Surface functional groups on acid-activated nutshell carbons

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 degree of copper uptake was correlated with the presence of various functional groups on 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 copper adsorption activity.