| The Flow-electrode Capacitive Deionization(FCDI)is a novel capacitive deionization technology of a positive/negative flow-electrode coupled with anion/cation exchange membranes.This paper focused on a flow-electrode with great material dispersion,suspension stability and specific capacitance based on sulfonated carbon nanotube(CNT-S)electrode materials,and a FCDI deionization process was successfully constructed with own FCDI cells to explore the operating parameters of FCDI process,which provide experiment references to practical application of FCDI process.In this paper,to fabricate a flow-electrode with excellent performance,the CNT-S as the active materials of flow-electrode was synthesized by sulfonation and the flow-electrode was prepared with deionized water,and the specific capacitance,dispersion and suspension stability of flow-electrodes of CNT and CNT-S were investigated.And the dispersants of sodium dodecyl sulfate(SDS)and cetyltrimethyl ammonium bromide(CTAB)were used to examine each effect on the performance of flow-electrodes,as well as the quality-ratio.The results show that the average particle size of 220 nm and Zeta potential of-18.4mV are achieved as for CNT-S flow-electrode,lower than that of the CNT flow-electrode(295nm,-5.447mV);the CNT-S flow-electrode has a better dispersion and suspension stability than CNT flow-electrode;the CNT-S flow-electrode has the special capacitive of 16.32F/g and the better capacitive stability.In addition,compared with CTAB dispersant,the SDS with identical negative charge characteristics as CNT-S can enhance the dispersion and suspension stability of the CNT-S flow-electrode;the specific capacitance of the CNT-S flow-electrode increase firstly and then decrease along with the increase of the SDS quality-ratio from 0 to 0.8,and the maximum specific capacitance reaches to 33.70F/g at SDS quality-ratio of 0.4.Based on own FCDI cells and the optimal CNT-S flow-electrode,a static-electrode capacitive deionization(SCDI)system and a flow-electrode capacitive deionization(FCDI)system were respectively formed to optimize the operating parameters by keeping the CNT-S liquid-electrode static and flow in the electrode-loop.In the SCDI system,the the effects of working voltage and feed water concentration on desalination performance were investigated.The results indicate that the desalting efficiency of 45.85% and the saturated adsorption rate of 0.244 mg/min are achieved at 1.3V voltage;as the feed water concentration from 1.0 g/L to 35.0 g/L,the salt removal efficiency of the SCDI cell decreases from 45.85% to 10.43% but the salt removal flux increases from 0.067g/min to 0.546g/min.The saturated adsorption experiments of the SCDI cell show that the adsorption capacity of CNT-S flow-electrode tends to saturation at 250 min,and the mean electro-sorption rate of 14.55mg/(g·min)and the high salt removal efficiency of 45.6% are achieved in 1.0g/L NaCl solution at the voltage of 1.3V,both of which are about 1.6 times that of the CNT flow-electrodes;the CNT-S flow-electrode shows an excellent recycle stability of the 95.1% regeneration rate after 20 regeneration cycles.In addition,under the optimal operating parameters,the effect of the flow rates ratio of feed water and flow electrode on the desalination performance was investigated in FCDI system.The results indicate that for FCDI cell,the salt removal efficiency maximizes at 83.34% and the saturated adsorption time minimizes at 240 min with 150mL/min of the flow electrode or 100ml/min of NaCl solution.The effects of the flow flux of washing water on electrode regeneration performance were investigated at the adsorption or desorption processes in the FCDI dual-cell system.The results show that as the flow-flux ratio of washing water and feed water decreases from 5/5 to 2/8,the desalination efficiency and regeneration efficiency of flow-electrodes reduced to 77.58% and 83.13%,respectively. |
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