Arsenite to Arsenate Oxidation and Water Disinfection via Solar Heterogeneous Photocatalysis: A Kinetic and Statistical Approach

Arsenic (As) poses a threat to human health. In 2014, more than 200 million people faced arsenic exposure through drinking water, as estimated by the World Health Organization. Additionally, it is estimated that drinking water with proper microbiological quality is unavailable for more than 1 billion people. The present work analyzed a solar heterogeneous photocatalytic (HP) process for arsenite (As^III) oxidation and coliform disinfection from a real groundwater matrix employing two reactors, a flat plate reactor (FPR) and a compound parabolic collector (CPC), with and without added hydrogen peroxide (H₂O₂). The pseudo first-order reaction model fitted well to the As oxidation data. The treatments FPR–HP + H₂O₂ and CPC–HP + H₂O₂ yielded the best oxidation rates, which were over 90%. These treatments also exhibited the highest reaction rate constants, 6.7 × 10⁻³ min⁻¹ and 6.8 × 10⁻³ min⁻¹, respectively. The arsenic removal rates via chemical precipitation reached 98.6% and 98.7% for these treatments. Additionally, no coliforms were detected at the end of the process. The collector area per order (A_CO) for HP treatments was on average 75% more efficient than photooxidation (PO) treatments. The effects of the process independent variables, H₂O₂ addition, and light irradiation were statistically significant for the As^III oxidation reaction rate (p < 0.05).