2013 WCU's Poster Presentation(ModifiedII)
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1) Capacitive deionization is a desalination technology that uses porous carbon electrodes to remove ions from water through an applied electric field. However, organic materials accumulating on the carbon electrodes can diminish performance over time. 2) The study investigated how humic acid fouling affects desalination performance and electrode properties of a capacitive deionization system. Results showed fouling decreased ion removal and electrode capacitance. 3) Cleaning the fouled electrodes with sodium hydroxide solution was able to recover desalination performance and increase electrode capacitance beyond that of the original virgin electrodes, with longer cleaning times providing better recovery.
2013 WCU's Poster Presentation(ModifiedII)
- 1. Poster template by ResearchPosters.co.za Fouling of carbon electrode by humic substance and its cleaning in capacitive deionization Wannacha Limthanakul, Taeyoung Kim, Seoni Kim, Jeyong Yoon School of Chemical and Biological Engineering, College of Engineering, Seoul National University, Seoul, Korea Introduction Objectives Experimental Works Results Summary Carbon Electrode Carbon Electrode + - + + + +- - - - - - - - - + + + + + + + + - - Treated WaterConcentrated Water Anode Cathode Fig. 1. Schematic diagram of CDI process Capacitive deionization (CDI) is a technology for desalination and water treatment in which ions are removed from water by applying an electric field between two porous (carbon) electrodes. Advantages: - Environmentally clean technology - Energy and cost saving - Simply operating Further study need Because electrode materials used in CDI has been fabricated from high-surface area carbon, the accumulation of organic material could effect the electrode property contributed to diminish the CDI performance. Fig. 2. Accumulation of organic matter on carbon surface Source: wateensolutions.com.au ⧄ To investigate the effects of organic matter to CDI performance. ⧄ To investigate the electrochemical property change of the electrodes after organic fouling. ⧄ For organic fouling remediation, chemical cleaning approach has been applied to observe the recovery of CDI performance. ⧄ Carbon Electrodes: Materials: Activated carbon YP50 + Super P + PTFE Fabrication: Rolling Press method(RP) ⧄ Dissolved Organic Solution 100 mg/L of Humic Acid(HA) ⧄ Soaking period 24 hr 100 mg/L of Humic Acid Roller Roller Carbon mixture 50 mm 0.3 mm (a) (b) Fig. 3. Schematic of organic fouling on carbon electrode. (a) electrodes were fabricated by RP method. (b) Fabricated electrodes were soaked in humic acid solution for 24 hr. Desalination ⧄ Reactor CDI cell : Flow type ⧄ Feed Solution NaCl : 10 mM ⧄ Operating Conditions Applied potential : 1.2 V Cycle time : 5 min charging, 5 min discharging 5 cycles Flow rate 10 ml/min Organic fouling Potentiostat Outlet Conductivity meter CDI cell NaCl 10mM Peristaltic pump Graphite sheet Graphite sheet Electrode Electrode Spacers Fig. 4. Schematic of experimental system for desalination ⧄ Cleaning agent: 10 mM of NaOH ⧄ Cleaning time: 10,25 and 50 min Fouling Remediation (1) Effect of organic fouling to desalination performance and electrochemical property of electrodes (a) (b) Fig. 5. Desalination performance of HA fouled electrode and virgin carbon electrode: (a) ion removal aspect; (b) amount of accumulated ion removal during charging step Electrodes Specific Capacitance (F/g carbon) Virgin YP50 81 HA fouled 73 Fig. 6. Cyclic voltammograms of HA fouled electrode and virgin electrode. (2) Recovery of desalination performance and electrochemical property by alkaline cleaning agent(NaOH) (a) (b) Fig. 7. Desalination performance of HA fouled electrode and different time cleaned electrodes. : (a) ion removal aspect; (b) amount of accumulated ion removal during charging step Electrodes Capacitance (F/g carbon) Virgin YP50 81 Fouled YP50 73 10 min cleaning 78 25 min cleaning 77 50 min cleaning 91 Fig. 8. Cyclic voltammograms of HA fouled electrode and different time cleaned electrodes. ⧄ The deionization performance after operating with HA fouled electrodes was significantly declined Decreasing in amount of ion removal (11 3 mg/g) and capacitance (8173 F/g) ⧄ The deionization performance and capacitance were recovered by 10 mM of NaOH as a cleaning agent for 50 min. ⧄ In particular, the capacitance became higher than the virgin electrode after cleaning. Contact Information Biofilm Engineering Laboratory env.snu.ac.kr 302 Bld. Room No.513(5th floor) Tel: 82-2-880-8941 Fax: 82-2-876-8911 Email: wannachalimthan@snu.ac.kr Acknowledgments This research was supported by WCU (World Class University) program through the Korea Science and Engineering Foundation by the Ministry of Education, Science and Technology (R31-10013), and also supported by Korea Ministry of Environment as “Converging technology project” (223-111-003).