Covalent Triazine-based Frameworks Polymer Preparation And Application For Capacitive Deionization

With the development of world economic and industry,fresh water scarcity is one of the top challenges to human habitationon Earth because of the unusable brackish water and regenerationdifficulty of industrial effluents and human activities are still wasting and polluting this precious rescources.Traditional desalination approaches including reverseosmosis,multistage flash distillation,ion exchange and electrodialysis require high energy consumption,high capital cost and causesecondary pollution.As an emerging technology for watertreatment,capacitive deionization?CDI?is attracting increasing attentiondue to its unique merits,such as being simple,safe,low-charge,highly efficient and contamination-free.CDI is an electro-adsorption process where the charged species in a feed solutionmigrate and adsorb the oppositely charged electrodes under anapplied potential and then desorb while a short-circuit or reversedvoltage are applied.CDI could form the electrical double layer?EDL?at the electrode-liquid interface during adsorption processes.Exploring and research an appropriate electrode is one of the key factors to address the CDI technology.In this thesis,self made CDI devices with COFs electrodes was used to test deionization performance.COFs is a kind of materials which have lots of merit like easy to control the structure and excellent heat/chemical stability.Covalent triazine-based frameworks?CTFs?polymer was chosen in this experiments.1,4-dicyanobenzene as raw materials and anhydrousZnCl2 as catalysis as well as solvent,and reacted in 400 ^oC?500^oC;20 hours and 40 hours in ionthermal method.SEM?TEM?FT-IR?PXRD?TGA?hydrophily test and nitrogen adsorption/deadsorption was carried out for CTFs characterization.CV,GC and EIS etc.electrochemical test was tested in electrochemical workstation.CTFs was mixed with carbon black and PVDF to make an electrode for CDI and carried out series of desalination experiments in different voltage and differe nt initial concertration and recycle test.Covalent triazin-based frameworks?CTFs?with high nitrogen content,porous structures and low electric resistance were synthesized and applied as membrane capacitive deionization electrodes for the first time.The obtained CTFs exhibit abundant micropore structure which provide adsorption site for ion and certain hydrophilicity ensure the whole pore volume is participating.The electrodes of p-CTFs showed ideal capacitive behavior with the maximum specific capacitance values of 122.63 F g^-1 at a scan rate of 1 mV s^-1 under 1 M NaCl solution.Besides,the further membrane capacitive deionization by batch mode experiment exhibits excellent electrosorption capacityof29.34 mg g^-1 under 1.2 V in a 1000 mg L^-1NaCl solution and stable regeneration performance.With the admirable properties mentioned above,the prepared CTFs can offer great opportunities as promising CDI electrodes for application of high-performance desalination.