Copper(II) adsorption by activated carbons from pecan shells: Effect of oxygen level during activation

Agricultural by-products represent a considerable quantity of harvested commodity crops. The use of by-products as precursors for the production of widely used adsorbents, such as activated carbons, may impart a value-added component of the overall biomass harvested. Our objective in this paper is to show how the partial oxidation of phosphoric acid-impregnated pecan shells resulted in activated carbons with different affinities for a typical metal ion, copper(II), in aqueous sorption studies. The oxygen level was varied during activation by altering the sweep gas (air) flow rate in the furnace. Surface area and micropore volume of the produced carbon did not vary significantly with degree of oxidation, while the surface charge and the adsorption capacity were strongly dependent on the oxidative conditions. Surface area functional groups of C = O, aromatics, and phosphorus were confirmed by infrared spectroscopy. The results show that the yield of activated carbon product was higher in the more oxygen-deprived atmosphere but that the product had a lower affinity for adsorbing copper from an aqueous solution. The carbon with the highest adsorptive capacity was produced by activation in approximately 14% oxygen atmosphere, yielding adsorption values of 0.97 and 1.3 mmol of copper(II) per gram of carbon when the carbon had been in contact with a copper(II) solution with initial concentration of 10 and 20 mM of copper. respectively. Published by Elsevier B.V.