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•An efficient method is presented for the recovery of In3+ from acidic solution.•The activated carbon electrode shows good capability for electrosorption of In3+.•The recovery of In3+ ...is mainly based on electrical double-layer charging.•In3+ ions are preferentially electrosorbed in a competitive environment.
High-efficiency recycling technology for endangered elements effectively mitigates the risk of resource shortages and promises the sustainability of supply chains, which is significant to the industry. In this study, an activated carbon (AC)-based capacitive deionization (CDI) for the selective electrosorption and recovery of indium ions (In3+) from acidic aqueous solution is proposed. The effects of applied voltage, pH, and initial concentration of indium were investigated to optimize the operation parameters for In3+ electrosorption. The results of cyclic voltammetry and the galvanostatic charge/discharge measurements indicate that the AC electrode shows good capability for the electrosorption of In3+ based on electrical double-layer capacitance. As demonstrated, In3+ can be successfully removed by CDI without deposition when the pH < 4, as confirmed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The deionization capacity of In3+ is 7.95 mg/g with an energy consumption of 0.84 kWh/mol in single-pass mode CDI with an initial concentration of 50 mg/L (pH = 3) at 1.2 V. However, the removal of In3+ is affected by the solution pH since hydrogen ions (H+) compete for electrosorption. Note that In3+ ions with high valence are preferentially electrosorbed on the electrode surface over H+ ions, exhibiting a selectivity coefficient of 2.12. Herein, in the charging step, a large number of H+ ions in solution are rapidly electrosorbed onto the electrode, while these H+ ions are gradually replaced by a small number of In3+ ions in solution. Therefore, this electrosorption process shows great potential for effectively recovering indium ions from acidic aqueous solutions.
•Multi-walled carbon nanotube-activated carbon composite electrode was prepared for capacitive deionization.•Composite electrode had strong hydrophilicity, high mesoporosity, good capacitive ...properties, and great pore accessibility.•The presence of mesopores could facilitate ion transport and provide more effective surface area for electrosorption of ions.•Composite electrode exhibited better deionization performance than that of activated carbon.
To improve the electrode performance in capacitive deionization, a multi-walled carbon nanotubes (MWCNTs) and poly(vinyl alcohol) (PVA) composite electrode was prepared in this study. The electrosorption performance of this composite electrode was evaluated in terms of capacitive characteristics, number cycles, desalting capability, and compared to that of commercial activated carbon. Results showed that the MWCNT/PVA composite electrode had strong hydrophilicity, high mesoporosity, and excellent capacitor characteristics. The cyclic voltammetry curves of the MWCNT/PVA composite represented less scan-rate and concentration dependency, reflecting better rate capacity for ion electrosorption. From the desalination experiments of 0.001M NaCl at 1.2V, the MWCNT/PVA composite electrode exhibited a larger ion removal capacity (13.07mgg−1), higher electrosorption rate (0.073min−1), and less energy consumption (0.038kWhm−3) as compared to that of the activated carbon electrode. The good electrosorption performance could be attributed to the mesoporous structure that is less affected by double-layer overlapping and then facilitates ion transport. Additionally, the MWCNT/PVA composite electrode revealed a higher effective surface area of 26.04% of the Brunauer–Emmett–Teller surface area, which was −10 fold than that of activated carbon electrode. Overall, because of its excellent electrode properties and morphology advantage, the composite electrode is a desirable material for the removal of ions in capacitive deionization.
plants are commonly used traditional medicinal herbs, and most of their extracts containing withanolides show anticancer effects. Physapruin A (PHA), a withanolide isolated from
, shows ...antiproliferative effects on breast cancer cells involving oxidative stress, apoptosis, and autophagy. However, the other oxidative stress-associated response, such as endoplasmic reticulum (ER) stress, and its participation in regulating apoptosis in PHA-treated breast cancer cells remain unclear. This study aims to explore the function of oxidative stress and ER stress in modulating the proliferation and apoptosis of breast cancer cells treated with PHA. PHA induced a more significant ER expansion and aggresome formation of breast cancer cells (MCF7 and MDA-MB-231). The mRNA and protein levels of ER stress-responsive genes (
and
) were upregulated by PHA in breast cancer cells. The co-treatment of PHA with the ER stress-inducer (thapsigargin, TG), i.e., TG/PHA, demonstrated synergistic antiproliferation, reactive oxygen species generation, subG1 accumulation, and apoptosis (annexin V and caspases 3/8 activation) as examined by ATP assay, flow cytometry, and western blotting. These ER stress responses, their associated antiproliferation, and apoptosis changes were partly alleviated by the
-acetylcysteine, an oxidative stress inhibitor. Taken together, PHA exhibits ER stress-inducing function to promote antiproliferation and apoptosis of breast cancer cells involving oxidative stress.
In this study, we employed carbon nanotubes (CNTs) to improve the performance of flow-electrode capacitive deionization (FCDI) for wastewater desalination in isolated closed-cycle (ICC) mode. The ...effects of CNTs loading and initial salt concentration on FCDI desalination were evaluated with energetic performance analysis. FCDI was carried out for the desalination with real wastewater for technology demonstration. The addition of CNTs significantly improved the average salt removal rate (ASRR), associated with a decrease in the flow-electrode flowability. FCDI with 0.25 wt% CNTs had an ASRR of 1.59 μmol/cm2–min, which was 1.7-fold higher than that without CNTs. This was attributed to the bridging effect of CNTs for more rapid charge transfer. Increasing the initial salt concentration from 0.05 to 0.30 M led to a higher ASRR, resulting from a reduction in the electrical resistance in the cell. After further increasing the salt concentration to 0.50 M, the charge efficiency was relatively decreased due to co-ion leakage. Notably, FCDI for the desalination of real saline wastewater achieved a high decrease in conductivity (94%), a high charge efficiency (>99%), and low energy consumption (0.034 kWh/mol). Our results demonstrated that adding CNTs is a feasible approach to achieve high-performance FCDI for sustainable wastewater desalination.
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•CNTs were employed to enhance the desalination performance of the FCDI process.•CNTs improved the salt removal rate and energy performance of ICC-mode FCDI.•FCDI can desalinate saline water with a wider concentration range.•FCDI exhibits great potential for real wastewater desalination.
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Capacitive deionization (CDI) technologies have the potential to become cost-competitive alternatives to reverse osmosis for the treatment of brackish waters. In this study, we report ...our findings on the effect of co-ion sorption and faradaic side reactions on our ion exchange resin functionalized desalination electrodes which passively capture salt and reject it upon charging. This system, which we previously reported on and refer to as electrically regenerated ion exchange (ERI), avoids the use of expensive ion exchange membranes in an effort to save costs. Surprisingly, we find that, compared to a reference CDI system, ERI electrodes capture salt most effectively at low applied voltages (0.5 mg/cm3 at 0.8 V). Both CDI and ERI systems also seem to suffer from co-ion sorption effects which negatively impact salt adsorption. However, Faradaic side reactions at higher voltages (1 V and 1.2 V) which we track via pH measurements, serve as a detriment to CDI but seem to facilitate the functionality of ERI.
Three-dimensional (3-D) ZIF-8 derived carbon polyhedrons with high nitrogen (N) content, (denoted as NC-800) are synthesized for their application as high-performance electrodes in electrosorption of ...salt ions. The results showed a high specific capacitance of 160.8 F·g(-1) in 1 M NaCl at a scan rate of 5 mV·s(-1). Notably, integration of 3-D mesopores and micropores in NC-800 achieves an excellent capacitive deionization (CDI) performance. The electrosorption of salt ions at the electrical double layer is enhanced by N-doping at the edges of a hexagonal lattice of NC-800. As evidenced, when the initial NaCl solution concentration is 1 mM, the resultant NC-800 exhibits a remarkable CDI potential with a promising salt electrosorption capacity of 8.52 mg·g(-1).
Based upon an international workshop, this perspective evaluates how nano-scale pore structures and unique properties that emerge at nano- and sub-nano-size domains could improve the energy ...efficiency and selectivity of electroseparation or electrocatalytic processes for treating potable or waste waters. An Eisenhower matrix prioritizes the urgency or impact of addressing potential barriers or opportunities. There has been little optimization of electrochemical reactors to increase mass transport rates of pollutants to, from, and within electrode surfaces, which become important as nano-porous structures are engineered into electrodes. A "trap-and-zap" strategy is discussed wherein nanostructures (pores, sieves, and crystal facets) are employed to allow localized concentration of target pollutants relative to background solutes (
i.e.
, localized pollutant trapping). The trapping is followed by localized production of tailored reactive oxygen species to selectively degrade the target pollutant (
i.e.
, localized zapping). Frequently overlooked in much of the electrode-material development literature, nano-scale structures touted to be highly "reactive" towards target pollutants may also be the most susceptible to material degradation (
i.e.
, aging) or fouling by mineral scales that form due to localized pH changes. A need exists to study localized pH and electric-field related aging or fouling mechanisms and strategies to limit or reverse adverse outcomes from aging or fouling. This perspective provides examples of the trends and identifies promising directions to advance nano-materials and engineering principles to exploit the growing need for near chemical-free, advanced oxidation/reduction or separation processes enabled through electrochemistry.
An international workshop identified how pore structures and unique properties that emerge at nano- to sub-nano- size domains can improve the energy efficiency and selectivity of electroseparation or electrocatalytic processes for treating water.
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•An energy recovery system was created based on a four-switch buck-boost converter.•A higher energy recovery was achieved with a higher influent NaCl concentration.•A shorter ...electrode distance is a favored geometry for energy recovery.•A superior energy recovery ratio of 49.6% was obtained.
The importance of energy recovered from desalination techniques has been of considerable interest because of increasing water scarcity and energy crises. Capacitive deionization (CDI), a promising desalination technology using pairs of carbon electrodes under an electric field, has an attractive advantage in that energy stored during the charging step for salt removal can be further recovered during the discharging step. In this research, an energy recovery system based on a four-switch buck-boost converter with variable frequency was successfully constructed to transfer electric energy from a CDI module to a supercapacitor. The effects of the influent NaCl concentration and the distance between two oppositely placed electrodes were investigated on both the desalination behavior and energy recovery performance. The experimental procedure involved a charging step for ion removal, stop-flow operation for energy recovery, and discharging step for electrode regeneration. For the desalination of a 10 mM NaCl solution, a deionization capacity of 10.1 mg g−1 and a total energy input of 0.09 kWh m−3 were obtained. Overall, as demonstrated, a higher energy recovery ratio was achieved with a higher influent NaCl concentration and a shorter distance between the two electrodes. Significantly, up to 49.6% of the energy stored in the CDI module while reducing the salinity of a 50 mM NaCl solution could be directly recovered, indicating that the energy recovery system based on a four-switch buck-boost converter shows superior performance. The utilization of CDI integrated with a supercapacitor in this work holds great potential in both low-energy-requirement desalination and high-efficiency energy storage.
The main objective of the study is to explore the removal characteristics of Cu2+ and Zn2+ ions in activated carbon-based capacitive deionization (CDI). In this work, CDI experiments were performed ...to remove divalent ions (e.g., Cu2+, Zn2+, and Ca2+) from single- and multicomponent aqueous solutions. As evidenced, divalent heavy metals could be successfully removed by charging the CDI cell at 1.2 V. Notably, the preferential removal of Cu2+ ions over Zn2+ and Ca2+ ions was observed in the charging step. The removal capacities for Cu2+, Zn2+, and Ca2+ ions in a competitive environment were 29.6, 19.6, and 13.8 μmol/g, respectively. In contrast, the regeneration efficiencies for the removal of Cu2+ and Zn2+ were much lower than that of Ca2+, suggesting the occurrence of irreversible Faradaic reactions on the cathode. X-ray photoelectron spectroscopy analysis demonstrated that Cu2+ ions were reduced to Cu(I) and Zn2+ ions were transformed to ZnO/Zn(OH)2 on the cathode. Therefore, there were two major mechanisms for the removal of divalent heavy metal ions: capacitive electrosorption and cathodic electrodeposition. Specifically, the reduction potential played a crucial role in determining the removal characteristics. When regarding divalent cations with similar hydrated sizes, the divalent cation with a higher reduction potential tended to be separated by cathodic electrodeposition rather than double-layer charging, indicating the high removal selectivity of activated carbon-based CDI. This paper constitutes a significant contribution to promoting the application of CDI for contaminant sequestration.
•CDI was successfully carried out to remove divalent metal ions.•Electrosorption and electrodeposition were the two main removal mechanisms.•The reduction potential played a key role in activated carbon-based CDI.•Electrode degradation was observed during the removal of Cu2+ and Zn2+ ions.•Selective removal was demonstrated in a competitive environment.
•Highly porous activated carbons were prepared from waste L. leucocephala wood.•Overgasification caused the pores of activated carbon mainly in mesopore range.•The carbons had typical capacitive ...behaviors for electrical double layer formation.•A mixture of mesopores/micropores caused greater electrosorption performance.•Carbons from L. leucocephala are suitable electrodes for capacitive deionization.
Highly porous activated carbons were resource-recovered from Leucaena leucocephala (Lam.) de Wit. wood through combined chemical and physical activation (i.e., KOH etching followed by CO2 activation). This invasive species, which has severely damaged the ecological economics of Taiwan, was used as the precursor for producing high-quality carbonaceous electrodes for capacitive deionization (CDI). Carbonization and activation conditions strongly influenced the structure of chars and activated carbons. The total surface area and pore volume of activated carbons increased with increasing KOH/char ratio and activation time. Overgasification induced a substantial amount of mesopores in the activated carbons. In addition, the electrochemical properties and CDI electrosorptive performance of the activated carbons were evaluated; cyclic voltammetry and galvanostatic charge/discharge measurements revealed a typical capacitive behavior and electrical double layer formation, confirming ion electrosorption in the porous structure. The activated-carbon electrode, which possessed high surface area and both mesopores and micropores, exhibited improved capacitor characteristics and high electrosorptive performance. Highly porous activated carbons derived from waste L. leucocephala were demonstrated to be suitable CDI electrode materials.
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