Influence of Different Electroplating Sludge Types on the Iron Ions Recovery Yield

Abstract

Electroplating sludge resulting from wastewater (washing wastewater and technological solutions) treatment is considered to be a hazardous waste, being a mixture of hydroxides of many heavy metals such us: iron, chromium, copper, nickel, cadmium or zinc. The metal compounds from electroplating sludge have a great economic value, thus, a number of techniques have been investigated in order to recover them. This paper presents the results of the research activity in the laboratory in order to recover Fe (II, III, VI) from two types of electroplating sludge: a fresh sludge from wastewaters treatment and an old sludge, stabilized by disposal for many years. Iron recovery was performed by the solubilization of the sludge in several stages, to yield hydroxides or metal salts of chromium, iron, or zinc. The iron recovery has been performed from the cake obtained after the chromium recovery. In this cake, the iron is present in the form of divalent, trivalent and hexavalent iron. The iron recovery yield was 98.50% from fresh sludge (recovery in one stage) and 96.80% from old sludge (recovery in two stages).