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Catalytic Ozonation of Dye Solutions in a Semi-Batch Reactor

Pirgalıoğlu, Saltuk
Treatment of textile wastewaters containing dye materials using the conventional methods based on biological treatment is not possible. In order to overcome this problem, ozonation based on the oxidation of organic pollutants with ozone gas dissolved in aqueous phase have been studied widely. Catalytic ozonation and advanced oxidation processes (AOP) are also used in order to increase the efficiency of sole ozonation In this work, catalytic ozonation processes in the presence of Copper Sulfide (CuS) powder and a synthesized catalyst by the impregnation of iron on alumina (Fe/Al2O3) were studied separately in the treatment of dye solutions, namely Remazol Brilliant Blue-R (RBBR) and Reactive Black-5 (RB-5). Besides catalytic ozonation runs, ozonation parameters and ozonation mechanism were also studied and a model was developed for the semi-batch ozonation. Both catalysts increased the oxidation of side products measured by the decrease in the amount of total organic carbon (TOC) in the treated dye solutions. Dye removal rates were also enhanced in the treatment of RB-5 dye solutions while no significant effect was observed on dye removal rates of RBBR solutions. TOC removals above 90% were observed in the catalytic ozonation using CuS for both of the dye solutions at pH =10 having initial dye concentration of 100 mg/L. The most significant effect of the catalyst addition was observed at pH = 3 where the TOC removals of non-catalytic ozonation were the lowest. CuS addition increased percent TOC removal at the end of the reaction period of 80 min by 123% in the treatment of 100 mg/L RBBR solution, and by 65% in the treatment of 100 mg/L RB-5 solution at pH = 3. On the other hand, addition of Fe/Al2O3 catalyst increased TOC removal of 100 mg/L RB-5 solution by 52 % at pH = 3. In addition, volumetric mass transfer coefficients (kLa) of ozone in the absence and in the presence of a chemical reaction between dye and ozone were estimated from modeling. A correlation for the enhancement factor of ozone absorbed into dye solutions in terms of initial dye concentration was obtained and reported.