Submitted to: Carbon
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 25, 1998
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 activated carbons from nutshell waste which are excellent adsorbers of copper, a metal commonly found in industrial wastewater. In order to produce these carbons, modification of the carbon surface is required to provide it with the ability to bind copper. This study examines how we successfully modified the carbons with our specific treatment, which involves exposure of the nutshell carbons to air at elevated temperatures, either after or during activation. Such materials would benefit both the nut producers (by providing them with added value for their waste materials) as well as industry responsible for the removal of toxic metals from wastewater. It was found that phosphoric acid-activation methods which provide the greatest contact of nutshells with air during carbonization and activation also have the greatest quantity of surface functional groups and the highest copper uptake.
Technical Abstract: Nutshells from agriculturally important nut crops (almond, black walnut, English walnut, macadamia nut and pecan) were converted to granular activated carbon using phosphoric acid activation in nitrogen or air. Surface functional groups (carbonyl, phenols, lactones, carboxyl) were quantified by titration with bases of different ionization potential. The presence of various surface functional groups was correlated with the degree of copper uptake of these carbons. The results indicate that acid-activation strategies which provide the greatest contact of nutshells with air during carbonization and activation also have the greatest quantity of surface functional groups and the highest copper uptake. Also, the type of nutshell used for activated carbon production has little effect on the types of surface functional groups produced and subsequent copper adsorption. This study demonstrates that a judicious choice of activation strategy for nutshell precursors can produce activated carbons with numerous surface functional groups and high metals adsorption activity.