ABSTRACT
Metal recovery in hydroxides and sulfides is observed in a large number of hydrometallurgical processes. This chapter provides an introductory appraisal of electrowinning processes and advancements in the field for two metals, copper and zinc. It discusses the commercial application of the iron precipitation process, first with respect to sulfate and then to chloride solutions. The crystallization process is found extensively used in the case of sulfate salts Cu, Ni, and Al, and ammonium salts of U, Mo, and W. The chapter presents some essential details for recovering these metals in their sulfate salts. The three basic steps involved in any crystallization process are supersaturation of solution, nucleation of crystals, and crystal growth. The chapter pertains to these aspects of crystallization and the description of process equipment needed to carry out crystallization. Depending on the type of the solution to be treated, one can choose any one from the following classes of crystallizers: cooling crystallizers, evaporating crystallizers, and vacuum crystallizers.
