Submitted to: Water Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 2, 2005
Publication Date: August 8, 2005
Citation: Wartelle, L.H., Marshall, W.E. 2005. Chromate ion adsorption by agricultural by-products modified with dimethyloldihydroxyethylene urea and choline chloride. Water Research. 39(13):2869-2876. Interpretive Summary: Materials that can remove environmentally harmful substances such as chromium, arsenic and selenium are expensive and in short supply. Our objective was to develop material called anion exchange resins that could effectively remove these substances through the modification of cheap and plentiful agricultural by-products. The by-products tested were soybean hulls, corn stover and sugarcane bagasse. Resins were prepared through a reaction designed to add a positive charge to the surface of the by-product. The modified by-products were able to adsorb chromium, selenium and arsenic from simulated wastewater, but preferentially adsorbed bound chromium. The anion exchange resin made from sugarcane bagasse had the greatest ability to adsorb chromium of the three by-products tested. The by-product-based resins should be considered as a potential extension of commercial resins on the basis of high anion adsorption and low cost.
Technical Abstract: The use of cellulose-containing agricultural by-products modified with the cross-linking reagent dimethyloldihydroxyethylene urea (DMDHEU) and the quaternary amine, choline chloride, as anion exchange resins, has not been reported. The objective of the present study was to convert the readily available by-products, soybean hulls, sugarcane bagasse and corn stover to functional anion exchange resins using DMDHEU and choline chloride. Optimization of the modification method was achieved using soybean hulls as a substrate. The optimized method was additionally used to modify sugarcane bagasse and corn stover. Adsorption efficiency results with chromate ion showed that modification with both DMDHEU and choline chloride was required for the highest efficiencies. Adsorption capacities of the modified by-products were determined using chromate ion and found to be 1.97, 1.61 and 1.12 mmol/g for sugarcane bagasse, corn stover and soybean hulls, respectively. Competitive adsorption studies were conducted at 10 and 50 times US Environmental Protection Agency (US EPA) limits for arsenic, chromium and selenium in a simulated wastewater at pH 7. The results showed preferential adsorption of chromate ion over arsenate or selenate ion. Estimated product costs for the three resins ranged from $0.88 to $0.99/kg, which was considerably lower than the market costs for the two commercial anion exchange resins QA-52 and IRA-400. DMDHEU/choline chloride modification of the three by-products produced an anion exchange resin with a high capacity to adsorb chromate ion singly or competitively in the presence of other anions from aqueous solutions.