Recovery of bismuth and other metals from blast furnace dust by leaching with oxalic acid-based deep eutectic solvent and precipitation

Abstract

Eutectic solvents, with the advantages of easy synthesis, high chloride content, non-aqueous environment, and low costs are the most promising alternatives to ionic liquids for leaching and recovery of metals from waste resources. The leaching of bismuth has been mainly conducted using chlorinated salts and strong acids in previous studies. The use of conventional ionic liquids can be costly. In addition, there has only been limited research into developing strategies for the recovery of bismuth from blast furnace (BF) dust using a deep eutectic solvent (DES) made of choline chloride and oxalic acid. In this work, an oxalic acid-based deep eutectic solvent was used for selective recovery of bismuth from blast furnace dust. A leaching efficiency of 94.9% Bi was achieved at the most suitable conditions (stirring speed: 300 rpm, liquid-solid ratio: 5 mL/g, temperature: 70°C, time: 20 h). The zinc and iron which are impurities in the leach solution were removed by hydrolysis and photoinduced reduction process, and the by-products of ZnC2O4·2H2O and FeC2O4·2H2O had purities of 86.6% and 96.8%, respectively. Another hydrolysis was employed to recover Bi(III) from the leach solution and the product of BiOCl was obtained with a total Bi recovery efficiency of 89.1%. The proposed process in this work is resource-saving and friendly to the environment.