The sustainable supply of fresh water is pressing issues that affect the overall global community. Membrane capacitive deionization (MCDI) is a promising electrical-driven ion separation technology for low-salinity desalination, in which ions can be electroadsoebed with low energy input, high water recovery, and environmental friendliness. In electrosorption process, a good electrode material should have characteristics of high specific surface area, well-balanced porous structures, and high electronic conductivity. Activated carbon is the most used in MCDI due to its low cost and scale-up potential. However, there are limitations of activated carbon electrodes cause by disordered porous structure and polymer binder (e.g., polyvinylidene fluoride (PVDF)). Especially, using polymer as binder causes a low conductivity, irregular pore structures and high ionic diffusion resistance for electrode. Noteworthy, electrospinning is simple approach to make activated carbon fiber (ACF) integrated with oxidation process, and a high-temperature short duration. ACF is attracting more attention due to the great advantages on binder-free and sheet electrodes of electrochemical applications. In this study, the electrospinning manufacturing method to fabricate ACF is developed for MCDI. ACF electrode make by electrospinning with polyacrylonitrile (PAN) as the precursor. The oxidation, carbonization, and activation processes were subsequently proceeded at different temperatures (800oC/900oC) and time (0.5 h/1.0 h/1.5 h) to control the pore structure and conductivity of ACFs. Salt adsorption capacities of electrodes were determined by batch-mode MCDI experiments at an applied voltage of 1.2 V for desalting NaCl solutions. As a result, ACF with activated at 900oC for 1.5 hours(ACF915) exhibited a high specific surface area of 1300 m2/g and good conductivity of a ID/IG ratio of 0.92. The specific capacitance of ACF915 measured at a scan rate of 5 mV/s is 76.47 F/g. By controlling the ratio of mesoporous to microspores, ACF915 shows an excellent salt adsorption capacity as high as 14.49 at 5 mM NaCl solution. The improvement can be attitude to the high specific surface area, well-balanced porous structures, and high electronic conductivity.

Controlling micro/mesoporosity of activated carbon fiber with electrospinning for membrane capacitive deionization

2019 Fall National Meeting

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