Effect of aluminum salts, copper salts and polyelectrolytes on charge neutralization of pectin macromolecules

Abstract

In sugar industry, there is a problem of the presence of undesirable macromolecules compounds such as pectins and proteins in sugar beet juice. Separation of these compounds is done mostly by compounds with calcium ion. Affinity of calcium binding with undesirable macromolecules from sugar beet juice is not significant. The aim of this study is application of alternative coagulants with divalent and trivalent cations, CuSO4 and Al2(SO4)3 with or without the addition of polyelectrolyte which cause the process of charge neutralization macromolecules followed by polymeric bridging effect. Mechanism of discharge of macromolecules compounds using a model of double electric layer are suggested. Volume 50 cm3 model solution of pectin (0.1 % w/w) was treated with seven volumes of CuSO4 solution, ranging of 0.47-3.29 cm3 and seven volumes of Al2(SO4)3 solution, ranging of 0.59-4.15 cm3. Optimal quantities of the applied coagulants, determined by measuring the Zeta potential values, where estimated as follows: 0.24 % (w/w) CuSO4 and 0.45 % (w/w) Al2(SO4)3 & Na2CO3 on sugar beet. This is much lower than 1-3 % (w/w) CaO commonly used in sugar production. Adding different concentrations of cationic polyelectrolytes in these solutions, the highest efficiency of clarification was noticed by applying cationic polyelectrolytes of concentration 3 mg/dm3. It was shown that this type of polyelectrolyte further reduced the value of Zeta potential. Zeta potential of sugar beet pectin macromolecules was determined by electrophoretic method.