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Laboratory studies were conducted to find out the efficacy of uniquely prepared zero valent iron impregnated silica in transforming xenobiotic chlorophenols namely 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. Continuous mode column experiments were performed to investigate the transformation of chlorophenols by varying pH, column height, flow rate and initial chlorophenol concentration. Reusability study of the zero valent iron impregnated silica was studied as well as the morphological changes and the chemical composition of the catalyst medium were also investigated. Dechlorination kinetic studies were conducted and the order of dechlorination of chlorophenols was found to be 2,4,6-trichlorophenol > 2,4-dichlorophenol > 4-chlorophenol. The optimum pH, column height and flow rate were found to be 7, 20 cm and 0.75 L/hr respectively for all chlorophenols in the reaction duration of 4 hr. Intermediates formed during dechlorination study were identified by gas chromatography-mass spectroscopy analysis. This method was applied to real pulp and paper wastewater and was found satisfactory.

This study presents the results of the Sono-Fenton process for the degradation of 2,4-dichlorophenol (DCP). The influential parameters such as H2O2, Fe2+ and pH for the Sono-Fenton process were investigated. Sono-Fenton method was found to be the best one for degradation efficiency of DCP when compared with that of the Fenton process. The optimum concentrations for the degradation of DCP using conventional Fenton’s method were found to be 20 mg/L of Fe2+ and 580 mg/L of H2O2 at pH 2.5. In the case of Sono-Fenton, the optimal concentrations were found to be 10 mg/L of Fe2+ and 400 mg/L of H2O2 at pH 2.5. Sono-Fenton method resulted in the reduction of required Fe2+ concentration (50%) and H2O2 concentration (31%). In addition, this method could be applicable even at pH 5.0 and a degradation efficiency of DCP was 77.6%. Kinetic studies for the degradation of DCP proved that the degradation of DCP tends to follow pseudo first order reaction and the rate constant was found to be 7 × 10−4 min−1.

Decolorisation of dye solutions by cobalt activated persulphate and ultrasonication has been investigated. Rhodamine B, Methylene Blue dye (basic dyes) and Acid orange II, Acid scarlet red 3R (acid dyes) were used as model compounds in this study. Immobilized cobalt ions, activated the persulphate to form highly reactive sulphate radicals. The degradation studies were conducted with only persulphate (PS), cobalt activated persulphate (PS+Co), persulphate+ultrasonication (PS+US) and cobalt activated persulphate+ultrasonication (PS+US+Co). The decolorisation efficiency were in the order of PSPS+CoPS+USPS+US+Co for all the four dye solutions. The effect of pH, dosage of persulphate as well as catalyst and contact time was investigated. Under the optimum condition, the decolorisation obeyed first-order kinetics. Nearly 90-97% of decolorisation was achieved with COD and TOC removal of about 65-73% and 53-62%, respectively, were achieved within an hour.