GB162030A - Improvements in or relating to the purification of zinc solutions - Google Patents

Abstract

A zinc-sulphate or other zinc solution is freed from foreign metals by treatment in the presence of a mercury salt with a subdivided metal electro-positive to the impurities. Zinc, aluminium, and alloys thereof are suitable electro-positive metals; they may be powdered or granulated, zinc fume or blue powder being advantageous. The mercury as mercuric chloride or nitrate, or, when zinc is to be electro-deposited, as mercuric sulphate, may be added as a solution or directly dissolved in the zinc solution before the treatment or at any suitable prior stage. Two pounds of mercury in the form of sulphate, and 40lb. of zinc, suffice for 10 tons of crude zinc solution. This may be obtained from ore by treatment with spent electrolyte or other solution, and before the purification is brought to an acidity of 0.1-0.2 per cent, by means of incomplete neutralization, or by neutralization for the removal of silica, &c. followed by acidification. During the purification the liquid may be heated to 70-100 DEG C. and gently agitated. Copper, arsenic, antimony. bismuth, cadium, nickel, cobalt, and other metals are precipitated as a sludge, from which mercury can be recovered by distillation or otherwise. Iron may be removed before or after the above purification. If aluminium is used as the electropositive metal, it may be subsequently removed, but is not injurious in the electrodeposition of zinc. Specification 138,950 is referred to.