Neodymium upgrading of tin slag using acid leaching and multistage precipitation

Tin metal production in Indonesia increased in 2018 and 2019. As the production of tin metal increases, the production of slag from tin smelting also increases. Tin slag can be further utilized by extracting valuable metals from it, such as rare earth elements (REE). One of the rare earth elements observed in this study is neodymium (Nd). The use of Nd includes the manufacture of Nd-based permanent magnets. According to individual REE oxide demand and production data in the world, the supply of Nd2O3 in the world is experiencing a shortage of 2,025 tons per year. The purpose of this study is to determine the optimal concentration and ratio of solids to nitric acid in tin slag leaching after the alkaline fusion process and the pH of Nd precipitation. Alkaline fusion as a pre-treatment step to open the silica structure in the slag fusion was carried out for 2 h at 700 °Cwith a ratio of NaOH: slag (gram: gram) = 2:1 to produce frit, which will be leached using water. The residue from water leaching was followed by nitric acid leaching with a concentration variation of 1.75 M, 2.25 M, 2.75 M, 3.25 M, and 3.75 M, then continued with a solid percentage variation of 8%, 11%, 15%, 20%, and 26%. The nitric acid leaching filtrate was precipitated with ammonia at pH 6, 8, and 10. The results obtained were a percent of Nd extraction of 65.172% obtained at a concentration of 3.25 M, a solid percent ratio of 15% with a temperature of 60 °C, a grain size of −200 + 325 mesh, a stirring speed of 250 rpm, and a leaching time of 60 min. Nd deposition efficiency occurred at a pH 6 of 47.79%. Increased Nd content from 1.036% to 3.257%.