Study on the solvent extraction of thioarsenite in alkaline solutions with transformed quaternary ammonium salt

Under the advocacy of the sustainable development concept, the extraction process and reaction mechanism for arsenic in alkaline solution were studied with the aim of optimizing the alkaline leaching process of high‑arsenic copper smelting ash and promoting the recovery and harmlessness of arsenic. At 25 °C, the extractant methyltrioctylammonium underwent 6–8 conversions of Na 2 CO 3 solution with a concentration fraction of 12%, and the extraction capacity of thioarsenite was increased to 86.91%. Furthermore, at 25 °C, at an O/A ratio of 1:1 and an phase contact time of 7 min, the thioarsenite stripping exceeded 99%, when using 4% H 2 O 2  + saturated Na 2 CO 3 solution as the stripping. Fourier transform infrared spectroscopy , nuclear magnetic spectroscopy, ultraviolet spectroscopy , and other analytical methods were used to determine the mechanism of the extraction process. It was evident from our experiments that the CO 3 2− -type TOMAC and Na 2 CO 3 solutions could be recycled and reused repeatedly. The overall process required simple materials and did not generate liquid waste . The technique involves a short process, with superior cycle performance, low cost, and high efficiency.