Sulphuric acid recovery from etching or leaching liquors - by neutralising and cementing metals with zinc and electrolysing

摘要

Sulphuric acid is recovered from etching or leaching liquors contaminated by metals more noble than Zn, by (a) neutralising the liquor by treating with Zn or ZnO; (b) treating with Zn until the metals more noble than Zn are ppted; (c) removing the ppte.; and (d) electrolysing the ZnSO4 soln. obtd. to liberate Zn at the cathode and H2SO4 at the anode. The process is esp. useful for recovering H2SO4 from spent iron and steel pickling baths.