Photocatalytic detoxification of metal-organic polluted waters: Magnetic vs. ultrasonic stirring comparison

The photocatalytic degradation of salicylic acid (2-hydroxybenzoic acid) and the reduction of gold (III) ion were investigated in aqueous solutions containing titanium dioxide (TiO2) suspensions under irradiation of simulated solar light. The TiO2---based photocatalytic process has proven effective for the removal of many of toxic metals and organic compounds found in polluted water effluents. Photocatalysis takes advantage of the simultaneous reduction of metal cations and oxidation of organic compounds present in solution. In an attempt to understand this process, variables such as concentration of the organic pollutant and agitation procedure with the photoirradiated solution were investigated. In our research, Au3+ ions have been used as a redox reagent for the photocatalytic oxidation of the organic in contact with illuminated titanium dioxide. Degradation of salicylic acid as the organic pollutant was studied. Magnetic and ultrasonic stirring were investigated to compare the reactant degradation pathway. Analytical AAS, HPLC and GC-MS were used for detection of reactants, intermediates and products. Several aromatic chlorinated intermediates that originated from salicylic acid during the photocatalytic treatment were detected. In addition, surface analyses show differences in the gold deposit characteristics between ultrasonic and magnetic stirring.