초록 ▼

A process for treating industrial waste water containing hexavalent chromium (Cr+6) and other heavy metals is disclosed which comprises reduction of Cr+6 to trivalent chromium (Cr+3) and the precipitation thereof with other heavy metals by addition of sulfide ion and ferrous ion to the waste stream

A process for treating industrial waste water containing hexavalent chromium (Cr+6) and other heavy metals is disclosed which comprises reduction of Cr+6 to trivalent chromium (Cr+3) and the precipitation thereof with other heavy metals by addition of sulfide ion and ferrous ion to the waste stream at a pH of about 7 to 9 under conditions such that sludge production by the process of the invention is substantially less than that characteristic of prior art processes. Polymers are added to the solution to assist flocculation and clarification of the waste stream. More specifically, the invention comprises adding sulfide ion in a sulfide to hexavalent chromium ratio of about 0.7-2.5:1 and adding ferrous ion in a ferrous to hexavalent chromium ratio of about 0.5-5.0:1. The waste stream pH is preferably maintained in the range of about 7.2 to 7.5.

대표청구항 ▼

A process of reducing hexavalent chromium to trivalent chromium and precipitating the trivalent chromium from a waste water stream to form a sludge for disposal, said process comprising the steps of: (a) adding soluble sulfide ion to said stream in a ratio of sulfide ion to hexavalent chromium of fr

A process of reducing hexavalent chromium to trivalent chromium and precipitating the trivalent chromium from a waste water stream to form a sludge for disposal, said process comprising the steps of: (a) adding soluble sulfide ion to said stream in a ratio of sulfide ion to hexavalent chromium of from about 0.7 to 2.5; (b) adding soluble ferrous ion to said stream in a ratio of ferrous ion to hexavalent chromium of from about 0.5 to 5.0; (c) thereafter adjusting pH of said stream to about 7.2 to 7.5; (d) adding a flocculating polymer to said stream to promote formation of a floc comprising precipitated trivalent chromium; (e) forming a sludge bed comprising said precipitated trivalent chromium; and (f) thereafter filtering the floc from said stream using said sludge bed containing said precipitated trivalent chromium.