B;

[0034] 4) Add acid to the filtrate B to adjust the pH value to below 4. After the pH value of the filtrate B is adjusted, add sufficient hydrogen peroxide to the filtrate B. After the hydrogen peroxide is added, perform a two-stage UV / Fenton treatment on the filtrate B. After the two-stage UV / Fenton treatment of the filtrate B is completed, add alkali to the filtrate B to adjust the pH value to above 9.

[0035] Furthermore, the calculation formula for the dosage of oxalic acid (H2C2O4·2H2O) is as follows:

[0036] a=r×c (3)

[0037] In formula (3), a is the amount of oxalic acid to be added per ton of water, in kg / t; c is the calcium content in the water, in g / L; and r is a coefficient, with a value between 3 and 20.

[0038] The formula for calculating the dosage of sodium oxalate (Na2C2O4) is as follows:

[0039] s=d×c (4)

[0040] In formula (4), s is the amount of sodium oxalate to be added per ton of water, in kg / t; c is the calcium content in the water, in g / L; and d is a coefficient, with a value between 3 and 20.

[0041] The formula for calculating the amount of hydrogen peroxide added to filtrate B is as follows:

[0042] V2=p2×c (5)

[0043] In formula (5), V2 is the volume of hydrogen peroxide to be added, and the mass percentage concentration of the hydrogen peroxide is 27%-27.5%, with units of L / m³. 3 Or L / t, where c is in g / L, and p2 is a coefficient with a value between 3 and 20.

[0044] Furthermore, the preferred value of r is between 9 and 15, the preferred value of d is between 10 and 20, and the preferred value of p2 is between 5 and 10.

[0045] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0046] After treatment using this method for the resource recovery of lithium compound production wastewater in the lithium battery new energy field, the lithium extraction wastewater achieved complete degradation of EDTA in the saturated sodium sulfate solution, reducing the COD value by more than 80%. The final filtrate became lighter in color, changing from nearly opaque to transparent. No lithium was lost from the water after treatment. Impurities such as Fe and Mn in the wastewater were below the detection limits of the testing instruments, and the contents of other elements such as Ca and Mg were also reduced to some extent. No new sodium was added to the water during the treatment process. + and SO4 2- Other than these substances, the complete degradation of EDTA after treatment allows for subsequent lithium precipitation, enabling the resource recovery of lithium. Furthermore, the iron sludge formed from the ferrous sulfate catalyst added during the EDTA oxidation step after its first use is soluble in EDTA. Therefore, the catalyst in the UV / Fenton reaction can be recycled. This method avoids lithium loss due to iron sludge entrainment. At the same time, the reuse of the catalyst greatly reduces the amount of solid waste / hazardous waste generated during the treatment process. Attached Figure Description

[0047] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] Please see Figure 1 This invention provides a method for the resource recovery of lithium compound production waste liquid in the field of lithium battery new energy. It is mainly applicable to the treatment of lithium compound production waste liquid. Before treatment, the EDTA mother liquor collected after lithium extraction needs to be pretreated. The pretreatment process is as follows:

[0050] First, the EDTA mother liquor after lithium extraction is collected, and the content of various substances is determined. After the content of various substances in the EDTA mother liquor after lithium extraction is determined, acid is added for acidification. The acid used for acidification is a kind of inexpensive and readily available inorganic acid. Considering cost and reducing subsequent equipment corrosion, sulfuric acid is preferred. The pH value of the EDTA lithium extraction mother liquor after acidification is between 1 and 5, and the preferred pH value for acidification is below 4. After acidification, the acidified mother liquor is allowed to stand for 5-24 hours. After the standing time, the supernatant is taken for subsequent treatment. After the standing time of the acidified mother liquor is reached, the lower sediment is dehydrated. The clear water obtained from the dehydration of the lower sediment is collected together with the supernatant. The sludge after the lower sediment is dehydrated is treated separately as solid waste. Finally, the COD value (COD1) and other parameters of the clear liquid are measured.

[0051] After pretreatment, the pretreated product was subjected to sequential EDTA oxidation removal and removal of calcium and other high-valence metal ions. The EDTA oxidation removal process is as follows:

[0052] Ferrous sulfate catalyst is added to the clear liquid obtained in the pretreatment step. The calculation formula for the amount of ferrous sulfate (FeSO4·7H2O) added is as follows:

[0053] m=n×COD1 (1)

[0054] In formula (1), m is the amount of ferrous sulfate (FeSO4·7H2O) to be added, in kg / m. 3 In this patent, the volume unit of water (cubic meter) and the weight unit (ton) are considered equivalent. The COD1 value is a parameter of the clear liquid described in the pretreatment step, with the unit being g / L. n is a coefficient, and the value of n ranges from 0.1 to 10. It should be noted that the factors affecting the value range of n are mainly the reaction rate and the final amount of sludge. Considering reducing the intensity of the reaction and the reaction time, the preferred value of n is between 0.1 and 1.

[0055] It should be noted that the catalyst is only added during the first use of the EDTA oxidation removal step, and ferrous sulfate is not added during the second and subsequent runs of the EDTA oxidation removal step.

[0056] After the ferrous sulfate addition is complete, hydrogen peroxide is added to the clear solution. The calculation formula for the amount of hydrogen peroxide added is as follows:

[0057] V1=p1×COD1 (2)

[0058] In formula (2), V1 is the volume of hydrogen peroxide to be added, and the mass percentage concentration of hydrogen peroxide is 27%-27.5%, with units of L / m³. 3 Or L / t. In this patent, the volume unit of water, cubic meters, and the weight unit, tons, are considered equivalent. The meaning or unit of COD1 value is the same as in formula (1). p1 is a coefficient. The value range of p1 is between 10 and 40. The main factors affecting the value range of p1 are the effect / efficiency of EDTA or COD removal. The salt content of the solution will also greatly affect the value range of p1. Considering the effect / efficiency of EDTA or COD removal, the preferred value range of p1 is between 20 and 30.

[0059] After hydrogen peroxide is added, a reaction solution is obtained. The reaction solution is then subjected to a first-stage UV / Fenton (ultraviolet) treatment. During the first-stage UV / Fenton treatment, acid is added to the reaction solution. The amount of acid added is sufficient to maintain the pH value of the reaction solution at no higher than 4. After the first-stage UV / Fenton treatment, alkali is added to the solution to adjust the pH value. The alkali is a type of inexpensive and readily available inorganic compound. The addition of alkali will not introduce impurities into the reaction solution. After the pH value is adjusted by adding alkali, the pH value of the reaction solution is no higher than 6. After the pH value is adjusted, the reaction solution is filtered. The filtrate obtained after filtering the reaction solution is further processed. The filtered sludge is dewatered, and the resulting water is mixed with the filtrate to obtain filtrate A. The dewatered sludge is returned to the aforementioned steps and reused as a catalyst.

[0060] The process of removing calcium and other high-valence metal ions is as follows:

[0061] Oxalic acid or sodium oxalate was added to filtrate A obtained after the above EDTA oxidation removal. After the addition of oxalic acid or sodium oxalate, alkali was added to the filtrate to adjust the pH value to above 10. After the pH value was adjusted, the filtrate was allowed to stand for more than 1 hour. After the standing time was reached, filtrate A was filtered. The sludge filtered from the filtrate was further processed by pressure filtration. The clear liquid from the sludge pressure filtration was mixed with the filtrate filtered from filtrate A to obtain filtrate B. The COD value (COD2) and the contents of calcium (C) and magnesium in filtrate B were analyzed and determined. Then, acid was added to filtrate B to adjust the pH value to below 4. After the pH value of filtrate B was adjusted, sufficient hydrogen peroxide was added to filtrate B. After the addition of hydrogen peroxide, filtrate B was subjected to a two-stage UV / Fenton treatment. After the two-stage UV / Fenton treatment of filtrate B was completed, alkali was added to filtrate B to adjust the pH value to above 9.

[0062] The formula for calculating the dosage of oxalic acid (H2C2O4·2H2O) is as follows:

[0063] a=r×c (3)

[0064] In formula (3), a is the amount of oxalic acid to be added per ton of water, in kg / t; c is the calcium content in the water, in g / L; and r is a coefficient, with a value between 3 and 20. It should be noted that the higher the value of r, the better the effect of calcium and magnesium removal. The higher the value of r, the higher the cost of secondary UV / Fenton treatment. Considering both cost and effect, the preferred value of r is between 9 and 15.

[0065] The formula for calculating the dosage of sodium oxalate (Na2C2O4) is as follows:

[0066] s=d×c (4)

[0067] In formula (4), s is the amount of sodium oxalate to be added per ton of water, in kg / t; c is the calcium content in the water, in g / L; d is a coefficient, and the value of d is between 3 and 20. It should be noted that the higher the value of d, the better the effect of calcium and magnesium removal. The higher the value of d, the higher the cost of secondary UV / Fenton treatment. Considering both cost and effect, the preferred value of d is between 10 and 20.

[0068] The formula for calculating the amount of hydrogen peroxide added to filtrate B is as follows:

[0069] V2=p2×c (5)

[0070] In formula (5), V2 is the volume of hydrogen peroxide to be added, and the mass percentage concentration of hydrogen peroxide is 27%-27.5%, with units of L / m³. 3Or L / t. In this patent, the volume unit of water, cubic meters, is considered equivalent to the weight unit, tons. The unit of c is g / L. p2 is a coefficient, and the value of p2 is between 3 and 20. Considering the effect and cost, the preferred value of p2 is between 5 and 10.

[0071] Next, UV / O3 treatment is carried out. The specific treatment process is as follows: the liquid obtained after removing calcium and other high-valence metal ions is treated with UV / O3. The solution after UV / O3 treatment is filtered again. The sludge filtered after UV / O3 treatment is dewatered and then processed separately. The water after UV / O3 treatment is dewatered and then mixed with the filtrate after UV / O3 treatment.

[0072] Finally, the filtrate obtained after UV / O3 treatment was analyzed and measured for various parameters. After measuring various parameters of the filtrate obtained after UV / O3 treatment in step S4, lithium precipitation was carried out according to the traditional or original lithium precipitation process for producing lithium compounds (lithium products).

[0073] After treatment using the aforementioned method for the resource recovery of lithium compound production wastewater in the lithium battery new energy field, the lithium extraction wastewater achieved complete degradation of EDTA in the saturated sodium sulfate solution, reducing the COD value by more than 80%. The final filtrate became lighter in color, changing from nearly opaque to transparent. No lithium was lost from the water after treatment. Impurities such as Fe and Mn in the wastewater were below the detection limits of the testing instruments, and the contents of other elements such as Ca and Mg were also reduced to some extent. No new sodium was added to the water during the treatment process. + and SO4 2- Other than these substances, the complete degradation of EDTA after treatment allows for subsequent lithium precipitation, enabling the resource recovery of lithium. Furthermore, the iron sludge formed from the ferrous sulfate catalyst added during the EDTA oxidation step after its first use is soluble in EDTA. Therefore, the catalyst in the UV / Fenton reaction can be recycled. This method avoids lithium loss due to iron sludge entrainment. At the same time, the reuse of the catalyst greatly reduces the amount of solid waste / hazardous waste generated during the treatment process.

[0074] Experimental example:

[0075] Jiangxi Xinyu High-tech Development Zone XX New Materials Co., Ltd. (002738) is a company that mainly produces lithium compounds for lithium batteries. It produces about 100 tons of EDTA-containing waste liquid per week after evaporation and concentration. The original disposal method was to discharge the condensate as wastewater after further evaporation of the concentrated liquid, and to dispose of the solid salt crystallized from the evaporation as hazardous waste.

[0076] The project's upgrade requirements include reducing COD by more than 80%, minimizing iron, calcium, magnesium, and other high-valence metal ions, and minimizing lithium loss after treatment.

[0077] The above-mentioned method for the resource utilization of lithium compound production waste liquid in the field of lithium battery new energy is adopted for modification. The treatment time of the first-stage UV / Fenton treatment is 3 hours, the treatment time of the second-stage UV / Fenton treatment is 2 hours, and the treatment time of UV / O3 is 0.5 hours.

[0078] 1. Pretreatment

[0079] A. The content of each substance in the EDTA mother liquor after lithium extraction was determined. After determining the content of each substance in the EDTA mother liquor after lithium extraction, sulfuric acid (mass content 98%) was added to adjust the pH value of the mother liquor to between 2 and 3.

[0080] B. After pH adjustment, let the mother liquor stand for 12 hours. After the standing time is over, take the supernatant for further processing.

[0081] C. After the mother liquor has been settling for the required time following pH adjustment, the lower sediment is dehydrated. The clear water from the lower sediment is collected together with the supernatant. The sludge from the lower sediment is treated as solid waste and its parameters, such as COD value (COD1), are measured.

[0082] 2. Oxidative removal of EDTA

[0083] A. Add ferrous sulfate catalyst to the clear liquid obtained in step 1. After the ferrous sulfate is added, add hydrogen peroxide to the clear liquid. After the hydrogen peroxide is added, the reaction solution is obtained.

[0084] B. The catalyst is added only during the first use in step 2, and ferrous sulfate is not added during the second and subsequent runs in step 2.

[0085] C. Perform a first-stage UV / Fenton (ultraviolet) treatment on the reaction solution; during the first-stage UV / Fenton treatment, acid is added to the reaction solution, and the amount of acid added is sufficient to maintain the pH value of the reaction solution at no higher than 4.

[0086] D. After the first-stage UV / Fenton treatment is completed, add caustic soda to the solution to adjust the pH value to between 5 and 6. After the pH value is adjusted, filter the reaction solution.

[0087] E. The filtrate obtained after filtering the reaction solution is further processed. The filtered sludge is dewatered and the resulting water is mixed with the filtrate (filtrate A). The dewatered sludge is returned to step 2 and reused as a catalyst.

[0088] 3. Removes calcium and other high-valence metal ions

[0089] A. Sodium oxalate is added to the filtrate A obtained in step 2. After the sodium oxalate is added, alkali is added to the filtrate to adjust the pH value of the filtrate to above 12.

[0090] B. After the pH value of the filtrate is adjusted, let it stand for more than 1 hour. After the standing time is reached, filter filtrate A. The sludge filtered from the filtrate is processed separately after pressure filtration. The clear liquid from the sludge pressure filtration is mixed with the filtrate filtered from filtrate A (filtrate B).

[0091] C. Analyze and determine the COD value (COD2) and the content of calcium, magnesium, etc. in filtrate B;

[0092] D. Add sulfuric acid to filtrate B to adjust the pH value to between 3 and 4. After the pH value of filtrate B is adjusted, add hydrogen peroxide to filtrate B. After the hydrogen peroxide is added, perform secondary UV / Fenton treatment on filtrate B.

[0093] E. After the secondary UV / Fenton treatment of filtrate B is completed, add caustic soda to filtrate B to adjust the pH value to between 9 and 10.

[0094] 4. UV / O3 treatment

[0095] A. After the pH value of filtrate B is adjusted, it is treated with UV / O3, and the solution after UV / O3 treatment is filtered again.

[0096] B. The dried sludge after dewatering from the sludge filtered after UV / O3 treatment is processed separately, and the purified water after dewatering the sludge after UV / O3 treatment is mixed with the filtrate after UV / O3 treatment.

[0097] 5. Lithium extraction from waste liquid

[0098] The filtrate obtained after UV / O3 treatment in step 4 was analyzed and measured for various parameters as shown in Tables 1 and 2:

[0099] Table 1 Content of each substance

[0100]

[0101] in:

[0102] 1 The content of each substance was determined according to the corresponding national standard method;

[0103] 2 N / A indicates that the value is below the instrument's detection limit.

[0104] Table 2 Various parameters during system operation

[0105]

[0106] After UV / O3 treatment in step 4, various parameters of the filtrate were measured. The lithium content was somewhat lost (due to the PO4 content in the original water). 3- (Due to the cause), the COD value decreased by approximately 89%, meeting the requirement that the COD value should decrease by no less than 80% after treatment. At the same time, after treatment, the iron and manganese content in the water was lower than the instrument detection limit, and the calcium and magnesium were also significantly reduced. After the treated waste liquid was re-added with sufficient EDTA, it can be precipitated for lithium according to the traditional process or the original lithium precipitation process for producing lithium compounds (lithium products).

[0107] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0108] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for the resource recovery of waste liquid from lithium compound production in the field of lithium battery new energy, characterized in that, Includes the following steps: S1: Collect the EDTA mother liquor after lithium extraction, determine the content of each substance, and perform pretreatment; S2: The liquid obtained after pretreatment in step S1 is subjected to EDTA oxidation removal; S3: Remove calcium and other high-valence metal ions from the liquid obtained by EDTA oxidation in step S2; S4: The liquid obtained in step S3 after removing calcium and other high-valence metal ions is treated with UV / O3. The solution after UV / O3 treatment is filtered again. The sludge filtered after UV / O3 treatment is dewatered and then processed separately. The water after UV / O3 treatment is dewatered and then mixed with the filtrate after UV / O3 treatment. S5: After the UV / O3 treatment in step S4, the filtrate is analyzed and measured for various parameters. After the UV / O3 treatment in step S4 is measured for various parameters, lithium precipitation is carried out according to the traditional or original lithium precipitation process for producing lithium compounds. The oxidative removal process of EDTA in step S2 is as follows: 1) Add ferrous sulfate catalyst to the clear liquid obtained in step S1. After the ferrous sulfate is added, add hydrogen peroxide to the clear liquid. After the hydrogen peroxide is added, a reaction solution is obtained. 2) The reaction solution is subjected to primary UV / Fenton treatment; During the first-stage UV / Fenton treatment, acid is added to the reaction solution to maintain the pH value of the reaction solution at no higher than 4. 3) After the first-stage UV / Fenton treatment is completed, alkali is added to the solution to adjust the pH value. After the alkali addition is completed to adjust the pH value, the pH value of the reaction solution is not higher than 6. After the pH value is adjusted, the reaction solution is filtered. 4) The filtrate obtained after filtering the reaction solution is further processed. The water obtained after dewatering the filtered sludge is mixed with the filtrate to obtain filtrate A. The dewatered sludge is returned to step 1) and reused as a catalyst. The process of removing calcium and other high-valence metal ions in step S3 is as follows: 1) Add oxalic acid or sodium oxalate to the filtrate A obtained in step S2. After the oxalic acid or sodium oxalate is added, add alkali to the filtrate to adjust the pH value of the filtrate to above 10. 2) After the pH value of the filtrate is adjusted, let it stand for more than 1 hour. After the standing time is reached, filter the filtrate A. The sludge filtered from the filtrate is further processed by pressure filtration. The clear liquid from the sludge pressure filtration is mixed with the filtrate filtered from filtrate A to obtain filtrate B. 3) Analyze and determine the COD value (COD2) and the contents of calcium and magnesium in the filtrate B; 4) Add acid to the filtrate B to adjust the pH value to below 4. After the pH value of the filtrate B is adjusted, add sufficient hydrogen peroxide to the filtrate B. After the hydrogen peroxide is added, perform a two-stage UV / Fenton treatment on the filtrate B. After the two-stage UV / Fenton treatment of the filtrate B is completed, add alkali to the filtrate B to adjust the pH value to above 9.

2. The method for resource recovery of lithium compound production waste liquid in the field of lithium battery new energy according to claim 1, characterized in that: The preprocessing procedure in step S1 is as follows: 1) After the content of various substances in the EDTA mother liquor after lithium extraction is determined, acid is added for acidification. The pH value of the acidified EDTA lithium extraction mother liquor is between 1 and 5. 2) After the acidification is completed, the acidified mother liquor is allowed to stand for 5-24 hours. After the standing time is completed, the supernatant is taken for subsequent processing. 3) After the acidified mother liquor has been left to stand for a certain period of time, the lower sediment is dehydrated. The clear water obtained from the dehydration of the lower sediment is collected together with the supernatant. The sludge obtained from the dehydration of the lower sediment is treated separately as solid waste. 4) Measure the COD value (COD1) of the clear liquid.

3. The method for resource recovery of lithium compound production waste liquid in the field of lithium battery new energy, as described in claim 2, is characterized in that: The preferred pH value for acidification is below 4.

4. The method for resource recovery of lithium compound production waste liquid in the field of lithium battery new energy, as described in claim 3, is characterized in that: The formula for calculating the dosage of ferrous sulfate (FeSO4·7H2O) is as follows: m = n × COD1 (1) In formula (1) m This refers to the amount of ferrous sulfate (FeSO4·7H2O) that needs to be added, in kg / m³. 3 Or kg / t, COD1 value is the parameter of the clarified liquid described in step S1, and the unit is g / L. n It is a coefficient. n The value range is between 0.1 and 10; The formula for calculating the amount of hydrogen peroxide added is as follows: V1 = p 1 × COD1 (2) In formula (2), V1 is the volume of hydrogen peroxide to be added, and the mass percentage concentration of the hydrogen peroxide is 27%-27.5%, with units of L / m³. 3 The meaning or unit of L / t COD1 value is the same as in formula (1). p 1 is the coefficient. p The value of 1 is between 10 and 40.

5. A method for resource recovery of lithium compound production waste liquid in the field of lithium battery new energy, as described in claim 4, characterized in that: The n The preferred value for this value is between 0.1 and 1. p The preferred value for 1 is between 20 and 30.

6. A method for resource recovery of lithium compound production waste liquid in the field of lithium battery new energy, as described in claim 5, characterized in that: The formula for calculating the dosage of oxalic acid (H₂C₂O₄·2H₂O) is as follows: a = r × c （3） In formula (3) a This refers to the amount of oxalic acid that needs to be added per ton of water, expressed in kg / t. c It refers to the calcium content in the water, expressed in g / L. r It is a coefficient. r The value range is between 3 and 20; The formula for calculating the dosage of sodium oxalate (Na₂C₂O₄) is as follows: s = d × c （4） In formula (4) s This is the amount of sodium oxalate that needs to be added per ton of water, expressed in kg / t. c It refers to the calcium content in the water, expressed in g / L. d It is a coefficient. d The value range is between 3 and 20; The formula for calculating the amount of hydrogen peroxide added to filtrate B is as follows: V2 = p 2 × c （5） In formula (5), V2 is the volume of hydrogen peroxide to be added, and the mass percentage concentration of the hydrogen peroxide is 27%-27.5%, with units of L / m³. 3 Or L / t, c The unit is g / L. p 2 is the coefficient. p The value of 2 is between 3 and 20.

7. A method for resource recovery of lithium compound production waste liquid in the field of lithium battery new energy, as described in claim 6, characterized in that: The r The preferred value for this value is between 9 and 15. d The preferred value for this value is between 10 and 20. p The preferred value for 2 is between 5 and 10.

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