Method for recycling battery-grade nickel sulfate from nickel-containing industrial waste

Abstract

The invention relates to a method for recycling battery-grade nickel sulfate from nickel-containing industrial waste, and belongs to the technical field of nonferrous metallurgy. The method comprises the steps that the nickel-containing industrial waste is subjected to water leaching treatment, and nickel-containing leachate is obtained; carrying out gradient pH regulation and control on the nickel-containing leaching solution by adopting calcium carbonate to obtain a purified solution; carrying out first countercurrent extraction on the purified liquid by adopting an organic phase I with the D2EHPA concentration of 0.1-0.3 mol / L; carrying out second counter-current extraction on the raffinate I obtained in the step (3) by adopting an organic phase II with the CYANEX 272 concentration of 0.05-0.2 mol / L; the raffinate II obtained in the step (4) is subjected to adsorption and oil removal through activated carbon and then is subjected to evaporative crystallization, and nickel sulfate crystals and crystallization mother liquor are obtained. The method is high in nickel recovery rate, the purity of nickel sulfate is larger than or equal to 99.9%, and the sodium content is low.

Description

Technical Field

[0001] The present invention relates to a method for recovering battery-grade nickel sulfate from nickel-containing industrial waste, belonging to the technical field of non-ferrous metal metallurgy. Background Art

[0003] Nickel-smelting yellow slag, as a typical by-product in the pyrometallurgical process, contains 20-40% nickel resources (existing in the form of NiO).

[0005] The traditional process adopts the acid leaching process. Although the mainstream sulfuric acid leaching method can achieve a nickel leaching rate of more than 90%, it produces a large amount of heavy metal-containing acidic wastewater (pH < 1.5, containing Fe 3+ 5-10 g / L, Al 3+ 2-5 g / L). Taking a production line with an annual output of 10,000 tons of nickel sulfate as an example, 300-500 m of acidic wastewater needs to be treated daily. The neutralization treatment consumes 4-6 tons of limestone per day and produces 15-20 tons of gypsum slag per day. This not only makes the wastewater treatment cost as high as 80-120 yuan per ton, but also there is a risk of heavy metal ions (such as Cd 3 in the gypsum slag 2+ 50-200 ppm, As 3+ 20-100 ppm) leaching. Chinese Patent (Publication No. CN113913606A) discloses the "two-stage countercurrent acid leaching" process, although the nickel leaching rate is increased to 95%, but the acid consumption increases by 30%, and the concentration of the end waste acid is as high as 2 mol / L, further increasing the environmental protection pressure.

[0006] The neutralization precipitation-sulfide precipitation series process is widely used for removing metal impurities. However, nickel coprecipitation will occur during the neutralization process. In the iron and aluminum precipitation window with a pH of 3.5-4.5, the nickel hydroxy complex coprecipitates with Fe(OH)3, resulting in a nickel loss of 3-8%. Experimental data shows that when the Fe 3+ concentration > 2 g / L, the amount of nickel coprecipitation increases exponentially with the increase of pH. When pH = 4.0, the nickel loss reaches 5.2%; at the same time, the selectivity of sulfide precipitation is poor: the addition amount of Na2S needs to be accurately controlled to 105-110% of the theoretical value. Excess will cause the formation of NiS colloid (particle size < 1 μm), resulting in difficult filtration; insufficient addition amount will cause Cu 2+ residue > 100 ppm. Chinese Patent (Publication No. CN119662982A) uses the sodium sulfide gradient addition method, although the copper removal rate is increased to 99.5%, but the nickel loss still reaches 2.1%.

[0007] Furthermore, the existing process generally uses NaOH to adjust the pH, resulting in the accumulation of Na + concentration in the solution to 8-15 g / L. In the evaporation crystallization stage, Na +Competing with Ni 2+ for the crystallization sites, two prominent problems are caused: First, the crystal morphology deteriorates: when the Na + concentration > 5 g / L, the nickel sulfate crystal transforms from the monoclinic system to the amorphous form, the specific surface area increases by 3 - 5 times, and the hygroscopicity is significantly enhanced; second, the product purity decreases.

[0008] Moreover, impurities such as calcium, magnesium, and cobalt have a significant impact on the battery performance, but it is difficult for the existing technologies to meet the requirements of deep removal simultaneously.

[0009] In the existing technologies, the three major technical problems of nickel loss, sodium pollution, and deep removal of impurities still cannot be solved simultaneously. Therefore, it is of great significance to develop an efficient, low-cost, and environmentally friendly yellow slag treatment process. Summary of the Invention

[0010] Aiming at the problems existing in the above-mentioned existing technologies, one of the purposes of the present invention is to provide a method for recovering battery-grade nickel sulfate from nickel-containing industrial waste. By using the method of the present invention, the nickel recovery rate is high, the purity of nickel sulfate is ≥99.9%, and the sodium content is low.

[0011] To achieve the above purpose, the first aspect of the present invention is to provide a method for recovering battery-grade nickel sulfate from nickel-containing industrial waste, and the method includes:

[0012] (1) Performing water leaching treatment on the nickel-containing industrial waste to obtain a nickel-containing leachate;

[0013] (2) Using calcium carbonate to perform gradient pH regulation on the nickel-containing leachate: first adjusting the pH value of the nickel-containing leachate to 1.2 - 1.8 to remove Fe 3+ , and then continuing to adjust the pH value of the solution to 2.7 - 3.5 to remove Al 3+ , and finally adjusting the pH value of the solution to 4.2 - 4.7 to remove Cr 3+ , and obtaining a purified solution after solid-liquid separation;

[0014] (3) Performing the first countercurrent extraction on the purified solution with an organic phase I with a D2EHPA concentration of 0.1 - 0.3 mol / L; and the pH of the first countercurrent extraction is 2.5 - 4;

[0015] (4) Performing the second countercurrent extraction on the raffinate I obtained in step (3) with an organic phase II with a CYANEX 272 concentration of 0.05 - 0.2 mol / L; and the pH of the second countercurrent extraction is 5.5 - 6.5;

[0016] (5) After using activated carbon to adsorb and remove oil from the raffinate II obtained in step (4), then performing evaporation crystallization to obtain nickel sulfate crystals and a crystallization mother liquor.

[0017] The innovative "water immersion pretreatment - iron, aluminum, chromium co - precipitation - double extraction and purification - deep adsorption - temperature - controlled crystallization" full - process system is adopted in the present invention to achieve the efficient preparation of battery - grade nickel sulfate. The water immersion pretreatment adopted in the present invention can preferentially remove soluble salts and preliminarily separate heavy metals, reduce acid consumption, optimize the reactivity of materials, and lay a foundation for efficient separation in subsequent processes. At the same time, the pH of the leaching solution is precisely regulated in gradients to precipitate metals step by step. Based on the solubility product differences of metal hydroxides, the pH is selectively regulated to achieve high - purity step - by - step recovery, taking into account resource utilization and precise impurity separation, and realizing high - purity recovery. Step - by - step precipitation avoids competitive adsorption of multiple metals, reduces the dosage of co - precipitants, and improves the precipitation efficiency of target metals. Moreover, the single - metal precipitates of iron, aluminum, chromium, etc. recovered step by step can be directly reused as raw materials (such as iron red pigments, aluminum salt coagulants).

[0018] Furthermore, aiming at the problem of deep removal of impurities such as copper, cobalt, and magnesium, the present invention breaks through the efficiency bottleneck of a single extractant and constructs a synergistic extraction system of D2EHPA and CYANEX 272 to achieve hierarchical targeted removal of heavy metals and alkaline earth metals. D2EHPA can remove metal ion impurities such as Ca, Cd, Cu, and Mn under low - pH (2.5 - 4) conditions. And CYANEX 272 can preferentially extract Co 2+ and Mg 2+ etc. through chelation at high - pH (5.5 - 6.5), and a small amount of impurities such as Cu, Mn, and Ca remaining in the D2EHPA extraction section can be basically completely removed in the CYANEX 272 extraction section. After two - stage extraction, a high - purity nickel sulfate raffinate for recrystallization can be prepared.

[0019] As a preferred solution, the crystallization mother liquor is returned to step (1) for recycling.

[0020] As a preferred solution, the number of stages of the first counter - current extraction is 2 - 4, and the number of extraction sections in each stage is 3 - 6.

[0021] As a preferred solution, the number of stages of the second counter - current extraction is 2 - 4, and the number of extraction sections in each stage is 3 - 6.

[0022] As a preferred solution, the conditions of the water immersion treatment include: the solid - liquid ratio is 1.2 - 3 g / L, the temperature is 80 - 100 °C, and the time is 0.5 - 3 h.

[0023] As a more preferred solution, the water immersion treatment is carried out under stirring conditions, and the stirring rate is 350 - 450 r / min.

[0024] As a preferred embodiment, the nickel-containing industrial waste is first subjected to sulfation roasting pretreatment and then to water leaching treatment. The sulfation roasting pretreatment can convert the target metal nickel into highly water-soluble sulfate, while impurities such as iron and arsenic are converted into stable insoluble oxides Fe2O3 and As2O5. Based on the solubility difference between sulfates and oxides, water leaching treatment is used to selectively leach the target metal, breaking through the dependence on strong acids in traditional acid leaching. During the leaching process, the undissolved SiO2 porous skeleton forms a composite filter layer with Fe2O3, dynamically adsorbing residual impurities (Fe 3+ interception rate > 95%), and can also achieve the impurity barrier effect of "filtering slag with slag", reducing the risk of co-dissolution from the source.

[0025] As a preferred embodiment, the conditions of the sulfation roasting pretreatment include: the temperature is 380 - 420 °C, and the time is 1.5 - 2.5 h.

[0026] As a preferred embodiment, the sulfation roasting pretreatment is carried out in a rotary kiln, the concentration of sulfuric acid is not less than 95 wt%, and the mass ratio of sulfuric acid to the nickel-containing industrial waste is 1:0.8 - 1.2.

[0027] As a preferred embodiment, the D 50 of calcium carbonate is 50 - 85 μm. The inventor found that appropriate particle size can ensure solubility and reaction rate. If the particle size is too large, the dissolution rate is too slow, the reaction is incomplete, and it is easy to leave unreacted solid particles. If the particle size is too small, the particles are prone to agglomeration and poor dispersibility, resulting in local over-reaction or blocking of the filter membrane, increasing the operation difficulty.

[0028] As a preferred embodiment, when performing gradient pH regulation, an online pH-ORP control system is used to control the pH value of the system.

[0029] As a preferred embodiment, the extraction phase ratio O / A of the first countercurrent extraction is 1.5 - 5:1.

[0030] As a preferred embodiment, the extraction phase ratio O / A of the second countercurrent extraction is 1 - 3:1.

[0031] As a preferred embodiment, the solid-liquid ratio of the activated carbon to the raffinate II is 0.5 - 15 g / L, and the oil adsorption removal time is 20 - 40 min.

[0032] As a preferred embodiment, the activated carbon is coconut shell activated carbon.

[0033] As a preferred embodiment, the organic phase I is first subjected to nickel saponification treatment and then to the first countercurrent extraction, and the saponification rate of the organic phase I is 30 - 80%. Using the nickel ion pre-loading saponification technology can eliminate sodium pollution.

[0034] As a preferred embodiment, the organic phase II is first subjected to nickel saponification treatment and then subjected to a second countercurrent extraction. The saponification rate of the organic phase II is 30-80%. The nickel ion preloading saponification technology can eliminate sodium pollution.

[0035] It should be noted that the present invention has no special requirements for the operation of nickel saponification treatment, and those known in the art can be used. As a preferred embodiment, the organic phase I or the organic phase II is first pre-contacted with a nickel sulfate solution to obtain the nickel-saponified organic phase I and the nickel-saponified organic phase II respectively. The nickel sulfate solution and the organic phase react through an ion exchange reaction to generate NiA - 2, A - 2 represents a deprotonated acidic phosphorus extractant.

[0036] As a preferred embodiment, the method of evaporation crystallization specifically includes: first heating the raffinate II after oil adsorption removal to 60-80 °C, and then cooling it to 10-30 °C at a cooling rate of 0.1-5 °C / min.

[0037] As a preferred embodiment, the nickel-containing industrial waste is nickel smelting yellow slag.

[0038] In the present invention, D2EHPA represents bis(2-ethylhexyl)phosphoric acid ester, and CYANEX 272 represents bis(2,4,4-trimethylpentyl)phosphonic acid.

[0039] Compared with the prior art, the present invention has at least the following advantages:

[0040] (1) The crystallization mother liquor obtained after crystallization in the present invention can be returned to the leaching process, reducing the consumption of fresh water and also reducing the loss of nickel.

[0041] (2) The stripping solutions containing copper, cobalt, and manganese generated by D2EHPA and CYANEX 272 are concentrated and then used for further extraction of valuable metals, improving the resource utilization rate.

[0042] (3) The method of the present invention has a high nickel recovery rate, the purity of nickel sulfate is ≥99.9%, and the sodium content is low. Description of the Drawings

[0043] Figure 1 is the process flow chart of Example 1 of the present invention;

[0044] Figure 2 is the XRF analysis chart of the nickel smelting yellow slag after drying;

[0045] Figure 3 is the XRD analysis chart of the nickel smelting yellow slag after drying. Detailed Embodiments

[0046] The endpoints and any values within the ranges disclosed in this document are not limited to the exact ranges or values. These ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the values between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this document.

[0047] The following further illustrates the present invention in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments. All other embodiments obtained by those skilled in the art without creative efforts still fall within the protection scope of the present invention.

[0048] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0049] Nickel-smelting yellow slag: After drying the nickel-smelting yellow slag (water content 6.56%), three-dimensional analysis is carried out. Combining the Figure 2 XRF analysis chart and Figure 3 XRD analysis chart of, it can be seen that the characteristic peaks (2θ = 20.7°, 24.3°, 29.6°, 33.1°, 38.5°) of nickel sulfate monohydrate (NiSO4·H2O) in the raw material match the standard card (PDF#01-077-2306). The sharp peak shape (full width at half maximum FWHM = 0.12°) indicates that the crystal development is complete. It should be noted that there is a weak miscellaneous peak at 2θ = 43.2° (intensity ratio 3.7%). After comparative analysis, it is the characteristic peak of α-FeOOH (goethite, PDF#00-029-0713), which corroborates the iron content of 1.387% detected by XRF. The background signal of the XRD pattern is stable (baseline intensity < 500 a.u.), confirming that the content of amorphous substances in the raw material is less than 2%.

[0050] Example 1

[0051] The water content of the nickel-smelting yellow slag is 15.61%.

[0052] (1) Water immersion pretreatment

[0053] The nickel-smelting yellow slag is subjected to sulfation roasting pretreatment in a rotary kiln to obtain intermediate I; the temperature of the sulfation roasting pretreatment is 400 °C, the time is 2 h, the sulfuric acid is concentrated sulfuric acid, and the mass ratio of the amount of sulfuric acid to the nickel-smelting yellow slag is 1:1;

[0054] The intermediate I was added to ultrapure water at a solid-liquid ratio of 1.2 g / L and dynamically leached at 90 °C for 2 hours (stirring rate was 400 r / min) to obtain a nickel-containing leachate. The composition of the leachate is shown in Table 1. It can be seen from Table 1 that the impurity concentrations of copper, iron, etc. are as high as 13713.72 ppm and 4118.60 ppm respectively, forming significant purification obstacles. After solid-liquid separation was achieved through a vacuum filtration system (membrane pore size 5 μm), the weight loss rate of the filter residue reached 62.3% after drying at 105 °C, confirming that the water leaching process effectively dissociated the soluble nickel. It should be noted that when the pH at the leaching end point was 0.45, impurities such as aluminum and iron still existed in ionic form, which created favorable conditions for subsequent fractional precipitation.

[0055] Table 1 Composition of the raw material leachate

[0056]

[0057] (2) Gradient pH regulation was carried out using calcium carbonate powder with D50 = 75 μm: First, the pH value of the nickel-containing leachate was adjusted to 1.5, and Fe was preferentially precipitated 3+ , and the solubility product of its hydroxide (Ksp = 2.79×10 -39 ) drove the iron concentration to drop sharply from 4118.60 ppm to 8.28 ppm (removal rate 99.8%); the pH value was adjusted to 3.0, and Al 3+ formed Al(OH)3 colloid through charge neutralization, with a removal rate of 99.30%; then the pH value was continuously adjusted to 4.5 to deeply remove the residual Cr 3+ , reducing its concentration from 195.40 ppm to 1.82 ppm. This process innovatively limited the calcium increment to 6.01% through particle size control (calcium carbonate powder ≤ 75 μm). After solid-liquid separation, a purified liquid was obtained, and the nickel loss rate in the purified liquid (Table 2) was only 0.26%.

[0058] Table 2 Composition of the purified liquid

[0059]

[0060] (3) The first countercurrent extraction

[0061] (3-1) The concentration of D2EHPA was 0.2 mol / L, and the diluent was sulfonated kerosene. The organic phase was saponified with a nickel sulfate solution, and the nickel saponification rate was 80%;

[0062] (3-2) The above organic phase was used to carry out three-stage countercurrent extraction on the purified liquid under the conditions of O / A = 2:1 and equilibrium pH = 3.5 to obtain raffinate I. The extraction results of raffinate I are shown in Table 3, and the concentration units in the table are all ppm.

[0063] In the table, R1-1 represents extraction in the 1st stage and 1st section, R1-2 represents extraction in the 1st stage and 2nd section, R2-1 represents extraction in the 2nd stage and 1st section, and so on. The expressions in the table for the remaining extraction sections are the same.

[0064] Table 3

[0065]

[0066] As shown in the data of Table 3, the removal of copper shows a significant stage effect: after extraction in the 1st stage and 1st section, the concentration drops from 13713.72 ppm to 496.91 ppm (removal rate 96.4%); after extraction in the 1st stage and 2nd section, the concentration is 38.73 ppm (removal rate 99.7%); after extraction in the 1st stage and 4th section, the concentration is only 7.92 ppm (total removal rate 99.9%). After extraction in the 1st stage and 2nd section, the calcium removal rate is high, from 945.47 ppm → 7.99 ppm (removal rate 99.15%), and in the last two deep purification stages of the 1st stage (8.06 ppm → 2.45 ppm). The nickel loss rate gradually increases in the 4th section of the 1st stage, which is closely related to the saturated loading amount of nickel in the organic phase (28.6 g / L), and the nickel loss rate is 10%.

[0067] (4) Second countercurrent extraction

[0068] (4-1) The concentration of CYANEX 272 is 0.2 mol / L, the diluent is sulfonated kerosene, and the organic phase is saponified with a nickel sulfate solution, with a nickel saponification rate of 80%;

[0069] (4-2) The above organic phase is used to perform three-stage countercurrent extraction on the raffinate I obtained in step (3) under the conditions of O / A = 2:1 and equilibrium pH = 6.07. The extraction results of raffinate II are shown in Table 4, and the concentration units in the table are all ppm.

[0070] Table 4

[0071]

[0072] As shown in Table 4, after extraction in the 1st stage and 4th section, the cobalt concentration drops from 36.10 ppm to 14.57 ppm, and its distribution ratio (D Co = 0.08) is much lower than that of nickel (D Ni = 12.6), and the separation factor β Ni / Co reaches 157.5. The migration behavior of sodium ions reveals the interfacial mass transfer characteristics: in the initial stage, the sodium concentration rises from 417.13 ppm to 489.65 ppm, which is due to the water phase volume shrinkage effect; in the subsequent stage, through the competitive extraction effect (crowding effect), the sodium is finally stably controlled at 317.13 ppm. And the nickel loss rate is within 4%.

[0073] After measurement, the total organic carbon value in the raffinate II after R3-2 level extraction is 856 ppm.

[0074] (5) Degreasing and crystallization process

[0075] The total organic carbon value of the raffinate II obtained in step (4) was reduced from 856 ppm to 3.2 ppm after adsorption degreasing with activated carbon (dynamic adsorption at 50 °C for 30 min, activated carbon dosage of 10 g / L), and then vacuum evaporation crystallization was carried out. First, the raffinate II after adsorption degreasing was heated to 70 °C, and by controlling the supersaturation to 1.3 and the cooling rate (0.5 °C / min), monoclinic nickel sulfate with D50 = 38 μm was obtained. The purity of nickel sulfate ≥ 99.9%, reaching the excellent grade standard.

[0076] The standard comparison of the evaporation crystallization product is shown in Table 5. The concentration units not specifically stated in the table are all ppm.

[0077] Activated carbon: 200-mesh coconut shell activated carbon (specific surface area 1120 m 2 / g), with its mesoporous structure of 2 - 50 nm.

[0078] Table 5

[0079] Element Ca Co Cu Mg Na Ni Raffinate II 0.17 1.47 0.31 3.95 317.13 67609.37 Product 0.02 0.06 0.07 0.03 16.75 /

[0080] To sum up, after being processed by the complete set of processes, the final nickel sulfate product has achieved a major breakthrough in key indicators: the calcium content is 0.02 ppm, the cobalt content is 0.06 ppm, and the copper content is 0.07 ppm, all of which are better than the excellent grade standard of HG / T 2824-2009.

[0081] Example 2

[0082] The same leaching raw materials as those in Example 1 were selected in this example.

[0083] The nickel-smelting yellow slag was subjected to sulfuric acid roasting pretreatment in a rotary kiln to obtain intermediate I; the temperature of the sulfuric acid roasting pretreatment was 400 °C, the time was 2 h, the sulfuric acid was concentrated sulfuric acid, and the mass ratio of sulfuric acid to nickel-smelting yellow slag was 1:1;

[0084] The intermediate I was added to ultrapure water at a solid-liquid ratio of 1.3 g / L and dynamically leached at 95 °C for 2.5 hours (stirring rate of 350 r / min) to obtain a nickel-containing leaching solution. The composition of the leaching solution is shown in Table 6.

[0085] Table 6 Composition of the raw material leaching solution

[0086]

[0087] (2) Gradient pH regulation is carried out using calcium carbonate powder with D50 = 75 μm: First, the pH value of the nickel-containing leaching solution is adjusted to 1.6 to preferentially precipitate Fe 3+ , and the solubility product constant of its hydroxide (Ksp = 2.79×10 -39 ) ensures a removal efficiency of 99.98%; the pH value is adjusted to 3.5, and 98.4% of Al is removed simultaneously through charge neutralization 3+ ; then the pH value is further adjusted to 4.3 to deeply purify the residual Cr 3+ , reducing its concentration from 259.63 ppm to below the detection limit. After stepwise precipitation treatment, as shown in Table 7, the total concentration of the three key impurities, iron, aluminum, and chromium, in the solution is reduced from 4654.77 ppm to 7.14 ppm, successfully reducing the impurity load by three orders of magnitude and creating favorable conditions for subsequent extraction.

[0088] Table 7 Composition of the purified solution

[0089]

[0090] (3) First countercurrent extraction

[0091] (3-1) The concentration of D2EHPA is 0.2 mol / L, and the diluent is sulfonated kerosene. The organic phase is saponified with a nickel sulfate solution, and the nickel saponification rate is 80%;

[0092] (3-2) The purified solution is subjected to three-stage countercurrent extraction with the above organic phase under the conditions of O / A = 1.8:1 and equilibrium pH = 3.8 to obtain raffinate I. The extraction results of raffinate I are shown in Table 8, and the concentration units in the table are all ppm.

[0093] Table 8

[0094]

[0095] From the countercurrent extraction data in Table 8, it can be seen that the copper concentration shows an exponential decline trend: it drops sharply from 7134.8 ppm to 465.27 ppm (removal rate 93.5%) after the first-stage first-stage extraction, the concentration is 43.8 ppm (removal rate 99.4%) after the first-stage second-stage extraction, and drops to 2.18 ppm (total removal rate 99.97%) after the third-stage second-stage extraction. The nickel loss rate is within 4%.

[0096] (4) Second countercurrent extraction

[0097] (4-1) The concentration of CYANEX 272 is 0.2 mol / L, and the diluent is sulfonated kerosene. The organic phase is saponified with a nickel sulfate solution, and the nickel saponification rate is 80%;

[0098] (4-2) The raffinate I obtained in step (3) is subjected to three-stage countercurrent extraction with the above-mentioned organic phase under the conditions of O / A = 2.5:1 and equilibrium pH = 6.4. The extraction results of the raffinate II are shown in Table 9, and the concentration units in the table are all ppm.

[0099] Table 9

[0100]

[0101] As shown in Table 9, during the extraction process, the removal of cobalt exhibits typical segmented characteristics: from the extraction in the first stage and the first segment to the extraction in the first stage and the third segment is the rapid removal stage (74.06 ppm → 11.54 ppm, removal rate 84.4%), the extraction in the first stage and the fourth segment and the extraction in the second stage and the second segment are the steady decline stages (9.97 ppm → 3.91 ppm), the extraction in the second stage and the third segment and the extraction in the third stage and the second segment are the deep purification stages (2.74 ppm → 0.09 ppm), and the cobalt removal rate is 99.88%. The loss rate of nickel is 5.8%.

[0102] It is measured that the total organic carbon value in the raffinate II after R3-2 stage extraction is 918 ppm.

[0103] (5) Degreasing and crystallization process

[0104] The raffinate II obtained in step (4) is subjected to oil adsorption by activated carbon (dynamic adsorption at 50 °C for 30 min, activated carbon dosage of 10 g / L), and the total organic carbon value is reduced from 918 ppm to 3.91 ppm. In the vacuum evaporation crystallization process, by controlling the supersaturation degree to 1.5 and the cooling rate (2 °C / min), nickel sulfate with a monoclinic crystal form and D50 = 45 μm is obtained. The purity of nickel sulfate ≥ 99.9%.

[0105] The standard comparison of the evaporation crystallization product is shown in Table 10, and the concentration units not specifically stated in the table are all ppm.

[0106] Activated carbon: 200-mesh coconut shell activated carbon (specific surface area 1120 m 2 / g), and its mesoporous structure is 2 - 50 nm.

[0107] Table 10

[0108] Element Ca Co Cu Mg Na Ni Raffinate II 0.08 0.09 0.07 0.02 218.34 77629.53 Product 0.03 0.08 0.05 0.02 18.75 /

[0109] To sum up, after being processed by the complete set of processes, the final nickel sulfate product has achieved a major breakthrough in key indicators: the calcium content is 0.03 ppm, the cobalt content is 0.08 ppm, and the copper content is 0.05 ppm, all of which are better than the first-class standard of HG / T 2824-2009.

[0110] 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 technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including any other suitable combination of technical features. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for recovering battery-grade nickel sulfate from nickel-containing industrial waste, characterized in that: (1) The nickel-containing industrial waste is subjected to water leaching treatment to obtain a nickel-containing leaching solution; (2) Gradient pH regulation of the nickel-containing leaching solution is carried out using calcium carbonate: First, the pH value of the nickel-containing leaching solution is adjusted to 1.2 - 1.8 to remove Fe 3+ , then the pH value of the solution is continuously adjusted to 2.7 - 3.5 to remove Al 3+ , and finally the pH value of the solution is adjusted to 4.2 - 4.7 to remove Cr 3+ . After solid-liquid separation, a purified solution is obtained; (3) The purified solution is subjected to a first countercurrent extraction with an organic phase I having a D2EHPA concentration of 0.1-0.3 mol / L; and the pH of the first countercurrent extraction is 2.5-4; (4) The raffinate I obtained in step (3) is subjected to a second countercurrent extraction with an organic phase II having a CYANEX 272 concentration of 0.05-0.2 mol / L; and the pH of the second countercurrent extraction is 5.5-6.5; (5) After the raffinate II obtained in step (4) is adsorbed and degreased with activated carbon, it is then evaporated and crystallized to obtain nickel sulfate crystals and a crystallization mother liquor.

2. The method for recovering battery-grade nickel sulfate from nickel-containing industrial waste according to claim 1, wherein: The conditions of the water leaching treatment include: a solid-liquid ratio of 1.2-3 g / L, a temperature of 80-100 °C, and a time of 0.5-3 h.

3. The method for recovering battery-grade nickel sulfate from nickel-containing industrial waste according to claim 1 or 2, characterized in that: The D of the calcium carbonate 50 is 50 to 85 μm.

4. A method for recovering battery-grade nickel sulfate from nickel-containing industrial waste according to claim 1 or 2, characterized in that: The extraction phase ratio O / A of the first countercurrent extraction is 1.5-5:

1.

5. A method for recovering battery-grade nickel sulfate from nickel-containing industrial waste according to claim 1 or 2, characterized in that: The extraction phase ratio O / A of the second countercurrent extraction is 1-3:

1.

6. A method for recovering battery-grade nickel sulfate from nickel-containing industrial waste according to claim 1 or 2, characterized in that: The solid-liquid ratio of the activated carbon to the raffinate II is 0.5-15 g / L, and the adsorption and degreasing time is 20-40 min.

7. A method for recovering battery-grade nickel sulfate from nickel-containing industrial waste according to claim 1 or 2, characterized in that: The organic phase I is first subjected to nickel saponification treatment and then to the first countercurrent extraction, and the saponification rate of the organic phase I is 30-80%.

8. A method for recovering battery-grade nickel sulfate from nickel-containing industrial waste according to claim 1 or 2, characterized in that: The organic phase II is first subjected to nickel saponification treatment and then to the second countercurrent extraction, and the saponification rate of the organic phase II is 30-80%.

9. A method for recovering battery-grade nickel sulfate from nickel-containing industrial waste according to claim 1 or 2, characterized in that: The method of evaporation and crystallization specifically includes: first heating the raffinate II after adsorption and degreasing to 60-80 °C, and then cooling it to 10-30 °C at a cooling rate of 0.1-5 °C / min.

10. A method for recovering battery-grade nickel sulfate from nickel-containing industrial waste according to claim 1 or 2, characterized in that: The nickel-containing industrial waste is nickel smelting yellow slag.

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