| Activated carbon with a high adsorption capacity for removal of metal ions from aqueous solution is produced from pecan shells by air/phosphoric acid activation. Based on the characterization results, it has been determined that the surface of the carbon is covered with a considerable concentration of phosphorus, present in the form of various functional groups. It is proposed that the acidic groups detected by using the Boehm titration method not only be considered as oxygen containing acidic groups, but also as oxygen/phosphorus groups. It is demonstrated that a minimum surface area is required, in addition to the proper surface functionalities, for a high metal ion uptake.; In the adsorption studies of single solute metal ions onto activated carbon, it is found that in most cases higher electronegativities and stability constants correspond to the higher adsorption levels. A correlation is developed that predicts the constants of Freundlich equation from the material parameters of the metal ions, and thus can predict the adsorption isotherms. A procedure is proposed for obtaining similar correlations for different conditions (temperature, pH, carbon type and dosage).; The ratio of equivalent metal ion adsorbed to proton released is calculated and it is found that in most cases, particularly at low concentrations, this ratio is close to one, suggesting the ion exchange of one proton with one equivalent metal ion as the dominant reaction mechanism.; The adsorption behavior of Cu(II) and Mn(II) in the presence of other metal ions that display strong or intermediate affinities for adsorption sites has been systematically investigated. In this investigation the following factors have been considered: (1) metal ion site competition; (2) charge accumulation near the carbon surface; and (3) speciation of the metal ions.; Two multicomponent adsorption models are proposed, and the results compared to two models presented in the literature. The performance of these models is evaluated by an analysis of error. It is found that models with three interaction parameters generally provide a better fit of the data. In most cases, the proposed two-parameter model gives acceptable results. |
