Study On Capacitive Deionization And Heavy Metal Removal Performance Of Ion Exchange Modified Porous Activated Carbon

Over the years,several major desalination technologies have been developed,such as reverseosmosis,distillationand electrodialysis.Capacitive deionization?CDI?,a technique based on electric double layer is considered to be a promising desalination technology due to its lower energy consumption,higher efficiency and non-pollution.Electrode materials are the most important components to determine the CDI performance during the electrosorption-desorption process.In general,activated carbon?AC?is likely the best choice as electrode material because of its wide range of sources,low cost,large specific surface area,abundant pore structure and good electrochemical stability.However,the AC mostly has low specific capacitance and large internal resistance.So it's necessary to modify AC further to enhance its adsorptive capacity.In this study,ion exchange resin was used as the precursor for AC preparation.Meanwhile,ZnCl₂ solution was used to allow sufficient ion exchange process to ensure uniform loading of the Zn²⁺ onto the resin.Because of its low boiling point,some of zinc would volatilize from resin at high temperature,resulting in the formation of porous structure in the AC.Next,various activators were selected to investigate their effects on the electrochemistry behavior and adsorptive performance of prepared AC.Finally,in the simulated seawater and wastewater,the adsorptive performance and regeneration ability of AC were evaluated under different operating conditions.The relevant conclusions were as follows:?1?After the CO₂ activation,the AC showed larger specific surface area(1162m2g^-1)and total pore volume(0.793cm3g^-1),possessing microporous-mesoporemacroporous coexisting hierarchical pore structure.It also exhibited smaller ion migration resistance and faster ion diffusion.In addition,the specific capacitance of AC was up to 340 F g^-1with good charge and discharge performance.Eventally,in the desalination experiment,the AC showed excellent adsorptive capacity and good regeneration ability.?2?The carbon material showed higher adsorptive capacity after the CO₂ activation.In this work,the effects of activation temperature?650,700 and 750??onthe structures and properties of AC was further investigated in order to determine the optimum conditions.After high temperature activation?750??,the AC showed the largest specific surface area,pore volume and specific capacitance,and it possessed more sulfoxide and thioether.In addition,it also reflected less electrochemical impedance and the fastest ion migration rate.In the desalination experiment,the effects of voltage and flow rate on the adsorptive capacity of AC were studied.As a result,the adsorptive capacity of AC was high to 24.4 mg g^-1 and it showed good stability after 20 cycles.?3?The influence of experimental parameters?operating voltage,flow rate,p H and initial concentration?on electrosorption of copper by AC in simulated wastewater was investigated.Finally,after the activation of CO₂ at 750?,the adsorptive capacity of AC could reach 160 mg g^-1.Combined with the integrated isotherm adsorption line and adsorption kinetics,it was found that the adsorption process of AC followed the Langmuir isotherm adsorption model and the adsorption kinetics was consistent with the pseudo-first-order kinetics.