Experimental Study And Mechanism Analysis Of Copper Adsorption From Wastewater By Carbon-based Adsorbents

Activated carbon（AC）and the pyrolytic char of dyeing sludge（DS）and the pyrolytic char of pear sawdust（PS）prepared at 650°C in the electrically heated fluidized bed were selected as raw materials.AC,DS and PS were modified by HNO₃ and urea to obtained modified carbons named UACN,UDSN and UPSN.The changes in morphology and chemical properties of adsorbents caused by modification methods were determined by characterization analysis methods,such as SEM-EDS,FTIR,BET,Boehm titration,elemental analysis and zeta potential.Raw carbon and modified carbon were used as adsorbents to remove copper from water.Single factor experiments were used to determine the optimal impregnation ratio of urea and the optimal adsorption conditions of copper.The adsorption processes of Cu（Ⅱ）on carbon-based adsorbents were judged by the cal Cu（Ⅱ）lation of adsorption isotherm,adsorption kinetics and adsorption thermodynamics.Acid washing can remove the ash of AC,DS and PS by HCl.The type and quantity of oxygen-containing functional groups on the adsorbents surface were increased by the oxidative modification of HNO₃.According to modification of HNO₃,the acidity of the adsorbents were increased and a small amount of nitrogen-containing functional groups were also added to the adsorbents.The impregnation of urea can further increase the type and quantity of nitrogen-containing functional groups on the adsorbents surface,causing the loss of some oxygen-containing functional groups and improving the basicity of the adsorbents.The adsorption capacity of the modified carbon was stronger than that of the original carbon in the adsorption experiments.Taking AC as an example,the adsorption capacity of Cu（Ⅱ）can be doubled after modification.The adsorption capacity of DS and PS can reach the level of commercial activated carbon after modification.The compositions of Cu（Ⅱ）adsorption by different carbon-based adsorbents are different due to the physicochemical properties of the adsorbents.According to the study of the adsorption mechanism of Cu（Ⅱ）on three modified carbons,it was found that the adsorption of Cu（Ⅱ）on UACN,UDSN and UPSN was mainly due to functional group complexation and ion exchange.