In sugar industry there is a problem of the presence of undesirable
macromolecules compounds such as pectin in sugar beet juice. The affinity of
calcium ions commonly used in the sugar industry for the removal of pectin
from the sugar beet juice is relatively small. Coagulation and precipitation
of pectin can be performed by process of discharging that is chemically
induced. Compounds with di- and trivalent cations such as pure CuSO4,
Al2(SO4)3 or their mixtures can be applied for clarification of pectin
colloidal systems. According to data from the order of pectin selectivity to
divalent metal ions, Cu2+ ions are the first order of ion binding. Also,
aluminum sulfate is commonly used in the waste water treatment. Two model
solutions of pectin whose concentration corresponds to the concentration of
these macromolecules in sugar beet juice (0.1% w/w) are investigated. Using a
method of measuring zeta potential, it was proven for both investigated
pectin that fewer quantities of Cu2+ ions compared to the values of Al3+ ions
are needed to reach zero zeta potential. In all the investigated coagulants
and their mixtures, zeta potential has changed the sign. In experiments with
mixtures has been shown that pure salts showed better coagulation properties.
The reduced strength of binding of cations in the case of most of the applied
mixture of Cu2+ and Al3+ ions, can be explained by the mutual competition of
these ions for the adsorption site (COO- groups) on the surface of
macromolecules. Mixture with approximately equal shares of ions Cu2+ and Al3+
had the most unfavorable coagulation ability (ion antagonism). Mechanism of
discharge as well as the model of double electric layer surrounding pectin
macromolecules in the presence of mixtures of Cu2+ and Al3+ ions are
suggested. However, due to possible undesirable effects of CuSO4 on food
processing, Al2(SO4)3 is proposed instead of traditional coagulant CaO, not
only because of lower consumptions of coagulants but owing to protection of
the environment.
Effect of Copper Ions upon the Sorption of Amino Acids onto a Fumed Silica Surface
