Short-term leaching of heavy metals from cement from co-processing of industrial sludge containing petroleum and heavy metals as an alternative fuel

Abstract

One of the severe environmental problems in developing countries involves hazardous waste. The traditional management of hazardous wastes usually employs physical and chemical processes to stabilize or reduce the toxicity of them. Then, the wastes are taken away to a secure landfill, which is nowadays hard to site, build, operate, and maintain effectively. A viable waste management option is co-processing in cement production. The co-processing technology consists of partial application of hazardous waste as alternative fuels and raw materials (AFR). It can reduce the use of non-renewable energy and natural resources as well as environmental problems stemming from mishandling by other management options. This research studied leaching of heavy metals from cement produced from the co-processing of industrial sludge containing petroleum and heavy metals as an alternative fuel. The sludge was utilized up to 20% by weight in raw meal. Analysis results of industrial sludge containing petroleum and heavy metals were used as a basis for selection of four heavy metals; namely, Cr, Ni, Pb and Zn. To study the sequential extraction test, approximately 5% to 45% of heavy metals were distributed in Fraction 3 (bound to iron and manganese oxide), and a major concentration of the heavy metals (54% to 87%) were found in Fraction 5 (residual fraction). The more the percentage of sludge increased, the more the concentrations of heavy metals in the clinker increased. In addition to the analysis, compressive strengths and leaching tests of cement mortars were also evaluated. The compressive strengths results were satisfactory according to ASTM C109/C109M–95 and the leached metal concentrations did not exceed the limits set by the Notification of the Ministry of Industry No.6 B.E.2540 (1997), the Notification of the Ministry of Industry B.E.2548 (2005) and the US Regulatory Toxicity Characteristic Leaching Procedure (TCLP).