Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2003
Publication Date: 9/26/2003
Citation: Bansode, R.R., Losso, J.N., Marshall, W.E., Rao, R.M., Portier, R.J. 2003. Adsorption of volatile organic compounds by pecan shell-and almond shell-based granular activated carbons. Bioresource Technology. 90:175-184.
Interpretive Summary: Activated carbon has long been recognized as one of the most versatile adsorbents to be used for the effective removal of organic contaminants in wastewater treatments. More recently, activated carbons made from almond shell and pecan shell have been recognized as excellent adsorbents for toxic metals that contribute heavily to the contamination of water and wastewater. However, the use of almond shell- and pecan shell-based carbons as adsorbents of toxic organic compounds called volatile organic compounds or VOCs has received much less attention than metal adsorption. This study evaluated the use of almond shell and pecan shell carbons for VOC adsorption compared to the VOC uptake of several commercial carbons. The results determined that there was no difference in the quantity of VOCs adsorbed by pecan shell-based carbons and commercial coconut shell-based carbons. Therefore, these carbons could be used interchangeably in applications that require adsorption of VOCs. The use of pecan shells rather than coconut shells as a source material for activated carbon production should be advantageous because pecan shells are an American product that is easily obtained, while coconut shells are an imported product that depend on availability of the coconuts and their cost includes transporting the shells to the United States.
Technical Abstract: The objective of this research was to compare the adsorption of volatile organic compounds (VOCs) using pecan- and almond shell-based granular activated carbons (GACs) and three commercial carbons made from coal or coconut shells. The VOCs used consisted of bromo-dichloromethane, benzene, carbon tetrachloride, 1,1,1-trichloroethane, chloroform, and 1,1-dichloroethane. The pecan shell-based GACs were activated using steam, carbon dioxide or phosphoric acid. An almond shell-based GAC was activated with phosphoric acid. Our results indicated that steam- or carbon dioxide- activated pecan shell carbons were superior in total VOC adsorption to phosphoric acid activated pecan shell or almond shell carbons, inferring that the method of activation selected for the preparation of activated carbons affected the adsorption of volatile organic compounds and hence are factors to be considered in any adsorption process. The steam activated, pecan shell carbon adsorbed more total VOCs than the other experimental carbons and had an adsorption profile similar to the two coconut-based commercial carbons, but had greater adsorption than the coal-based commercial carbon. All the carbons studied adsorbed benzene more effectively than the other organics. Pecan shell, steam activated and acid activated GACs showed higher adsorption of 1,1,1-trichloroethane than the other carbons studied. Multivariate analysis was conducted to group experimental carbons and commercial carbons based on their physical, chemical, and adsorptive properties. The results of the analysis conclude that steam-activated and acid-activated pecan shell carbons clustered together with a coal-based and a coconut shell-based commercial carbons, thus inferring that these experimental carbons could potentially be used as alternative sources for VOC adsorption in an aqueous environment.