Intensification of degradation of Rhodamine B using hydrodynamic cavitation in the presence of additives

In the present work, degradation of Rhodamine B, a waste dye effluent, has been studied using a hydrodynamic cavitational reactor with intensification studies in the presence of hydrogen peroxide, carbon tetrachloride and Fenton's reagent as the possibly intensifying additives. In hydrodynamic cavitation reactor, the effect of two different cavitating devices viz. orifice plate and venturi has been investigated. The effect of operational conditions such as the inlet pressure (over a range 2.9–5.8 atm), operating temperature (30 and 40 °C) and pH (over a range 2.5–11) on the extent of degradation has also been investigated. In the intensification studies, the H2O2 loading was optimized over a range of 10–200 mg/l whereas for study related to Fenton's reagent, FeSO4:H2O2 was used in the optimum ratio of 1:5. In all the systems investigated, 99.9% of Rhodamine B (10 ppm initial concentration) was obtained using a combination of cavitation and H2O2 as well as a combination of cavitation with Fenton chemistry. Combination of cavitation with CCl4 resulted in 82% degradation. TOC analysis at various optimum conditions was also performed to quantify the extent of mineralization and it has been observed that the degradation of parent compound is faster as compared to the extent of mineralization. Some insights into possible mechanistic details for degradation of Rhodamine B have also been established using a spectra scan.

Research highlights▶ Rhodamine B can be effectively oxidized from water by using hydrodynamic cavitation. ▶ Venturi gives better efficacy as compared to a single hole orifice plate. ▶ The extent of degradation can be maximized by using optimum inlet pressure, inlet temperature and acidic conditions. ▶ Hydrogen peroxide or Fenton chemistry is a better intensifying additive as compared to carbon tetrachloride.