THERMAL IMMOBILIZATION OF Cr, Cu AND Zn OF GALVANIZING WASTES IN THE PRESENCE OF CLAY AND FLY ASH

• Published in: Environmental technology 2007-07, Vol.28 (7), p.713-721
• Main Authors: Singh, I.B., Chaturvedi, K., Yegneswaran, A.H.
• Format: Article
• Language: English
• Subjects: Aluminum Silicates - chemistry; Applied sciences; Carbon - chemistry; Chemical engineering; Chromium - chemistry; CLAY; Coal Ash; Compressive Strength; Copper - chemistry; Crystallization, leaching, miscellaneous separations; Exact sciences and technology; FLY ASH; GALVANIZING WASTE; Hot Temperature; Industrial Waste; Metals, Heavy - chemistry; Metals, Heavy - isolation & purification; Particulate Matter - chemistry; Pollution; Reactors; Refuse Disposal - methods; Solubility; THERMAL TREATMENT; TOXIC METALS; X-Ray Diffraction; Zinc - chemistry
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593332808618836

In the present investigation thermal treatment of galvanizing waste with clay and fly ash has been carried out to immobilize Cr, Zn, Cu and other metals of the waste at temperature range 850&#176C to 950&#176C. Leaching of the metals from the waste and solidified product was analyzed using toxic characteristic leaching procedure (TCLP). Results indicated that the composition of waste and clay treatment temperature are the key factors in determining the stability of solidified product. After heating at 950&#176C, the solidified specimens of 10% waste with clay have shown comparatively a high compressive strength and less water absorption. However, a decrease in compressive strength and increase in water absorption were noticed after addition of 15% of waste with clay. The leachability of all the metals present in the waste was found to reduce considerably with the increase of treatment temperature. In the case of Cr and Zn, their leachabilty was found at unacceptable levels from the treated product obtained after heating at 850&#176C However, their leachability was reduced significantly within an acceptable level after treatment at 950&#176C. The thermal treatment has shown an increase of re-oxidation trend of Cr (III) to Cr (VI) up to 900&#176C of heating and this trend became almost zero after heating at 950&#176C. Addition of fly ash did not show any improvement in strength, durability and leachability of metals from the thermally treated product. X - ray diffraction (XRD) analysis of the product confirmed the presence of mixed phases of oxides of toxic metals.