Nitrogen And Sulfur Co-Doped Carbon Cryogel Electrode For Membrane Capacitive Deionization

Capacitive deionization with porous carbon has shown a strong ability to remove various inorganic species from aqueous solutions. In this paper, we propose a novel sulfur-nitrogen doped carbon cryogel form embrane capacitive deionization electrodes. The carbon cryogel is prepared via the polycondensation of thiourea, resorcinol and formaldehyde in a weakly alkaline aqueous solution followed by a pyrolysis process at 800 degrees C. The present work focuses on the influence of dual doping on the structure and electrosorption properties. Also, adsorption capacities of the doped carbon cryogel electrode in the capacitive deionization mode and the membrane capacitive deionization mode are compared. The results confirm that the carbon cryogel prepared with thiourea/resorcinol molar ratio of 0.2:1 displays high specific capacitance (182 F/g), maximum adsorption capacity (37.16 mg/g) and higher charge efficiency (65.8%) at 1.8 V in the membrane capacitive deionization. The Freundlich isothermal model is suitable to simulate the adsorption behavior of NaCl onto the carbon cryogel electrodes in the membrane capacitive deionization mode. Moreover, the electrode can remove most of the adsorbed salt ions after full desorption with an excellent regeneration in the next adsorptions, indicating that the dual doping cryogel electrode is suitable for membrane capacitive deionization.