Mesoporous Carbon for Capacitive Deionization of Saline Water

Tsouris, Costas; Mayes, Richard T.; Kiggans, James O.; Sharma, Ketki; Yiacoumi, Sotira; DePaoli, David W.; Dai, Sheng

doi:10.1021/es201551e

Cited by 371 publications

(160 citation statements)

References 40 publications

(81 reference statements)

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“…The best performance was observed for sample MRF-Act/CB (7.3 mg/g), likely due the combined effects of an adequate porosity obtained upon activation and the presence of carbon black additive finely dispersed in the electrode. Table 4 shows the desalting capacities of herein synthesized aerogels compared to those reported in the literature [31,40,[52][53][54]. Data reveals that the N-doped carbon aerogel/carbon black composites are competitive electrode materials for the removal of ionic species from saline water.…”

Section: G/l)mentioning

confidence: 88%

On the use of carbon black loaded nitrogen-doped carbon aerogel for the electrosorption of sodium chloride from saline water

Rasines¹,

Lavela

Macías³

et al. 2015

Electrochimica Acta

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Highly micro-mesoporous carbon electrodes have been synthesized by the polycondensation of resorcinol-formaldehyde-melamine mixtures in the presence of a carbon conductive additive.The materials showed high surface functionalization (N-and O-groups) provided by the precursors. Despite the low amount used, the conductive additive had a marked effect on the porosity of the aerogels; for a given series, the carbon black loaded materials showed similar micropore volumes and a more developed mesoporosity than the pristine aerogels. Furthermore, the activation treatment under CO 2 atmosphere led to an increase in the surface area along with a widening of the mesoporosity. The synthesized aerogels were explored as electrodes for the electro-assisted removal of sodium chloride from saline water. A desalting capacity of 7.3 mg/g was obtained for monolith electrodes of sample MRF-Act/CB, along with an excellent chemical stability upon charge and discharge at high polarization voltages. Such good electrochemical performance is due to the combination of an adequate pore network and surface functionalization with an enhanced electrical conductivity achieved upon the incorporation of the carbon black additive during the polycondensation of the aerogel precursors.

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Section: G/l)mentioning

confidence: 88%

On the use of carbon black loaded nitrogen-doped carbon aerogel for the electrosorption of sodium chloride from saline water

Rasines¹,

Lavela

Macías³

et al. 2015

Electrochimica Acta

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“…Therefore, the electrosorption capacity is determined by the volume (porosity) of the micropores and the energy barrier. The microporosity-based electrosorption theory is critical in analyzing energy consumption during CDI.z E-mail: kkarthikeyan@wisc.edu Although significant progress has been made recently in the development of diverse electrode materials, 13,[19][20][21][22][23][24][25][26][27] theoretical models, [16][17][18] water treatment and desalination devices, 28-30 only very few studies address the issue of energy consumption during CDI. The role of electrode materials in electrosorption and energy consumption is not completely understood and, more importantly, the impact of operational conditions on energy consumption has not been rigorously evaluated when nanoscale porous electrode is applied.…”

mentioning

confidence: 99%

Energy Consumption and Recovery in Capacitive Deionization Using Nanoporous Activated Carbon Electrodes

Han

Karthikeyan

Gregory

2015

J. Electrochem. Soc.

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Capacitive deionization (CDI) is an emerging desalination technology which utilizes porous electrodes to remove ions in water by electrosorption. Similar to electric capacitors, energy is stored and released during charging and discharging cycles, respectively. In this study, a nanoporous activated carbon coupled flow-through CDI device was used to evaluate energy consumption and recovery under various operational conditions by charging and discharging the cell at a constant current, respectively. Results indicated that the charging/discharging current, salt concentration and water flow rate were major factors impacting electrosorption and energy consumption, by changing the structure of the electrical double layer (EDL) and how ion transport occurs between the interface and bulk solution. A porosity-based EDL theory was applied to explain the experimental observations. Between 30 and 45% of the energy consumed during charging could be recovered depending on operational conditions, although thermodynamically more than 98% of the total energy should be recoverable. Results indicated that overpotential and faradaic reactions induced irreversible energy are the major reasons for gaps in observed energy losses. Energy consumption for reducing the salinity of brackish water from 32.7 to 5.5 mM by our device could be as low as 0.85 kWh/m 3 under most optimized conditions (dependent on materials used and cell configuration). The energy consumption can be dramatically reduced by employing more electron-conductive and Faradaic-resistant electrode materials. Increasing demand for freshwater is driving the need for energyefficient and cost-effective technologies to generate potable water from unconventional sources such as brackish water.1 Due to its simplicity and reliability, capacitive deionization (CDI) has attracted a growing interest for water desalination.1-7 Capacitive deionization utilizes highly porous electrodes to remove charged ions in water by electrosorption (Figure 1). During charging, an electric voltage is applied and ions are driven to oppositely charged electrodes by electrostatic force and entrapped at the electrode-water interface by the formation of an electric double layer (EDL). After removing the ions, the electric voltage is removed or reversed to discharge and regenerate the electrodes. Ions return to solution and the concentrated brine is discarded. Desalination is realized by means of consecutive charging/discharging cycles to separate influent water into freshwater and brine (concentrate) streams.Energy consumption is a major factor driving the synthesis of new CDI electrode materials. Energy-efficient CDI devices are required for up-scaling the process and for broader adoption of this technology for potable or agricultural water treatment. An important feature of CDI is that part of the energy consumed during charging can be recovered during discharging, a process similar to charge/discharge in electric capacitors.6,8 CDI could become more cost competitive compared with well-established desa...

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“…It is generally accepted that porous electrodes for electrochemical applications should have a hierarchical pore size distribution including macropores (d p ≥ 50 nm) as ion reservoirs, mesopores (2 nm ≤ d p ≤ 50 nm) to facilitate ion transport, and micropores (d p ≤ 2 nm) for increased ion storage (Tsouris et al [9], among others).…”

Section: Introductionmentioning

confidence: 99%

One- and Two-Equation Models to Simulate Ion Transport in Charged Porous Electrodes

Gabitto

Tsouris

2018

Colloids and Interfaces

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Energy storage in porous capacitor materials, capacitive deionization (CDI) for water desalination, capacitive energy generation, geophysical applications, and removal of heavy ions from wastewater streams are some examples of processes where understanding of ionic transport processes in charged porous media is very important. In this work, one-and two-equation models are derived to simulate ionic transport processes in heterogeneous porous media comprising two different pore sizes. It is based on a theory for capacitive charging by ideally polarizable porous electrodes without Faradaic reactions or specific adsorption of ions. A two-step volume averaging technique is used to derive the averaged transport equations for multi-ionic systems without any further assumptions, such as thin electrical double layers or Donnan equilibrium. A comparison between both models is presented. The effective transport parameters for isotropic porous media are calculated by solving the corresponding closure problems. An approximate analytical procedure is proposed to solve the closure problems. Numerical and theoretical calculations show that the approximate analytical procedure yields adequate solutions. A theoretical analysis shows that the value of interphase pseudo-transport coefficients determines which model to use.

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Mesoporous Carbon for Capacitive Deionization of Saline Water

Cited by 371 publications

References 40 publications

On the use of carbon black loaded nitrogen-doped carbon aerogel for the electrosorption of sodium chloride from saline water

On the use of carbon black loaded nitrogen-doped carbon aerogel for the electrosorption of sodium chloride from saline water

Energy Consumption and Recovery in Capacitive Deionization Using Nanoporous Activated Carbon Electrodes

One- and Two-Equation Models to Simulate Ion Transport in Charged Porous Electrodes

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