Recovery of Hg from mercury sludge enhanced by oxidizing roasting in a microwave field

The management of residues from the metallurgical industry is an integral part of waste management. Mercury sludge is a by-product of the acid-making step and has a high content of Hg in the form of HgS and HgO. With the development of zinc industry, proper utilization of the high-risk mercury sludge has drawn great attention. In this paper, a new technology for recovery of Hg from mercury sludge enhanced by NaClO addition and microwave heating is proposed. By adopting various analysis techniques, effect of NaClO addition and microwave-assisted drying in the pre-treatment process are demonstrated. Results showed that microwave-assisted drying can increase the oxidation of mercury sludge, and NaClO can react with HgS to produce HgO and Hg, two volatile materials. The pretreatment effect is optimum when mixing ratio of NaClO to mercury sludge is 1:2. Moreover, upon roasting this sample in microwave equipment at 450 degrees C for 20 min, Hg recovery can reach 92.31%.