A method of purifying a copper electrolytic solution circulated in a copper electrorefining system, wherein a portion of the solution is withdrawn and recycled to the system after purification treatment. The purification treatment includes the addition of a hydrosulfide to the withdrawn solution to generate only the necessary quantity of hydrogen sulfide gas required in the reaction. The hydrogen sulfide gas generated is utilized for purification treatment. One process comprises dividing the solution withdrawn into two portions. Sodium hydrosulfide is added to the first portion to precipitate and separate metals as sulfides. Excess sodium hydrosulfide is further added to the first portion for reaction with residual sulfuric acid in the solution to generate hydrogen sulfide gas, then contacting the second divided portion with the hydrogen sulfide gas thus produced to precipitate and separate metals in the form of sulfides. The filtrate is then recycled to an electrorefining system. There is also provided a process comprising contacting the solution with hydrogen sulfide gas to separate and remove Cu, As, Sb and Bi in the form of sulfides from the solution, then dividing the solution into two portions; The first portion is recycled to the electrorefining system, whereas excess sodium hydrosulfide is added to the second portion to separate and recover Ni as nickel sulfide from the solution. Resultant hydrogen sulfide gas is used for contact with solution to be treated.