Oxidative degradation of bisphenol A in municipal wastewater reverse osmosis concentrate (ROC) using ferrate(VI)/hydrogen peroxide

Abstract

The combination of ferrate(VI) with hydrogen peroxide (H2O2) was used for the degradation of bisphenol A (BPA) spiked in municipal wastewater reverse osmosis concentrate (ROC). The results showed that the combined Fe(VI) and H2O2 oxidant provided an additive effect to achieve greater degradation efficiencies of BPA in ROC compared to the use of Fe(VI) or H2O2 alone. The degradation efficiency of BPA was studied in detail by assessing the operating conditions, including Fe(VI) dosage, H2O2 dosage, the dosing strategy of Fe(VI) and H2O2, solution pH, and the initial concentration of BPA. It was found that over 99.0% of BPA was degraded (50 µg L−1) by using [Fe(VI)]/[H2O2] at a ratio of 1050:5000 and at pH 8.0. In addition, the degradation was also accompanied by 37.2% of dissolved organic carbon (DOC) removal and 94.0% of UV254 reduction. However, when the excess amount of H2O2 was added, it was found that H2O2 started to inhibit the degradation and the degradation efficiency of BPA in ROC lowered. It was also found that the simultaneous addition of Fe(VI) and H2O2 provided satisfactory BPA degradation. Similar degradation efficiency could be achieved by injecting the second oxidant into the system 10 min after adding the first oxidant at time zero. The apparent second-order reaction rate constant (kapp) obtained was 67.9 × 103 M−1 s−1 at a [Fe(VI)]/[H2O2] ratio of 1050:5000. The overall ecotoxicity of the treated water samples as measured by the Microtox bioassay technique decreased after the Fe(VI)/H2O2 treatment, which indicated that an insignificant amount, if not none, toxic degradation by-products was formed by the oxidative action of the Fe(VI)/H2O2 combined oxidant. The use of Fe(VI)/H2O2 as an alternative treatment option of cost-effectiveness than Fe(VI) alone in water and wastewater industries.