The Toxic Compounds and Leaching Characteristics of Spent Foundry Sands

In foundry industry, the millions tones of spent sands weresuccessfully used as landfill materials for many years. Butthis practise is becoming a problem as the disposal costsincrease rapidly and legislation gets tighter. However, thereis not much experimental data to describe their chemicalcharacteristics, especially for the leaching behaviour andtoxic compounds of the different kinds of spent sands. Thisarticle aims to present the analysis of organic compounds andleaching characteristics of the spent foundry sands. Based onthe evaluation of the chemistry of spent sands, the contentsof the selected 32 polyaronmatic hydrocarbon (PAH) and otherorganic compounds in 11 different spent foundry sands wereanalysed. The concentrations of As, Ba, Cd, Cr, Pb, Hg, Se,Ag, Cu and Zn in 11 different spent foundry sands were alsomeasured with regard to leaching characteristics. ThepH-dependent leaching characteristics of chromium were furtherinvestigated. It was found that all spent foundry sandscontain PAHs in which naphthalene is about 30%. The PAHs ingreen sands are much higher than those in chemical binderspent sands, even though phenolic/ester sands have higher PAHsthan furan/acid and silicate sands. The leaching metals arevery low in all spent foundry sands. The leached Cr increaseswith increasing pH of the eluted solution, which can be usedin practise for shortening the leaching time of the spentfoundry sands.