Calorimetric and Other Interaction Studies on Mineral-Starch Adsorption Systems

Abstract

Studies have been made on adsorbabilities of starch, phosphorylated starch and starch constituents — amylose and amylopectin — on hematite and also calcite. The adsorption process is slow, partially irreversible, non-physical and appreciably exothermic. For a small starch concentration, Ali on hematite reaches a maximum of 314 Jig starch adsorbed, and then falls off at higher conc-entration, probably due to partial deanchorage and reorientation of adsorbed molecules initially lying flat on the surface. Adsorption isotherm patterns, including pH-dependence behaviour, are similar for starch and amylopectin. The magnitude of adsorption of amylose, compared to that of amylopectin (nearly 20 times bulkier), is larger on a molar basis but smaller on a g/cm3 basis. Thus, inter-pretation of calcite—starch adsorption data should be made in terms of amylose as well as amylopectin. For the hematite—starch system, adsorption of amylopectin is of crucial importance. Conductometric data and IR spectrograms point to speci-fic chemical interactions between starch constituents and ions such as Fe'* and CO*. These are evidence of the existence of chemisorption bonds of amylose as well as of amylopectin interacting on calcite and hematite surfaces.