Freestanding cylindrical metal-nylon mesh electrochemical modules for flexible and scalable water softening treatment

Electrochemical softening offers a sustainable and chemical-free approach for hardness removal in industrial circulating cooling water, but its widespread adoption is limited by cathodic scaling and limited scalability. In this work, we developed a freestanding cylindrical electrochemical module featuring a coaxial "mesh cathode, nylon nets separator, and mesh anode" architecture. This design strategically regulates ion migration to promote homogeneous nucleation of scale-forming ions in the bulk solution, effectively inhibiting electrode scaling. Under optimal conditions (10 mA/cm²), scaling on cathode was reduced by 88 %. The modular configuration allowed flexible scalability, achieving a treatment capacity of 30 L/h through module duplication and geometric enlargement while maintaining a high softening rate (153.0 g/(h·m²)) and low energy consumption (3.60 kW·h/kg CaCO₃), positioning it as a leader in the field. Critically, the system recovered CaCO₃ and Mg(OH)₂ as value-added products. Furthermore, under continuous operation for 20 days in real circulating cooling water treatment conditions, the modules demonstrated robust stability and promising practical applicability.