Improvement of capacitive deionization performance via using a Tiron-grafted TiO2 nanoparticle layer on porous carbon electrode

A novel ion-selective inorganic-carbon composited electrode was designed to improve the performance of a capacitive deionization (CDI) process. Disodium 4,5-dihydroxy-1,3-benzenedisulfonate (Tiron) was grafted on the surface of titania nanoparticles, and a thin titania layer with a thickness of 10-12 mu m was formed on porous activated-carbon (AC) electrode and used as the negative electrode in a CDI full cell. The resulting Tiron-grafted titania nanoparticles showed an excellent ion-exchange capacity (1.51 meq/g). As a result, the Tiron-titania/AC composited electrode was found to have improved desalination properties in terms of specific adsorption capacity, specific adsorption rate and current efficiency compared with the pristine CDI electrode. Improved desalination performance was attributed to a reduction in co-ion expulsion effect by ion-exchangeable functional groups in Tiron-grafted titania. In addition, the improved desalination performance through the introduction of a porous layer of Tiron-grafted titania was similar to that of the conventional membrane capacitive deionization (MCDI) using an ion-exchange membrane. From the results obtained, it has been experimentally proven that the use of Tiron-grafted TiO2/AC composite as the negative electrode in the CDI process is a simple and effective way to achieve high desalination performance.