Degradation of Food industrial pollutants by photocatalysis with immobilized titanium dioxide

Abstract

The paper deals with application of advanced oxidation processes in degradation of surfactants, which represent large group of pollutants in food industrial waste waters. The photocatalytic degradation of two surfactants, an anionic sodium dodecyl sulphate (SDS) and cationic N-cetyl-N,N,N-trimethylammonium bromide (CTAB), was tested in a lab-scale UV reactor (Mikropur, Czech Republic) with immobilized titanium dioxide catalyst (P25, Degussa). Various conditions were verified, e.g. initial detergent concentrations (1.2–18.7 mg/l), oxygen flow rates (0 or 72.2 ml/min) and amount of catalyst used. The degradation in a presence of catalyst, oxygen and UV irradiation was the fastest process with maximum achieved rate constants of 0.0503 min − 1 at anionic surfactant degradation and 0.342 min − 1 at cationic detergent degradation. The energy demands for SDS degradation were also calculated and possible scale-up into large industrial scale discussed. Due to the relatively high organic content, food industrial waste waters contribute to the overall pollution problem. A need for water purification at low cost and energy with limited use of chemicals is still rising. Therefore, new advanced oxidation processes (AOPs), which are capable to oxidize and mineralize almost any organic contaminant, represent rapidly developing field of recent technological research. This study deals with possible application of photocatalysis with immobilized TiO 2 in degradation of surfactants, which are quite common pollutants in food industrial waste waters, and compares this method with others. The energy balance of the process and an outline of possible industrial application were mentioned as well. • Applications of advanced oxidation processes in food waste water treatment. • Anionic and cationic surfactants decomposed by photocatalysis with immobilized TiO 2 . • The effect of UV, oxygen flow and catalyst surface density on oxidation was tested. • The energy demands for the degradation of SDS were calculated. • Photocatalysis compared with other degradation methods.