| :In this study, crude nickel sulfate which was recovered from copper electro-refining system was taken as the raw material and treat with combined purifying and refining processes so as to obtain refined nickel sulfate with a battery-grade quality. Based on the composition of the raw material, the processes including recovery of copper solvent extraction,iron and arsenic removed by oxidation-hydrolysis-precipitation, calcium and magnesium removed by chemical precipitation and deeply purification by solvent extraction.The impurities in the solution which was obtained by dissolving crude nickel sulfate were removed. Followed with nickel extraction and stripping, a nickel sulfate solution was eventually obtained with high purity. After concentration and crystalizing, the crystalized nickel sulfate was obtained with good quality.Copper was recovered from the crude nickel sulfate solution using efficient extractant AD100. The optimum conditions were:initial pH2.0, phase ratio(O:A)1:3,25%(volume fraction) AD100in the organic phase and the reaction time5min.Over99%of the copper in the solution was transferred into the organic phase with three-stage extraction at room temperature under the above conditions.After stripping of the copper in organic phase with a two-stage extraction using2mol/L of sulfuric acid solution, over99%of copper was stripped into the copper sulfate solution which can be directly electrowining to produce copper powder.The electrowining solution can be recycled after stripping copper from AD100. Recovery of copper was over99%through the extraction and stripping processes.The solution after copper removed was oxidized with hydrogen reoxide precipitated with polymeric and neutralize with sodium carbonate.Iron and arsenic were removed from crude nickel sulfate solution after copper extraction. Optimum conditions were determined when amount of H2O2(30wt.%) was26.7mL/L,d oxidating time was10min,16.7mL/L of polymeric ferric sulfate solution(20wt.%) was added and keep final pH was4.0, reacted1h at70℃, under the above conditions, the content of arsenic in the solution was reduced from1.36g/L to1mg/L the content of iron was reduced from1.36g/L to lOmg/L at the same time, the removal ratio of iron and arsenic were higher than99%and99.9%,respectively.Sodium fluoride was used as precipitant to remove calcium and magnesium from the nickel sulfate solution after to iron and arsenic removed. Under optimum conditions that the reaction temperature was90℃, excessive ratio of sodium fluoride was1.5, final pH was5.0and reaction time was1h, remove rate of calcium and magnesium were over98%and99%,respectively. Concentration of calcium and magnesium remained in the solution were lower than10mg/L and5mg/L respectively.Deeply purification process was followed by removing calcium and magnesium from the nickel sulfate solution. Saponified extractant P204was taken to remove impurities including zinc, manganese, lead and the residual iron and copper in the solution. Optimum conditions were determined by batch experiments. After six-stage extraction under the optimum conditions as:saponification rate of P204was50%, initial pH4.0, phase ratio(O:A)1:1, concentration of P204(volume fraction)20%and reaction time10min, concentration of Cu, Fe, Pb, Zn and Mn remained in the solution was0.002g/L,0.001g/L,0.002g/L,0.001g/L and0.002g/L, respectively. The remained content of the ions as formers showed that the purpose of deeply purification was achieved successfully.After recovered Cu and removed the impurities including Fe, Zn, Pb, Mn, Ca and Mg, P204was adopted as the extractant to separate nickel from the high sodium solution so as to ensure the quality of the products. Nickel was extracted by saponified P204and transferred into the organic phase. Adopting deionized water to wash the organic phase and then stripped nickel with400g/L sulfuric acid solution, nickel sulfate solution with high purity was obtained. By optimizing the Concentration and crystallization processes from the nickel sulfate solution, the crystallized nickel sulfate was filtered out from the mother liquor with the quality of HG/T2028-2009, the component of the product reached the requirement of Ⅱ-level superior products which showed it can be used as the raw material of battery materials.This study was a laboratory-scale experiment. The obtained conclusions were verified by semi-industrial tests based on the above experiment. And, the tests also provided theoretical basis and technical supports with the implementation of industrial production. |
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