Enhancement of photocatalytic oxidation of humic acid in Tio₂suspensions by increasing cation strength

Abstract

This study aimed at improving the photocatalytic (PC) oxidation of humic acids (HA) in TiO₂suspensions 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 TiO₂in suspensions at different pH and calcium concentrations. The experiment demonstrated that the adsorption of HA onto the TiO₂particles 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 TiO₂played 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 TiO₂suspensions with different initial concentrations was also studied using the Langmuir–Hinshelwood model.