Studies on Treatment of Textile Industry Wastewater

Abstract

The removal of COD and Dye from synthetic textile wastewater (STW) by electrochemical treatment (ECT) using Aluminum (Al) electrode material followed by adsorption with activated carbon was investigated in this study. STW was prepared by dissolving commercial grade reactive black dye with other chemicals as listed in table 4.1, in distilled water (DW). The prepared STW showed 3148 mg/l of COD and 200 mg/l of dye concentration Three factors and five level full factorial central composite (CC) design, based on response surface methodology (RSM) were used for experimental design and analysis of data.Three operational parameters, namely J: 14.17–308.64 mA/cm2; t: 30–180 min and pH: 4–10, have been taken as input parameters and percentage COD removal (Y1), percentage Dye removal (Y2), and specific energy consumed (KWh per litre of effluent treated) (Y3) have been taken as a responses of the system. Multi-response processes optimization by desirability function approach was used to optimize the ECT of STW which maximize the Y1 and Y2 simultaneously minimize Y3. The optimum values of operational parameters were found to be J 14.17 mA/cm2, t 102 min, and pH 6.25. Optimum Y1, Y2 andY3 were found to be 63.41%, 90.93% and 0.0035 kWh/kg effluent treated. First order kinetics fitted the kinetic data for COD removal and dye removal. Kinetic constant for dye removal and COD removal at 30°C was 0.0205 min-1 and 0.0097 min-1 and at 50°C was 0.037 min-1 and 0.011 min-1, respectively, which indicated removal increases with increase in temperature. Aluminium balance showed that aluminium in treated STW, sludge and scum was 25.16 mg/l, 0.50778g and 0.06006 g, respectively. Electrochemically treated STW COD content was found to be 1152 mg/l and this was further treated by adsorption process with activated carbon to meet the discharge standard. Optimum condition for the adsorptive treatment of STW was found to be: initial pH ≈ 3.0, adsorbent dose of 35 g/l and contact time ≈22 h giving 88.28% COD removal (135mg/l of residual COD). Langmuir isotherm was found to fit the equilibrium data by showing R2=0.95. Value of Langmuir isotherm parameters KL and qm were found to be 0.00004 l/mg and 4509.02 mg/g, respectively. A high qm value indicates a higher affinity of adsorbate to adsorbent.