Dual activation of porous nitrogen-doped carbon materials for highly efficient mine water desalination by flow electrode capacitive deionization

HE Qiongqiong; PENG Haisen; MENG Zhen; MIAO Zhenyong; WAN Keji; XU Enle; GAO Mingqiang; HUANG Shaomeng

doi:10.13225/j.cnki.jccs.2024.0509

Abstract：Driven by stringent environmental regulations,coal mines are facing escalating challenges in recycling and treating highly saline mine water,so highly efficient deep desalination technologies are urgently needed to break through the industry's dilemmas and enable the utilization of non-conventional water resources.Although flow electrode capacit-ive deionization(FCDI)technology is emerging within the field of desalination,there is still a barrier to desalination cap-ability due to electrode material properties.In this study,a new method for the preparation of dual-activated porous nitro-gen-doped carbon electrode materials is proposed.Using sucrose as the carbon source and melamine as the nitrogen source,the advantages of the dual template method,water vapor activation,acid-impregnated oxidation,and nitrogen dop-ing were integrated,and the wettability and conductivity of the materials were improved.Furthermore,the electrode mater-ial has a unique neatly arranged columnar structure,larger specific surface area(1 039.76 m2/g),richer pore structure(0.32 cm3/g),more nitrogen-oxygen electronegativity sites,and better wettability,which can be used to realize highly effi-cient and low-energy consumption desalination of mine water.The material(H2O(g)-HNO3/CN)was applied in the FCDI device and desalted 1 g/L NaCl solution for 5 h after process optimization of voltage,active material content,initial con-centration of treatment solution and pH,and the desalination rate was as high as 100％,and the average desalination rate,desalination amount,charge efficiency and standard desalination energy consumption were 0.009 52 mg/(min·cm2),37.08 mg/g,24.02％and 481.98 J/mol,respectively.Even after seven cycles of suction-desorption experiments,the desal-ination rate could still reach 95.71％.In order to investigate the adsorption and desalination mechanism of H2O(g)-HNO3/CN,the electrochemical properties,adsorption kinetics and isotherms were analyzed.The results showed that its specific capacitance was as high as 99.38 F/g and the internal resistance was extremely small;the adsorption of Na+ions was more consistent with the pseudo-second-order kinetic model and Langmuir isotherm model,and the saturated adsorp-tion amount of Na+ions was 4.30 mg/g,and the saturated adsorption time was 120 min.