Aspects of the kinetics and solubility of silica and calcium oxalate composites in sugar solutions

Abstract

Fouling of industrial surfaces by silica and calcium oxalate can be detrimental to a number of process streams. Solution chemistry plays a large roll in the rate and type of scale formed on industrial surfaces. This study is on the kinetics and thermodynamics of SiO₂ and calcium oxalate composite formation in solutions containing Mg²+ ions, 'trans'-aconitic acid and sucrose, to mimic factory sugar cane juices. The induction time (ti) of silicic acid polymerization is found to be dependent on the sucrose concentration and SiO₂ supersaturation ratio (SS). Generalized kinetic and solubility models are developed for SiO₂ and calcium oxalate in binary systems using response surface methodology. The role of sucrose, Mg, 'trans'-aconitic acid, a mixture of Mg and 'trans'-aconitic acid, SiO₂ SS ratio and Ca in the formation of composites is explained using the solution properties of these species including their ability to form complexes.