Capacitive deionization (CDI) which removes ionic species from solution by applying electric energy to carbon based electrodes is one of excellent convergence technologies combined with energy ...storage technology and environmental systems. In recent decades, the technology for synthesizing new carbon materials has advanced, the electrical double layer capacitance in porous structures has become better understood, and novel deionization systems have been developed. Nevertheless, achieving a higher deionization performance is required for CDI to compete with reverse osmosis for deionization. The recently introduced Hybrid CDI (HCDI), which utilizes sodium manganese oxide (Na4Mn9O18) and carbon material, successfully demonstrated its superior deionization performance over conventional CDI systems. Despite the great promise of the HCDI system, the limited availability of aqueous based intercalation materials and the lack of information regarding the characteristics of the HCDI system operations are obstacles to the advancement of HCDI. Thus, we report a new HCDI system with sodium iron pyrophosphate (Na2FeP2O7), which is a promising material for sodium ion batteries due to its high capacity, low cost and environmentally benign nature. The major results of the HCDI system with Na2FeP2O7 showed a superior maximum deionization rate performance (0.081mgg−1s−1) with a comparable deionization capacity (30.2mgg−1) compared to the previous HCDI system with Na4Mn9O18. Furthermore, the analysis of the CDI Ragone plot revealed the hybrid behavior characteristics of this HCDI system and that the high deionization capacity originated from the high capacity of Na2FeP2O7 at a low current density, whereas the fast deionization rate originated from the supercapacitor system at a high current density. Consequently, this study on a new HCDI system with Na2FeP2O7 contributes to expanding the understanding of the kinetic properties of the HCDI system with respect to its diverse operations.
The demand for fresh water has been increasing, caused by the growing population and industrialization throughout the world. In this study, we report a capacitive-based desalination system using ...Prussian blue materials in a rocking chair desalination battery, which is composed of sodium nickel hexacyanoferrate (NaNiHCF) and sodium iron HCF (NaFeHCF) electrodes. In this system, ions are removed not only by charging steps but also by discharging steps, and it is possible to treat actual seawater with this system because the Prussian blue material has a high charge capacity with a reversible reaction of alkaline cations. Here, we demonstrate a rocking chair desalination battery to desalt seawater, and the results show that this system has a high desalination capacity (59.9 mg/g) with efficient energy consumption (0.34 Wh/L for 40% Na ion removal efficiency).
The exploration of transition state (TS) geometries is crucial for elucidating chemical reaction mechanisms and modeling their kinetics. Recently, machine learning (ML) models have shown remarkable ...performance for prediction of TS geometries. However, they require 3D conformations of reactants and products often with their appropriate orientations as input, which demands substantial efforts and computational cost. Here, we propose a generative approach based on the stochastic diffusion method, namely TSDiff, for prediction of TS geometries just from 2D molecular graphs. TSDiff outperforms the existing ML models with 3D geometries in terms of both accuracy and efficiency. Moreover, it enables to sample various TS conformations, because it learns the distribution of TS geometries for diverse reactions in training. Thus, TSDiff finds more favorable reaction pathways with lower barrier heights than those in the reference database. These results demonstrate that TSDiff shows promising potential for an efficient and reliable TS exploration.
In this paper, we propose the concept and design methodology for a resonant reactive shield for the reduction of magnetic field leakage from a wireless power transfer (WPT) systems. By using LC ...resonance, the reactive shield can generate a cancelling magnetic field to reduce the incident magnetic field from WPT coils and effectively reduce the total magnetic field without consuming additional power. The shielding effectiveness of the resonant reactive shield and its effect on WPT efficiency are analyzed with simulation and measurements. For practical application to wirelessly charged electric vehicles, an automatic tuning system for the resonant reactive shield is also proposed and implemented. The effectiveness of a resonant reactive shielding is verified by experiments in a wirelessly charged electric bus.
Recently, electrochemically self-doped TiO2 nanotubes (R-TiO2 NTs) have emerged as promising anodes in the electrochemical oxidation process for wastewater treatment, owing to their high degradation ...capability of organic compounds. However, the degradation mechanism of organic compounds on R-TiO2 NTs has not been well demonstrated, and therefore, industrial practices have been limited. This study aimed to elucidate the oxidation mechanism of organic compounds on R-TiO2 NTs by investigating phenol degradation. The performance of phenol degradation on R-TiO2 NTs was comparable to that on the boron-doped diamond (BDD) electrode that is well-known as an excellent anode for phenol degradation. In particular, phenol degradation on R-TiO2 NTs was completely achieved at the electrode potential of 5.0 V while negligible degradation was found at the electrode potential of 2.0 V. In addition, no peaks associated with phenol oxidation in cyclic voltammograms were noticed on R-TiO2 NTs at the potential range between 1.0–2.5 V. Considering direct oxidation is a fundamental factor for phenol degradation at low electrode potential, it contributes less to phenol degradation on R-TiO2 NTs. Therefore, phenol degradation on R-TiO2 NTs is mostly owing to indirect oxidation mediated by hydroxyl radicals.
•Iso-HVO has many merits of physico-chemical properties to use instead of biodiesel.•Various blending ratios of iso-HVO and BD were tested for engine performances.•Iso-HVO blended fuels have better ...power and fuel efficiency than BD blended fuels.•Iso-HVO blended fuels showed low THC and CO, but similar NOx and PM to BD.•Biofuels showed decrease of particle concentrations at all size range than petro-diesel.
Biodiesel, of which typical material is known as FAME (Fatty Acid Methyl Ester), has some demerits such as high density and low caloric value despite better reduction on emission and lubricity when compared to petro-diesel (petroleum-derived diesel). Iso-HVO (isomerized-hydrotreated biodiesel), on the other hand, has strong competitive advantages that overcome such weak points of conventional biodiesel. The study of engine performance was carried out to compare iso-HVO with BD (Biodiesel). The test samples were prepared 16 kinds of fuels, which are petro-diesel and 2%, 10%, 20%, 30%, 50% of BD, HVO, and iso-HVO blended diesel, respectively. The engine performances and emission were tested on engine dynamometer and chassis dynamometer with 1.5l diesel engine and passenger car, for evaluating maximum power, fuel consumption, and emission, especially PM (Particulate Matter) and NOx. Iso-HVO has much better engine performance than BD and slightly better than HVO, but slightly worse than petro-diesel. On the emission, iso-HVO and HVO blended diesel emit less THC and CO than BD, even though iso-HVO blended diesel emits similar level of NOx and PM to BD blended. All three kinds of 50% blended biofuels showed that the decrease of particle concentrations at all size range than petro-diesel.
Capacitive deionization (CDI) is considered an alternative desalination technology due to its easy operation, high energy efficiency, and environmentally friendly process. However, a separate ...regeneration step is required in typical CDI technologies that releases the absorbed ions on the electrodes which results in an inefficient and cost-intensive process. This study proposed a novel CDI system referred to as rocking-chair capacitive deionization (RCDI) that has a continuous brackish water desalination process which consists of a pair of Nafion-coated activated carbon electrodes and an anion-exchange membrane. The coated Nafion contributed to the cation selectivity of the carbon electrode, and it enabled a continuous desalination process during constant-current operation through a rocking-chair ion movement. From the desalination tests that included the analysis of the CDI Ragone plot, the RCDI has a high salt adsorption capacity (maximum of 44.5 mg g–1) with continuous operation. Furthermore, the RCDI desalted brackish water under rapid operation conditions (up to ±30.0 A m–2) which is a constant-current operation condition that is several times higher than that of previously reported desalination technologies using battery materials. Consequently, this study proposes a new strategy for a continuous desalination CDI system that provides a high-performance and energy-efficient desalination process for brackish water.
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•Redox flow desalination (RFD) valorize tetramethylammonium hydroxide (TMAH)•TMAH is a waste and also value-added organic compound from semiconductor wastewater.•RFD exhibited high ...performance of TMAH removal with removal rate of ∼4.3 mM/g/h.•TMAH recovery was approximately 40% in RFD.•Techno-economic analysis addresses RFD is economical TMAH valorization process.
As part of humankind’s path towards more sustainable water technologies, redox flow desalination (RFD) has emerged as a promising technology due to its high energy efficiency and easy operation. So far, RFD research has focused on removing and recovering inorganic salts such as lithium-ions, heavy metal ions, or phosphate and nitrate ions. Thus, the potential of RFD in water desalination and resource recovery processes has not been fully demonstrated. Therefore, this study aimed to assess RFD for the valorization of tetramethylammonium hydroxide (TMAH) as value-added organic compounds from wastewater beyond inorganic elements, which is widely being used as an etching solvent, photoresist developer, and surfactant in semiconductor and display industries. By applying a low cell voltage (<1.2 V), a reversible redox reaction allowed a continuous removal of TMAH from the wastewater stream and a simultaneous recovery for reuse as a form of tetramethylammonium cation. The TMAH removal rate was approximately 4.3 mM/g/h with a 40% recovery ratio. With various operational conditions (i.e., TMAH concentration, cell voltage, and flow rate), our system exhibited a high potential for the valorization of TMAH with 60% reduction in capital cost compared to conventional desalination processes.
Great interest in anode materials has dramatically emerged with increasing demand for electrochemically generated oxidants in industrial electrochemistry. For the last five decades, these needs have ...been mostly achieved by the introduction of two well-known anode materials, the dimensional stable anode (DSA®) and boron-doped diamond (BDD) electrodes. Nevertheless, the high cost and complicated process in fabricating these electrodes remains as a big obstacle for further development. Here, we report a novel anode material for the production of oxidants, the dark blue colored TiO2 nanotube array (NTA) (denoted as Blue TiO2 NTA) which has never been successfully achieved with titania-based materials. This titania-based electrocatalyst with irreversible electrochromism and high conductivity was successfully fabricated with simple cathodic polarization of anatase TiO2 NTA and exhibits the excellent electrocatalytic activity in generating chlorine (Cl2) and hydroxyl radical (•OH) which is comparable to the commercial DSA® and BDD electrodes, respectively. Thus, this Blue TiO2 NTA is suggested as a potential cost effective anodic material in industrial electrochemistry. In addition, even in other metal oxides other than titania, the cathodic polarization (accompanied with irreversible electrochromism) method may be applied to explore a new route for low-cost and novel anodic materials.
Odor-causing substances are generated by various emission sources in urban areas. Recently, urbanization has greatly increased the density of odor emission facilities, implying the identification of ...odorants emission source is challenging. Identifying emission source is multifactorial, and a machine learning approach is considered useful for these complicated matters. The objectives of this study were to propose a method using machine learning-based classification models to identify odor sources in urban areas. We collected 34,539 data points regarding quantitative data of 22 compounds emitting from 11 types of facilities in urban areas (i.e., automobile industry, bio factory, wastewater treatment plant, landfill, construction site, farm industrial complex area, restaurant, gas station, roadside, park) and odor intensity of these 11 facilities. Decision tree (DT) and random forest (RF) algorithms were used as classification models for identifying odor sources with 23 variables (22 compounds + odor intensity). The DT model identified 7 out of 11 emission sources with 87.15% accuracy. The RF model identified all 11 emission sources with 99.23% accuracy. When including 6 important variables only (i.e., hydrogen sulfide, ammonia, trimethylamine, methyl mercaptan, acetaldehyde, odor intensity) in the RF model, accuracy (99.15%) was almost same with that (99.23%) obtained from all 23 variables included as variables in the model. Our findings imply that a machine learning approach can help to identify odor emission sources with high accuracy and we can save time and cost in the identification of odor emission sources by including the 6 important variables only.
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•Identified odor emission sources in urban areas using machine learning algorithms.•Collected 34,539 data sets of 22 substances from 11 types of emission sources.•Random forest model identified all 11 emission sources with 99.23% accuracy.•Simplified RF model with 6 important variables presented the almost same accuracy.
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