ABSTRACT
Treatment of textile dyeing industry (TDI) effluent was investigated using hydrodynamic cavitation (HC) and in combination with advanced oxidation reagents such as air, oxygen, ozone and Fenton's reagent. Slit venturi was used as the cavitating device in HC reactor. The effects of process parameters such as inlet pressure, cavitation number, effluent concentration, ozone and oxygen flow rate, loading of H2O2 and Fenton's reagent on the extent of reduction of TOC, COD and color were studied. Efficiency of the hybrid treatment processes were evaluated on the basis of their synergetic coefficient. It was observed that almost 17% TOC, 12% COD, and 25% color removal was obtained using HC alone at inlet pressure of 5bar and pH of 6.8. The rate of reduction of TOC and COD decreased with dilution of the samples. HC in combination with Fenton's reagent (FeSO4·7H2O:H2O2 as 1:5) was most effective with reduction of 48%TOC and 38% COD in 15min and 120min respectively with almost complete decolorization (98%) of the TDI effluent. Whereas HC in combination with oxygen (2L/min) and ozone (3g/h) produced reduction of 48% TOC, 33% COD, 62% decolorization and 48% TOC, 23% COD, 88%, decolorization of TDI effluent respectively.
ABSTRACT
Decolorization of reactive blue 13 (RB13), a sulphonated azo dye, was investigated using hydrodynamic cavitation (HC). The aim of research article is to check the influence of geometrical parameters (total flow area, the ratio of throat perimeter to its cross-sectional area, throat shape and size, etc.) and configuration of the cavitating devices on decolorization of RB13 in aqueous solution. For this purpose, eight cavitating devices i.e. Circular and slit venturi, and six orifice plates having different flow area and perimeter were used in the present work. Initially, the effects of various operating parameters such as solution pH, initial dye concentration, operating inlet pressure and cavitation number on the decolorization of RB13 have been investigated, and the optimum operating conditions were found. Kinetic analysis revealed that the decolorization and mineralization of RB13 using HC followed first order reaction kinetics. Almost 47% decolorization of RB13 was achieved using only HC with slit venturi as a cavitating device at an optimum inlet pressure of 0.4MPa and pH of the solution as 2.0. It has been found that in case of orifice plates, higher decolorization rate of 4×10-3min-1 was achieved using orifice plate 2 (OP2) which is having higher flow area and perimeter (α=2.28). The effect of process intensifying agents (hydrogen peroxide and ferrous sulphate) and different gaseous additives (oxygen and ozone) on the extent of decolorization of RB13 were also examined. Almost 66% decolorization of RB13 was achieved using HC combined with 2Lmin-1 of oxygen and in combination with ferrous sulphate (1:3). Nearly 91% decolorization was achieved using HC combined with H2O2 at an optimum molar ratio (dye:H2O2) of 1:20 while almost complete decolorization was observed in 15min using a combination of HC and ozone at 3gh-1 ozone feed rate. Maximum 72% TOC was removed using HC coupled with 3gh-1 ozone feed rate.
ABSTRACT
In the present study, decolorization and mineralization of a cationic dye, Rhodamine 6G (Rh6G), has been carried out using hydrodynamic cavitation (HC). Two cavitating devices such as slit and circular venturi were used to generate cavitation in HC reactor. The process parameters such as initial dye concentration, solution pH, operating inlet pressure, and cavitation number were investigated in detail to evaluate their effects on the decolorization efficiency of Rh6G. Decolorization of Rh6G was marginally higher in the case of slit venturi as compared to circular venturi. The kinetic study showed that decolorization and mineralization of the dye fitted first-order kinetics. The loadings of H2O2 and ozone have been optimized to intensify the decolorization and mineralization efficiency of Rh6G using HC. Nearly 54% decolorization of Rh6G was obtained using a combination of HC and H2O2 at a dye to H2O2 molar ratio of 1:30. The combination of HC with ozone resulted in 100% decolorization in almost 5-10min of processing time depending upon the initial dye concentration. To quantify the extent of mineralization, total organic carbon (TOC) analysis was also performed using various processes and almost 84% TOC removal was obtained using HC coupled with 3g/h of ozone. The degradation by-products formed during the complete degradation process were qualitatively identified by liquid chromatography-mass spectrometry (LC-MS) and a detailed degradation pathway has been proposed.
