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This work investigates the degradation kinetics of a recalcitrant organic pollutant, cetyltrimethylammonium bromide (CTAB), using direct UV and UV-HO advanced oxidation processes. Direct photolysis at 253.7 nm showed only 55% degradation up to fluence dose of 40.65 J/cm for an initial CTAB concentration of 100 mg/L. The apparent fluence-based pseudo-first-order rate constant and quantum yield were 2.29(±0.325) × 10 cm/mJ and 0.305(±0.043) mol/Einstein, respectively. In case of UV-HO, >99% degradation was observed up to a fluence dose of 0.79 J/cm. The rate constant was ∼200 times higher compared to direct photolysis, which was due to hydroxyl radical generation in the UV-HO process. The second-order hydroxyl radical rate constant for CTAB was found to be 1.59(±0.18) × 10 M s. The effects of HO dose, initial CTAB concentration and relevant water quality parameters (pH, alkalinity and nitrate concentrations) were studied; all of these influenced the rate constants. CTAB degradation was also examined in the municipal wastewater matrix. It is concluded that UV-HO represents an efficient treatment process for CTAB in environmental matrices.

This paper deals with the degradation kinetics of an anionic surfactant (sodium dodecyl sulfate, SDS) under UV and UV-H2O2 advanced oxidation process (AOP). Experiments were performed in a batch reactor which emits monochromatic light centered at 253.7 nm. The photon flux of the UV reactor was 1.9(±0.1)×10-4 Einstein/L-min. Under direct UV, only 45% SDS degradation was observed at a fluence of 40.65 J/cm 2 for initial SDS concentration of 0.35 mM. The apparent fluence-based pseudo-first order rate constant was found to be 1.77(±0.24)×10-5 cm 2 /mJ. However, very fast degradation (almost 100%) was observed for UV-H2O2, process at a fluence of 0.45 J/cm 2. The apparent fluence-based rate constant in this case was found to be about 450 times higher than direct photolysis. Further, using a probe compound (para chlorobenzoic acid) competition kinetics study was performed to determine the second order hydroxyl radical rate constant for SDS. The rate constant thus obtained was 8.18 (±0.26)×10 9 M-1 s-1. Effects of different operating parameters like H2O2 concentration, initial SDS concentration and water quality parameters, including pH (7-12), alkalinity (0-10 mM HCO3-) and nitrate concentration (0-1 mM as NO3-), were investigated. The observed rate constants were influenced by all the studied parameters and these parameters were optimized for field application. Degradation of SDS was also carried out in municipal wastewater. In conclusion, UV-H2O2 AOP is an efficient treatment method for SDS in environmental matrices.