Advances in the sources, chemical behaviour, and whole process distribution of Hg, As, and Pb in the iron and steel smelting industry.

The Chinese iron and steel industry, with its large production volume and reliance on coal-dominated energy structures and blast furnace/basic oxygen furnace processes, is a significant contributor to heavy metals (HMs) emissions and a potential threat to the environment and human health. This study systematically reviews the sources, chemical behaviour transformations, and whole process distribution of mercury (Hg), arsenic (As), and lead (Pb) throughout iron and steel smelting processes. Coal and iron ore were the major input sources of the three HMs. The chemical transformations of HMs are closely related to temperature changes. During combustion, HMs volatilise, condense in the scrubbing system, and remain gaseous or are removed as products/by-products during flue gas treatment. Sintering was identified as the primary emission source of Hg, accounting for 36.79 % of the total process emissions, with an average emission factor of 108.36 mg/t-CS. The blast furnace process is the main emission source for As and Pb, contributing 75.19 % and 59.10 % of total process emissions, respectively, with average emission factors of 43.82 mg/t-CS for As and 231.16 mg/t-CS for Pb. Throughout the iron and steel smelting process, Hg is primarily released as dust ash and desulfurisation by-products (33.30-76.91 %). As mainly remains in hot rolled steel products (57.60-75.04 %). Meanwhile Pb forms a recycling loop between the sintering and basic oxygen furnace processes, with some Pb being released as blast furnace slag (11.41-79.22 %). The results of this study can provide a scientific basis for the development of future HMs reduction technologies and control strategies. More attentions should be paid to HMs in wastes from the whole process of iron and steel smelting in future policy making.