Enhancement of photocatalytic oxidation of humic acid in Tio?suspensions by increasing cation strength

Abstract

This study aimed at improving the photocatalytic (PC) oxidation of humic acids (HA) in TiO?suspensions by adding cationic ion such as calcium or magnesium. A set of tests was first conducted in the dark to study the adsorption of HA onto TiO?in suspensions at different pH and calcium concentrations. The experiment demonstrated that the adsorption of HA onto the TiO?particles was either pH-dependent or calcium strength-dependent due to electrostatic interaction and calcium ion bridging. The photodegradation of HA in the presence of UV irradiation was investigated as a function of pH and the concentration of calcium and magnesium ions. The results showed that the adsorption behavior between HA and TiO?played a very important role during the PC oxidation process. The PC oxidation could be enhanced at neutral pH by increasing the cation strength. The kinetics of HA PC degradation in TiO?suspensions with different initial concentrations was also studied using the Langmuir¡VHinshelwood model.