Multiscale Optical Imaging Unveils the Distinct Roles of Supersaturation and Substrate in Interfacial Crystallization

Area of Science:

• Interfacial Science
• Materials Science
• Chemical Engineering

Background:

• Mineral scaling presents significant operational and economic challenges in water treatment and industry.
• Current models often overlook homogeneous nucleation, focusing instead on heterogeneous nucleation driven by surface chemistry.

Purpose of the Study:

• To quantitatively understand how substrate properties influence homogeneous nucleation and bulk deposition of mineral scales.
• To develop a methodology for designing scale-mitigation surfaces by controlling post-nucleation processes.

Main Methods:

• Development of a label-free integrated imaging platform combining bright-field microscopy and low-angle rotational interferometric scattering microscopy (LRISM).
• Tracking crystal populations and quantifying 3D orientation during interfacial crystallization of calcium sulfate (CaSO4) and calcium carbonate (CaCO3).

Main Results:

• Calcium sulfate (CaSO4) consistently exhibited heterogeneous nucleation with morphology dependent on supersaturation.
• Calcium carbonate (CaCO3) predominantly followed a homogeneous nucleation-bulk deposition pathway.
• Hydrophilic surfaces captured denser nuclei, limiting crystal size and promoting horizontal alignment, confirmed by LRISM.

Conclusions:

• Substrate properties significantly impact mineral scale formation pathways, especially homogeneous nucleation.
• Controlling post-nucleation capture and orientation offers a novel strategy for scale mitigation, complementing traditional nucleation inhibition methods.