Photocatalytic degradation of bisphenol A as an endocrine disruptor in aqueous suspension using Ag-TiO₂ catalysts

A novel photocatalyst, titanium dioxide (TiO₂) deposited with silver (Ag), was prepared by an ultrasonic-assisted sol-gel method and studied for the photocatalytic degradation of endocrine disrupting chemicals such as bisphenol A (BPA) under UV illumination, in order to determine its photocatalytic properties. A series of Ag-TiO₂ catalysts prepared with different Ag dosage were characterised by SEM, EDX, XRD, XPS, and UV-Visible absorption spectroscopy and their photocatalytic activity was evaluated in the degradation of BPA in aqueous suspension. The experiment demonstrated that the presence of Ag in TiO₂ catalysts could enhance the photocatalytic oxidation of BPA in aqueous suspension. It was found that the degradation of BPA by these catalysts followed the first-order kinetic model. The enhanced reduction of oxygen through better electron-hole separation in Ag-TiO₂ particles compared to pure TiO₂ particles increased the rates of BPA degradation. In the reaction of BPA degradation, the presence of two methyl groups in the BPA structure were initially attacked with OH and/or OOH radicals which have strong oxidising power, and then followed by the cleavage of the two phenyl moieties. Finally, the photomineralisation to CO₂ gas occurred via oxidative processes involving carboxylic acids and aldehydes.