Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/27/2005
Publication Date: 2/12/2006
Citation: Wilson, K., Yang, H., Seo, C.W., Marshall, W.E. 2006. Select metal adsorption by activated carbon made from peanut shells. Bioresource Technology. 97(18):2266-2270
Interpretive Summary: Commodity crops, such as peanuts, generate considerable quantities of shells each year with little or no value. The conversion of peanut shells to activated carbon with the ability to remove harmful metals from the environment would be a beneficial application of this waste material. This study involves the utilization of a stepwise sequence of chemical reactions that first creates an activated carbon with good surface area, then secondly changes the surface properties of the carbon into a material with good metal binding properties. This was accomplished by first subjecting the peanut shells to heat and steam to produce an activated carbon, then exposing the activated carbon to a flow of breathing air to improve its metal binding properties. The results showed that activated peanut shell carbon produced by this method had greatly improved metal binding characteristics; greater than the metal binding properties of commercial carbons used for comparison. These peanut shell-based carbons may extend the use of activated carbons in applications where metal adsorption is required.
Technical Abstract: Agricultural by-products, such as peanut shells, contribute large quantities of lignocellulosic waste to the environment each growing season; but few, if any, value-added uses exist for their disposal. The objective of this study was to convert peanut shells to activated carbons for use in adsorption of select metal ions, namely, cadmium (Cd2+), copper (Cu2+), lead (Pb2+), nickel (Ni2+) and zinc (Zn2+). Milled peanut shells were pyrolyzed in an inert atmosphere of nitrogen gas, and then activated with steam at different activation times. Following pyrolysis and activation, the carbons underwent air oxidation. The prepared carbons were evaluated either for adsorption efficiency or adsorption capacity; and these parameters were compared to the same parameters obtained from three commercial carbons, namely, DARCO 12X20, NORIT C GRAN and MINOTAUR. One of the peanut shell-based carbons had metal ion adsorption efficiencies greater than two of the three commercial carbons but somewhat less than but close to Minotaur. This study demonstrates that peanut shells can serve as a source for activated carbons with metal ion-removing potential and may serve as a replacement for coal-based commercial carbons in applications that warrant their use.