Kinetics of aqueous photocatalytic oxidation of fulvic acids in a photocatalysis–ultrafiltration reactor (PUR)

The photocatalysis of natural organic matter, fulvic acid (FA), by P25 TiO2 in terms of UV254 and TOC concentrations was investigated in this study. The experiments were conducted in a lab-scale photocatalysis–ultrafiltration reactor (PUR) with TiO2 suspension. Groups of experiments were designed to examine the effects of pH of bulk solution, TiO2 concentration and additives strength as well as light intensity on the degradation of FA. Results from this study revealed that the degradable behaviour of FA can be reasonably described by first-order kinetics. In addition, it was demonstrated that low pH value, increased additives concentration and relative high light intensity were all beneficial parameters for TOC removal. By inspecting the relationship between rate constant (k) and influencing factors, an overall FA oxidation rate kinetic model was established. The utility of the model was demonstrated by the agreement of predictive and experimental results.