Deepening the understanding of scaling processes would facilitate the improvement of membrane distillation (MD) as a promising technique for sustainable development. This study investigated the scaling of calcium sulfate in MD via an approach based on optical coherence tomography (OCT). The OCT-based characterization enabled an analysis that correlated the flux decline with the morphological evolution of the scaling layer. It was revealed by this analysis that the reduction in the evaporation rate could be dominated by different mechanisms as the crystalline particles grew and deposited on the membrane surface; the striping phenomenon visualized by mapping the local growth rates provided evidence for the hydrodynamic instability induced by the coupled mass and heat transfer in MD. Moreover, the OCT-based characterization was exploited to unravel the interplay between the crystallization and the porous structure by quantifying the membrane deformation as a function of time; the varied precipitation kinetics in the boundary layer was confirmed by comparing the temporal variations in the OCT signals at different depths. All these results shed light on mechanisms underlying complex scaling processes, which are the basis for optimizing the design of MD.

加深对结垢过程的理解将促进膜蒸馏（MD）的改进，将其作为可持续发展的有前途的技术。这项研究通过基于光学相干断层扫描（OCT）的方法研究了MD中硫酸钙的结垢。基于OCT的特征分析可以使通量下降与缩放层的形态演变相关联。该分析表明，随着晶体颗粒的生长和沉积在膜表面上，蒸发速率的降低可能受不同机制的控制。通过绘制局部增长率来可视化的条带化现象提供了由MD中传质和传热耦合引起的水动力不稳定性的证据。此外，通过基于OCT的表征，通过量化随时间变化的膜变形来揭示结晶与多孔结构之间的相互作用。通过比较不同深度的OCT信号的时间变化，可以确定边界层中变化的降水动力学。所有这些结果揭示了复杂缩放过程的机制，这是优化MD设计的基础。