Operationally determined speciation of chromium in tannery sludges

Sludges formed as a result of chrome recovery process (A) and due to basic tanning activities (B) have been characterized and speciated. The concentra tion of chromium in both of these sludges (A) and (B) is elevated, being 2, 700 and 970 mu g g(-1), respectively. The sludge (A) has a major portion (4 8%) bound to inert sulfide form and 22% in the exchangeable fraction while the sludge (B) contains a sizeable fraction (46%) of the metal in the organ ic phase. Though the organic bound chromium is apparently safe, analysis of some plants growing on this sludge shows elevated concentrations (1,200 pp m) of chromium. In a scenario like this, development of effective methods o f chromium recovery from the sludges seems to be an important consideration .