Abstract:The photocatalytic, sonolytic and sonophotocatalytic degradation of 4-chloro-2-nitrophenol (4C2NP) using heterogeneous (TiO 2 ) was investigated in this study. Experiments were performed in slurry mode with artifi cial UV 125 watt medium pressure mercury lamp coupled with ultrasound (100 W, 33+3 KHz) for sonication of the slurry. The degradation of compound was studied in terms of fi rst order kinetics. The catalyst concentration was optimized at 1.5 gL -1 , pH at 7 and oxidant concentration at 1.5 gL -1 . The results obtained were quite appreciable as 80% degradation was obtained for photocatalytic treatment in 120 minutes whereas, ultrasound imparting synergistic effect as degradation achieved 96% increase in 90 minutes during sonophotocatalysis. The degradation follows the trend sonophotocatalysis > photocatalysis > sonocatalytic > sonolysis. The results of sonophotocatalytic degradation of pharmaceutical compound showed that it could be used as effi cient and environmentally friendly technique for the complete degradation of recalcitrant organic pollutants which will increase the chances for the reuse of wastewater.
A B S T R A C TThe sonophotocatalytic degradation of pharmaceutical industry wastewater was studied with a TiO 2 slurry mode process with UV 125 W medium-pressure mercury lamp coupled with ultrasound (100 W, 33 ± 3 kHz). The degradation of wastewater was investigated in terms of reduction in COD that confirmed the apparent first-order degradation kinetics. The rate constant was greatly affected by catalyst dose, variation in pH, and concentration of oxidant (H 2 O 2 ).The catalyst concentration was optimized at 1.0 g L À1 , pH at 4, and the oxidant concentration at 0.075 g L À1 . The first-order rate constants obtained from coupled sonophotocatalysis were two-folds than those obtained from photocatalysis and approximately ten-folds than sonolysis. The COD reduction follows the trend, sonophotocatalysis > photocatalysis > sonocatalytic > sonolysis. The study demonstrates better efficiency of coupled sonophotocatalysis over independent treatment processes.
Sequential treatment studies have been done using photo-Fenton and sono-photo-Fenton, and compared with individual processes to analyze possible favorable effects of combined systems for the degradation of Reactive Black 5 (RB5). The coupled system enhances the degradation as compared to the ultrasound or UV-light irradiation processes along with the reduction in treatment time. Batch runs were carried out to investigate the process operational conditions: pH, H 2 O 2 dosage, Fe 2+ dosage, and RB5 concentration; to obtain the results at best possible operating conditions render advanced oxidation processe (AOP) competitive with other processes; and to ensure the rapid and complete transformation of the toxic organic compounds to benign chemicals. Degradation observed was 69% under Fenton and 93% under photo-Fenton with experimentally optimized conditions i.e. pH 4, Fe 2+ concentration 0.050 gL −1 and H 2 O 2 0.150 gL −1 after 20 min. Sono-photo-Fenton treatment enhances the degradation up to 98% with experimentally optimized parameters within 12 min of reaction.
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