Method for refining nickel sulfate at normal pressure and nickel extractant used therein

A method for refining nickel sulfate at a normal pressure, comprising:

• adding a sulfuric acid solution in a plurality of high nickel matte powders to form an acid leaching solution, wherein the concentration of the sulfuric acid solution is at least 25 vol %, the high nickel matte powders contain 60-80 wt % of nickel, and the particle sizes of the high nickel matte powders are 45 to 500 μm;
• adding a nickel extractant into the acid leaching solution in batches to form an acid leaching extraction solution, and performing an acid leaching extraction reaction on the acid leaching extraction solution, wherein the volume ratio of the nickel extractant to the sulfuric acid solution is about 1:1 to 5:1, the nickel extractant comprises an acid etching agent, pure water and an auxiliary agent, the acid etching agent accounts for at least 40 wt % of the nickel extractant, the pure water accounts for 50 to 60 wt % of the nickel extractant, the auxiliary agent is selected from the group consisting of a surfactant, an organic salt and an inorganic salt, and accounts for 0.1 to 10 wt % of the nickel extractant, and the solid-liquid weight ratio of the high nickel matte powders to the acid leaching extraction solution is 1:1 to 1:15;
• maintaining the acid leaching extraction reaction for 3 to 10 hours;
• and
• filtering out a solid residue in the acid leaching extraction solution to obtain a nickel sulfate-containing filtrate.