Release of Heavy Metals from Concrete Made with Cement from Cement Kiln Co-Processing of Hazardous Wastes in Pavement Scenarios

摘要

Environmental safety assessments of products using cement from co-processing of hazardous wastes in cement kilns and formulation of criteria for pollution control of the cement products are necessary in Chinese environmental management departments. This article discusses the release of heavy metals from concrete using cement from the co-processing of hazardous wastes in cement kilns. The leaching test was based on typical applications of concrete in China. Total amount of heavy metals are much greater than leachability, and the ratio of total amount to leachability was dependent on the type of heavy metal. A good linear correlation between total amount and leachability of Cd was found (R2 is 0.994), but this was not the case for Cr, As, and Pb. pH influenced the release of heavy metals significantly, and the influences were related to the kinds of heavy metals. Diffusion control was the major release mechanism of Cr and Cd in concrete and the release curves fit very well the standard line with a slope of 0.5. Slopes of different increments were all between 0.35 and 0.65. For As and Pb, diffusion control was also the major release mechanism, although other release mechanisms were also present. In the continuous leaching condition, the cumulative release amounts of Cr, Pb, and Cd were all larger than in the intermittent wetting condition, but this was not the case for As.