Study On The Configuration Of Polypyrrole/Carbon Nanotube Electrodes And Their Tolerance In Different Solution Conditions Of Capacitive Deionization

Capacitive deionization(CDI)technology is a novel desalination technology which achieves desalination by using a pair of electrodes with high capacitance and the adsorption/desorption cycle principle.It has an important practical value to conduct the practical investigation about the novel composite material electrode,including the coating methodology fabrication,electrode configuration optimization,CDI application condition optimization and electrode desalination stability evaluation.In this paper,the no ion-doped polypyrrole/carbon nanotube(PPy/CNT)composite material has been synthesized by chemical oxidation method,and then the PPy/CNT electrode was fabricated by the coating methodology.The size of the obtained PPy/CNT electrodes was enlarged to 80×160 mm.The influences of the drying temperature on the surface form and performance homogeneity of the electrode were investigated.The results indicated that the obtained PPy/CNT electrode under the constant drying temperature of 40? and drying time of 8h was fabricated well,and its specific capacitance and specific adsorption capacity got to the optimum which could reach up to the high value of 180.86 F/g and 89.76 mg/g respectively.And the performance of enlarged PPy/CNT electrode were not decreased compared to the small electrode sample(25×45mm)under the same condition.In addition,the hydrochloric acid(HCl)and sodium dodecyl benzene sulfonate(SDBS)were selected as the dopant,and the carbon nanotube(CNT)electrode and the PPy/CNT electrode doped with different doping ions,including the PPy-Cl/CNT electrode and PPy-DBS/CNT electrode were fabricated by the coating methodology under the optimized magnifying preparation parameters obtained from the previous section.The influences of the seven type electrode configurations assembled by the above-mentioned electrodes on the potential distribution,saturated adsorption characteristic and cyclic desalination stability of the electrode were studied,and the reason was explored from the point of the electrode potential of zero charge(PZC).The results showed that when the PPy-Cl/CNT electrode acts as anode and the PPy-DBS/CNT electrode acts as cathode,the cell exhibited potential loss of 0 V vs.SCE due to the PZC of electrode positioning outside the each electrode working domain,and then the corresponding Cell Cl-DBS obtained the optimal specific adsorption capacity(92.75 mg/g)and favourable desalination stability.Based on the optimum electrode configuration,the influence of the solution conditions,including the acidic condition,alkaline condition and temperature condition on the structure property,electrochemical characteristic,desalting performance and their stability of the electrode was also researched in this paper.And the long-term cyclic desalination stability of the Cell Cl-DBS under the optimum solution condition was tested and evaluated.The results indicated that the appropriate solution conditions of PPy/CNT electrode were pH=6~8 and solution temperature of 5~25?.And under this situation,the electrode could hold favourable electrochemical characteristic and desalting performance.The specific capacitance and the specific adsorption capacity of the electrode could reach above 165F/g and 73mg/g respectively,and the attenuation ratio for the normalized capacitance after 100 scan circle and the normalized adsorption capacity after 20 desalination cycle were less than 16.4% and 17.4% respectively.However,the adsorption capacity of the cell under the optimum solution condition(pH=7,15 ?)could reach the high value of 94.5 mg/g but decreased by 47% after 100 times cyclic desalination.The long-term cyclic desalination stability of the cell still needs to be improved.