Removal routes of hazardous sodium oxalate in the alumina industry based on Bayer process: A review

As a key organic impurity in Bayer process, sodium oxalate seriously affects the quality of alumina products, thereby threatening the effective utilization of aluminum resources. Specifically, sodium oxalate continues to accumulate in the recovery solution and can eventually co-precipitate with aluminum trihydroxide. This is detrimental to the quality of the alumina, refines the trihydroxide particle size, and also causes the precipitated particles to become embrittled and therefore need to be removed. Herein, this review first outlines the sources of sodium oxalate in the Bayer process, then clearly summarizes the hazards of sodium oxalate, highlights on the existing disposal routes for sodium oxalate, and finally focuses on the opportunities and challenges faced by this area. The results of the literature review show that the existing sodium oxalate treatment process still has the problems of lower removal rate, higher usage cost and greater energy consumption. Advanced oxidation processes (AOPs) in chemical reaction methods is a promising technology for removing sodium oxalate. Furthermore, combining outfield with various sodium oxalate removal pathways can effectively increase the reaction rate and reduce disposal costs.