Mechanisms for Reduction of Heavy Metal Leaching by Natural Chemical Weathering Reactions

摘要

One of the important aspects of using recycled materials in a beneficial manner in roadway construction is assurance of human health and environmental protection. Long-term leaching of metals from ash, slags, and foundry materials, that are excellent candidates for base materials, is a process that requires further elucidation, particularly as these materials are subject to chemical weathering over time. Chemical weathering has the potential to significantly impact estimates of long-term leaching from byproduct materials, but the mechanisms by which this occurs are still not well understood or documented. This paper presents an investigative technique reliant largely on Fourier transform infrared spectroscopy (FTIR), in combination with complementary analytical techniques, to characterize phase changes in municipal solid waste (MSW) bottom ash that has been weathered in a lysimeter for 3 years. FTIR results demonstrate the weathering of allophane and proto-immogolite allophane tending toward halloysite, which implies a limiting factor in the weathering process and further suggests that the weathering products of ash materials may be intentionally altered by control of the pore-water chemistry.