A method for preparing nickel salt by using nickel-magnesium waste liquid

Abstract

The application relates to a method for preparing a nickel salt by using a nickel-magnesium-containing waste solution, and the method specifically comprises the following steps: (1) mixing an extractant and a diluent to form an organic phase with a certain concentration; (2) using liquid alkali to saponify the organic phase to obtain a saponified organic phase; (3) using the saponified organic phase obtained in the step (2) to extract a nickel-magnesium-containing solution to obtain a loaded organic phase and a raffinate aqueous phase; and (4) washing and stripping the loaded organic phase to obtain a regenerated organic phase and a high-purity nickel solution. In the step (1), the extractant is a carboxylic acid extractant BC194, the carboxylic acid extractant BC194 has good ion selectivity, a high nickel-magnesium separation coefficient, low water solubility and is environment-friendly. The method adopted by the application can effectively separate nickel and magnesium in the nickel-magnesium-containing waste solution, and has the advantages of a short process, low acid consumption, small pollution and high economic benefits.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal hydrometallurgy and resource recycling, and specifically relates to a method for preparing nickel salts using nickel-magnesium-containing waste liquid. Background Technology

[0002] Nickel resources are mainly found in laterite nickel ore and sulfide nickel ore, with laterite nickel ore accounting for about 55%. Existing technologies inevitably encounter the influence of magnesium ions in the extraction process of high-purity nickel metal, whether it is laterite nickel ore, sulfide nickel ore, or nickel metal recovery process in batteries. Developing a new process that can achieve efficient one-step separation of nickel and magnesium can significantly improve economic benefits, reduce production costs, and reduce resource waste and environmental pollution.

[0003] Existing hydrometallurgical technology can effectively separate nickel and magnesium, but the separation process often requires the magnesium to be extracted first, and then the nickel to be enriched in order to obtain pure nickel liquid. This process consumes a lot of acid and alkali and is very long, which is increasingly incompatible with the requirements of industry development.

[0004] CN102814058B discloses a method for separating, enriching, and purifying nickel and magnesium using adsorbent materials. The method involves adjusting the pH of a solution containing nickel and magnesium ions to 1.0–5.5 to obtain an acid leaching solution. This acid leaching solution is then mixed with the adsorbed heavy metal adsorbent material. The heavy metal adsorbent material adsorbs nickel ions from the acid leaching solution, while magnesium ions remain in the solution. The heavy metal adsorbent material is then washed with a 5–30% sulfuric acid solution to perform desorption, yielding a nickel-containing desorption solution and the desorbed heavy metal adsorbent material. Electrowinning with the nickel-containing desorption solution yields nickel metal or nickel metal powder. The desorbed heavy metal adsorbent material can be repeatedly recycled. This method has the advantages of convenient operation and simple equipment. However, the production process of the heavy metal adsorbent material is complex. After multiple uses, the capacity and adsorption efficiency of the heavy metal adsorbent material decrease, and it is susceptible to the influence of insoluble substances and impurities in the system, requiring replacement of the heavy metal adsorbent material and further processing after replacement.

[0005] CN101824550B discloses a high-purity nickel extraction and purification process. In this process, hydrogen peroxide is added to a nickel sulfate solution as an oxidant, and after complete reaction, sodium carbonate is added to form a complex precipitate to remove iron. Co, Mn, Ca, and Zn are removed using countercurrent extraction with P204. Magnesium is then extracted from the solution using P507. The remaining organic phase is then back-extracted with anolyte or dilute sulfuric acid to obtain electronic-grade nickel sulfate from the aqueous phase. This purification process first uses P507 to extract magnesium from the nickel-magnesium ion-containing solution after removing Co, Mn, Ca, Zn, and Fe, followed by enrichment and back-extraction to obtain electronic-grade nickel sulfate. However, this process requires two steps for nickel-magnesium separation, consuming large amounts of acid and alkali, resulting in low economic efficiency.

[0006] Therefore, developing a nickel-magnesium separation system that can preferentially extract nickel before extracting calcium and magnesium ions, reduce the cost of calcium and magnesium extraction, lower acid and alkali consumption, and achieve high extraction efficiency, in order to improve the separation efficiency and recovery rate of nickel and magnesium, has become a key research focus in this field. Summary of the Invention

[0007] In view of the problems existing in the existing process, the purpose of the present invention is to provide a method for preparing nickel salts using nickel-magnesium waste liquid. The carboxylic acid extractant BC194 used in the present invention can extract nickel before extracting calcium and magnesium ions, which has a good separation effect on nickel and magnesium, thereby achieving the goal of one-step purification of nickel. Moreover, the carboxylic acid extractant BC194 has low water solubility, is environmentally friendly, has low loss in actual use, and has high stability; it has a high back-extraction rate, and the organic phase after back-extraction can be recycled, resulting in low operating costs and high economic benefits.

[0008] The specific technical solution of the present invention is as follows:

[0009] A method for preparing nickel salts using nickel-magnesium waste liquid includes the following steps:

[0010] (1) Prepare organic phases of appropriate concentrations using extractant and diluent;

[0011] (2) The organic phase prepared in step (1) is saponified using liquid alkali to obtain a saponified organic phase;

[0012] (3) Use the saponified organic phase obtained in step (2) to extract the nickel-magnesium waste liquid, let it stand and separate into layers to obtain the loaded organic phase and the raffinate aqueous phase;

[0013] (4) The loaded organic phase obtained in step (3) is washed and back-extracted to obtain a nickel enrichment solution.

[0014] The extractant mentioned in step (1) is a carboxylic acid extractant BC194; the structural formula of carboxylic acid extractant BC194 is shown in Formula I:

[0015]

[0016] Compared with existing processes, the method provided by this invention can achieve one-step extraction and obtain high-purity nickel, reduce the cost of magnesium extraction in existing processes, reduce acid and alkali consumption, and the carboxylic acid extractant has a good separation effect on Ni and Mg, with an extraction rate of more than 99.0% for Ni and a sulfuric acid back-extraction rate of more than 99.5%.

[0017] As a preferred technical solution of the present invention, the volume fraction of the extractant in the organic phase in step (1) is 5-30%.

[0018] Preferably, the volume fraction of the extractant in the organic phase is 5% to 30%, for example, it can be 5%, 6%, 8%, 10%, 12%, 15%, 18%, 20%, 21%, 23%, 25%, 27% or 30%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0019] Preferably, the diluent for the extractant in step (1) is any one or a combination of at least two of Escaid 110, sulfonated kerosene, toluene, hexane, heptane, dodecane, or kerosene;

[0020] Preferably, the diluent is Escaid110 and / or dodecane.

[0021] As a preferred technical solution of the present invention, the liquid alkali used for saponification in step (2) includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide or ammonia water.

[0022] Preferably, the concentration of the liquid alkali is 6 to 14 mol / L, for example, it can be 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L or 14 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] As a preferred technical solution of the present invention, the volume ratio of the saponified organic phase and the nickel-magnesium waste liquid in step (3) is 1:(0.1-10).

[0024] Preferably, the volume ratio of the saponified organic phase to the nickel-magnesium-containing waste liquid is 1:(0.1 to 10), for example, it can be 1:0.1, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9 or 1:10, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0025] As a preferred technical solution of the present invention, the volume ratio of the saponified organic phase and the nickel-magnesium waste liquid in step (3) of the present invention is 1:(0.1~10). If the volume ratio is too large, the volume ratio of the nickel-magnesium waste liquid will be too small, resulting in the magnesium-containing extract being entrained or magnesium ions being extracted, which will affect the purity of the nickel-containing solution in the later stage. If the volume ratio is too small, the extraction capacity of the organic phase will be insufficient, resulting in the ineffective extraction of nickel ions and difficulty in mixing evenly.

[0026] Preferably, the nickel-magnesium waste liquid in step (3) is a chloride-based nickel-magnesium waste liquid or a sulfate-based nickel-magnesium waste liquid;

[0027] Preferably, the nickel-magnesium ratio in the nickel-magnesium waste liquid in step (3) is 1:(0.5-20), for example, it can be 1:0.5, 1:1, 1:1.5, 1:2, 1:3, 1:5, 1:8, 1:10, 1:12, 1:14, 1:15, 1:16, 1:18, 1:19 or 1:20, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0028] As a preferred technical solution of the present invention, the extraction in step (3) is a multi-stage countercurrent extraction.

[0029] Preferably, the number of extraction stages in the multi-stage countercurrent extraction is 2 to 20, for example, it can be 2, 3, 4, 5, 8, 10, 12, 14, 15, 17, 18, 19 or 20 stages, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Preferably, the extraction stirring speed in step (3) is 100 to 250 rpm / min, such as 100 rpm / min, 120 rpm / min, 140 rpm / min, 150 rpm / min, 180 rpm / min, 200 rpm / min, 220 rpm / min, 230 rpm / min, 240 rpm / min or 250 rpm / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] Preferably, the mixing time in step (3) is 3 to 30 minutes, for example, it can be 3 minutes, 5 minutes, 8 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, 22 minutes, 25 minutes, 28 minutes or 30 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the settling time in step (3) is 2 to 30 minutes, for example, 2 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 27 minutes, 28 minutes, 29 minutes or 30 minutes, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the pH value of the raffinate phase in step (3) is 3.0 to 6.5, for example, it can be 3.0, 3.8, 4.0, 4.4, 4.7, 5.0, 6.1, 6.2, 6.3, 6.4 or 6.5, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] As a preferred technical solution of the present invention, the pH value of the raffinate aqueous phase is 3.0 to 6.5. If the pH value is too low, the nickel extraction rate is low; if the pH value is too high, the amount of magnesium extracted by the organic phase increases, thus increasing the washing cost.

[0035] As a preferred technical solution of the present invention, the loaded organic phase in step (4) is washed organic phase after being subjected to multi-stage countercurrent washing.

[0036] Preferably, the number of multi-stage countercurrent washing stages in step (4) is 2 to 20, for example, it can be 2, 5, 8, 10, 15, 17, 18, 19 or 20, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0037] Preferably, the washing in step (4) is performed using an acid solution.

[0038] Preferably, the washing acid solution is one or a combination of at least two of inorganic acid, acidified water, and / or nickel sulfate solution.

[0039] Preferably, the pH value of the washing acid solution is 0.1 to 4, for example, it can be 0.1, 0.2, 0.5, 0.6, 0.8, 1, 2, 3 or 4, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] Preferably, the concentration of the nickel sulfate solution is 0.5 to 20 g / L, for example, it can be 0.5 g / L, 1 g / L, 3 g / L, 5 g / L, 10 g / L, 12 g / L, 13 g / L, 15 g / L, 18 g / L, 19 g / L or 20 g / L, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0041] Preferably, the volume ratio of the washing liquid to the loaded organic phase in step (4) is 1:(5-10), for example, it can be 1:5, 1:7, 1:8, 1:9 or 1:10, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] As a preferred technical solution of the present invention, the washed organic phase is subjected to acid back-extraction to obtain a nickel-enriched solution, which is then evaporated and crystallized to obtain a nickel salt.

[0043] Preferably, the number of back-extraction stages is 1 to 6, such as 1, 2, 3, 4, 5 or 6, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, the acid solution used for back-extraction is H2O. +A sulfuric acid or hydrochloric acid solution with a concentration of 3 to 6 mol / L, such as 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5 mol / L, or 6 mol / L, but not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0045] Preferably, the volume ratio of the back-extraction solution to the washing organic phase is 1:(5-20), for example, it can be 1:5, 1:8, 1:10, 1:13, 1:15, 1:17, 1:18, 1:19 or 1:20, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] Preferably, the crystallization method is MVR evaporation;

[0047] Preferably, a regenerated organic phase is obtained after the back-extraction operation.

[0048] Preferably, the regenerated organic phase is returned to the saponification process for recycling.

[0049] As a preferred technical solution of the present invention, the method includes the following steps:

[0050] (1) Prepare an organic phase with a concentration of 5-30% by mixing the extractant and diluent, wherein the extractant is a carboxylic acid extractant BC194, and the structural formula of the carboxylic acid extractant BC194 is shown in Formula I:

[0051]

[0052] (2) Saponify the organic phase prepared in step (1) with 6-14 mol / L liquid alkali to obtain a saponified organic phase;

[0053] (3) The saponified organic phase obtained in step (2) is used to extract the nickel-magnesium waste liquid. The extractable organic phase and the nickel-magnesium waste liquid are mixed and stirred at a volume ratio of 1:(0.1~10) and then subjected to multi-stage countercurrent extraction. The stirring speed is 100~250rpm / min, the stirring time is 3~30min, the number of extraction stages is 2~20, and the contact layering after extraction is 2~50min to obtain the loaded organic phase and the raffinate aqueous phase with a pH value of 3.0~6.5.

[0054] (4) The loaded organic phase described in step (3) is subjected to 2 to 20 stages of countercurrent washing using a washing solution with a pH value of 0.1 to 4, wherein the volume ratio of the washing solution to the loaded organic phase is 1:(5 to 10); then H +The washed organic phase is subjected to 1 to 6 stages of back-extraction with a back-extraction solution of 3 to 6 mol / L. The volume ratio of the back-extraction solution to the washed organic phase is 1:(5 to 20). After back-extraction, a nickel-enriched solution and a regenerated organic phase are obtained. The nickel-enriched solution is evaporated and concentrated to obtain nickel salt. The regenerated organic phase is returned to the saponification process for recycling.

[0055] In this invention, the reaction equations for the relevant processes are as follows:

[0056] Saponification of carboxylic acid extractants: HA(org) + NaOH → NaA(org) + H2O

[0057] Extraction with carboxylic acid extractants: 2NaA(org) + MSO4 → MA2(org) + Na2SO4

[0058] Sulfuric acid back-extraction: MA2(org) + H2SO4 → 2HA(org) + MSO4

[0059] Where: M is Ni 2+ Metal.

[0060] The nickel salt preparation method provided by this invention first involves saponifying an organic phase containing a carboxylic acid compound with a specific structure to obtain a saponified organic phase. Subsequently, the saponified organic phase is used to extract nickel ions from nickel-magnesium wastewater, while magnesium remains in the raffinate aqueous phase. Finally, the nickel-loaded organic phase is back-extracted to obtain a regenerated organic phase and a nickel-enriched solution. The entire process is simple to operate, has low acid consumption, and is environmentally friendly. Furthermore, the method provided by this invention not only has good nickel-magnesium separation effect, but also uses a carboxylic acid extractant with low water solubility and stable performance. It can be recycled after regeneration, which helps to reduce costs and can be applied to large-scale industrial applications. Attached Figure Description

[0061] Figure 1 This is a schematic diagram of the recycling process in Embodiment 1 of the present invention.

[0062] Figure 2 This is the E-pH curve of BC194, the novel carboxylic acid extractant used in this invention.

[0063] The present invention will now be described in further detail. However, the examples described below are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims. Detailed Implementation

[0064] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows:

[0065] Preparation Example 1

[0066] A novel carboxylic acid extractant, BC194, has the following structure:

[0067]

[0068] The preparation method includes the following steps:

[0069]

[0070] In a 500 mL round-bottom flask, 20 g (0.12 mol) of pyridine dicarboxylic acid was added. While stirring at room temperature, 200 mL of thionyl chloride was slowly added dropwise. A rise in temperature indicated the reaction had occurred. After the addition was complete, the mixture was refluxed for 30 minutes, and excess thionyl chloride was removed by distillation. Subsequently, 200 mL of dichloromethane and 25 g (0.25 mol) of triethylamine were added to the flask, followed by dropwise addition of 24.6 g (0.12 mol) of p-octylaniline. The reaction was stopped after reacting at room temperature for 1 hour. The product was washed twice with hydrochloric acid (pH=1), then once with water, dried over sodium sulfate, and the solvent was evaporated to obtain 32.1 g of the target product, with a yield of approximately 75%.

[0071] Characterization data: 13 C NMR(101MHz, CDCl3)δ168.1(s),142.3(s),139.2(s),135.1(s),127.7(s),125.6(s),128 .3(m),121.6(m),51.6(m),32.5–31.1(m),29.7(m),27.4(m),24.7(m),14.3(d,J=5.9Hz); 1 H NMR (400MHz, CDCl3) δ9.86 (1H), 8.81 (1H), 8.75 (1H), 8.52 (1H), 7.58 (2H), 7.15 (1H), 2.52 (2H), 1.56 (2H), 1.27 (10H), 0.86 (3H); MS: 354.2

[0072] Example 1

[0073] A method for preparing nickel salts using nickel-magnesium-containing waste liquid, the specific steps of which are as follows:

[0074] (1) Dissolve the carboxylic acid extractant BC194 obtained in Preparation Example 1 in diluent Escaid 110 so that the volume fraction of BC194 in Escaid 110 is 25%, and then add a 10 mol / L NaOH solution to mix, to obtain a saponified organic phase with a saponification degree of 30%, and the saponified organic phase is used as the organic phase system;

[0075] (2) The nickel-magnesium waste liquid is used as an aqueous phase system (containing 2.3 g / L of nickel, 19 g / L of magnesium, and a pH value of 3.20, specifically derived from the wastewater after nickel extraction from nickel intermediate leaching solution), and flows into the extractor from both ends of the saponified organic phase obtained in step (1) (the flow ratio of the saponified organic phase and the nickel-magnesium waste liquid is 1:4). Multi-stage countercurrent extraction is carried out. The mixing and stirring speed is 250 rpm / min, the mixing time is 15 min, the temperature is 20℃, the number of extraction stages is 8, and the phase separation is allowed to stand for 10 min to obtain the organic phase loaded with nickel ions and the outlet aqueous phase containing magnesium ions with a pH value of 6 (i.e., the raffinate aqueous phase).

[0076] (3) The loaded organic phase obtained in step (2) is washed with sulfuric acid solution with pH value of 1 in 12 stages of countercurrent washing, and then back-extracted with sulfuric acid with a concentration of 2 mol / L. The back-extraction stage is 5 stages. The flow ratio of the washing sulfuric acid solution to the loaded organic phase is 1:5, and the flow ratio of the 2 mol / L back-extraction sulfuric acid to the loaded organic phase is 1:15, so as to obtain a nickel ion enrichment solution and a regenerated organic phase.

[0077] Example 2

[0078] A method for preparing nickel salts using nickel-magnesium-containing waste liquid, the specific steps of which are as follows:

[0079] (1) Dissolve the carboxylic acid extractant BC194 obtained in Preparation Example 1 in Escaid 110, where the volume fraction of BC194 in Escaid 110 is 25%, and then add a 10 mol / L NaOH solution to mix, to obtain a saponified extractant with a saponification degree of 20%, wherein the saponified extractant is used as an organic phase system;

[0080] (2) The nickel-magnesium waste liquid was used as an aqueous phase system (containing 2.30 g / L of nickel, 19 g / L of magnesium, and a pH value of 3.20, specifically derived from the wastewater after nickel extraction from the nickel intermediate leaching solution), and the saponification extractant mentioned in step (1) flowed into the extractor from both ends (the volume ratio of the saponification extractant to the nickel-magnesium waste liquid was 1:5), and multi-stage countercurrent extraction was carried out. The mixing speed was 200 rpm / min, the mixing time was 10 min, the temperature was 25℃, the number of extraction stages was 6, and the mixture was allowed to stand for 20 min to separate into layers, resulting in an organic phase loaded with nickel ions and a raffinate aqueous phase containing magnesium ions with a pH value of 6.5.

[0081] (3) The loaded organic phase obtained in step (2) is washed with sulfuric acid with a pH of 0.5 in 8 stages of countercurrent washing, and then back-extracted with sulfuric acid with a concentration of 2.5 mol / L for 2 times; the volume ratio of the washing sulfuric acid to the loaded organic phase is 1:8, and the volume ratio of the 2.5 mol / L back-extraction sulfuric acid to the loaded organic phase is 1:16, to obtain a nickel ion enrichment solution and a regenerated organic phase.

[0082] Example 3

[0083] A method for preparing nickel salts using nickel-magnesium-containing waste liquid, the specific steps of which are as follows:

[0084] (1) Dissolve the carboxylic acid extractant BC194 obtained in Preparation Example 1 in dodecane, the volume fraction of BC194 in dodecane is 20%, and then add an ammonia solution with a concentration of 11 mol / L to mix, to obtain a saponified organic phase with a saponification degree of 20%, and the saponified organic phase is used as the organic phase system.

[0085] (2) The nickel-magnesium waste liquid was used as an aqueous phase system (containing 2.30 g / L of nickel, 19 g / L of magnesium, and a pH value of 3.20, specifically derived from the wastewater after nickel extraction from the nickel intermediate leaching solution), and the saponified organic phase described in step (1) flowed into the extractor from both ends (the volume ratio of the saponified organic phase and the nickel-magnesium waste liquid was 1:4.5). The mixture was stirred at a speed of 180 rpm / min for 5 min, and the temperature was 25°C. Multi-stage countercurrent fractionation extraction was carried out with 6 extraction stages. The separation was clarified and separated for 10 min to obtain an organic phase loaded with nickel ions and a raffinate aqueous phase containing magnesium ions with a pH value of 5.5.

[0086] (3) The loaded organic phase obtained in step (2) is washed with sulfuric acid with a pH of 1.0 in 8 stages of countercurrent washing, and then back-extracted with sulfuric acid with a concentration of 2.5 mol / L for 4 times; the flow ratio of the washing sulfuric acid to the loaded organic phase is 1:10, and the flow ratio of the 2.5 mol / L back-extraction sulfuric acid to the loaded organic phase is 1:10, to obtain a nickel ion enrichment solution and a regenerated organic phase.

[0087] Example 4

[0088] A method for preparing nickel salts using nickel-magnesium waste liquid, which differs from Example 1 only in that the sulfuric acid washing solution in step (3) is replaced with a nickel sulfate solution of 5.0 g / L and pH 1.5, while the dosage of other components and experimental conditions are the same as in Example 1.

[0089] Comparative Example 1

[0090] A method for preparing nickel salts using nickel-magnesium waste liquid, which differs from Example 1 only in that the carboxylic acid compound BC194 in step (1) is replaced with an equal amount of extractant P507 (2-ethylhexylphosphonic acid mono-2-ethylhexyl ester), while the amounts of other components and experimental conditions are the same as in Example 1.

[0091] Performance testing:

[0092] The saponification ratio refers to the proportion of alkali metal NH in the extractant. +4 and / or Na+ The proportion of hydrogen ions to the original hydrogen ions, i.e., η = (V 碱 ×C 碱 ) / (V 有 ×C 有 )×100% (1)

[0093] In equation (1), V 碱 C is the volume (mL) of the added alkali aqueous solution. 碱 V represents the concentration of the added alkali in the aqueous solution (mol / L). 有 The volume of the organic phase is mL, C 有 The concentration of the extractant in the organic phase is expressed in mol / L.

[0094] In this embodiment of the invention, the metal ion content in the aqueous phase is determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and then the metal ion content in the organic phase is obtained by the difference method.

[0095] The raffinate aqueous phase and nickel ion enrichment solution obtained in step (2) of the extraction method described in Examples 1 to 4 were tested according to the above test method, and the results are shown in Table 1.

[0096] Table 1

[0097]

[0098]

[0099] As shown in Table 1, the method for preparing nickel salts from nickel-magnesium-containing wastewater provided by this invention achieves a high nickel recovery rate, consistently exceeding 99%, and a low nickel content in the raffinate, generally below 5 mg / L, meeting direct discharge requirements. The resulting nickel sulfate product has high purity, meeting battery-grade nickel sulfate purity requirements. This method for preparing nickel salts from nickel-magnesium-containing wastewater is short, eliminating the traditional step of pre-extracting magnesium, reducing acid and alkali consumption, and lowering nickel recovery costs. The wastewater generated by this method has low metal ion content, resulting in minimal environmental pollution and low subsequent treatment costs.

[0100] The applicant declares that this invention illustrates a method for preparing nickel salts using nickel-magnesium-containing waste liquid through the above embodiments, but this invention is not limited to the above process steps, that is, it does not mean that this invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials used in this invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A method for preparing nickel salts using nickel-magnesium-containing waste liquid, characterized in that, The method includes the following steps: (1) Prepare an organic phase with a concentration of 5-30% by mixing the extractant and diluent; (2) Saponify the organic phase prepared in step (1) with 6~14 mol / L liquid alkali to obtain a saponified organic phase; (3) The saponified organic phase obtained in step (2) is used to extract the nickel-magnesium waste liquid. The extractable organic phase and the nickel-magnesium waste liquid are mixed and stirred at a volume ratio of 1:(0.1~10) and then subjected to multi-stage countercurrent extraction. The stirring speed is 100~250 rpm, the stirring time is 3~30 min, the number of extraction stages is 2~20, and the contact layering is carried out for 2~50 min after extraction to obtain the loaded organic phase and the raffinate aqueous phase with a pH value of 3.0~6.

5. The nickel-magnesium ratio in the nickel-magnesium waste liquid is 1:(0.5~20). (4) The loaded organic phase obtained in step (3) is subjected to 2 to 20 stages of countercurrent washing with a washing solution with a pH of 0.1 to 4, and the volume ratio of the washing solution to the loaded organic phase is 1:(5 to 10); then H + The washed organic phase is subjected to 1 to 6 stages of back-extraction with a back-extraction solution of 3 to 6 mol / L. The volume ratio of the back-extraction solution to the washed organic phase is 1:(5 to 20). The nickel-enriched solution obtained after back-extraction is evaporated and crystallized to obtain nickel salt. The regenerated organic phase is returned to the saponification process for recycling. The extractant mentioned in step (1) is a carboxylic acid extractant BC194, and the structural formula of the carboxylic acid extractant BC194 is shown in Formula I: Formula I The extractant is prepared by the following method: ； 20 g of pyridine dicarboxylic acid was added to a 500 mL round-bottom flask. 200 mL of thionyl chloride was slowly added dropwise while stirring at room temperature. A rise in temperature indicated the reaction had occurred. After the addition was complete, the mixture was refluxed for 30 minutes, and excess thionyl chloride was removed by distillation. Subsequently, 200 mL of dichloromethane and 25 g of triethylamine were added to the flask, followed by the dropwise addition of 24.6 g of p-octylaniline. The reaction was stopped after 1 hour at room temperature. The product was washed twice with hydrochloric acid (pH=1), then once with water, dried over sodium sulfate, and the solvent was evaporated to obtain 32.1 g of the target product, with a yield of approximately 75%.

2. The method according to claim 1, characterized in that, The diluent for the extractant in step (1) is any one or a combination of at least two of Escaid110, sulfonated kerosene, toluene, hexane, heptane, dodecane, or kerosene.

3. The method according to claim 2, characterized in that, The diluent is Escaid110 and / or dodecane.

4. The method according to claim 1, characterized in that, The liquid alkali used for saponification in step (2) includes any one or a combination of at least two of sodium hydroxide, potassium hydroxide, or ammonia water.

5. The method according to claim 1, characterized in that, The nickel-magnesium waste liquid mentioned in step (3) is either a chloride system nickel-magnesium waste liquid or a sulfate system nickel-magnesium waste liquid.

6. The method according to claim 1, characterized in that, The washing in step (4) is carried out using a washing acid solution.

7. The method according to claim 6, characterized in that, The washing acid solution in step (4) is one or a combination of at least two of the following: inorganic acid, acidified water and / or nickel sulfate solution.

8. The method according to claim 6, characterized in that, The pH value of the washing acid solution is 0.1~4.

9. The method according to claim 7, characterized in that, The concentration of the nickel sulfate solution is 0.5~20 g / L.

10. The method according to claim 6, characterized in that, The volume ratio of the washing acid solution to the supported organic phase in step (4) is 1:(5~10).

11. The method according to claim 1, characterized in that, The crystallization method is MVR evaporation.

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