Method for separating out nickel ion crystals

The invention discloses a method for separating out nickel ion crystals, which comprises the following steps: S1, carrying out copper removal and arsenic, antimony and bismuth impurity removal treatment on copper electrolysis waste liquid to obtain nickel removal pre-liquid; s2, putting the nickel removal pre-liquid obtained in the step S1 into a nickel removal pre-liquid head tank; s3, moving a sulfuric acid liquid outlet of the concentrated sulfuric acid head tank to a liquid inlet of the nickel removal tank; s4, starting a nickel removal tank stirrer, and adding the nickel removal pre-solution in the step S2 and the concentrated sulfuric acid in the step S3 into the nickel removal tank; s5, feeding the mixed solution obtained in the step S4 into a cooling crystallizer, reducing the temperature to 15-35 DEG C, and separating out nickel sulfate crystals to obtain a cooled mixture consisting of the nickel sulfate crystals and the solution; and S6, the cooled mixture in the step S5 is subjected to filtration a