Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2003
Publication Date: 3/12/2004
Citation: Ahmedna, M., Marshall, W.E., Husseiny, A.A., Rao, R.M., Goktepe, I. 2004. The use of nutshell carbons in drinking water filters for removal of trace metals. Water Research. 38:1062-1068. Interpretive Summary: Despite the assurance offered by numerous regulatory agencies that the domestic drinking water in the United States is safe, many consumers are wary of tap water and question its quality and health effects. As a result, American households spend over $5 billion annually on bottled water and home water treatment systems. Therefore, there is a growing need to produce water filters that are low cost and effective at removing potentially harmful components in drinking water. Scientist at the USDA-ARS, Southern Regional Research Center in collaboration with scientists at Technology International Inc. of Virginia, LaPlace, LA and the Department of Food Science, Louisiana State University, Baton Rouge, LA have developed granular activated carbons from almond shells, English walnut shells and pecan shells that are particularly effective at sequestering metal contaminants commonly found in drinking water. These carbons removed more metal contaminants than four different commercial water filters and were considerably less costly to produce than the retail price of the commercial filter units. Nutshell carbons appear to be excellent substitutes for commercial coal-based carbons and coal-based carbons combined with ion exchange resins in metal removal from drinking water and should be considered as an alternative to existing commercial home filters.
Technical Abstract: Filtration of drinking water by point-of-use (POU) or point-of-entry (POE) systems is becoming increasingly popular in the United States. Drinking water is filtered to remove both organic and inorganic contaminants. The objective of this study was to evaluate the use of granular activated carbon from nutshells (almond, English walnut, pecan) in a POU water filtration system to determine its effectiveness in removing select, potentially toxic metal ions, namely, copper (Cu2+), lead (Pb2+) or zinc (Zn2+) found in drinking water. The nutshell-based carbon system was designated "Envirofilter" and was compared to four commercial POU systems with brand names of BRITA, Omni Filter, PUR and Teledyne Water Pik. Eight prototype "Envirofilters", consisting of individual or binary mixtures of carbons made from acid-activated almond or pecan shells and steam-activated pecan or walnut shells were constructed and evaluated for adsorption of the three metal ions. The results indicated that a binary mixture of carbons from acid-activated almond and either steam-activated pecan or walnut shells were the most effective in removing these metals from drinking water of all the POU systems evaluated. Binary mixtures of acid-activated almond shell-based carbon with either steam-activated pecan shell- or walnut shell-based carbon removed nearly 100% of lead ion, 90-95% of copper ion and 80-90% of zinc ion. Overall the performance data on the "Envirofilters" suggest that these prototypes require less carbon than commercial filters to achieve the same metal adsorption efficiency and may also be a less expensive product.