Provided are an impurity-element removing method for selectively removing magnesium from a nickel-containing solution, and a method for producing high-purity nickel sulfate using the impurity-element removing method. The production method includes a production process in the production method of producing high-purity nickel sulfate from a nickel-containing solution, and the nickel-containing solution in the production process is subjected to an impurity-element removal treatment that includes: a hydroxylation step of adding an alkali hydroxide to the nickel-containing solution in the production process to form a hydroxylated slurry; a carbonation step of adding an alkali carbonate to the hydroxylated slurry to form a carbonated slurry, and recovering nickel component from the solution; a solid-liquid separation step for the slurry thus obtained; and a neutralization step of subjecting a solution after reaction obtained by solid-liquid separation to a neutralization, and recovering an impurity element included in the nickel-containing solution in the production process.

The invention provides a process for production of fine spherical particles of a carbonate or a hydroxide of nickel, cobalt or copper which comprises: dissolving a carbonate or a hydroxide of nickel, cobalt or copper having the general formula (I)



        M(CO₃)_x/2·(OH)_y



wherein M represents Ni, Co or Cu, and x and y are numerals satisfying the followings: 0≦x≦2, 0≦y≦2 and $\text{x+y=2}$, in aqueous ammonia, converting the resulting solution to a W/O emulsion containing droplets of the solution in a non-aqueous medium, and then removing volatile components including ammonia from within the droplets, thereby precipitating a basic carbonate or a hydroxide of a metal selected from nickel, cobalt and copperin the droplets.

The fine spherical particles of a carbonate or a hydroxide of nickel, cobalt or copper obtained according to the process of the invention are especially useful as a precursor for the manufacture of uniform, fine spherical particles of nickel, copper or cobalt metal, as well as useful as themselves as a catalyst for use in organic synthesis, a carrier, a pigment, a filler or a glaze.

The recovery of cobalt and/or nickel from solvent extraction strip solutions containing copper and zinc is effected by sequentially precipitating copper and then zinc (as contaminant metals) from the strip solution by individual sulfide sparges. After these metals are removed, the cobalt or nickel values are precipitated from the solution by the addition of carbonate ions.