Optimization of pH value and aluminium sulphate quantity in the chemical treatment of molasses

Abstract

The aim of this investigation was to find the optimal working conditions for the chemical treatment of molasses that guarantee coagulation and precipitation of undesired macromolecules. Twenty experiments were performed, within the limits: 3.5≤pH≤8.5 and 0.1 mol Al/l≤c≤0.5 mol Al/l, on samples of molasses treated with Al2(SO4)3 as a precipitant. The efficiency of the treatment was controlled through measuring both the zeta potential and solution absorbance at 560 nm. By analysing the experimental results, it was concluded that the optimum lies within reduced limits of: 4≤pH≤7 and 0.2 mol Al/l≤c≤0.4 mol Al/1, which covers nine experimental points. Based on these measurements, a mathematical model of absorbance changes was defined, in terms of pH and Al2(SO 4)3 quantity. The model was taken as the objective function, and the optimal calculated values were obtained: pH=5.3 and c=0.34 mol Al/1. They guarantee a minimal absorbance value of: 0.124 at 560 nm.