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

This work evaluates the feasibility of a solar-enhanced Fenton-like process using S₂O₈^2- (PS) and Fe²⁺ 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/Fe²⁺> Solar/PS > PS/Fe²⁺> Solar/Fe²⁺> Solar. The complete degradation of BPA was achieved by Solar/PS/Fe²⁺ treatment at a [PS]:[BPA] ratio of 20 in less than t_30W 5 in deionised water. The high efficiency of the Solar/PS/Fe²⁺ 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/Fe²⁺ 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 Fe²⁺ concentrations. Experimental evidence suggests that exposure to solar irradiation maintains suitable quantities of free Fe²⁺ in the reaction mixture, even at low catalyst concentrations (the molar ratio of [PS]:[Fe²⁺] varied from 1:0.01 to 1:0.08). The effects of HCO₃^-, SO₄^2-, and Cl^- were also examined. As expected, HCO₃^- and SO₄^2- 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 Fe²⁺concentration. Finally, the efficiency of Solar/PS/Fe²⁺ process was examined in diluted natural surface water and wastewater effluent. On eliminating the buffering action of HCO₃^-/CO₃^2- ions by lowering the pH value to 4.5, complete BPA degradation was achieved in all real water matrices.