Formation of nickel and copper ferrites in ceramics: a potential reaction in the reuse of iron-rich sludge incineration ash

摘要

This study investigates potential solid-state reactions for the stabilization of hazardous metals when reusing the incineration ash from chemically enhanced primary treatment (CEPT) sludge to fabricate ceramic products. Nickel and copper were used as examples of hazardous metals, and the iron content in the reaction system was found to play a major role in incorporating these hazardous metals into their ferrite phases (NiFe_2O_4 and CuFe_2O_4). The results from three-hour sintering experiments on NiO + Fe2O_3 and CuO + Fe2O_3 systems clearly demonstrate the potential for initiating metal incorporation mechanisms using an iron-containing precursor at attainable ceramic sintering temperatures (above 750℃). Both ferrite phases were examined using a prolonged leaching experiment modified from the widely used toxicity characteristic leaching procedure (TCLP) to evaluate their long-term metal leachability. The leaching results indicate that both the NiFe_2O_4 and the CuFe_2O_4 products were significantly superior to their oxide forms in immobilizing hazardous metals.