Adsorption of Cu2+ from water using raw and modified coal fly ashes

In this study, we found that both raw and modified coal fly ashes effectively adsorb Cu2+ from wastewater. The adsorption capacities followed the order CFA> CFA-600> CFA–NaOH. The adsorption isotherms for Cu2+ on the raw and modified coal fly ashes fit the Langmuir, Freundlich, and DKR isotherms quite well. These adsorptions were endothermic in nature; the values of E (between 1.3 and 9.6 kJ mol−1) were consistent with an ion-exchange adsorption mechanism. The adsorptions of Cu2+ onto CFA, CFA-600, and CFA–NaOH followed pseudo-second-order kinetics.