Hybrid-capacitive deionization with combined Faradaic and capacitive reactions for silicate removal

Capacitive deionization (CDI) is an electrochemical method that effectively removes various ionic substances, and it is widely applied in desalination, water treatment, and material purification. Since CDI is based on an electric field effect that drags substances from the solution, its applicability is limited to charged species. Substances such as silicates lose their ionic charge depending on the solution pH, which makes it difficult to remove them using CDI techniques. The current study aims to overcome these limitations by proposing a hybrid-CDI (HCDI) system. The proposed HCDI system combines the functions of pH adjustment and ion removal. At the cathode of the HCDI, OH– is generated through water reduction via a Faradaic reaction, thus elevating the pH inside the system. In this high pH environment, silicates exist as ionic forms. These ionic silicates are then effectively separat…