Removing and recycling mercury from scrubbing solution produced in wet nonferrous metal smelting flue gas purification process

Abstract

Wet purification technology for nonferrous metal smelting flue gas is important for mercury removal; however, this technology produces a large amounts of spent scrubbing solution that contain mercury. The mercury in these scrubbing solutions pose a great threat to the environment. Therefore, this research provides a novel strategy for removing and recycling mercury from the scrubbing solution, which is significant for decreasing mercury pollution while also allowing for the safe disposal of wastewater and a stable supply of mercury resources. Some critical parameters for the electrochemical reduction of mercury were studied in detail. Additionally, the electrodeposition dynamics and electroreduction mechanism for mercury were evaluated. Results suggested that over 92.4% of mercury could be removed from the scrubbing solution in the form of a Hg-Cu alloy under optimal conditions within 150 min and with a current efficiency of approximately 75%. Additionally, mercury electrodeposition was a quasi-reversible process, and the controlled step was the mass transport of the reactant. A pre-conversion step from Hg(Tu)42+ to Hg(Tu)32+ before mercury electroreduction was necessary. Then, the formed Hg(Tu)32+ on the cathode surface gained electrons step by step. After electrodeposition, the mercury in the spent cathode could be recycled by thermal desorption. The results of the electrochemical reduction of mercury and subsequent recycling provides a practical and easy-to-adopt alternative for recycling mercury resources and decreasing mercury contamination.