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Open AccessArticle

Sustainable Desalination by 3:1 Reduced Graphene Oxide/Titanium Dioxide Nanotubes (rGO/TiONTs) Composite via Capacitive Deionization at Different Sodium Chloride Concentrations

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Chemical Engineering Department, Malayan Colleges Laguna, Pulo-Diezmo Rd. Cabuyao City, Laguna 4025, Philippines
2
Chemical Engineering Department, De La Salle University, 2401 Taft Avenue, Manila 1004, Philippines
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Chemical Engineering Department, University of the Philippines Los Baños, College, Laguna 4031, Philippines
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Institute of Environmental Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
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Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Sec. 2 Kuang-Fu Road, Hsinchu 30013, Taiwan
*
Authors to whom correspondence should be addressed.
Nanomaterials 2019, 9(9), 1319; https://doi.org/10.3390/nano9091319
Received: 1 August 2019 / Revised: 21 August 2019 / Accepted: 9 September 2019 / Published: 15 September 2019
The capability of novel 3:1 reduced graphene oxide/titanium dioxide nanotubes (rGO/TiONTs) composite to desalinate using capacitive deionization (CDI) employing highly concentrated NaCl solutions was tested in this study. Parameters such as material wettability, electrosorption capacity, charge efficiency, energy consumption, and charge-discharge retention were tested at different NaCl initial concentrations—100 ppm, 2000 ppm, 15,000 ppm, and 30,000 ppm. The rGO/TiONTs composite showed good material wettability before and after CDI runs with its contact angles equal to 52.11° and 56.07°, respectively. Its two-hour electrosorption capacity during CDI at 30,000 ppm NaCl influent increased 1.34-fold compared to 100 ppm initial NaCl influent with energy consumption constant at 1.11 kWh per kg with NaCl removed. However, the percentage discharge (concentration-independent) at zero-voltage ranged from 4.9–7.27% only after 30 min of desorption. Repeated charge/discharge at different amperes showed that the slowest charging rate of 0.1 A·g−1 had the highest charging time retention at 60% after 100 cycles. Increased concentration likewise increases charging time retention. With this consistent performance of a CDI system utilizing rGO/TiONTs composite, even at 30,000 ppm and 100 cycles, it can be a sustainable alternative desalination technology, especially if a low charging current with reverse voltage discharge is set for a longer operation. View Full-Text
Keywords: reduced graphene oxide; titanium dioxide nanotubes; sodium chloride; sustainable desalination; capacitive deionization reduced graphene oxide; titanium dioxide nanotubes; sodium chloride; sustainable desalination; capacitive deionization
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Lazarte, J.P.L.; Bautista-Patacsil, L.; Eusebio, R.C.P.; Orbecido, A.H.; Doong, R.-A. Sustainable Desalination by 3:1 Reduced Graphene Oxide/Titanium Dioxide Nanotubes (rGO/TiONTs) Composite via Capacitive Deionization at Different Sodium Chloride Concentrations. Nanomaterials 2019, 9, 1319.

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