Research And Application Of Coconut Shell Carbon Electrode For Capacitance Deionization Technology

Fresh water is the basic material for human survival.However,due to the discharge of industrial sewage,the environmental pollution is becoming more and more serious,and the fresh water resources are in short supply.So it is very important to solve the problem of using water resources.As we all know,sea water resources occupy the vast majority of water resources on the earth.However,because seawater contains a large number of salts such as sodium chloride and magnesium chloride,it can not be directly used,so it needs to be desalinated before it can be used.Among them,capacitive deionized Technology（CDI）has been widely concerned because of its advantages of good desalination,low cost and good comprehensive benefits.The electrode is core part of the capacitive deionization,and its performance greatly affects the desalination performance.While selecting electrode materials to ensure desalination,a wide range of materials with low cost should be selected.In this paper,coconut shells and sodium manganese oxides are selected as the raw materials for the preparation of the electrode.The coconut shell was treated by muffle furnace and chemical procedures and coconut shell activated carbon was obtained.The coconut shell charcoal together with other materials were roled into electrode pieces.The desalting performance of the prepared electrode was tested by the CDI module test system.The electrical conductivity of the solution varies with time,indicating that the CDI module can successfully remove and deactivate the salt in the solution.At the flow rate of different salt solutions,the conductivity of the solution first descends faster and then gradually tends to slow.With the increase of the flow velocity of the solution,the effect of CDI gradually becomes better,but the effect of CDI becomes worse when the flow rate of the solution increases to 35 r.The maximum energy consumption and efficiency are maximized,and the flow velocity of 30 r（10 mL/min）is the best choice.Under the different operating voltages,the greater the operating voltage,the decrease of the conductivity in the solution.When the voltage in the voltage is 1V,the adsorption effect is the best and the conductivity is lower to 950μS/cm.The charging and discharging device will reverse,the maximum conductivity solution desorption values obtained with the initial conductivity values are consistent,which indicate that the coconut shell carbon electrode preparation also has good desorption performance.The adsorption of different ionic charge and ion radius is different when different salt solutions are treated.The adsorption of different ions is high in the high charge of charge.When the charge is consistent,the small adsorption capacity is higher.Using sodium manganese oxide（NMO）as raw material,solid phase reaction is used to synthesize Na₄Mn₉O₁₈,mixed with other materials,roll press is rolled into sheet type electrode.The AC electrode was prepared by the same method.The NMO electrode and the AC electrode were assembled into asymmetric systems.NMO electrode and AC electrode were tested by cyclic voltammetry.The two electrodes showed excellent stability and high capacity in aqueous solution.At the same time,the desalting effect of NMO/AC asymmetric system was tested.The maximum removal rate of ion can reach 0.066 mg（NaCl）/g/s.Compared with the results obtained from the CDI system（0.048 mg/g/s）using a symmetrical activated carbon electrode,the performance is better.It also has good treatment effect when treating high concentration of salt solution.Na₄Mn₉O₁₈8 has a larger charging capacity（40 mA h/g-50 mA h/g）,and the value is over 300 F/g,and has a higher capacitance than the AC material.At the same time,the charge/discharge capacity shows excellent stability during the cycle,and the coulomb efficiency is close to 100%after 300 cycles.This indicates that the electrochemical performance of the NMO/AC asymmetric system is stable and can be used repeatedly in the sodium chloride solution.