Submitted to: Separation Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2001
Publication Date: N/A
Interpretive Summary: Almond shellers produce over 650 million pounds of almond shells each year in the United States. The shells have little monetary value and create a disposal problem. However, they can be converted to highly adsorbent activated carbon. In this study, almond shells were converted to granular activated carbon that has a high affinity for common metals, such as copper, commonly found in both ground and surface water and in residential, municipal and industrial wastewater. Almond shell carbon was compared to several different commercial carbons for metals uptake and was found to have greater metal binding than all the commercial carbons evaluated in both batch and column adsorption situations. Based on these results, and considering the low cost of almond shells, shell-based carbons may be less expensive adsorbents to manufacture and market than comparable commerical products made from coal and wood. Therefore, this product should be considered a potentially marketable commodity. Companies that treat their liquid waste for hazardous metals may want to consider this effective metal adsorbent.
Technical Abstract: Phosphoric acid-activated/oxidized, and steam-activated and steam-activated/oxidized almond shell granular activated carbons (GACs) were investigated for their utility in removing copper ion (Cu2+) from solution in both batch and column applications compared to commercially available GACs. Adsorption isotherms were developed and found to best fit the Freundlich model. Experimental and commercial carbons were packed into columns and exposed to two different empty bed contact times using a solution of 3 mM CuCl2 buffered at pH 4.8. The most effective GACs for removal of copper ions in batch mode were the phosphoric acid-activated/oxidized and steam-activated/oxidized experimental carbons. The most effective carbon in column mode appeared to be the phosphoric acid-activated/oxidized sample. A column packed with this carbon showed higher breakthrough volumes and greater estimated hours of operation than other experimental carbons and commercial carbons evaluated. This carbon could function as an effective metal ion adsorbent in water and wastewater treatment.