Electrochemical precipitation is a promising technique for hardness abatement without the addition of external ions. However, the scale layer on cathode deteriorated the removal efficiency and limited the practical application. Herein, a fenced cathode structure was designed to prevent cathodic precipitation. The cathode was fenced by a crystallization-inducing material for separating the OH⁻ production and crystallization processes. Precipitation on the cathode was confirmed to shift to the crystallization-inducing material, and the clean fenced cathode provided efficient long-term OH⁻ production. At a current density of 40 A/m², the Ca²⁺ or Mg²⁺ removal efficiency increased by 12.8% or 46.1%, respectively, compared to those of a traditional cathode. Thermodynamic equilibrium in synthetic water and mine water, mass transfer and the location of precipitation were analyzed to elucidate the electrochemical precipitation process. The enhanced mechanism was ascribed to the crystallization-inducing material, which remarkably promoted the crystallization process, and hindered OH⁻ migration, thereby increased the pH of alkaline microenvironment. Notably, a recovery design was proposed to recover pure calcite and brucite from alkalinity-free wastewater. The design reveals a promising strategy for enhancing the crystallization process and reducing cathodic scale, also initiating a new research direction toward hardness removal.

电化学沉淀是一种有前景的硬度降低技术，无需添加外部离子。然而，阴极上的水垢层降低了去除效率并限制了实际应用。在此，设计了围栏阴极结构以防止阴极沉淀。阴极被结晶诱导材料围起来，用于分离 OH ^{- 的}产生和结晶过程。阴极上的沉淀被证实转移到结晶诱导材料，清洁的栅栏阴极提供了有效的长期 OH ^-生产。在 40 A/m ²的电流密度下，Ca ²⁺或 Mg ²⁺与传统阴极相比，去除效率分别提高了 12.8% 或 46.1%。分析合成水和矿井水的热力学平衡、传质和沉淀的位置，以阐明电化学沉淀过程。这种增强机制归因于结晶诱导材料，它显着促进了结晶过程，并阻碍了 OH ^-迁移，从而提高了碱性微环境的 pH 值。值得注意的是，提出了一种回收设计，以从无碱废水中回收纯方解石和水镁石。该设计揭示了一种增强结晶过程和减少阴极氧化皮的有前景的策略，同时也开启了一个新的去除硬度的研究方向。