Experimental Investigation on Preparation of NaMgF 3 and MgF 2 from the Leaching Solution of SPL

Generally, there is a large amount of sodium fluoride in the spent potlining of aluminum electrolysis (SPL), which is a high-value fluorine resource. Therefore, recycling the fluorine resource from SPL is of profound significance, which not only saves the primary fluorine resource but also reduces energy consumption and carbon emissions. In this paper, co-precipitation method for the preparation of NaMgF 3 and MgF 2 was explored by using the leaching solution of SPL as raw material and magnesium sulfate as reagent. The results showed that the decisive factor for the type of product was the molar ratio of magnesium ion to fluorion (M/F) rather than the reaction temperature and holding time. When M/F is < 0.33, the product was mainly NaMgF 3 . When M/F increased further to 0.33–0.81, MgF 2 was gradually produced, and the product was a mixture of NaMgF 3 and MgF 2 . When M/F exceeded 0.81, the product was mainly MgF 2 .