Removal of Cl(−I) from strongly acidic wastewater using NaBiO3: A process of simultaneous oxidation and precipitation

Abstract

It was proposed to recycle strongly acidic wastewater generated from nonferrous smelting industries as diluted sulfuric acid after the contaminants being removed, however, Cl(−I) removal from strongly acidic wastewater remains a difficulty. In this work, a process of simultaneous oxidation and precipitation using NaBiO3 for Cl(−I) removal from strongly acidic wastewater was proposed, and 98.1% of Cl(−I) was efficiently removed at the stoichiometric NaBiO3 dosage under 30 °C. The mechanism exploration indicated that Cl(−I) was removed in two ways. In the first way, Cl(−I) was oxidized to generate Cl2: (1) NaBiO3 was dissolved, and the produced BiO3− oxidized Cl(−I) and OH− to Cl and OH, respectively; (2) OH oxidized Cl(−I) to generate Cl−; and (3) Cl combined to produce Cl2. In the second way, Bi3+, the reduced product of BiO3−, reacted with H2O and Cl(−I) to produce BiOCl precipitates. Additionally, through treatment by the NaOH absorption solution for Cl2, almost all of BiOCl product was transformed to the regenerated NaBiO3, which was further employed in Cl(−I) removal. Finally, Cl(−I) was transferred from wastewater to the NaOH/NaCl concentrate. This study offered a theoretical foundation for the development of the method to remove Cl(−I) through oxidation.