Adsorption of organic pollutants from coking wastewater by activated coke

Activated coke (AC) was studied to adsorb organic pollutants from coking wastewater. This study initially focused on the sorption kinetics and equilibrium sorption isotherms of AC for the removal of chemical oxygen demand (COD) from coking wastewater. UV-vis spectra and gas chromatograph/mass spectroscopy (GC/MS) were used to detect the changes of coking wastewater quality. The surface morphology of AC before and after adsorption was observed using environmental scanning electron microscope (ESEM). The results showed that when the dose of AC was 200 g L-1, 91.6% of COD and 90% of color could be removed after 6 h of agitation at 40 degrees C. The kinetics of adsorption of COD from coking wastewater onto AC was fit to the pseudo-second order model. The intraparticle diffusion of COD onto AC was identified to be the rate limiting step. The adsorption of COD onto AC was enhanced with an increase of temperature, indicating that the adsorption process would be a chemical adsorption rather than a physical one. Redlich-Peterson gave a better fit to all adsorption isotherms than the Langmuir and Freundlich, which might simulate the adsorption of high concentration of organic pollutants in coking wastewater. (C) 2010 Elsevier B.V. All rights reserved.