Capacitive Desalination ?CDI? Performance And Electrosorption Of Cu²⁺ On Manganese-based Electrodes

With the development of human society,rapid growth of the population,development of industry and technological progress have brought tremendous pressure on the demand for freshwater.At the same time,the various types of pollutants produced by human production interfere with the natural water system more than the environmental carrying capacity,making the crisis increasingly serious.Therefore,how to desalinate and purify water is the key.Capacitive deionization has attracted wide attention due to low energy consumption,low cost and great recycling ability.Different from the traditional electrostatic adsorption method based on electric double layer,faradaic deionization can remove ions through redox reaction process.In this paper,manganese-based material was used as the cathode to prepare a hybrid capacitive deionization device?HCDI?for investigating the desalination and heavy metal removal performance.The main research results are as following:?1?The crystal phase and structure of MnO₂ can be controlled by hydrothermal reaction duration.The influence on the desalination performance during the phase transition process was investigated.The salt adsorption capacity will decrease with the crystallinity and crystal phase transformation during the growth of manganese dioxide crystals.Moreover,the desalination performances are effected by surface adsorption and sodium ion intercalation together.High crystallinity MnO₂ is mainly controlled by ion intercalation,while for poorly crystalline MnO₂ electrodes,the surface adsorption is more prominent.The results show that the low crystallinity layered structure?-phase MnO₂-1h exhibits the best deionization capacity and charge efficiency.Meanwhile,in 500 mg L^-1 solution of Na Cl,it exhibits that the salt adsorption of MnO₂-1h is 21.32 mg g^-1.?2?According to poor cycling stability of traditional activated carbon electrode materials due to electrode degradation,KOH-activated nitrogen-doped mesoporous carbon microspheres?K-NMCS?were synthesized and further coated with MnO₂?MK-NMCS?to explore its desalination performance and removal capacity of Cu²⁺and Pb²⁺.The salt adsorption capacity of MK-NMCS electrode in a solution of 500 mg L^-1 Na Cl is 25.39 mg g^-1.The loading of ?-MnO₂ greatly improved the adsorption capacity of MK-NMCS for heavy metals.Therefore,the removal capacities of copper and lead ions are 22.7 mg g^-1 and 26.7 mg maintains great performance of removal of heavy metal.?3?By adjusting the ? phase manganese dioxide interlayer ions,the interlayer spacing of the as-synthesized Na B,KB,and Mg B is 7.17?,7.23?,and 9.70?.After adjustment of interlayer spacing by Mg ions,the desalinization of Mg B in 500 mg L^-1 solution of Na Cl is59.9 mg g^-1.The ion adsorption capacity of different cations is related to the distance of interlayer spacing,the radius of the hydrated and the valence.In the solution of 100 mg L^-1 maintained good stability after 60 cycles.