Preparation Of Porous Carbon Material Used For Capacitive Deionization

Capacitive deionization?CDI?technology is considered to be the one of most promising sustainable technologies in the filed of seawater desalination,because of its high efficiency,low energy consumption,low cost,and no secondary pollution.The practical application of CDI relies on the development of highly stable electrode materials.In this work,a highly porous nitrogen-doped carbon aerogels?NCAs?were prepared by polymerizing pyrrole and formaldehyde monomers under excessive zinc chloride?ZnCl₂?and then carbonizing at different temperatures?800 and 900 °C?.Throughout the preparation process,ZnCl₂ is used not only to provide a high salt reaction environment for the polymerization of pyrrole and formaldehyde but also as a catalyst and activator.Experimental results show that ZnCl₂ catalyse the Friedel-Crafts Reaction between-CHO in formaldehyde and-CH in pyrrole ring.The excess ZnCl₂ ensure the structure of hydrogels after 105 °C drying.Temperature is the key factor which influences the nitrogen content,nitrogen type,and porous structure in the high temperature process.The prepared NCAs with high specific surface area?1450 m2/g for NCA-800 at 800 °C,1670 m2/g for NCA-900 at 900 °C?,ultra-high micropore structure of more than 98% of the total pore volume,and moderate nitrogen content?The NCA-800 is 10.86 atom% and NCA-900 is 4.09 atom%?were acquired by high temperature process.The performance of electric double layer of NCA-800 and NCA-900 were characterized in 1mol/L H2SO4 and 1mol/L Na Cl electrolyte,showing that NCA-800 has higher chemical stability and specific capacitance.Further,the electric double layer behavior of the NCA-800 and NCA-900 electrodes in Na Cl solution were further studied.The NCA-800 eletrodes showed excellent capacitance retention arrived at 95 %,higher capacitance of 116 F/g,and the corresponding adsorption capacity arrived at 63 mg/g,also exhibited acarcely any redox reaction during adsorption-desorption,good cycle performance under Na Cl as the electrolyte.Finally,the CDI sequencing batch reactor of the NCA-800 as a CDI electrode was used to investigate the desalination performance on different electrode voltages and different concentrations of Na Cl solution.The adsorption capacity of NCA-800 to 2000 mg/L Na Cl solution at 1.2 V voltage and 20 m L/min can reach 31.44 mg/g.And there is no significant reduction for capacity of NCA-800 after 6 adsorption-regeneration cycles.The NCA-800 material is easy to prepare and has low cost,also owns high nitrogen content and high microporous structure,and good stability and moderate salt adsorption capacity when used as a CDI electrode.Therefore,NCA-800 has great potential as CDI eletrode.