Abstract
Capacitive deionization (CDI) method has drawn much attention for its low energy consumption, low pollution, and convenient manipulation. Activated carbon fibers (ACFs) possess high adsorption ability and can be used as CDI electrode material. Herein, two kinds of PAN-based ACFs with different specific surface area (SSA) were used for the CDI electrodes. The CDI performance was investigated; especially asymmetric electrodes’ effect was evaluated. The results demonstrated that PAN-based ACFs showed a high electrosorption rate (complete electrosorption in less than half an hour) and moderate electrosorption capacity (up to 0.2 mmol/g). CDI experiments with asymmetric electrodes displayed a variation in electrosorption capacity between forward voltage and reverse voltage. It can be attributed to the electrical double layer (EDL) overlap effect and inner pore potential; thus the ions with smaller hydrated ionic radius can be adsorbed more easily.
Highlights
Water scarcity has become an increasing concern on the earth
The Activated carbon fibers (ACFs) samples were designated as P7 and P10 according to their Brunauer-Emmett-Teller (BET) surface areas of 700 and 1000 m2/g
PAN-based activated carbon fibers were used as Capacitive deionization (CDI) electrodes, which demonstrated a moderate electrosorption capacity
Summary
Water scarcity has become an increasing concern on the earth. Fresh water accounts for only 0.007% of the global water resources. CDI’s performance relies on its adsorbing efficiency [7], which is mainly influenced by electrode materials, apart from external conditions such as solution’s concentration. Many kinds of carbon materials have been used and tested as CDI’s electrode, and the high CDI performance usually depends on the physical and structural properties of the electrode materials such as specific surface, conductivity, and pore size distribution. We exploited activated carbon fibers (ACFs) electrodes with different specific surfaces and studied the influence of electrodes asymmetry’s on CDI performance. Electrodes with size asymmetry and material asymmetry were used in CDI process and electroadsorption performances were analyzed. Different from Porada’s research, we used electrodes with various geometric sizes other than thickness and evaluated the CDI performance
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