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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 (8173 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).