Modeling the co-precipitation of silica and calcium oxalate in sugar solutions

Abstract

Solution chemistry plays a significant role in the rate and type of foulant formed on heated industrial surfaces. This paper describes the effect of sucrose, silica (Si0₂), Ca²⁺ and Mg²⁺ ions, and trans-aconitic acid on the kinetics and solubility of SiO₂ and calcium oxalate monohydrate (COM) in mixed salt solutions containing sucrose and refines models previously proposed. The developed SiO₂ models show that sucrose and SiO₂ concentrations are the main parameters that determine apparent order ('n') and apparent rate of reaction ('k') and Si02 solubility over a 24 h period. The calcium oxalate solubility model shows that while increasing [Mg²⁺] increases COM solubility, the reverse is so with increasing sucrose concentrations. The role of solution species on COM crystal habit is discussed and the appearance of the uncommon (001) face is explained.