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 studies 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°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.