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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Plant Polymer Research » Research » Publications at this Location » Publication #96548
Title: METAL CHELATION OF CORN PROTEIN PRODUCTS/CITRIC ACID DERIVATIVES GENERATED VIA REACTIVE EXTRUSION

Author
item Sessa, David
item WING, ROBERT - RETIRED ARS

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Industrial companies pollute our waterways with heavy metal discharges which result in imposed EPA fines. Agricultural commodities such as coproducts of ethanol production from corn can be chemically modified to generate value-added products that will lessen this pollution. Reaction of citric acid with either corn gluten meal or distillers' dried grains will generate biodegradable products that bind heavy metals. We devised a method for the continuous production of biobased compounds; evaluated the metal-binding capacities of these compounds; and assessed the biodegradation of these materials. These biobased derivatives, less costly to produce than petrochemically available materials, can substitute petrochemically-based materials now used to remove heavy metals from industrial wastewaters.

Technical Abstract: Citric acid (CA) was thermochemically reacted with corn coproducts from the ethanol industry -- i.e., corn gluten meal (CGM) and distillers' dried grains (DDG), to generate value-added, acid-insoluble reaction products with enhanced metal-binding properties. Heated CA produces an anhydride that can react with the nucleophilic groups on starch, fiber, and proteins to produce ester or acyl derivatives. Short-term reactive extrusion with Brabender Plasti-Corder PL2000 single screw extruder through zone temperatures of 140, 200, and 196 deg C yielded reaction products that possessed similar degrees of carboxylation as a lengthy 24 hour oven-baking procedure previously reported. Equilibrium binding capacity for CGM/CA derivative was: 0.54, 0.33, 0.85, 1.00, 0.59, 0.28, 0.30, 0.72, and 0.45 mmole/g for Cd**2+, Co**2+, Cu**2+, Fe**2+, Pb**2+, Mn**2+, Ni**2+, Ag**+, and Zn**2+, respectively; whereas for the DDG/CA derivative the metal binding was: 0.78, 0.66, 1.04, 1.08, 0.64, 0.51, 0.60, 1.02, and 0.73 respectively. Comparison of metal binding ability for both CGM/CA and DDG/CA derivatives were of the same order of magnitude when compared with a commercially available, sulfonic acid, styrene type cation exchange resin. The corn-based derivatives produced in this study were found to be biodegradable and can be produced at considerable cost savings when compared with petroleum based resins.