In this study,a lignite was used as the adsorbent to remove COD in coal gasification wastewater at controlled conditions of reaction time,temperature,initial concentration,coal loading,etc. The adsorption behaviors were analyzed with reaction kinetic models and isothermal models. The results indicated that the adsorption reactions of COD on the lignite could be explained well by pseudo-second-order model,and the reaction rate was controlled mainly by film diffusion. In isothermal tests,Freundlich model could describe the mechanism of the adsorption of COD on the lignite. Through calculating the thermodynamic parameters,the adsorption was found spontaneous,exothermic and entropy dropping. Although the removal rate of COD reached as high as about 90%,the coal loading was so large as to use this method to completely remove COD in actual coal gasification wastewater treatment. However,this method could be used at a lower coal loading as a pretreatment with the purpose of decreasing treating difficulty for the subsequent bio-chemical treatment.
coal gasification wastewater