The effect of calcium sulphate, aluminium sulphate and polyelectrolyte on separation of pectin from the sugar beet juice

Abstract

In the sugar industry, calcium ions (in the form of CaO) that are commonly used to eliminate the pectin from beet juice have a relatively low binding affinity. The quantities of used lime are very large (15 g/100 g juice). The precipitation of pectin could be achieved by the charge neutralization. Compounds with bi- and trivalent cations such as CaSO4 and Al2(SO4)3 could be used to extract pectin from colloidal systems. Application of polyelectrolyte previously referred to the improvement of flocculation in water treatment and sugar cane juice. Model - pectin solutions (50 cm3 and 0.1 % wt.) were treated with different concentration of CaSO4 and Al2(SO4). Optimal amounts of applied coagulants, determined using measurements of zeta potential were: 410 mg/dm3 for CaSO4 and 110 mg/dm3 for Al2(SO4)3. By adding a cationic polyelectrolyte (1, 3 and 5 mg/dm3), the most efficient separation of pectin was achieved with polyelectrolyte concentration 3 mg/dm3. Adding this type polyelectrolyte, amounts of applied coagulants required for charge neutralization (zero zeta potential) were reduced. These amounts were 460 mg CaSO4 and 128 mg Al2( SO4)3/gpectin and significantly less than the amount of CaO used in the conventional process of sugar beet juice clarification (9 g/gpectin).

Keywords

• calcium and aluminium sulphate
• pectin
• sugar beet
• zeta potential