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United States Department of Agriculture

Agricultural Research Service


item Johns, Mitchell
item Marshall, Wayne
item Toles, Christopher

Submitted to: Journal of Chemical Technology & Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/29/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Pecan shells represent one of the most plentiful nutshell materials in the United States and as such also represent a major disposal problem for pecan shellers. The research reported in this study was carried out to provide a value-added product, namely an activated carbon, from pecan shells. Our research shows that pecan shell carbons can be manufactured by several different methods. These methods provide a number of different shell-based carbons which result in a wide range of adsorption capabilities toward various environmentally important organic chemicals and metal ions. Our results could directly benefit pecan shellers by providing an outlet for an agricultural waste and also benefit companies involved in environmental pollution control by providing a powerful tool for environmental remediation.

Technical Abstract: Pecan shell chars were activated using steam, carbon dioxide (CO2), or phosphoric acid (H3PO4) to produce granular activated carbons (GACs). The GACs were characterized for select physical, chemical and adsorption properties. Air oxidation of the GACs was used to increase copper ion (Cu2+) adsorption. BET surface areas of pecan carbons were as high or higher than commercial GACs used as reference. Meso- and micropore development differed between activation types. Carbon dioxide activation favored microporosity, while the other activations increased both mesoporosity and microporosity. Bulk densities and particle attrition of the pecan shell GACs were generally similar to the commercial carbons. Air oxidation of steam- and CO2-activated GACs increased copper ion adsorption, although not to the extent as GACs made by H3PO4 activation. Copper ion adsorption and the amount of titratable functional groups greatly exceeded the values for the commercial GACs. Both steam- and CO2- activated pecan carbons were similar to but in some cases exceeded commercial GACs in removing select organic compounds from water. GACs made from pecan shells showed considerable commercial potential to remove metal ions and organic contaminants from water.

Last Modified: 10/15/2017
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