Intensification of textile effluent chemical oxygen demand reduction by innovative hybrid methods

This study presents the reduction of textile effluent chemical oxygen demand (COD) by sonolysis, sorption, sono-sorption and sono-Fenton-sorption methods. Eco-friendly, cost effective, easily available tea waste activated using sodium hydroxide, formaldehyde, ultrasound irradiation (US), formaldehyde followed by US, and sodium hydroxide followed by US was used as an adsorbent. Better activation was obtained with formaldehyde followed by US treatment and this was confirmed from scanning electron microscopy (SEM) images obtained and Boehm titration. The effect of sorbent dosage, particle size and initial pH of the effluent on COD reduction was studied. The sono-Fenton-sorption with 50 mg/L of Fe(II) and 400 mg/L of H2O2 offered a maximum COD reduction of 95.5%. Langmuir-Hinshelwood kinetics was used to fit the data obtained with sono-sorption and sono-Fenton-sorption. The analysis of adsorption mechanism revealed that the intra-particle diffusion coefficient was enhanced by several folds by the incorporation of ultrasound. The changes in morphology of the sorbent before and after sono-Fenton-sorption were analyzed using SEM images. The changes in surface functional groups of the sorbent before and after sono-Fenton-sorption were analyzed using Fourier transform infrared (FT-IR) spectroscopy and Boehm titration. This novel hybrid treatment enhanced the biodegradability (BOD/COD) of the waste water from 0.31 to 0.71. The ecotoxicity test using disk diffusion method showed that the treated effluent was less toxic than untreated one. It was found that, the tea waste can be reused up to three cycles effectively. (C) 2010 Elsevier B.V. All rights reserved.