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

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. [Display omitted] •Cl(−I) was efficiently removed from strongly acidic wastewater using NaBiO3.•Cl(−I) was removed in the form of Cl2 gas and BiOCl precipitates.•NaBiO3 was regenerated from BiOCl using Cl2 under alkaline conditions.•Cl(−I) was transferred from wastewater to the NaOH/NaCl concentrate.