Biosorption of Na+, K+ and Ca2+ from alkalized sugar juice by unmodified pressed sugar beet pulp in closed-loop column system

Abstract

Sucrose crystallization process is greatly inhibited by high Na+, K+ and Ca2+ content in the crystallizing medium—sugar juice. In this study, unmodified pressed sugar beet pulp was used as a weak polyfunctional cation exchanger for the removal of Na+, K+ and Ca2+ from an alkalized sugar juice in a closed-loop column system. Cation removal effect was evaluated through the influence of temperature (30–70 °C), pH (8.5–12.5) and volume (150–300 ml) of alkalized juice. Sugar beet pulp exhibited the highest Ca2+ removal (56.58%) at 70 °C and pH value of 12.5, indicating strong impact of cation solubility, precipitation and valence. Milder conditions of alkalized sugar juice such as temperature (50 °C) and pH value (10.5) contributed to the maximum removal of Na+ (15.07%) and K+ (10.58%). Component analysis of the heteroporous sugar beet pulp with total porosity of 53% and specific surface area of 0.9 m2/g indicated hydroxyl and carboxyl groups as the main centers for an ion-exchange process in the material used, which was confirmed by FTIR analysis. This is the first time that unmodified pressed sugar beet pulp (PSBP) has been used as biosorbent for Na+, K+ and Ca2+ removal in a closed-loop column system.