Aluminium and calcium ions binding to pectin in sugar beet juice: Model of electrical double layer

In sugar industry, there is a problem of the presence of undesirable macromolecules such as pectins in sugar beet juice. Separation of these compounds is done mostly by CaO. Calcium may cause undesirable process of alkalization of soil in the near environment of the sugar factory. The theoretical basis of new juice purificatin method based on the application of Al2(SO4)3, CaSO4 and their mixtures are presented. Two model solutions of pectin (0.1 % w/w) are investigated using a method of measuring zeta potential. Pure salts Al2(SO4)3 and CaSO4, showed better binding properties with the pectin than mixtures. Amount of all studied pure salts and mixtures of Al3+ and Ca2+ ions were significantly less (142 - 710 mg/gpectin) than the average amount of CaO used in classical process (about 9 g/gpectin). Mechanism of discharge of pectin macromolecules in the presence of mixtures of these ions using a model of double electric layer are suggested.