Electrochemical water softening technology: From fundamental research to practical application

In recent decades, the environmentally benign electrochemical softening process has been gaining widespread interest as an emerging alternative for water softening. But, in spite of decades of research, the fundamental advances in laboratory involving electrolytic cell design and treatment system development have not led to urgently needed improvements in industrially practicable electrochemical softening technique. In this review, we firstly provide the critical insights into the mechanism of the currently widely used cathode precipitation process and its inherent limitations, which seriously impede its wide implementation in industry. To relieve the above limitations, some cutting-edge electrochemically homogeneous crystallization systems have been developed, the effectiveness of which are also comprehensively summarized. In addition, the pros and cons between cathode precipitation and electrochemically homogeneous crystallization systems are systematically outlined in terms of performance and economic evaluation, potential application area, and electrolytic cell and system complexity. Finally, we discourse upon practical challenges impeding the industrial-scale deployment of electrochemical water softening technique and highlight the integration of strong engineering sense with fundamental research to realize industry-scale deployment. This review will inspire the researchers and engineers to break the bottlenecks in electrochemical water softening technology and harness this technology with the broadened industrial application area.