Pecan shell activated carbon: synthesis, characterization, and application for the removal of copper from aqueous solution Original Research Article

Activated carbon with a high adsorption capacity for removal of copper ions from aqueous solution is produced from pecan shells. Air and phosphoric acid are used for the oxidation and the modification or development of oxygen- or phosphorus/oxygen-containing groups on the carbon surface. It was found that the adsorption capacity of the produced carbon is significantly higher than that of the commercial activated carbons that were tested, and comparable to an ion exchange resin designed for copper adsorption. Based on the results obtained from a variety of characterization methods, 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 using the Boehm titration method not only be considered as oxygen-containing acidic groups, but also as oxygen/phosphorus groups. From pH studies, it was observed that adsorption of copper at very low concentrations occurs by ion exchange of 2H+ from the surface with a Cu2+ ion from solution; while at higher concentrations, other forms of ion-exchange and surface complexation with oxygen- and phosphorus-containing functional group sites can be proposed as well.