Removal of pollutants of coking wastewater by adsorption

Electrocoagulation treated coking wastewater was subjected to further treatment using adsorption in batch mode. A commercial powder activated carbon (PAC) was used as an adsorbent. Effects of pH, adsorbent dose, phenol concentration, adsorption temperature and contact time were studied on removal of phenol and chemical oxygen demand (COD). First- and second-order kinetics models were tested, conforming second-order to fitted well. Adsorption was found to decrease slightly with increase in temperature. Sorption performances were also evaluated using Freundlich, Langmuir and Temkin isotherm models. All the models were fitted well with similar accuracy (maximum deviation 5%). The thermodynamic study shows the process to be exothermic. Adsorption at best condition: pH = 6, PAC load = 3 kg/m(3) and contact time = 4 h; phenol, COD and ammonia N removal were found to 99%, 33.5% and 91%, respectively, from 272 mg/dm(3) phenol, 793 mg/dm(3) COD and 65.9 mg/dm(3) ammonia N. Pareto analysis of variance (ANOVA) showed a high coefficient of determination values for phenol removal (R-2 = 0.9766) between the experimental values and predicted values in a second-order regression model. Treated effluent can be recycled for quenching of hot coke of coke oven.