Hydrometallurgical recovery of zinc from hot dip galvanizing ash

In this laboratory study a process has been developed for zinc recovery from chloride-containing zinc ash formed during hot dip galvanizing. The ash is leached with diluted H2SO4 and the main impurities, such as iron, copper, cadmium, and organic compounds are removed from leach liquors by pH-controlled precipitation using ZnO as a neutralizing agent. The process is finished by active carbon and cementation precipitation. Chloride-free zinc hydroxy-carbonate is precipitated from purified leach solutions. Metallic zinc is obtained by the electrowinning process performed with zinc sulphate solution originating from dissolution of zinc hydroxy-carbonate prepared in diluted H2SO4.