Abstract
Industrial sludge frequently contains high concentrations of heavy metals, and these heavy metals can potentially leach out when industrial sludge is managed inadequately. Cadmium (Cd) is one such heavy metal, with very high toxicity. The cadmium-laden industrial sludge poses severe risks to the environment and public health. To control the hazards of cadmium effectively, the stabilization of Cd into crystalline product phases is essential. Thermal treatment of metal-laden sludge with different low-cost and easily attainable ceramic precursors, generating various durable crystal structures, is a versatile technology for metal stabilization. To probe the feasibility and mechanism of cadmium stabilization, we alternatively blended CdO (a simulated Cd source in industrial sludge) with Si-, Al-, and Fe-rich ceramic precursors and sintered these tailored mixtures at targeted temperatures. X-ray diffraction results revealed that with thermal treatment, CdO can be effectively converted to specific crystal structures, such as CdSiO3, Cd2SiO4, Cd3SiO5, CdAl4O7, and CdFe2O4. The sintering temperature and precursor type affected cadmium incorporation considerably. The results of the constant pH leaching test indicated that Cd leachability substantially decreased because Cd-hosting crystalline products formed.
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