Pramoninių nuotekų valymui naudojamų geležies koaguliantų tyrimas

Abstract

The method most frequently used in industry for waste treatment is chemical precipitation of heavy metals. The treatment of galvanic waste from sixvalent chrome is especially problematic. Numerous authors indicate that the waste containing chromium should be reduced by sodium sulphate, sodium bisulphate, ferriferous sulphate, ferriferous chloride or metallic iron before treating it with slack lime. Sixvalent chrome must be reduced to the trivalent chrome, since only the latter can form hydroxides which are only partly soluble and after being treated by flocculant may quickly precipitate. A better and less expensive methods of waste treatment is the one which combines neutralization, coagulation, sorption, flocculation and chemical precipitation, when electrogenerated ferriferous coagulant is used for reducing chrome. The present research has established that with the application of electrogenerated coagulant salt concentration is much lower then when using ferrous (II) chloride and ferrous (II) sulphate; the demand for ferriferous salt is 12,5 % higher.