A new treatment strategy for lead anode mud: Removal of fluorine and recovery of silver

Abstract

Lead anode mud contains a variety of valuable metals and harmful elements such as fluorine. The current treatment methods usually have a long noble metal recovery cycle and ignore the fluorine problem. In this paper, a new treatment strategy for lead anode mud was proposed. Firstly, the metals were leached into the HCl-FeCl₃-XCl (X = Na, Ca, NH₄) solution system and the fluorine simultaneously precipitated into the residue. The species distribution of metals in the HCl-FeCl₃-XCl system was simulated as a function of temperature and Cl concentration. The reaction conditions were optimized experimentally to Fe³⁺ concentration of 40 g/L, temperature of 90 °C, Cl concentration of 300 g/L (CaCl₂), liquid-solid ratio of 13:1, and reaction time of 10 min, achieving leaching efficiencies of Sb, As, Bi, Pb, and Ag above 99 %. Subsequently, the leaching residue yielded SiO₂ and NaF products by alkali conversion and evaporation concentration. Ag was selectively recovered from leaching solution with recovery efficiency of 98.8 % when NaI amount was 0.07 g/g mud. As a result, efficient recovery of Ag and stabilization of F from lead anode mud were realized.