Exploring a sustainable binder for capacitive deionization technology to achieve high salt and zinc ion removal efficiency

As a newly developed water purification technology, capacitive deionization (CDI) is a promising technology for water desalination. The influence of binders on the performance of CDI electrodes, especially on the performance of heavy metal ion removal, has been rarely discussed so far. On the other hand, searching sustainable materials to replace those made from non-renewable resources is attracting more and more attention. Herein, the influence of the sustainable binders on CDI performance is studied. For the NaCl adsorption, the chlorinated rubber (CLR) electrode shows a higher capacity and rate capability than the other binders. Particularly, we explored the CDI process for zinc ion in water and claimed that the formation of hydroxide of zinc ion should be considered. Surprisingly, CLR can inhibit Zn4SO4(OH)6•5H2O generation and structural disruption of electrode. CLR electrode has the highest desalination performance, 79.8 mg g−1 of ZnSO4 and the longest cycle lifetime remaining 95.4 % of adsorption capacity after 10,000 cycles. Moreover, CLR can be made from sustainable natural rubber and its price is only 14.3 % of PVDF. Obviously, CLR is promising for heavy metal salt removal and large-scale water purification devices. CLR also shows superior performance than PVDF in aqueous zinc capacitor.