Increasing the circularity of the copper metallurgical industry: Recovery of Sb(III) and Bi(III) from hydrochloric solutions by integration of solvating organophosphorous extractants and selective precipitation

Abstract

The lack of high-purity ores has made the copper industry exploit low-impurity ores containing As, Sb and Bi which can affect the final product quality due to the floating insoluble arsenates. This is usually solved by treating the electrorefining electrolyte in a polishing stage devoted to removing Sb and Bi using aminophosphonic resins. Once the resin is saturated, it is regenerated using 6 M HCl, and the eluate produced is treated with CaO(s) to precipitate both Sb and Bi. However, this stream is of interest due to the inclusion of both elements in the Critical Raw Material list from the European Union. Therefore, the linear management option must be substituted by a circular approach. This work aims to develop such approach by the selective separation and recovery of Sb and Bi from HCl stream polluted with As. The method presented was based on the use of using a solvating mixture of alkylphosphine oxides commercialized as Cyanex 923 dissolved in kerosene and 1-decanol (10 %) as phase modifier. The separation factors of Sb(III) and Bi(III) from As(V) were evaluated and optimized as function of both extractant concentration and the aqueous to organic phase ratio. Results showed that at the lowest Cyanex 923 concentration (0.15 mol/L) and working at an A/O ratio of 1/3, it could be possible to extract 39 % Bi and 78 % Sb with As co-extraction below 2.5 %. Both Sb and Bi were easily recovered (>90 %) using 8 M HNO3 as stripping agent. Following a treatment using NaOH/NaCl or NaOH, both elements could be recovered either as oxychlorides (SbOCl(s) and BiOCl(s)) or oxides (Sb2O3(s) and BisO3(s)).