Liu Yiming, Xiao Minhao, Huang Xiaochuan, Park Jane, Hoffman Matthew E, Feng Yuren, An Alicia Kyoungjin, Li Qilin, Hoek Eric M V, Jassby David
Department of Civil & Environmental Engineering, University of California Los Angeles (UCLA), Los Angeles, CA, USA.
National Science Foundation (NSF) Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment, Rice University, Houston, TX, USA.
Nat Commun. 2025 Jan 2;16(1):35. doi: 10.1038/s41467-024-55176-z.
Mineral crystal formation poses a challenge on surfaces (e.g., heat exchangers, pipes, membranes, etc.) in contact with super-saturated fluids. Applying alternating currents (AC) to such surfaces can prevent surface crystallization under certain conditions. Here, we demonstrate that ion displacement induced by periodic charging and discharging of the electrical double layer (EDL) inhibits both heterogeneous and homogeneous nucleation (and crystal growth) of CaCO. Titanium sheets (meant to simulate metallic heat exchanger surfaces) are immersed in super-saturated CaCO solutions with a saturation index >11. We show that at relatively high AC frequencies, incomplete EDL formation leads to an alternating electric field that propagates far into the bulk solution, inducing rapid ion migration that overwhelms the Brownian motion of ions. Electrochemical characterization reveals EDL charging/discharging under AC conditions that greatly inhibits precipitation. Operating at 4 V, 0.1-10 Hz reduces turbidity by over 96% and reduces CaCO coverage on the metal plates by over 92%. Based on electrokinetic and crystallization models, the ion displacement velocity (exceeding the mean Brownian velocity) and displacement length disrupts ion collision and crystal nucleation. Overall, the technique has potential for preventing mineral crystal formation in heat exchangers and many other industrially relevant systems.
矿物晶体的形成对与过饱和流体接触的表面（如热交换器、管道、膜等）构成了挑战。在这些表面施加交流电（AC）在某些条件下可以防止表面结晶。在此，我们证明由双电层（EDL）的周期性充电和放电引起的离子位移会抑制CaCO的异质成核和均质成核（以及晶体生长）。将钛片（旨在模拟金属热交换器表面）浸入饱和指数>11的过饱和CaCO溶液中。我们表明，在相对较高的交流频率下，不完全的双电层形成会导致一个交变电场传播到本体溶液中很远的地方，引起快速的离子迁移，从而超过离子的布朗运动。电化学表征揭示了交流条件下双电层的充电/放电，这极大地抑制了沉淀。在4 V、0.1 - 10 Hz下运行可使浊度降低超过96%，并使金属板上CaCO的覆盖率降低超过92%。基于电动和结晶模型，离子位移速度（超过平均布朗速度）和位移长度会破坏离子碰撞和晶体成核。总体而言，该技术在防止热交换器和许多其他工业相关系统中矿物晶体形成方面具有潜力。
