Rich heteroatom doping magnetic carbon electrode for flow-capacitive deionization with enhanced salt removal ability

Abstract

Core-shell nanoparticles were prepared by coating magnetic nanoballs (Fe3O4) with highly cross-linked polymer poly(-cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) to serve as heteroatomic-rich doping electrodes (MZPS). After formation by carbonization, C-MPZS acts like a flowing electrode used for flow-capacitive deionization (FCDI), which has fast ion transfer and diffusion performances because of its rich heteroatom content and the prominent synergistic effect of N, P, S atoms. Moreover, the FCDI performance of C-MPZS is enhanced due to its increased synergistic effect from its excellent available specific surface area, unique porous characteristics with large micro-/mesopores, and favorable conductivity with high graphitization. The optimal carbonization temperature was 500 °C with an optimum specific capacitance of 211.54 F g−1, which was tested in a 1 M sodium chloride solution at a scan rate of 1 mV s−1. Then, the C-MPZS flowing electrode was found to have a high electrosorption capacity (50.07 mg g−1), removal efficiency (68.50%) and removal rate (83.07%) at an applied potential of 1.0 V in a sodium chloride solution with a conductivity of 1200 μS cm−1 at 6 rpm. An additional cyclic test demonstrated good stability performance after 10 cycles due to the magnetic nanoparticles effect. Finally, through the successful application in tail water from printing and dyeing wastewater, the results indicated that the as-prepared C-MPZS flowing electrode has promise for application in high-performance electrochemical deionization.