Chloride removal from sewage using bismuth trioxide: Characterization and optimization by response surface methodology (RSM)

Abstract

Chloride ions, omnipresent environmental pollutants, can have devastating and irreversible effects on sustainable water ecosystems worldwide. Herein, bismuth oxide (Bi2O3) was employed as an antichlor to effectively dislodge chloride, and systematic investigations were conducted to assess the effect of various factors on dechlorination. Response surface methodology with Box-Behnken designs was used to optimise the dechlorination process, and the control parameters were determined by fitting high quality predictive model incorporating saliency variables and interactions. Furthermore, X-Ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS) were performed to determine the phase composition, micromorphology and binding energy of the dechlorinated products. The optimum parameters for dechlorination, as determined by response surface methodology (RSM), were found to be pH 0.53, bismuth trioxide multiple of 1.48, and initial chloride concentration of 3.62 g/L, giving a theoretical removal rate of 90.0563 %. The data analysis presented provides evidence that response surface methodology is a reliable approach for optimizing the interaction effects of dechlorination process parameters, resulting in improved performance in the removal of almost non-removable chloride.