Removing low concns. of metal esp. zinc from aq. soln. - by precipitating metal as hydroxide, off metal contg. sludge, redissolving sludge and selectively recovering metal

摘要

A process for removing a low concn. of metal impurity, esp. Zn from an aq. soln. by pptn. in the form of a hydroxide from a basic medium, comprises the stages of (i) adjusting the pH of the aq. soln. to 8.5-11, (ii) separating the aq. soln. contg. the hydroxide into a low concn. filtrate and a high concn. sludge with a dry solids content of more than 10 g/l, (iii) bringing the sludge back into soln. by adding a solvent and (iv) treating the dissolved sludge in a membrane electrolysis unit for the selective removal of the metal.