Starch citrate: Preparation and ion exchange properties

Starch was allowed to react thermochemically (oven versus drum drying-oven) with citric acid to potentially yield biodegradable products possessing high ion exchange capacity. Reaction variables studied were: starch type (amylose content 0-70%), pH (0.5-8.5), sodium level (0-3 moles), citric acid level (0.1-0.5 moles), reaction time, temperature (110-140 degrees C) and sodium dihydrogen phosphate catalysis. Reaction efficiencies approaching 100% were achieved, while minimizing crosslinking and maximizing carboxyl content. Carboxyl content was determined and copper binding capacity at pH 4.5 was evaluated.