(173ao) The Saturation Dependence of BaSO4 Surface Precipitation Kinetics

Crystal growth on surfaces (crystallisation fouling) decreases the functionality of components in multiple industries. Fouling mitigation protocols include chemical dissolution or mechanical scrubbing, however, BaSO₄ remains a challenge, due to its low solubility in most common dissolution agents and its mechanical resilience. Therefore, to optimize BaSO₄ mitigation, it is important to understand its formation mechanism over a wide range of supersaturation conditions. A systematic study of BaSO₄ surface precipitation kinetics is missing in the literature.

In this work, we present a comprehensive investigation of BaSO₄ surface precipitation kinetics at saturation indices from 1.39 to 3.08. The saturation indices were calculated as SI=log10(a_Ba²⁺*a_SO4²⁺/K_BaSO4)

Deposition studies were performed in a custom-built once-through flow setup. Deposition rates were obtained through gravimetric analysis. High resolution X-ray microtomography was used to visualize the crystal formation. The morphology was quantified from texture parameters, including the spikiness (Pku), and the height of the tallest clusters. Furthermore, the distribution of crystal clusters was classified on a µm scale.

We observe a shift in growth modes, as the saturation indices are increased (see Figure 1). At low saturation indices (SI between 1.39 and 2.61), the growth occurs at a constant rate, while at higher saturation indices, the growth rate increases. These results provide new insights on crystallization fouling phenomena that are applicable in multiple industries.