Oxidative treatment of bisphenol A in municipal wastewater reverse osmosis concentrate using Ferrate(VI)

Abstract

Reverse osmosis concentrate (ROC) resulting from the municipal wastewater recycling processes poses significant environmental and health risks as it contains significant concentrations of harmful compounds, including phenolic chemicals including bisphenol A (BPA). In this study, the effect of ferrate(VI) (or Fe(VI)) oxidation on the degradation of BPA (50 µg L−1) in a typical ROC matrix was investigated. The influence of process variables including the [Fe(VI)]/[BPA] ratios (7–50), initial pH (5.0–8.0) and reaction temperature (15–25 °C) was studied. Fe(VI) was found to be highly effective in degrading BPA in the complex ROC matrix with various operating conditions. At 25 °C, over 90% degradation of BPA was achieved at the [Fe(VI)]/[BPA] ratio of 50, and an initial pH of the ROC at 8.0 after 90 min of reaction. Under such conditions, the reduction in dissolved organic carbon (DOC) was found to be 34% accompanied by a 95% reduction in UV254 absorbance (initial value 0.750 cm−1) with 96.4% SUVA reduction. Additionally, the residual concentration of Fe(III) at pH 8.0 was the lowest compared to other pH conditions at a fixed [Fe(VI)]/[BPA] ratio of 50. Fluorescence regional integration (FRI) analyses revealed that Fe(VI) preferentially react with fulvic acid-like and humic acid-like compounds, and aromatic protein II in the ROC. This indicated Fe(VI) effectively breaking down electron-rich moieties groups including phenols and other organics in ROC. The apparent second-order rate constant (kapp) for BPA degradation was determined to be 2.27 × 102 M−1 s−1 at pH 8.0 at a [Fe(VI)]/[BPA] ratio of 50, and the value of reaction rate constant increased proportionally with increasing molar ratio at the range studied. The effectiveness of Fe(VI) in the degradation of BPA in the ROC demonstrates the potential of using Fe(VI) as an efficient oxidant to remediate the micropollutants present in water and wastewater.