Selective recovery of mercury from high mercury-containing smelting wastes using an iodide solution system

The mercury resources recovery and safe disposal of mercury-containing waste is an urgent problem. In this study, a new method using an iodide solution system was proposed to selectively recover mercury from high mercury-containing smelting wastes. The mercury leaching efficiency, yields, leaching kinetics and thermodynamics were researched. The major factors which affect mercury leaching efficiency including iodide concentration, oxidant, pH and temperature were evaluated. Over 97% and 93% of mercury can be efficiently leached from wastewater treatment sludge (W-S) and acid sludge (A-S). After leaching, the mercury concentration during leaching toxicity test is under the limits set for hazardous waste. Additionally, the electrolytic technology can efficiently recover mercury from leachate in the form of elemental mercury, and the leachate after electrolytic can be reused for mercury leaching. The mercury leaching kinetics follows the shrinking core diffusion model and is controlled by solid product diffusion. The mechanism research shows the leaching efficiency was strongly dependent on the distribution of mercury species in smelting waste. The consequence on mercury leaching and recovery could provide nonferrous smelters with a practical and yet easy-to-adopt perspective to reduce the risk of mercury contamination and selectively recover mercury resources from mercury containing smelting wastes.