Photo-Fenton-like degradation of bisphenol A by persulfate and solar irradiation.

Abstract

This work evaluates the feasibility of a solar-enhanced Fenton-like process using SO (PS) and Fe for the elimination of BPA, a model endocrine-disruption compound. This comparative study of BPA removal showed that among the approaches employed, the effectiveness of BPA degradation (10 mg/L) decreased in the order: Solar/PS/Fe> Solar/PS > PS/Fe> Solar/Fe> Solar. The complete degradation of BPA was achieved by Solar/PS/Fe treatment at a [PS]:[BPA] ratio of 20 in less than t 5 in deionised water. The high efficiency of the Solar/PS/Fe process revealed a synergistic effect (ϕ = 2.38) between the applied activation agents on the formation of reactive oxygen species (ROS) and subsequent decomposition of BPA. The treatment was accompanied by total organic carbon (TOC) removal (44%) in 45 min. Sequential generation of reactive oxygen species has made Solar/PS/Fe a kinetically effective process for removing BPA without accumulation of toxic intermediates. The reaction rate followed pseudo-first-order kinetics that increased with increasing PS and Fe concentrations. Experimental evidence suggests that exposure to solar irradiation maintains suitable quantities of free Fe in the reaction mixture, even at low catalyst concentrations (the molar ratio of [PS]:[Fe] varied from 1:0.01 to 1:0.08). The effects of HCO, SO, and Cl were also examined. As expected, HCO and SO inhibited BPA oxidation. The effect of Cl on the oxidation efficiency of BPA in Fenton-like systems depends not only on actual Cl concentrations but it is also highly influenced by molar ratios of Cl to oxidant and catalyst. Inhibition, which was caused by Cl in the mM range can be overcome by prolonging the reaction time or increasing the initial Feconcentration. Finally, the efficiency of Solar/PS/Fe process was examined in diluted natural surface water and wastewater effluent. On eliminating the buffering action of HCO/CO ions by lowering the pH value to 4.5, complete BPA degradation was achieved in all real water matrices.