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S. CHAMARTHY¹, C. W. Seo, and W. E. Marshall. (1) Food and Nutrition, Dept. of Human Environment and Family Sciences, North Carolina A&T State University, 161 Carver Hall, Greensboro, NC 27411

Disposal of agricultural byproducts such as peanut shells has become a serious problem in the U.S. due to the enactment of more stringent federal and state regulation. Water contamination by heavy metals is another serious ongoing problem in this country. Conversion of these low-value peanut shells into adsorbent that can remove toxic metals from wastewater would increase their market value and ultimately benefit peanut producers.

The objective was to modify peanut shells to enhance the adsorption efficiency. Ground peanut shells were modified using combinations of various wash and acid treatments. Wash treatments consisted of water wash, base wash with 0.1N NaOH, and unwash. Acid treatments were applied using 0.6M citric, 0.6M phosphoric acid, and no acid treatment. A 3x3 factorial design was used in the experiment. The modified peanut shell samples were evaluated for their adsorption efficiency with 5 different single metal ions individually in 20mM concentration and with all 5 metal combined in one solution. The metals used were Cd(II), Cu(II), Ni(II), Pb(II) and Zn(II). Adsorption efficiency for the commercial resins namely, Amberlite-200, Amberlite-IRC-718, Duolite GT-73, and carboxymethyl cellulose was determined to compare with the modified peanut shells.

For the individual metal adsorption efficiency, washed and acid-modified peanut shells statistically had the same adsorption efficiency as Duolite GT-73 for Cd(II), Cu(II), Ni(II), which was 0.49 mmoles/g, 0.70 mmoles/g, and 0.40 mmoles/g, respectively. The adsorption efficiency was more when compared to carboxymethyl cellulose for Zn(II) which had 0.34 mmoles/g. For the mixed metal adsorption efficiency, all the nine types of modified peanut shells had better adsorption for Cd(II) than Duolite GT-73 and Amberlite-IRC-718, which was 0.09 mmoles/g and 0.05 mmoles/g, respectively. Acid-treated samples had better adsorption efficiency than Amberlite-200 for Cu(II) and Amberlite-IRC for Pb(II), which were 0.15 mmoles/g and 0.55 mmoles/g, respectively.

Modified peanut shells are promising adsorbents for selected toxic metals.