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 consists of blending this waste with suitable amount of reducing agents (aluminum or aluminum and silicon) and ferric oxide, and igniting the resulting mixture so that a self-propagating reaction in the form of a combustion wave rapidly travels through the mixture without requiring additional energy. Reactants are converted into two solid products (P-1 and P-2) with different mass, composition and structure, and a gas constituted by SO2. Aluminum and silicon should be preferred as reducing agents, since the reaction product P-1 obtained in larger quantity, is constituted by an amorphous glassy structure of alumino-silicates which embodies heavy metals, such as Pb and Cd. Leaching 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