Study On The Activated Carbon Fiber Electrodes Of Capacitive Deionization Technology

Capacitive deionization (CDI) is a novel technology for removing ionic species from aqueous solutions. This electrochemical process is conducted at low voltages and requires no high-pressure pumps, membranes, distillation columns, or thermal heaters. So no secondary waste is generated. The price of carbon aerogel which is studied on CDI electrodes is expensive. In order to reduce cost of CDI apparatus and make it easy to industrialize, activated carbon fiber (ACF) were studied as electrodes in this paper. First, activated carbon fiber was compared with granule activated carbon (GAC) and activated carbon powder. Second, the influence factors of CDI by electrode pairs, the spacing between electrodes, voltage, the concentration and flow rate of the treated solutions were investigated. Third, the electrosorption characteristics of various voltages, electric current of solution, electrosorption and desorption of electrodes and application of CDI were studied. Furthermore, the modification of ACF was studied.ACF worked as electrodes was better than GAC and activated carbon powder. CDI with 5 successive electrodes pairs between which the spacing was 4mm. The voltage was under 1.2V and the flux of the treated solution was 10mL/min. The desalinization rate was increased along with prolonging the cycle.The laboratory datas showed that ion electrosorption followed a Langmuir isotherm, indicating monolayer adsorption. And it followed Freundlich isotherm, indicating electrosorption on ACF electrodes was easy. The electrosorption capacity of ACF electrodes at 0.4, 0.6, 0.8, 1.0 and 1.2V were 2.1, 3.3, 4.5, 7.6 and 10.2 mg/g respectively. Ions were adsorbed onto the surface of porous electrodes by applying electric field. Adsorbed ions were desorbed from the surface of the porous electrodes by eliminating electric field, resulting in the regeneration of the electrodes. Successive deionization and regeneration showed that ACF electrodes could be used many times. Findings indicated that incorporated titania could be effective to increase electric field adsorption, resulting in a significant enhancement of CDI performance, increased by 94.3%.Findings showed ACF worked as electrodes was feasible and was effective to treat the low salt waste water. The energy consumption of this method was lower, moreover the apparatus was very simple, and the industrialization and automated control was easy to be realized. ACF will have a better application prospect after modification.