Effect of aqueous matrix species on synergistic removal of bisphenol-A under solar irradiation using nitrogen-doped TiO₂/AC composite

A bi-functional composite, namely nitrogen-doped titanium dioxide anchored on activated carbon (N-TiO₂/AC) was synthesized using the sol-gel method with two-stage calcination procedure. Bisphenol-A (BPA) was used as a model contaminant. The effects of co-existing aqueous species viz. prevalent inorganic anions (Cl^-, NO₃^-, SO₄^2-, HCO₃^-, H₂PO₄^- and silica), organic anion (C₂O₄^2-), photocatalysis inhibitor (CH₃OH) and oxidant (H₂O₂) were comprehensively studied using the best performing composite, i.e. N-TiO₂/AC (400M-700T). Introduction of H₂PO₄^- (0.01-0.1mM) led to a slight enhancement in the photocatalytic degradation (PCD) efficiency for BPA removal. Provision of AC support for N-TiO₂ abated the inhibitory effect induced by SO₄^2- at high concentration (up to 100mM). Decreased BPA photodegradation was observed with increasing concentrations of C₂O₄^2-, thus suggesting that direct hole (h⁺) oxidation occurred. Variation of pH (from 4 to 10) in the presence of 0.1mM of silica induced little effect on BPA photodegradation. Addition of H₂O₂ into N-TiO₂/AC system apparently resulted in decreased BPA removal because some adsorbed BPA was released from surface-degraded AC.