Activation with Polyvalent Metal Salts in the Anionic Flotation of Starch

—Fundamental Study on the Removal of Organic Matters from Wastewater—

Abstract

The effects of hydrolysable metal salts on the flotation of potato starch with anionic surfactant, sodium dodecylsulfate, were investigated. It was presented that negatively charged starch surface was activated by the hydrolysable metal salts of Al(III), Fe(III), Cu(II) and Ni(II). The pH range in which the activation was observed ranged from the precipitation pH of each metal hydroxide to the isoelectric point, IEP, of each hydroxide precipitate. SEM images indicated that starch particles were covered with hydroxide precipitate above the precipitation pH. The results of adsorption test and micro electrophoresis indicated that the effect of adsorbed hydroxy complex was not sufficient to reverse the negative charge of starch surface. These results suggested that in the anionic flotation of starch it was not hydroxy complexes but hydroxide precipitates that acted as an activating species which modified the starch particle surface.