New Process for Removing Zinc from Crude Nickel Sulfate
Aiming at the low efficiency of zinc removal from nickel sulfate solution and the high number of steps in the extraction process,a new process of zinc removal from crude nickel sulfate solution by pretreatment with modified nickel hydroxide and re-extraction was carried out.The effects of the excess coefficient of modified nickel hydroxide,reaction time,reaction temperature and solution pH on the zinc removal effect of pretreatment were investigated,and the effects of the volume fraction of P204 in the re-extraction step,phase ratio(O/A)and the pH value of the pre-extraction solution on the zinc removal were also investigated.The results showed that the pretreatment of crude nickel sulfate solution with modified nickel hydroxide could effectively reduce the Zn2+concentration in the solution from 3.25 g/L to less than 100 mg/L without Ni2+loss under the conditions of 200％excess coefficient of modified nickel hydroxide,60 min reaction time,60 ℃ reaction temperature,and solution pH=4,while the re-extraction step with a P204 volume In the re-extraction step,P204 volume fraction is 10％,O/A is 1∶1,and the pH value of the former liquid is 4,P204 extracts Zn2+with the best effect,currently,the concentration of Zn2+is about 1.5 mg/L,the removal rate is about 98.5％,and the loss rate of Ni2+is only 2.7％,and the effect of the decontamination reaches the national standard.
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