Treatment and recycling of zinc hydrometallurgical wastes by self-propagating reactions

A novel technique for treating and recycling of a highly toxic solid waste from electrolytic zinc plants, i.e. goethite waste, is proposed. It consist s of blending this waste with suitable amount of reducing agents (aluminum or aluminum and silicon) and ferric oxide, and igniting the resulting mixtu re so that a self-propagating reaction in the form of a combustion wave rap idly travels through the mixture without requiring additional energy. React ants are converted into two solid products (P-1 and P-2) with different mas s, composition and structure, and a gas constituted by SO2. Aluminum and si licon should be preferred as reducing agents, since the reaction product P- 1 obtained in larger quantity, is constituted by an amorphous glassy struct ure of alumino-silicates which embodies heavy metals, such as Pb and Cd. Le aching tests of the reaction products P-1 are also performed to verify the possibility of their disposal. The solid product P-2 on the other hand may be recycled in the roasting unit of the industrial zinc production plant. A waste treatment process is also proposed. (C) 1999 Elsevier Science Ltd. A ll rights reserved.