Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2008
Publication Date: 5/16/2009
Citation: Shogren, R.L. 2009. Flocculation of Kaolin by Waxy Maize Starch Phosphates. Carbohydrate Polymers. 76(1):639-644.
Interpretive Summary: Synthetic, petroleum-based polymers such as polyacrylamide (PAM) are used commercially to speed the settling of fine particles from water. It would be desirable to replace PAM with a non-toxic, biobased, biodegradable polymer such as a modified starch. This work showed that corn starch modified with phosphate was effective at removing clay particles from water in the presence of a small amount of calcium salts. Although more starch phosphate than PAM was required, the lower cost of starches should make them economically competitive. These results should be useful to companies making flocculants and modified starches and may be of importance to farmers in helping to reduce soil erosion.
Technical Abstract: Waxy maize starch phosphates were tested as flocculants in order to determine if they have the potential to replace petroleum-based polymer flocculants currently used commercially. Phosphorylation was carried out by drying heating of starches and sodium orthophosphates at 140 deg C for 4 h. Native and phosphorylated waxy maize starches were ineffective as flocculants for kaolin in deionized water. However in the presence of small amounts of Ca++ (1-4 mM), starch phosphates were effective flocculants of kaolin at concentrations as low at 3-4 ppm. The optimal degree of substitution (DS) for flocculation was 0.024 but the effect of DS was rather small over the range DS 0.007-0.08. Although a common synthetic polymer flocculant (polyacrylamide-co-acrylic acid) was effective at 1 ppm, the lower cost of starches should make them economically competitive.