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United States Department of Agriculture

Agricultural Research Service

Title: Acid-Activated Carbons from Almond Shells: Physical, Chemical and Adsorptive Properties and Estimated Cost of Production

Authors
item Toles, Christopher
item Marshall, Wayne
item Johns, Mitchell - FORMER USDA EMPLOYEE
item Wartelle, Lynda
item McAloon, Andrew

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 16, 1999
Publication Date: N/A

Interpretive Summary: Activated carbons are used for environmental cleanup of polluted wastewater from industry and other sources. However, commercial activated carbons are poor adsorbers of toxic metals, which constitute a growing industrial pollution problem. We have developed methods of creating activated carbons from almond nutshell waste which are excellent adsorbers of copper as well as organic pollutants commonly found in industrial wastewater. A series of phosphoric-acid activated carbons were made from almond shells using six different methods. The carbons were compared to each other and to two commercial carbons in an effort to determine the relative value of the carbons in terms of yield, surface area, attrition, surface charge, organic uptake, metals uptake, as well as estimated cost of production. Such materials would benefit both the almond producers by providing them with added value for their waste materials, as well as industry responsible for the removal of toxic metals from wastewater who will have an interest in the relative cost of production of these materials. It was found that phosphoric acid-activation in the presence of air produced the most economical and effective activated carbon from among the six methods investigated for metals and organic uptake.

Technical Abstract: A series of phosphoric-acid activated carbons were made from almond shells using six different activation or activation/oxidation methods. The carbons were compared to each other and to two commercial carbons in an effort to ascertain the relative value of the carbons in terms of yield, surface area, attrition, surface functional groups, organic uptake, metals uptake, as well as estimated cost of production. Of the six methods investigated, the method that produced the best overall performing almond shell carbon and least expensive carbon in terms of production cost was the "Air-Activation" method. This method involved the simultaneous activation and oxidation of almond shells under an air atmosphere.

Last Modified: 8/21/2014
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