Browsing by Author "Teshima, Katsuya"

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Adsorption-capacitive deionization hybrid system with activated carbon of modified potential of zero charge
(Elsevier, 2023-02-15) Sufiani, Omari; Elisadiki, Joyce; Tanaka, Hideki; Teshima, Katsuya; Sahini, Mtabazi; Machunda, Revocatus; Jande, Yusufu
In this study water solutions are desalinated with carbon electrodes of modified surface charges. The idea is to endow the electrodes with the ability to physically adsorb salt ions without applying potential so as to save energy. The modification enhanced to decrease the energy consumption of a newly invented adsorption-CDI hybrid system by 19%, since modified activated carbon cell consumed 0.620 (relative error 3.00%) kWh/m3 compared to pristine activated carbon cell which consumed 0.746 (relative error 1.20%) kWh/m3. Further analysis revealed high adsorption capacity of the modified activated carbon electrode cell which exhibited 9.0 (relative error 2.22%) compared to activated carbon cell with 5.3 (relative error 5.66%) mg g−1. These results show the potential of surface modification in adding value to low cost activated carbons for application in CDI.
Capacitive deionization for water desalination using Na3Fe2(PO4)3/activated carbon composite electrodes
(Elsevier, 2025-05-28) Sufiani, Omari; Alfredy, Tusekile; Tanaka, Hideki; Teshima, Katsuya; Machunda, Revocatus; Jande, Yusufu
Water desalination technologies are attracting growing global attention as critical solutions to address water scarcity torturing mankind worldwide. Capacitive deionization (CDI) is an emerging desalination technology that offers multiple advantages, including low voltage operation and diverse material options for electrode synthesis. In this work the Na3Fe2(PO4)3 (NFP) is composited with the activated carbon (AC) to synthesize AC/NFP composites and tested in water desalination. The characterization results from several techniques reveal the successful composite synthesis. When tested in CDI experiments for brackish water desalination much higher salt removal capacity of around 22.0 was attained by AC/NFP 1:2 compared with 18.65 mg/g of AC electrode. Also, the synthesized AC/NFP 1:2 retain satisfactorily performance efficiency when cycled for twenty runs. However, owing to low resistance at the electrode-electrolyte interface the AC is more energy efficient as it exhibits much low energy consumption of about 0.056 kWh/m3 compared with the AC/NFP 1:2 cell attained 0.15 kWh/m3. This study reveals a trade-off between performance and efficiency: while the AC/NFP 1:2 cell exhibits higher salt removal capacity, it consumes significantly more energy than the AC electrode, which demonstrate superior energy efficiency.
Capacitive deionization: Capacitor and battery materials, applications and future prospects
(Elsevier, 2024-09-15) Sufiani, Omari; Tanaka, Hideki; Teshima, Katsuya; Machunda, Revocatus; Jande, Yusufu
Water scarcity all over the world attracts alternative methods to purify saline water and supplement the available dwindling freshwater resources. Capacitive deionization (CDI) is hopeful to supply water to the population due to operation at low potential along with low energy expenditure when low salinity (5 mM NaCl) feed water solutions are desalinated. Electrode material is the main controlling factor in CDI system and a lot of efforts are devoted to develop excellent materials for better CDI performance. So far, carbon materials are widely used as the electrode for CDI, though limitations such as co-ion expulsion and faradaic reactions hinder their full utilization. Alternatively, battery materials are used since their performance is great due to mitigation of co-ions ejection as well as faradaic reactions. In 2019 our group reviewed factors affecting the performance of activated carbon electrode materials and revealed lack of selectivity, co-ion expulsion, low electrical conductivity and inappropriate pore size distribution to largely contribute to its low salt removal capacity [1]. Therefore, herein, we extend the discussion beyond AC to include other carbons such as aerogels, nanotubes, graphenes etc., and battery materials such as MXenes, sodium super ionic conductors, and BiOCl to mention the few. This article also discusses the extent CDI is applied in the laboratory scale as well as in the field for desalination of real water, wastewater remediation and removal of harmful contaminants to substantiate what it can offer beyond the laboratory experiments. The work is expected to save as a complete reference for the progress of CDI electrode materials and its applications in water purification.
Enhanced electrosorption capacity of activated carbon electrodes for deionized water production through capacitive deionization
(Elsevier Ltd., 2020) Sufiani, Omari; Tanaka, Hideki; Teshima, Katsuya; Machunda, Revocatus; Jande, Yusufu
The deionized water (DI) of high purity standards is used in several industrial processes to manufacture products and technologies for high end applications. Currently, DI water is produced by either reverse osmosis or continuous electrodeionization systems, however; both of them are facing several limitations. Therefore there is an urgent need for the alternative technologies for DI water production. This study investigated suitability of producing DI water by using capacitive deionization (CDI) with nitric acid treated activated carbon electrodes (NTAC). Activated carbon (AC) was etched in nitric acid solution to introduce various oxygen functional groups on its surface. The Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy were used to confirm the increased surface oxygen containing groups on AC after nitric acid treatment that enhanced its salt adsorption capacity. CDI experiments were conducted using water solution of 12.0 μS/cm as a result DI water with the conductivity of 1.6 μS/cm (DI water grade III, according to International Organization of Standards) was produced. Also, electrochemical tests revealed good capacitive behavior due to improved conductivity with NTAC having highest specific capacitance of 381.7 F/g compared to 106.6 F/g of AC electrode. This study provides an insight of the electrosorption performance of materials in desalination of solutions of low ionic strength
The enhanced performance of NaFe2PO4(SO4)2/C electrode materials in the desalination of brackish water by capacitive deionization
(Elsevier, 2024-12-15) Sufiani, Omari; Tanaka, Hideki; Teshima, Katsuya; Machunda, Revocatus; Jande, Yusufu
In this study partial substitution of phosphates in Na3Fe2(PO4)3/C (NFP/C) by sulphates to prepare Na2Fe2(PO4)2SO4 (NFP2S/C) and NaFe2PO4(SO4)2/C (NFPS/C) was carried out by dissolution-evaporation method. The idea is to adjust the properties of NFP/C owing to the differences in the inductive effect and sizes of sulphates and phosphates which results the obtained NFPS/C to record excellent electrochemical and desalination performance. Several characterization techniques used to analyse the synthesized materials confirm the successful doping and structure integrity. Electrochemical study reveals NFPS/C to exhibit the highest capacitance of 127.4 F/g when scanned at 10 mV/s. The results show that when the potential of 1.2 V is applied to desalinate 500 mg/L salt solution the salt removal of about 17.3 mg/g is achieved by NFPS/C while NFP/C attaining 9.8 mg/g. The NFPS/C was then tested in the desalination of real Ocean water and promising results obtained. The salt removal performance presented makes the developed materials promising for application in brackish water desalination by capacitive deionization.
Research progress of sodium super ionic conductor electrode materials for capacitive deionization
(Elsevier, 2024-07) Sufiani, Omari; Tanaka, Hideki; Teshima, Katsuya; Machunda, Revocatus; Jande, Yusufu
The world is suffering from water shortage and the hope relies on the desalination of salty water. Several technologies are available for desalination such as reverse osmosis and electrodialysis. However, the application of these technologies in desalination is limited by the higher energy consumption, high investment and maintenance costs. Capacitive deionization (CDI), an up-coming technology at an infant stage is able to supplement the dwindling freshwater resources and provide water to the population. The performance of CDI is directly affected by the electrode materials. Since its inception carbon has been the principal electrode materials for CDI technology. However, low salt removal capacity due to inaccessibility of nanopores and ejection of co-ions hinder the application of carbon materials. Battery materials have been developed as an alternative to accompany carbon materials. Specifically, sodium superionic conductor (NASICON) materials have been used in brackish water desalination by CDI due to having the diffusion channels forming a three dimensional open structure and availability at low cost. However, the NASICON materials have not yet applied in the desalination of water with high salinity such as sea water. This paper reviews the present status of NASICON materials as CDI electrode materials and fairly compares it with carbon materials. It further compares the cost of NASICON and carbon materials, highlights the possibility of NASICON to desalinate high ionic strength solutions such as seawater. Moreover, the paper, discuss the methods which can be used to enhance the salt removal capacity of NASICON materials and provide examples of NASICON materials in the field of energy storage that can be borrowed and used in CDI. From the analysis of this work, NASICON materials are great companion of the carbon materials, are cost effective and are promising for the desalination of sea water.