Bisphenol A mineralization by integrated ultrasound-UV-iron (II) treatment

Bisphenol A (BPA), an organic compound largely used in the plastic industry as a monomer for production of epoxy resins and polycarbonate, is an emerging contaminant that is released in the environment from bottles and packaging. BPA degradation (118 mu mol L-1) under sonochemical conditions was investigated in this study, using a 300 kHz frequency, with a 80 W electrical power. Under these conditions, BPA was eliminated by the ultrasound process (similar to 90 min). However, even after long ultrasound irradiation periods (10 h), more than 50% of chemical oxygen demand (COD) and 80% of total organic carbon (TOC) remained in the solution, indicating that most BPA intermediates are recalcitrant toward ultrasonic action. Accumulation of hydrogen peroxide from degrees OH and degrees OOH radical recombination was also observed. To increase the efficiency of BPA treatment, experiments combined ultrasound with Fe2+ (100 mu mol L-1) and/or UV radiation (254 nm): Ultrasound/UV; Ultrasound/Fe2+; Ultrasound/UV/Fe2+. Both UV and Fe2+ induced hydrogen peroxide dissociation, leading to additional degrees OH radicals and complete COD and TOC removal. Thus difficulties in obtaining mineralization of micropollutants like BPA through ultrasonic action alone, can be overcome by the Ultrasound/UV/Fe2+ combination. Moreover, this technique was found to be the most cost-effective one. So, the integrated ultrasound-UV-iron(II) process was shown to be of interest for the treatment of wastewaters contaminated with BPA.