Thermal stabilization of metal finishing waste with clay.
Thermal treatment of metal finishing waste with locally available clay, in their varying ratios, was carried out at 850 degrees C and above temperatures. In the presence of 1:1 ratio of waste and clay a solidified product was obtained at 950 degrees C. Measurement of an appreciably high compressive strength, approximately 500 kg cm(-2) and a very small (0.4%) water absorption from the solidified product indicated its stable nature. Toxicity Characteristic Leaching Procedure (TCLP) test of the waste showed nearly 85 to 90% decrease of leaching of Fe, Cu, Ni, Zn, Mn and Cr after thermal treatment compared to their leaching without treatment. No hexavalent chromium (Cr(VI)) was observed from the leachate of the solidified product. This indicates the absence of re-oxidation phenomena of chromium during thermal treatment up to 950 degrees C. X - ray diffraction (XRD) of solidified product indicated the presence of hematite, and aluminum silicate as main phases of the solidified product. Involvement of the above waste metals with these phases during thermal treatment could be the reason for their immobilization.
Singh
I B
IB
Regional Research Laboratory, Council of Scientific and Industrial Research Hoshangabad Road, Bhopal 462026, India.
Chaturvedi
K
K
Singh
D R
DR
Yegneswaran
A H
AH
D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D006358:Hot Temperature; D007220:Industrial Waste; D008669:Metallurgy; D019216:Metals, Heavy / Q000737:chemistry*; D014874:Water Pollutants, Chemical; D018508:Water Purification / Q000379:methods*
D000538:Aluminum Silicates; D007220:Industrial Waste; D019216:Metals, Heavy; D014874:Water Pollutants, Chemical; D000077215:Clay