Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/25/2009
Publication Date: 7/1/2009
Citation: Klasson, K.T., Wartelle, L.H., Rodgers III, J.E., Lima, I.M. 2009. Copper (II) Adsorption by Activated Carbons from Pecan Shells: Effect of Oxygen Level During Activation. Industrial Crops and Products. 30(1):72-77.
Interpretive Summary: Agricultural wastes represent a large amount of harvested crops. The use of wastes as starting material for the production of adsorbents (material that removes pollutants), such as activated carbons, may give a value-added component of the overall biomass harvested. Our objective in this paper is to show how some intentional chemical destruction of acid-soaked pecan shells resulted in activated carbons with different capabilities of removing metal pollutants from a water solution. The degree of chemical destruction was varied by changing the air flow rate in the oven. The results show that the amount of activated carbon product was when little air was used in the oven but that the product was not as good in removing a copper metal pollutant from water. The carbon with the best copper metal removal capacity was made when a lot of air was used in the oven. The amount of surface or small pores in the carbon did not change much, regardless of the amount of air used. However, the chemical make-up of the surface changed significantly, which was proven with chemical and other measurement techniques.
Technical Abstract: 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 metal ion in aqueous sorption studies. The degree of oxidation was varied by altering the sweep gas (air) flow rate in the furnace. The results show that the yield of activated carbon product was higher in a more oxygen-deprived atmosphere but the product had a lower affinity for adsorbing a typical metal cation, copper (II), 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 was in contact with 10 mM and 20 mM of copper (II) solution, respectively. Surface area and micropore volume did not vary significantly with the degree of oxidation, while the surface charge and the adsorption capacity was strongly dependent on the oxidative conditions. Surface area functional groups of C=O, aromatics, and phosphorus were confirmed by infrared spectroscopy.