Zinc recovery from suspensions of zinc cpds. - by electrodeposition onto aluminium cathodes from sulphuric acid-contg. electrolytes

摘要

Zn is recovered by electrolysing a suspension of residual Zn cpds., such as froths and galvanising residues, Zn oxides or hydroxides from the chemical industry and from paints. The Zn is deposited on Al cathodes the anodes being made of a Pb-based alloy. The Zn cpds. are added continuously to the slurry to maintain the concn. of metals. The electrolyte is an aq. soln. of H2SO4 with a concn. of 5-25% an delectrolysis is carried out at a current density of 2.5-20 A/dm2 at 25-60 degrees C and with a Zn concn. in the electrolyte of 20-100 g/l. The Zn may be obtd. as a homogeneous sheet from these residues without dissolving the Zn cpds. separately e.g. by converting them into soluble salts. Thus avoiding filtration of these soln. Impurities e.g. Fe remaining in suspension can be opt. removed by decantation, sedimentation or filtering. Continuous operations can be achieved by adding Zn cpds. at predetermined intervals. The deposit has a high purity (99-99.8%). During melting higher efficiencies are achieved than with Zn deposit from alkaline suspensions. The electrolyte may be re-used several times.