PROCESS FOR FRACTIONAL SEPARATION OF TOXIC HEAVY METALS FROM COMPLEX SLUDGE

摘要

The invention relates to a process of fractional separation of toxic heavy metals from complex sludge having a metal content of Fe, Cr, Cu, Ni, Cd, Zn, Al, Pb resulting during the neutralization of washing water and exhaust solutions in metal coating units. According to the invention, the process of separation of toxic heavy metals from complex sludge ensures the step separation of toxic heavy metals by solubilizing the sludge in autoclave, namely in treating a sludge quantity with an ammonium sulphate solution at a ratio sludge : ammonium sulphate of 1: 1 ....1 :1.5 and S: L of 1 : 6 ....1 : 7 at temperatures ranging from 140 degree to 180 degree C and at pressures of 5 ... 18 at, for 4 ...6 h. The solubilization takes place under continuous oxygen barbotage at a flow rate of 15 l / h, afterwards the iron is separated from chromium and the final suspension is separated into two phases, namely liquid and solid, by filtering or centrifuging. The solid phase is further treated by calcination producing iron pigments at 600 ...800 degree C, while the liquid phase is precipitated in an alkaline medium, chromium being separated therefrom.