Study of quantitative interactions of potato and corn starch granules with ions in diluted solutions of heavy metal salts

•The study provides new insight on interactions of starch with ions in aqueous solution.•Quantitative results depend on the origin and water content of starch and a type of salt ions.•Potato starch due to the higher content of phosphorous retains about three times more cations than corn starch.•Both cations and anions can penetrate into the granule interiors but nitrates remain on surface of potato starch granules.•Cations assist starch thermal breakdown in line with their standard redox potentials.•Nitrates support starch thermal decomposition only in the presence of base metal ions. Interactions of potato and corn starch granules with ions in diluted solutions of silver, lead, copper or iron salts were investigated. It was shown experimentally that granules accumulated the cations in amounts depending on the granule structure and water content as well as a type of both metal and counter-ions present in solution. Potato starch retained almost three times more cations compared to corn starch what was proportional to the total phosphorous content in these starches. Quantity of milligrams of cations bound by 1g of starch was inversely correlated with the cation hydration. Ag+, Pb2+ and Cu2+ were connected in stoichiometric amounts of moles to semicrystalline and amorphous parts of the granules. Fe3+ ions were accumulated in higher than stoichiometric quantities mainly in granule amorphous regions. Metal ions penetrated into granules together with anions except nitrates which remained on surface of potato starch granules. Cations facilitated the starch thermal decomposition in accordance with values of their standard redox potentials. Nitrates supported this process only in the presence of base metal cations.