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Electrochemical storage of neutralised protons in porous carbon materials such as activated carbons and multi-layer graphene is becoming possible using novel technologies such as the proton battery and proton flow reactor. This set-up is a promising option for electrical energy storage at various scales, and possibly for exporting a zero-emission hydrogen-based fuel. This paper focusses on understanding and identifying the contributions to hydrogen storage in activated carbon from phenolic resin (aC PR) from processes such as electric double layer capacitance, electrosorption, cationic concentration by intercalation in ultramicropores, and reversible faradaic (redox) reactions between hydronium, and negatively-charged carbon surfaces inside pores with and without intermediary oxygen groups. A combination of XPS, Raman, and infrared spectroscopy is employed to identify the forms of C ⋯ H reactions involved, together with temperature programmed desorption, cyclic voltammetry and galvanostatic charging and discharging. Experimental evidence for the formation of C⋯H bonding in aC PR is presented, which promises to be sufficient for use of this and similar carbon materials as a solid-state hydrogen storage material with competitive energy density. [Display omitted] • Principal mechanisms for electrochemical hydrogen storage in carbon-based materials are discussed. • C...H bonding is characterised through XPS, Raman, and infrared techniques. • Hydrogen stored in an activated carbon is retained and recovered after drying the powder. [ABSTRACT FROM AUTHOR]

• The continuous adsorptive removal of phenol using low-cost activated carbon was studied. • Effects of electromagnetic field (EMF), and electric potential (EP) in the phenol removal were studied. • EMF enhanced the removal performance of activated carbon electrodes on the aluminum substrate. In this study, we introduce an electrode configuration setup to study the effect of an electromagnetic field (EMF) and electric potential (EP) on phenol removal in a continuous adsorption process. Feed water contaminated with dissolved phenol was exposed to EMF and passed through charged activated carbon electrodes prepared from Phoenix dactylifera (palm tree) biowaste. This study investigated the effects of magnetic field exposure, electric potential, feed salinity, and electrode substrate type. The results revealed that the highest adsorption uptake capacity of 47.2 mg/g was achieved using an aluminum substrate (AS) with EMF at zero salinity. The phenol adsorption kinetics followed a pseudo-second-order adsorption rate and diffusion model, indicating that intraparticle diffusion was the primary rate-limiting mechanism. The increased phenol adsorption uptake capacity brought on by the EMF may result from the improved mass transfer and mobility of the adsorbate and, consequently, the increased effectiveness of the internal diffusion of the pollutants. Finally, a regeneration efficiency of 99 % was achieved using NaOH at a salinity of 5,000 ppm. [ABSTRACT FROM AUTHOR]

This study used heat-activated carbon (350 °C in the air) for the adsorption and removal of furfural from wastewater. The characteristics of air oxidation activated carbon (ACAOx) were tested. The results indicated that oxygen-containing functional groups were generated, with 1306 m2/g BET surface area of ACAOx. Salt concentration, temperature, and initial pH slightly affected the adsorption of furfural. Furfural removal efficiency was dependent on the dosage of ACAOx. The intra-particle and boundary-layer diffusions were likely contributed to the rate-limiting mechanisms of furfural adsorption. The activated carbon via air oxidation emerged as an acceptable and cost-effective adsorbent for furfural from wastewater. [ABSTRACT FROM AUTHOR]

This work reports the development of multifunctional or polymorphous surfaces using zinc oxide (ZnO) nanorods, silica (SiO 2), and fluoropolymer functionalization in a sequential process. Firstly, zinc oxide nanorods were grown on activated carbon cloth (ACC) using a simple low-temperature synthesis process. ZnO nanorods-coated ACC substrate was applied to investigate the antimicrobial properties, and the results showed inhibition of 50% for Escherichia coli (E.coli) and 55% for Bacillus subtilis (B.subtilis) over 48 h of incubation time. Subsequent in-situ modification of silica nanoparticles like layer on ZnO nanorods-coated ACC surface was developed and used as an electrode for brackish water desalination in a capacitive deionization system. ZnO–SiO 2 modified ACC surface enhanced the desalination efficiency by 1.6 times, the salt removal rate (SRR) by threefold, and the durability (fouling prevention) for long-term usage compared to pristine ACC. Further modification of the ZnO–SiO 2 -ACC surface using fluoropolymer rendered the surface superhydrophobic and oleophilic. Vegetable (1.4 g/g) and crude oil (1.6 g/g) adsorption capacities were achieved for modified surface which was 70% enhancement compared with pristine ACC. The dynamic oil spill adsorption test exhibited the complete removal of oil spills on water surfaces within a few seconds, suggesting a potential application in oil spill cleaning. [Display omitted] • ZnO nanorods coated activated carbon cloth (ACC-ZnO) showed antibacterial properties. • In-situ deposition of SiO2 layer on ACC-ZnO was made and used as CDI electrode. • ACC-ZnO-SiO2 electrodes exhibited higher salt removal efficiency and rate. • Fluoropolymer functionalized ACC-ZnO-SiO2 surface improved oil adsorption capacity. • Multifunctional surface can be utilized as simple and cost-effective wastewater treatment. [ABSTRACT FROM AUTHOR]

Achieving a net-zero target via a circular economy approach necessitates maximizing the recycling of waste into higher-value materials. In the present study, spent coffee grounds (SCG) from industrial food processing biomass waste are converted into a high-performance anode material used in lithium-ion batteries via one-step carbonization of ZnCl 2 at 550 °C. The hybrid composites (HCs) are collected after the process contained C- and Zn-based mixed oxides, such as zinc silicate (Zn 2 SiO 4) and zinc ferrate (ZnFe 2 O 4). The content of Zn-based mixed oxides in HCs increases with the initial ZnCl 2 :SCG mass ratio and reaches its maximum at a ratio of 2:1 wt/wt (HCs_2). The electrochemical performance of the HC-based anodes is proportional to the loaded Zn content when the ZnCl 2 :SCG mass ratio increases from 0 to 2. The optimized anode (HCs_2) exhibits a charge capacity of 692 mAh g−1 and capacity retention of 86 % at the 100th cycle, whereas the corresponding values for HCs_0 anode (without ZnCl 2 treatment) are 311 mAh g−1 and 73.3 %. The superior electrochemical performance of the optimized anode is attributed to the nanosized Zn 2 SiO 4 and ZnFe 2 O 4 , stabilization effect of activated carbon matrices, and a strategy that increases the proportions of high-capacity components. [Display omitted] • ZnCl 2 activation converts spent coffee grounds to valuable hybrid composites (HCs). • The HCs consisting of C-based and Zn-based oxides is prepared via a simple pyrolysis. • Carbon matrices and nanosized Zn-based oxides support to improve electrochemical performance. • HCs_2 electrode exhibits stable cyclability, delivers a capacity of 692 mAh g−1 after 100 cycles. • The HCs are suggested as a low-cost and green anode for advanced lithium-ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • A parametric investigation of the electrochemical desalination cell was carried out. • The longer residence time of the flow electrode and the feed water augmented the desalination. • Surface area of carbon and redox couple play a crucial role in desalination. • A reduction of 235 mg/L of total dissolved solids in tap water was observed. Flow Electrode Capacitive Deionization (FCDI) is a promising technology that uses carbon materials as flow electrodes in aqueous conditions to enable continuous desalination. In this work, the parametric investigation of the FCDI cell was carried out for low and high surface area activated carbon. When 1 mM/1 mM ferri-/ferrocyanide redox couple in the 1 M NaCl supporting electrolyte containing the 5 wt% high surface area activated carbon and 0.5 wt% MWCNT is circulated as flow electrode at the flow rate of 8 mL/min in the electrode chamber and 0.1 mM NaCl feed water is circulated in single-pass mode at 8 mL/min, the FCDI system achieved a significant improvement in desalination performance up to 76.38 % of SRE, with a high average salt removal rate of 43.925 µg/cm2s @ 2 V, charge efficiency of 20.11 % and average energy consumption of 0.27 kWh/mol, through a thorough parametric investigation. When the FCDI cell was tested with tap water, the average salt removal rate, average energy consumption, and salt removal efficiency were calculated at 6.11 μg/cm2s, 2.46 kWh/mol, and 46.61 % respectively, resulting in the reduction of total dissolved solids of 600 mg/L at the inlet to 365 mg/L at the outlet. The combination of microporous high surface area carbon and ferro-ferri redox couple propelled the desalination performance in comparison with the macroporous low surface area carbon, maximizing the ion removal rate, which further reduced the energy consumption and operating voltage for the process. [ABSTRACT FROM AUTHOR]

Edible white-rot fungi are commonly cultivated on wood-based substrates and selectively degrade lignin to a larger extent during their growth. Spent mushroom substrate (SMS) is produced in huge amounts by the mushroom industry and today there is a lack of proven methods to valorize this kind of biomass waste, which in most cases is landfilled or used as fuel. This study demonstrates that birch wood-based SMS from the cultivation of oyster mushrooms can be converted into high-quality activated carbon (AC) with an extremely high surface area of about 3000 m2/g. These activated carbons showed good performance when used in electrodes for supercapacitors, with energy storage parameters nearly identical to AC produced from high-quality virgin birch wood. Moreover, AC produced from SMS showed high potential as an adsorbent for cleaning reactive orange-16 azo dye from aqueous solutions as well as contaminants from synthetic effluents and from real sewage water. The kinetics of adsorption were well represented by the Avrami fractional order model and isotherms of adsorption by the Liu model. The theoretical maximum reactive orange-16 adsorption capacities were approximately 519 mg/g (SMS-based carbon) and 553 mg/g (virgin birch-based carbon). The removal of contaminants from synthetic effluents made of different dyes and inorganic compounds was around 95% and 83% depending on the effluent composition. The removal of contaminants from raw sewage water was around 84%, and from treated sewage water was around 68%. Overall, the results showed that activated carbon prepared from waste generated during cultivation of white-rot fungi is as good as activated carbon prepared from high-quality virgin wood. [Display omitted] • Spent mushroom substrate (SMS) was used as precursor for production of activated carbon (AC). • Chemical activation with KOH at 850 °C led to specific surface area of around 3000 m2/g. • SMS-based AC showed excellent properties for supercapacitors and water treatment. • SMS-based supercapacitors retain 91% of their capacitance after 10,000 cycles. • Maximum reactive orange-16 adsorption capacity according to the Liu model was 519 mg/g. [ABSTRACT FROM AUTHOR]

The CoNi-based hydroxide nanosheets (CoNiNSs) are promising active materials for supercapacitors. At the same time, the fabrication of freestanding electrodes is essential to achieve high electrochemical performance without introducing inactive components. To further improve the utilization of electrochemically CoNiNSs, in this study, a nickel-based foam/tube current collector (NF@NT) is rationally fabricated to support CoNiNSs (NF@NT/CoNiNSs). As expected, the freestanding NF@NT/CoNiNSs-2 electrode with optimum CoNiNSs content exhibits favorable electrochemical performance: (i) in the three-electrode system, the specific capacitance is 4.2 F cm−2 at 10 mA cm−2 and 2.38 F cm−2 at 50 mA cm−2, as well as capacitance retention of 97.1 % after 20,000 cycles at 20 mV s−1; (ii) matched with activated carbon (AC), the capacitance of corresponding NF@NT/CoNiNSs-2//AC device maintains 90.74 % after 27,500 cycles at 50 mA cm−2, which also delivers an energy density of 80.8 Wh kg−1 at a comparable power density of 5997.52 W kg−1. • The freestanding NF@NT/CoNiNSs electrode for supercapacitors is fabricated via direct growth of CoNiNSs on NF@NT. • The NF@NT/CoNiNSs electrode endows large contact area with electrolyte, short ion diffusion transport, and fast electron pathway. • The NF@NT/CoNiNSs//AC maintains 90.74 % capacitance after 27,500 cycles at 50 mA cm−2. • The NF@NT/CoNiNSs//AC delivers an energy density of 80.8 Wh kg−1 at a comparable power density of 5997.52 W kg−1. [ABSTRACT FROM AUTHOR]

A novel approach was employed to fabricate a biofilm-derived activated carbon (BioAc) electrode on a carbon cloth (Cc) substrate for electrochemical nitrite sensing in water samples. The biofilm/Cc electrode was developed using a bioelectrochemical reactor, featuring a three-electrode system with nutrient media and microbial sources. The resultant biofilm electrode was activated at 450 °C for 2 h to eliminate impurities and enhance porosity. Morphological analysis of the BioAc/Cc electrode revealed a surface characterized by a compact film composed of numerous carbon nanoparticles. X-ray diffraction (XRD) analysis exhibited broad, highly crystalline peaks, enhancing both the electrode surface area and conductivity. Amperometry tests on the modified BioAc/Cc electrodes demonstrated a detection limit of 0.015 μM, a sensitivity of 1946.54 μA mM−1 cm−2, and a linear range spanning 0.35–478.21 μM at neutral pH conditions. Moreover, the electrodes demonstrated good stability with a RSD of 2.25% after 60 days and high reproducibility with an RSD of 1.64%. Real-time results showed 99.2 and 100.1% recovery for tap water and drinking water, respectively, highlighting the potential for commercialization in the future. These findings suggest that the BioAc/Cc electrode holds substantial potential for precise nitrite detection in environmental and wastewater applications. [Display omitted] [ABSTRACT FROM AUTHOR]

This study presents the development of green and sustainable supercapacitor electrodes using activated carbons derived from industrial waste from red pepper (RPW) via conventional chemical activation using ZnCl 2 at various carbonization/activation temperatures. The activated carbon samples were subjected to various analytical techniques, including elemental analysis, N 2 adsorption-desorption, Raman, FT-IR, and SEM-EDS. The resulting carbon samples were then used to prepare standard coin-sized supercapacitor cells, which were tested using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques with a 6 M KOH electrolyte. The BET surface area and surface functionality of the samples decreased as the temperature increased. The material produced at the highest temperature (AC800) exhibited the lowest gravimetric capacitance value (131 F/g). However, it demonstrated perfectly reversible electrochemical behavior with the highest capacitance retention of 50 % (between 0.5 A/g and 10 A/g) and cyclic stability (>96 %) over 10,000 cycles among all the other materials. Conversely, the electrode material produced at the lowest temperature (AC600) had the highest gravimetric capacitance value of 175 F/g but the lowest electrochemical stability due to the contribution of pseudo faradaic processes in the storage mechanism. [Display omitted] • Activated carbons (ACs) were derived from RPW with ZnCl 2 at various temperatures. • ACs were examined as supercapacitor electrodes materials. • The temperature had significant impact on the textural properties and capacitive behavior of ACs. • AC600 had the highest gravimetric capacitance thanks to the contribution of pseudo capacitance. • AC800 showed best reversibility, cyclic stability, and capacitance retention as the electrode material. [ABSTRACT FROM AUTHOR]

Global demand for lithium (Li) resources has dramatically increased due to the demand for clean energy, especially the large-scale usage of lithium-ion batteries in electric vehicles. Membrane capacitive deionization (MCDI) is an energy and cost-efficient electrochemical technology at the forefront of Li extraction from natural resources such as brine and seawater. In this study, we designed high-performance MCDI electrodes by compositing Li+ intercalation redox-active Prussian blue (PB) nanoparticles with highly conductive porous activated carbon (AC) matrix for the selective extraction of Li+. Herein, we prepared a series of PB-anchored AC composites (AC/PB) containing different percentages (20%, 40%, 60%, and 80%) of PB by weight (AC/PB-20%, AC/PB-40%, AC/PB-60%, and AC/PB-80%, respectively). The AC/PB-20% electrode with uniformly anchored PB nanoparticles over AC matrix enhanced the number of active sites for electrochemical reaction, promoted electron/ion transport paths, and facilitated abundant channels for the reversible insertion/de-insertion of Li+ by PB, which resulted in stronger current response, higher specific capacitance (159 F g−1), and reduced interfacial resistance for the transport of Li+ and electrons. An asymmetric MCDI cell assembled with AC/PB-20% as cathode and AC as anode (AC//AC-PB20%) displayed outstanding Li+ electrosorption capacity of 24.42 mg g−1 and a mean salt removal rate of 2.71 mg g min−1 in 5 mM LiCl aqueous solution at 1.4 V with high cyclic stability. After 50 electrosorption-desorption cycles, 95.11% of the initial electrosorption capacity was retained, reflecting its good electrochemical stability. The described strategy demonstrates the potential benefits of compositing intercalation pseudo capacitive redox material with Faradaic materials for the design of advanced MCDI electrodes for real-life Li+ extraction applications. [Display omitted] • Redox-active PB intercalation material with AC for efficient Li+ extraction. • AC facilitate electron and Li + transport to redox-active sites of PB. • AC/PB exhibit high specific capacitance (159 F g−1) and rapid Li+ diffusion. • Excellent Li + extraction of 24.42 mg g−1 in Asymmetric AC//AC/PB-20 MCDI cell. • Excellent cyclic stability and Li + retention of 95.11% even after 50 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • State of the art in electrosorption of organic compounds (EOC) critically reviewed. • EOC shows promise against poorly adsorbable, highly polar, and ionized pollutants. • Enhanced adsorption and active control of ad-/desorption by electric potential. • Insightful performance parameters proposed to unify rapidly growing EOC research. • EOC application for on-site regenerable adsorbers and in treatment trains discussed. The widespread contamination of water resources with emerging organic contaminants necessitates the development of sustainable and cost-effective water treatment technologies. Adsorption, as a widely used water remediation process, is hampered by severe performance limitations against ionic and hydrophilic organic contaminants. In addition, no facile on-site regeneration techniques are available. Electrosorption of organic compounds (EOC) is a promising alternative to not only improve adsorption performance, but also to facilitate adsorbent regeneration by green electricity. The number of studies on EOC has grown exponentially over the past decades. There are numerous examples showing that applied electric potentials can significantly enhance the adsorption affinity, capacity, and kinetics of conductive carbon adsorbents. However, whether these effects are specific to certain compound classes or more generally applicable remains unclear as well as the optimal criteria for designing EOC processes. Therefore, we critically evaluated the current state of the art of EOC in terms of active control of adsorption and desorption processes and the achievable effects for ionic and neutral organic compounds. Through a detailed consideration of compound speciation and surface chemistry of electrode materials, we derive mechanistic insights into the EOC process and discuss differences between electrosorption of inorganic and organic compounds. We provide definitions and propose insightful performance parameters to unify the rapidly growing EOC research. Potential application scenarios and future research directions are discussed. Overall, EOC is less likely to be a one-fits-all solution for removing contaminants, but adds a valuable tool especially for the hydrophilic and ionic organic contaminants that challenge conventional adsorption processes. [ABSTRACT FROM AUTHOR]

In this study, adsorption kinetics of phenanthrene (PNT) and trichloroethylene (TCE) by a graphene nanosheet (GNS), a graphene oxide nanosheet (GO), a single-walled carbon nanotube (SWCNT), a multi-walled carbon nanotube (MWCNT), and two coal based activated carbons (ACs) (F400 and HD3000) were examined in distilled and deionized water (DDW) and under natural organic matter (NOM) preloading conditions. The results showed the times needed for the adsorption of PNT and TCE to reach apparent equilibrium (i.e., ≤3% change per day) followed the order of GO ≥ MWCNT > GNS > SWCNT ∼ HD3000∼F400 and SWCNT > GNS ∼ HD3000 > F400 ∼ MWCNT > GO, respectively. The pseudo second order model successfully represented kinetics data for three classes of carbonaceous adsorbents. The Weber-Morris intraparticle diffusion model indicated three steps adsorption process for PNT and two step adsorption for TCE. In addition, the times needed to reach apparent equilibrium for the adsorption of PNT and TCE in the presence of hydrophobic (HPO) and hydrophilic (HPI) NOM solutions increased for all adsorbents (except for GO). In general, both NOM showed similar impacts on the adsorption rates of PNT and TCE. Aggregation of both GNS and CNTs rapidly occurred during initial couple hours of contact time during preloading, and spiking both PNT and TCE further increased their aggregation. Image 1 • Graphenes and CNTs showed faster sorption kinetics for PNT and TCE as compared to ACs. • The adsorption kinetics rate of TCE on graphenes, CNTs and ACs were faster than PNT. • The Pseudo-Second-Order Kinetic Model successfully described the kinetic data. • The presence of NOM reduced the PNT and TCE uptakes of all adsorbents. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract In this study, nitrite desorption from activated carbon fiber (ACF) in capacitive deionization (CDI) and membrane capacitive deionization (MCDI) was examined and the effects of the operation parameters (pH, voltage, temperature and flow rate) and co-existing matters were deeply investigated. Desorption mechanisms were analyzed via Brunauer–Emmett–Teller (BET) and Fourier transform infrared spectroscopy (FTIR). Results showed that the final desorption ratio increased from 0 to 100% in MCDI and the enhancement was also observed in CDI that the ratio increased from 18.7 to 83.5% when solution pH increased from 2 to 10. Increasing the voltage and solution temperature also contributed to the ion desorption both in CDI and MCDI, while the effect of flow rate was negligible. Generally, MCDI showed greater desorption performance than CDI due to the elimination of co-ions effect. However, it was interesting to find that when the voltage was in the range of 0.4-0.6 V, the desorption ratio increased from 38.4% to 50.8% in MCDI which was lower than that in CDI (45.4% to 55.8%). One possible explanation was that the presence of membranes would inevitably introduce additional resistance into the system and decrease effective voltage especially at lower voltage. Compared to the desorption performance in MCDI when the solution pH was 2, the greater desorption performance was observed in CDI which was mainly attributed to the site competition. As for the influence of coexisting matters, the presence of bovine serum albumin (BSA) posed an adverse effect for the ion desorption both in CDI and MCDI. The inhibition effect was more serious in CDI, and pore blockage caused by BSA attachment onto ACF was the main mechanism. Therefore, this study would provide some referential advice for the investigation of ion desorption in CDI and MCDI. [ABSTRACT FROM AUTHOR]

Abstract Three kinds of anion exchange resins (AERs) (D201, D301, D314) and one kind of cation exchange resin (D860) were used with activated carbon (AC) to fabricated the ion exchange resin-AC (IER/AC) composite electrodes in capacitive deionization (CDI) for selective adsorption of V(V). The characteristics of four kinds of composite electrodes, such as wettability, pore distribution and electrochemical properties, indicates IER/AC composite has great potential as electrode materials for the electro-adsorption in CDI. The pH of solution has apparent influence on the adsorption capacity of the composite electrodes for V(V) because of the various V(V) species in the solution with different pH. The reduction rate of V(V) on IER/AC electrodes mainly relates to the amount of V O 2 + in solution. The adsorption capacity of AER/AC electrodes for V(V) is slightly affected by the applied voltage may be due to that the adsorption of V(V) is mainly dependent on ion exchange with AERs and only a minority of V(V) is adsorbed by electrostatic adsorption. The adsorbed V(V) on D860/AC electrode decreases with the rising applied voltage because the pH increases with the increase of voltage. The separation of V(V) from V(V), Al and P indicates that the selective adsorption capability of IER/AC composite electrode is related to the migration rate of V(V), Al, P at different voltages and the selectivity of resins. This study may provide reference for recovering and separating metal ions from aqueous solution with CDI. Highlights • Resin-carbon electrodes were fabricated to explore the effect of resins on the electrodes. • Resin-carbon electrode had great potential application in capacitive deionization. • The ionic species of vanadium in solution affect its adsorption and reduction. • The applied voltage has apparent influence on the selectivity of electrodes. [ABSTRACT FROM AUTHOR]

A high quality of activated-carbon electrode materials is of great importance for improving the electrochemical performance of desalination in membrane capacitive deionization. In this study, porous activated carbon was prepared by pyrolytic carbonization and chemical activation of lignocellulosic loofa sponge ( Luffa cylindrica , LS) to act as a carbonaceous electrode. After activation, a hierarchically porous structure formed, characterized by the generation of micro-/mesopores on the channel walls. The total specific surface area and pore volume of the activated carbon material rose as the alkali/char ratio increased. The LS-based carbon electrode LSCK14, referring to the activation product produced with a KOH/char ratio of 4, displayed excellent electrochemical behavior, characterized by a remarkable specific capacitance of 93.0 F g −1 at 5 mV s −1 in 1 M NaCl solution, as well as extraordinary reversibility for capacitive charge storage. Moreover, the electrosorption capacity was investigated in batch-mode membrane capacitive deionization at 1.0 V while treating a 10 mM NaCl electrolyte. As demonstrated, the LSCK14 activated carbon electrode presented a superior electrosorption capacity of 22.5 mg g −1 . The improved capacitor characteristics and high electrosorptive performance of this material can be attributed to its unique porous characteristics (high surface area, micrometer-scale channels and both meso- and micropores). Consequently, activated carbons derived from resource-recovered LS, which combine a multi-channeled structure, mesopores and micropores, were demonstrated to be a promising electrode material for electrochemical water desalination. [ABSTRACT FROM AUTHOR]

Asymmetrical capacitive deionization (A-CDI) is expected to be a promising desalination technique with high salt removal capacity. In this work, the novel A-CDI are proposed where the negative and positive electrode are Na 4 Ti 9 O 20 (NTO) and activated carbon (AC), respectively. Basically, the NTO nanotubes with the specific surface area of 142.43 m 2 /g have been prepared by hydrothermal reaction. The electrochemical test shows that the specific capacitance of optimum NTO electrode can reach 120.45 F/g in 1 M Na 2 SO 4 solution with the scan rate of 1 mV/s by employing three-electrodes method. Moreover, the electrosorption capacity of AC/NTO asymmetrical electrodes is approach to 23.35 mg/g in NaCl solution with an initial concentration of 250 ppm. To improve the conductivity of NTO, reduced graphene oxide (rGO) is proposed to couple with NTO, named as rGO@NTO, to constitute the AC/rGO@NTO A-CDI. As a result, the AC/rGO@NTO A-CDI exhibited an ultrahigh desalination capacity of 41.8 mg/g in NaCl solution with an initial concentration of 250 ppm under 1.4 V, which is almost twice higher than that of AC/NTO electrodes and the highest value among all reported data anywhere. Besides, the charge efficiency of AC/rGO@NTO approaches to 1, implying the co-ions impaction has been successfully restricted. [ABSTRACT FROM AUTHOR]

A feasibility study for water recycling and reuse of a reverse osmosis (RO) brackish wastewater by capacitive deionization (CDI) was carried out in the present work. Palm-shell wastes enriched in carbon was recycled to yield valuable activated carbon (AC) that has advantages of high surface area, high specific capacitance, and low electrical resistance as the CDI electrodes. The GAC prepared by dispersion of AC in the graphene (rGO) layers has a high surface area and electrical conductivity for CDI. The GAC electrodes have increasing electrosorption efficiencies from 1.6 to 3.0% during the repeated electrosorption-regeneration cycles under +1.2 → 0 → +1.2 V while the efficiencies the AC electrodes decrease from 2.7 to 1.6%. It is clear that the GAC-based electrodes have a better electrosorption efficiency and stability in, for example, the three repeated electrosoption-regeneration cycles for CDI of the wastewater. This work also exemplifies that the AC recycled from biomass such as palm-shell wastes can be used in CDI electrodes for recycling and reuse of wastewater. [ABSTRACT FROM AUTHOR]

A single-pass-mode capacitive deionization (CDI) reactor was used to remove arsenic from groundwater in the presence of multiple ions. The CDI reactor involved an applied voltage of 1.2 V and six cell pairs of activated carbon electrodes, each of which was 20 × 30 cm 2 . The results indicate that this method achieved an effluent arsenic concentration of 0.03 mg L −1 , which is lower than the arsenic concentration standard for drinking water and irrigation sources in Taiwan, during the charging stage. Additionally, the ability of the CDI to remove other coexisting ions was studied. The presence of other ions has a significant influence on the removal of arsenic from groundwater. From the analysis of the electrosorption selectivity, the preference for anion removal could be ordered as follows: NO 3 − > SO 4 2− > F − > Cl − >As. The electrosorption selectivity for cations could be ordered as follows: Ca 2+ > Mg 2+ > Na + ∼ K + . Moreover, monovalent cations can be replaced by divalent cations at the electrode surface in the later period of the electrosorption stage. Consequently, activated carbon-based capacitive deionization is demonstrated to be a high-potential technology for remediation of arsenic-contaminated groundwater. [ABSTRACT FROM AUTHOR]

In the electro-Fenton process, there still suffers concern of low H 2 O 2 generation caused by inadequate mass transfer of oxygen and low selectivity of oxygen reduction reaction (ORR). To solve it, in this study, various particle sizes (850 μm, 150 μm, and 75 μm) of granular activated carbon filled in a microporous titanium-foam substate was used to develop a gas diffusion electrode (AC@Ti–F GDE). This facile-prepared cathode has seen a 176.15% improvement in H 2 O 2 formation compared to the conventional one. Aside from a much higher oxygen mass transfer by creating gas-liquid-solid three-phase interfaces coupled with much high dissolved oxygen, the filled AC played a significant role in H 2 O 2 accumulation. Among these particle sizes of AC, the one in 850 μm has observed the highest H 2 O 2 accumulation, reaching 1487 μM in 2 h electrolysis. Because there is a balance between chemical nature for H 2 O 2 formation and micropore-dominant porous structure for H 2 O 2 decomposition, resulting in an electron transfer of 2.12 and H 2 O 2 selectivity of 96.79% during ORR. In a word, the facial AC@Ti–F GDE configuration is promising for H 2 O 2 accumulation. [Display omitted] • Titanium-based air diffusion cathode was designed by filling in activated carbon. • This facile-prepared cathode has seen a 176.15% improvement in H 2 O 2 formation. • H 2 O 2 accumulation was a balance between porous structure and chemical nature. • Filled activated carbon with 850 μm has an electron transfer of 2.12 during ORR. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a promising desalination technology, and activated carbon is a most commonly used electrode material. In this work, coal-based activated carbon (AC) was prepared from residual carbon of coal gasification fine slag (CGFS) and functionalized with cationic surfactant (cetyltrimethyl ammonium bromide, CTAB) and anionic surfactant (sodium dodecyl sulfate, SDS), respectively. The prepared activated carbon named CTAB-AC and SDS-AC was assembled into the asymmetric CDI electrodes to remove low concentration nitrate in water. The results show that the average pore size, surface Zeta potential and specific capacitance of AC after modification by CTAB and SDS respectively. The surfactant modification slightly decreased the surface hydrophilicity of AC, but increased the electrical conductivity and improved the charge-discharge cycle stability. Compared with the symmetrical electrode AC, the asymmetric electrodes of CTAB-AC and SDS-AC largely improved the CDI performance, the total capacitive deionization capacity and the desalination efficiency for NaNO 3 increased by 38.01% and 25.08%, and the continuous batch CDI process were shortened by 10 cycles. The final nitrate concentration could meet the drinking water requirement. This work proposed a new raw material for carbon electrode and a method for high value utilization of residue carbon in the coal gasification slag. [Display omitted] [ABSTRACT FROM AUTHOR]

• Strong coupling was established between NiCo-DH and OAC by oxidation modification. • NiCo-DH@OAC exhibited excellent electrochemical performance for synergistic effects. • ASCs were demonstrated effective in solar panel integrated supercapacitors. NiCo double hydroxide (NiCo-DH) and oxidized activated carbon (OAC) were used to synthesize a three-dimensional (3D) NiCo-DH@OAC via hydrothermal method. OAC acts as the support for in-situ growth of NiCo-DH nanowires, and oxygen-containing groups on the surface of OAC are crucial for the uniform loading of NiCo-DH and keeping structural stability of the composites. Due to the synergistic effect between NiCo-DH and OAC, NiCo-DH@OAC presents an excellent specific capacitance (1990 F g−1 at 1 A g−1). The asymmetric supercapacitor (ASC) is assembled with NiCo-DH@OAC as the positive electrode and OAC as the negative electrode, and exhibits a superior energy density (46.5 Wh kg−1 at 800 W kg−1) and a cycling stability (90.7% after 10,000 cycles). Furthermore, ASC has been demonstrated effective in solar panel integrated supercapacitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modified carbon black (CB) by O 2 plasma technology for improving CDI capacity. • The effect and mechanism of plasma modified CB (PCB) to improve CDI were explored. • PCB improved the salt removal performance 6.9 times that of the original CB (OCB) • PCB can be applied to improve CDI of various active materials. • PCB has universal applicability in purifying brine, heavy metals and radionuclides. Previous research on capacitive deionization (CDI) mainly focuses on electrode active materials, while the research on conductive additive and their modification for improving CDI performance are rarely reported. In this work, we mainly investigate the effect and mechanism of oxygen (O 2) plasma-modified carbon black (PCB) to enhance CDI performance. The CB treated with O 2 plasma at 100 W for 10 min (CB-100 W-10 min) was assembled with activated carbon (AC) to form a CB-100 W-10 min/AC electrode with excellent desalination performance (32.54 mg g−1), 6.9 times that of the original CB/AC electrode (OCB/AC, 4.91 mg g−1). The roles of the specific surface area, hydrophilicity, electrical conductivity, and specific capacitance of CB in enhancing the performance of CDI were explored, and the interaction mechanism between H 2 O molecules and CB was investigated using molecular dynamics (MD) simulations. The advantages of PCB are mainly attributed to the synergy of the following aspects: (i) The excellent three-dimensional network structure acts as a "bridge" between activated carbon and increases the contact sites for allowing more PCB and AC to participate in the electrosorption process; (ii) Shorter electron transmission paths and more electron transmission channels between PCB and AC promote the electrosorption rate; (iii) High surface roughness and oxygen-containing functional groups of PCB boost hydrophilicity and dispersibility. Interestingly, we found that PCB possesses universal applicability in the enhancement of deionization performance of various active materials for purification of brine, heavy metals and radionuclides. This work unprecedentedly applies plasma technology to the modification of conductive additive, providing new ideas for material modification and improvement of CDI technology. [ABSTRACT FROM AUTHOR]

The functional combination of methylene blue and activated carbon successfully introduced a significant redox reaction in the activated carbon, increasing the specific capacitance of the material and significantly improving the rate performance. The methylene blue adsorbed on the surface of activated carbon enables fast proton-coupled electron transfer. [Display omitted] • Anthracite can be activated at low temperature and show large specific surface area. • Oxygen groups could effectively contribute the pseudo-capacitance to AC. • The π-π binding endows AC/MB excellent electrochemical properties. • The optimized AC/MB as positive can deliver ultrahigh energy and power density. • Mathematical simulation can optimize the ratio of positive to negative electrodes. Supercapacitors are desired to deliver high power and energy density concurrently, and the introduction of a redox reaction is an effective strategy to improve their capacitive performance. Herein, methylene blue (MB) with redox was employed to functionalize coal-based activated carbons (ACs) as electrode materials for energy storage. The optimized AC shows a high specific capacitance of 408.1 F g−1 in 6 M KOH, deriving from the contribution of the electrical double-layer capacitance of pores and pseudocapacitance of oxygen groups. Interestingly, pure MB shows no capacitive performance mainly due to its low conductivity, while the optimized composite of AC adsorbed MB (AC/MB) surpasses the pure MB and optimized AC in any capacitive performance, displaying a relationship of mutual promotion based on functional combination. The best AC/MB sample exhibits a high specific capacitance of 431.8 F g−1 at 1 A g−1, and 356.1 F g−1 (82.5%) at an ultrahigh current density of 180 A g−1, implying an excellent rate performance. Aiming to deliver maximum energy density, an accurate universal method is proposed to match the mass ratio of negative to positive. The optimized asymmetric supercapacitor AC/MB(+) || AC(-) delivers an energy density of 11.0 Wh kg−1, a power density up to 15.3 kW kg−1 and a high capacity retention rate of 96.3% after 10,000 cycles, displaying good chemical stability. This work proposes a promising strategy for ultrafast store/release energy at high energy density, and also provides an application direction for AC and MB. [ABSTRACT FROM AUTHOR]

In this study, the electrosorption selectivity of porous activated carbon (AC) and nickel hexacyanoferrate (NiHCF), which represent two working mechanisms of capacitive electrosorption and redox intercalation, was investigated to separate cations in capacitive deionization (CDI). The cyclic voltammetry diagrams of AC showed the rectangular shape of double-layer charging, while that of NiHCF showed separated peaks associated with redox reactions. The specific capacitance of NiHCF was 143.6 F/g in 1 M NaCl, which was almost two times higher than that of AC. Cation selectivity experiments were conducted in single-pass CDI for a multi-cation solution. The electrosorption preference of the AC cathode was determined by a counterbalance between the ionic charge and hydrated size, reflecting the selectivity coefficient of different cations over Na+ in the range of 0.86–2.63. For the NiHCF cathode, the cation selectivity was mainly dominated by the hydrated radius and redox activity. Notably, high selectivities of K+/Na+ ≈ 3.57, Na+/Ca2+ ≈ 9.97, and Na+/Mg2+ ≈ 18.92 were obtained. A significant improvement in the electrosorption capacity and monovalent ion selectivity can be achieved by utilizing the NiHCF electrode. The study demonstrates the fundamental aspects and promising opportunities of CDI in regard to ion selectivity. [Display omitted] • NiHCF was fabricated as an intercalating electrode for cation separation. • CDI was conducted to examine selective cation separation in a multi-ionic solution. • Cation selectivity of AC was restricted by a counterbalance of ion charge and size. • High selectivity of NiHCF was achieved by its ion-size affinity and redox activity. • CDI with NiHCF is a promising approach for selective monovalent ion removal. [ABSTRACT FROM AUTHOR]

Herein, cherry flower waste-derived activated carbon (CFAC) with self-doped nitrogen is synthesized as a viable energy storage material for green and sustainable energy solutions. The activated carbon derived in this way is examined as an electric double-layer capacitance (EDLC)-type electrode material and sodium-ion battery (NIB) electrode material, and commendable performance is demonstrated for both of these energy storage applications. The specific surface area (SSA) and nitrogen content are observed to play a very delicate role in determining the charge storage ability of the CFAC, and the performance is optimized only by carefully balancing both of these properties. The optimized CFAC electrode supplied an excellent performance with a specific capacitance of 333.8 F g−1 and capacity is maintained to more than 96% even after 38,000 charge-discharge cycles as an EDLC-type supercapacitor electrode material. Likewise, the CFAC/NIB also yielded remarkable performance with an average specific capacity of 150 mAh g−1 and capacity retention of more than 84% after 200 charge-discharge cycles. Furthermore, an electrokinetic study was performed for both supercapacitor and NIB applications to identify the contribution from surface and diffusion type charge storage phenomena, consequently highlighting the role of the SSA and nitrogen content in the CFAC matrix. [Display omitted] • Scalable synthesis of cherry flower waste-derived activated carbon (CFAC). • CFAC shows a significant amount of self-doped nitrogen and a large SSA. • Applied as an EDLC type supercapacitor and sodium-ion battery electrode material. • 334 F g−1 sp. Capacitance and over 96% capacity retention after 38,000 cycles. • Commendable sodium-ion battery performance with high sp. Capacity and stability. [ABSTRACT FROM AUTHOR]

Cadmium (Cd2+) is the main toxic heavy metal in desulphurisation wastewater for coal-fired power plants. Here, a novel carbon skeleton/molybdenum disulphide composite material (MoS 2 /AC) with expanded layer spacing was synthetized in one step for Cd2+ removal through the capacitive deionization method. As the results showed, the Cd2+ removal capacity of the MoS 2 /AC cell was 22.15 mg g−1, and the concentration of Cd2+ in the simulated wastewater was effectively reduced from 10 ppm to <0.1 ppm. According to the characterisation, the layer spacing of MoS 2 nanosheets in MoS 2 /AC increased by 58.06% compared with the original commercial MoS 2 , which could provide more active sites for Cd2+ adsorption. Moreover, the XPS results showed that electrosorption and complexation on the surface of MoS 2 /AC were the main routes for Cd2+ removal, especially the complexation between Cd2+ and metal-sulphur. In addition, the selective adsorption efficiency of MoS 2 /AC was more than 98% under the coexistence of other ions, such as Na+, Mg2+, and Ca2+. The regenerated MoS 2 /AC also had a high adsorption capacity for Cd2+ even after 5 cycles. The MoS 2 /AC material also exhibited excellent removal capability for heavy metal ions in the actual desulphurisation wastewater from coal-fired power plants (<1 ppb). The results indicated that MoS 2 /AC may be a prospective material for heavy metal ion removal from wastewater. [Display omitted] • MoS 2 /AC was developed as an effective CDI electrode material. • High Cd2+ absorption capacity of 22.15 mg g−1 and excellent recyclability. • The obtained MoS 2 /AC possess enlarged interlayer spacing to expose S adsorption sites. • The exposed sulphur atoms complexed with cadmium ions to remove Cd2+. [ABSTRACT FROM AUTHOR]

[Display omitted] • First attempt to remove salt from the anaerobic OMBR sludge by FCDI. • The hybrid FCDI-OMBR obtained a higher net energy gain. • Desalination performance of AC, CB, CNT as FCDI electrode material were compared. • Synergistic desalination between different electrode materials was found. Osmotic membrane bioreactors (OMBRs) for anaerobic digestion of waste sludge have many advantages, but salt accumulation in the feed solution is a major problem. In this study, the feasibility of using flow-electrode capacitive deionization (FCDI) to mitigate salinity buildup was investigated. Three types of carbon materials, i.e., activated carbon (AC), carbon black (CB), and carbon nanotubes (CNTs), were tested as flow-electrode materials in desalination via FCDI. The results showed that, the salt removal efficiency (SRE) of CNTs was 110% higher than that of AC. Addition of CB and CNTs to 5.0 wt% AC as conductive additives at concentrations of 0.5 or 1.0 wt% synergistically enhanced the FCDI desalination performance. Cyclic voltammetry, galvanostatic charge–discharge, and electrical impendence spectroscopy showed that use of a combination of 5.0 wt% AC and 1.0 wt% CNTs gave an excellent capacitive performance, and the highest SRE, fastest average salt adsorption rate (0.84 μg cm−2 s−1), and the highest charge efficiency (85.0%) were achieved. The optimal voltage and sludge flow rate for FCDI of real OMBR sludge were 1.5 V and 80 mL min−1, respectively. In comparison with a control OMBR, a hybrid FCDI-OMBR system showed many advantages such as slower salinity buildup, alleviation of inhibition by ammonia, lower production of soluble microbial products, greater volumetric methane production, and higher net energy gains. The proposed hybrid FCDI-OMBR system provides a novel and cost-effective approach to recovering resources and energy from waste sludge or other types of biomass. [ABSTRACT FROM AUTHOR]

[Display omitted] • Charging activated carbon (AC) tunes adsorption of ionic but not nonionic compounds. • Defunctionalized AC allows better electro-assisted trap&release performance. • Combine surface modification and electric polarization for promoted removal. • Long-term (20 d) stable electro-assisted trap&release with high enrichment effects. • Electro-assisted trap&release promising for on-site AC regeneration. Highly water-soluble, persistent, and mobile organic compounds (PMOCs) are more and more often detected in surface and groundwater, evoking potential threats to the environment and human health. Traditional water treatment strategies, including adsorption by activated carbon materials, fail to efficiently remove PMOCs due to their hydrophilic nature. Electro-assisted sorption processes offer a clean, facile, and promising solution to remove PMOCs on activated carbon-based electrodes and potentially allow an easy on-site sorbent regeneration (trap&release). In this work, the electrosorption of five selected PMOCs, that is, tetrapropylammonium (TPA+), benzyltrimethylammonium (BTMA+), p -tosylate (p -TsO-), p -toluenesulfonamide (p -TSA), and methyl- tert -butyl ether (MTBE), were investigated on two comprehensively characterized activated carbon felt (ACF) types carrying different surface functionalities. Significant enrichment factors in ranges of 102 to 103 for charged PMOCs were expected by our first estimation for electro-assisted trap&release on ACFs in flow systems applying potentials in the range of −0.1 V/+0.6 V vs. SHE for ad-/desorption, respectively. Defunctionalized ACF carrying larger density in surface π-systems and lower O-content promises a higher capability in electrosorption processes than the pristine material in terms of better material stability (tested for 5 cycles over 500 h) and better removal efficiency of ionic PMOCs. To improve ACFs adsorption performance for cationic and anionic PMOCs, permanent chemical surface modification and reversible electric polarization as alternative strategies are compared. Our findings explore future electrode and process design of electrosorption for applications to treat water contaminated by emerging PMOCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fungal hypha activated carbon pad (FhACPad) is a promising electrode for desalination. • FhACPad is a freestanding electrode readily prepared from the fungus suspension for CDI. • The continuous and porous structure of FhACPad facilitates both electron and ion transfer. • FhACPad with hierarchical pores exhibits a high desalination capacity of 35.6 mg NaCl /g. Capacitive deionization (CDI) is an emerging technology for water desalination, especially low-salinity water. Freestanding porous carbon-based electrodes with rapid electron transfer rate and effective ion diffusion features are desired to achieve high desalination performance. Here, a porous carbon pad derived from the fungal hyphae of Aspergillus niger was prepared as a precursor of the electrode. After carbonization and activation, the intertwined and hierarchical porous structure of the fungal hypha pad was well-preserved, producing a freestanding fungal hypha activated carbon pad (FhACPad) electrode for MCDI. The interconnected carbon fibers and open pore structure of the FhACPad yielded an electrode with high electrical conductivity and rapid ion transport properties. The novel FhACPad exhibited a gravimetric salt adsorption capacity of 35.6 ± 2.3 mg NaCl /g with an average desalination rate of 1.2 mg NaCl /g electrode /min from a 585 mg/L NaCl aqueous solution at a cell voltage of 1.2 V and a flow rate of 1 mL/min. As a result, the FhACPad outperformed conventional powdered activated carbon (PAC) electrodes and the most recently reported porous carbon electrodes under similar desalination conditions. This work also provides insights into the structure-performance relationships of CDI electrodes and shows a great potential of fungal biomass-derived porous carbon electrodes for high-performance MCDI applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Crude glycerol from biodiesel was used to obtain a new sustainable activated carbon. • The polyglycerol activated carbon electrodes successfully desalinate brackish water. • Operation within the potential stability window ensured the long-term stability. • Asymmetric configurations (CDI) and MCDI improved the charging efficiency. • The best stable desalination performance was achieved using the membrane CDI at 1.6 V. Capacitive deionization (CDI) is a promising electrochemical technology for water desalination that can contribute to reducing water scarcity. At the same time, appropriate routes for the disposal or reuse of liquid wastes are also a major current concern. Based on the water-waste nexus concept, this work demonstrates that crude glycerol from biodiesel plants can be successfully used to obtain a new sustainable activated carbon. After polymerization, the crude glycerol was carbonized and activated to obtain polyglycerol activated carbon (PGAC), which was employed as an electrode for CDI desalination of brackish water. Evaluation was made of the electrode performance and stability over cycles of electrosorption/desorption, using different cell configurations (symmetric, asymmetric, and membrane CDI) and cell voltages (E cell). It was observed that maintaining the potential of zero charge of the negative and positive electrodes outside their working domains during the cycles enabled minimization of that part of the applied potential deviated to co-ion repulsion, consequently improving the salt adsorption capacity (SAC) and charge efficiency (Q E). Furthermore, maintaining the potential of the positive electrode below the oxidation potential by controlling the applied E cell could ensure electrode stability. The best desalination performance using the PGAC electrode was achieved using the membrane CDI configuration (at 1.6 V), resulting in stable SAC (∼ 27.1 mg g−1) and Q E (∼100%) over 50 cycles. The low cost and high SAC and Q E values suggested that the PGAC electrode could be considered a potential candidate for use in CDI desalination. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ion sorption on EDL and pseudocapacitor was studied at constant potential. • α-MnO 2 was the best in diffusive capacitance among polymorphs. • Effects of ion solvation and valence on sorption of inert ions were studied. • Monolayer capacity as affected by electrode polarity was estimated via Langmuir model. • Isoelectric point of the reversible MnO 2 /AC composite was modified. The capability of manganese dioxide (MnO 2) supported on loofah-derived activated carbon (AC) in the electrosorptive removal of common inert ions was studied in constant potential mode. Four MnO 2 polymorphs were prepared by redox chemical precipitation and characterized by XRD, SEM, BET and XPS. The pseudocapacitance property of the MnO 2 /AC electrode, significantly affected by the surface- and diffusion-controlled charge storage mechanism, was assessed via voltammetry and modified Langmuir adsorption isotherm. Batch electrosorption experiments were then performed at constant potential in the range of −1.5 V to + 1.5 V (vs. Ag/AgCl) using AC and α-MnO 2 /AC electrodes in the presence of common simple electrolytes, including NaNO 3 , Li 2 SO 4 , and Ca(ClO 4) 2. Consequently, the applied working potential (E app) positively affected the ion electrosorption rate and capacity. Faradaic processes occurred on MnO 2 , i.e., Mn(III)/Mn(IV) transition, increased the diffusion capacitance of AC, thus enhancing the first-order rate and monolayer capacity, mainly for the electrosorption of cations. Results showed that ion solvation, controlled by the ionic radius and valence of an ion, which impacted ion intercalation in MnO 2 and affected ion adsorption characteristics. The cation sorption capacity of α-MnO 2 /AC followed the order of Na+ (2.8 × 10-4 mol g−1) > Ca2+ (2.1 × 10-4 mol g−1) > Li+ (0.76 × 10-4 mol g−1) at E app = -1.5 V. The differential capacitance as affected by polarized potential and the shift of zero net charge or IEP toward more positively charging potential further highlighted the contribution of pseudocapacitance to ion adsorption on α-MnO 2 /AC electrode. [ABSTRACT FROM AUTHOR]

[Display omitted] • QRAC electrodes selectively adsorb NO 3 – due to the difference in binding energy. • The selectivity coefficient of QRAC-5 to NO 3 – reaches 2.7 at 0.4 V. • The electrosorption behavior of QRAC depends on physical adsorption and ion exchange adsorption. Nitrate pollution has become an increasingly serious water pollution problem worldwide. Capacitive deionization (CDI) technology is an emerging water treatment technology that can efficiently remove nitrate in water with advantages of simple process, high water recovery rate, low cost and energy consumption. In this work, we engineer a covalently bonded quaternized activated carbon (QRAC) material by silanization and investigate its selective adsorption of nitrate in mixed solution with extended voltage capacitive deionization (eV-CDI) mode. The results show that (1) the QRAC electrodes achieve selective adsorption due to the different adsorption binding energies of the quaternary ammonium group with Cl- and NO 3 –. The selectivity coefficient of QRAC-5 to NO 3 – reaches 2.7 at 0.4 V and the electrosorption capacity is 140% higher than that of AC in 5/5 mM KCl/KNO 3 solution. (2) The electrosorption of QRAC electrodes are dominated by two aspects: physical adsorption by external electric field which occurs in the incipient stage and ion exchange adsorption by quaternary ammonium groups occurring in the following stage. (3) CDI experiments in simulated municipal wastewater show that SO 4 2- had a negative effect on the adsorption capacity of NO 3 –, but QRAC electrode can still achieve separation effect in Cl-/NO 3 – solution system. These results show that covalently bonded quaternized activated carbon can achieve the effective separation and removal of NO 3 – in polluted water, and our work provides new insights into the selective electrosorption of CDI technology. [ABSTRACT FROM AUTHOR]

Conversion of bio-waste into activated carbon is an environmentally friendly approach that reduces the pressure on biowaste disposal. Here we describe the preparation of activated carbon from the biowaste of the lemon peel by carbonization at 400 °C followed by chemical activation employing KOH. The activation parameters like temperature and mass ratio of precursor and KOH are optimized to obtain carbon material of better capacitive performance. The mass ratio and temperature of activation are optimized as 1:1 and 600 °C (ALP-600) respectively by systematic analysis of the capacitive performance of carbon materials in acidic (0.5 M H 2 SO 4) and alkaline (2 M KOH) electrolytes. The superior performance of ALP-600 despite its lower surface area (744.78 m2 g-1) is attributed to its hierarchical porosity as the mesopores improve the capacitive performance by providing connectivity between the pores. ALP-600 delivers a higher specific capacitance of 152.14 Fg-1 and better power rate capability evident from the quasi-rectangular shape of cyclic voltammogram even at a higher scan rate of 100 mVs−1 in the acidic electrolyte. The high energy density of 4.67 Whkg−1 and a high-power density of 8113 Wkg-1 is achieved with the symmetric capacitor. The symmetric capacitor of configuration ALP-600 || 0.5 M H 2 SO 4 || ALP-600 exhibits excellent cycling stability over 10,000 cycles with 99.5% coulombic efficiency and insignificant capacitance loss. • Carbon electrodes are derived from the biowaste of lemon peel by chemical activation employing KOH. • Activation temperature and the mass ratio of precursor and KOH are optimized to achieve hierarchical porosity. • Carbon obtained at the activation condition of 1:1 mass ratio and 600 °C (ALP-600) exhibits excellent capacitive performance. • ALP-600 shows high specific capacitance of 152.14 Fg-1 in 0.5 M H 2 SO 4. • The symmetric capacitor employing ALP-600 retains 99.5% of coulombic efficiency over 10,000 cycles. [ABSTRACT FROM AUTHOR]

Capacitive deionization (CDI) is a promising method to remove metal contaminants in water. Herein, we report on the preparation of activated carbon from cation-exchange resin by introducing ZnCl 2 via ion exchange followed by heat treatment and CO 2 activation, which is evaluated for removal of Cu2+ in water via CDI technology. The results have shown that both the heat treatment and the CO 2 activation are helpful to tune the pore structure of the activated carbons in terms of ions adsorption and transportation. The activated carbon prepared by heat treatment at 600 °C and CO 2 activation at 750 °C, named as AC-600-750, has the highest specific surface area of 1162 m2 g−1 and a specific capacitance of 247.4 F g−1 at 50 mV−1, with a Cu2+ adsorption capacity of 77.8 mg g−1 at 1.2 V in 50 mg L−1 CuCl 2 solution that is much higher than that of the commercial activated carbon. The electrosorption of Cu2+ ions over activated carbon follows a monolayer adsorption scheme, of which the kinetic can be well explained by pseudo-first-order kinetic model. The resin-based activated carbons are of potential as an electrode material for efficient removal of heavy metal from contaminated water by CDI process. Image 1 • Activated carbon from cation-exchange resin was prepared by ion exchange with ZnCl 2. • Activated carbon showed high Cu2+ adsorption capacity of 77.8 mg g−1 by CDI process. • The electrosorption of Cu2+ followed pseudo-first order kinetic and Langmuir model. [ABSTRACT FROM AUTHOR]

Conversion of carbon-containing biomass into useful carbon products is highly demanded. A rising understanding of environmental problems explains the growing focus on evaluating bioproducts and wastes in numerous applications. Herein, the wheat husks derived activated carbon (WHAC) was employed as electrode material for supercapacitors' energy storage. Three samples of activated carbon were made using wheat husks, which were activated at different temperatures. The prepared electrodes were characterized and electrochemically tested using Fourier-transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscope, cyclic voltammetry, galvanostatic charge-discharge, and electrical impedance spectroscopy. The maximum capacitance (271.5 F g−1 at a current density of 0.5 A g−1) was observed for AC-800, activated at 800 °C. The electrochemical impedance showed low resistance (3.659 Ω) and low-frequency response (6.84 s). The AC-800 electrode exhibited the capacitance retention of 82% after 5000 cycles. The excellent electrochemical properties reveal the utilization of biomass waste as a potential electrode material for supercapacitors. The process used is simple, environmentally friendly, and could significantly reduce the county's biomass wastes from wheat husks. The approach can not only reduce environmental pollution but develop porous carbon electrodes for energy storage devices. Image 1 • The wheat husks derived activated carbon was prepared on Ni foam substrate. • The activated carbon was chemically activated by impregnating KOH. • The optimum activation temperature was found to be 800 °C. • The electrode showed a high specific capacitance of 271.5 F/g. • The electrode exhibited high energy, power density and cyclic stability. [ABSTRACT FROM AUTHOR]

Pb2+ adsorption onto activated carbon was studied as a function of the different liquid medium during batch adsorption process without shaking/agitation of flasks (where adsorbate and adsorbent coexist). As liquid medium deionized water (DW) enhanced with gases bulk nanobubbles (bNBs) was used. The adsorbent material used was activated carbon from potato peels. The maximum Pb2+ adsorption capacity (Q m) was 9 mg/g in the case of adsorption process in DW without agitation, whereas the respective Q m was 94 mg/g by using DW-bNBs as medium without agitation. It was also found that Q m increased to 171 mg/g in the adsorption process with DW-bNBs and agitation (150 rpm). This finding was the start point of a new experimental design where after re-agitation (intense shaking of 225 rpm) of the respective experimental case (94 mg/g), the final Q m was 163 mg/g i.e. very close to the one corresponding to simultaneous adsorption and agitation from the beginning. The results are analyzed and discussed intensively to lead in several important implications on the influence of bNBs to the bulk solute mass transfer. Based on our experimental equilibrium data a modified-Langmuir equation was developed, applied and proposed so as to better simulate the whole (complicated) process. [ABSTRACT FROM AUTHOR]

• Adding low dose carbon materials can inhibit bromate formation in O 3 /PMS process. • The inhibition of bromate formation by three carbon materials is: GO > CNT > PAC. • Carbon materials can reduce HOBr/OBr− to form Br− and block bromate formation. • Formation of bromate in O 3 /PMS/carbon material was further reduced in actual water. Ozone/peroxymonosulfate (O 3 /PMS), firstly proposed by our group, is an efficient advanced oxidation process for the degradation of organic pollutants. However, the elevation of bromate formation was the main problem in the treatment of bromide-containing water. In this work, adding low dosage of powdered activated carbon (PAC), carbon nanotube (CNT) and graphene oxide (GO) in the inhibition of bromate formation and the enhanced degradation of organic pollutants during the O 3 /PMS process were firstly investigated. As 10 mg/L of PAC, CNT and GO were added, the bromate conversion efficiency (25.1%) was decreased to 15.9%, 14.1%, and 8.8% at pH = 7.0, 50 μM PMS addition and 1.135 mg min−1 ozone injection after 25 min reaction. It is shown that the carbon materials played a crucial role in reducing intermediate products (HOBr/OBr−) in the reaction, thereby blocked the bromate formation. This may be due to the defects such as vacancies and zigzag/armchair-like edges on the graphene boundary, which were reported as active sites for oxygen reduction reaction. Meanwhile, the addition of three carbon materials would also promote the degradation of oxalic acid and para -chlorobenzoic acid, and the effect of GO was better than the other two. According to the release of TOC in the reaction, the stability of GO was obviously stronger than that of PAC and CNT, which was attributed to that GO had a relatively stable lamellar structure. Finally, compared with the deionized water, the water matrices that would trap free radicals in actual water samples can significantly inhibit the bromate formation. Therefore, adding low dosage of carbon materials is an effective way to control the bromate formation and promote the degradation of organic pollutants in the O 3 /PMS process. [ABSTRACT FROM AUTHOR]

We developed a continuous-flow three-dimensional electrode reactor (3DER) to remove ibuprofen (IBP) from water. The effects of the operating parameters on the 3DER performance were investigated. The 3DER was constructed by filling a conventional two-dimensional electrode reactor with granular activated carbon, which acted as particle electrodes. The IBP removal efficiency of the 3DER was 98% in 4 h, which was 2.5 times higher than the removal efficiency for the two-dimensional electrode reactor. IBP removal kinetics tests indicated that the current density (1–20 mA/cm2) correlated better than the other operating parameters with the first-order rate constant (k). The flow rate affected the IBP removal kinetics to a small degree. Chloride and sulfate supporting electrolyte concentrations between 17 and 100 mM affected the IBP removal kinetics in opposite ways. Increasing the chloride concentration increased k, but increasing the sulfate concentration decreased k. Radical quenching experiments indicated that much more IBP degradation occurred through both indirect and direct oxidation mechanisms in the 3DER than in the two-dimensional electrode reactor. The particle electrodes caused hydroxyl radicals to form when the 3DER treatment was started, but the particle electrodes later acted as third electrodes and favored direct oxidation of IBP. Image 1 • A continuous-flow 3DER was developed for treating ibuprofen (IBP). • Current density had the greatest influence on the IBP removal rate. • 3DER enhanced both indirect and direct oxidation of IBP compared to 2DER. • Direct oxidation of IBP became dominant as 3DER operation proceeded. [ABSTRACT FROM AUTHOR]

• The microscale hybrid fuel cells for NO 3 − separation and hydrogenation are reported. • Microscale fuel cell comprises carbon-made capacitive and Pt-Cu faradaic electrodes. • Oxygen reduction reaction induces adsorption of NO 3 − ions by carbon. • Hydrogen oxidation reaction induces desorption of NO 3 − ions from carbon. • Released NO 3 − ions are simultaneously reduced by the H 2 gas on Pt-Cu catalyst. A new electrochemical process is proposed for a zero-discharge removal of nitrate ions from water. The process utilizes micro-scale capacitive-faradaic fuel cells (CFFC) made of activated carbon particles loaded with a Pt-Cu catalyst capable of oxygen reduction, hydrogen oxidation and nitrate hydrogenation reactions. Every CFFC comprises capacitive activated carbon electrode and faradaic Pt electrode. Oxygen reduction on Pt results in electrons' deficiency in activated carbon which is equilibrated by an adsorption of nitrate ions from the treated water. Once the CFFCs are saturated with NO 3 − they must be regenerated. To repel NO 3 − ions into the regenerant solution the dissolved H 2 is oxidized on Pt electrode of the CFFC. The accumulation of electrons in capacitive activated carbon electrode results in release of NO 3 − ions. Simultaneously the nitrate ions are reduced by the H 2 gas on the Pt-Cu catalyst of the CFFC. Operation of CFFCs with 5%Pt-1%Cu catalyst resulted in highly effective separation and hydrogenation of nitrate ions into the N 2 gas and ammonia. The adsorption density for nitrate ions was 0.175 meq/g_carbon. Selectivity for N 2 gas was ≈ 55%. Further studies are required to decrease costs of CFFCs and to increase the N 2 selectivity of the hydrogenation step. [ABSTRACT FROM AUTHOR]

The impurities of coal plague its values not only for fuels but also for preparing functional carbon materials. Herein, we aim to develop a clean and one-step strategy to prepare activated carbon by molten salt leaching and electrolysis approach to converting anthracite/lignite to carbon for electrochemical supercapacitors. First, the major impurities such as silica and alumina were removed by a combined molten salt and water leaching process without using any toxic acid or alkaline solutions. Meanwhile, the carbonization and activation of coals take place together in the water- and oxygen-free molten salt medium. Moreover, the electrolysis can further increase the specific capacitance of the coal-derived carbon by the electrochemical regulation of carbon in molten salt using a low-cost and oxygen-evolution inert anode. The as-obtained carbon delivers a capacitance of 190 F g−1 at 5 A g−1 and shows nearly no capacitance loss after 10,000 cycles. This paper provides a clean molten salt approach to utilizing both high-rank and low-rank coals for the preparation of capacitive carbons. • Al 2 O 3 and SiO 2 in the coal can be removed by molten carbonate leaching. • The coal-derived carbon was regulated at the cathode in molten carbonate. • The coal-derived carbon delivered a specific capacitance of 190 F g−1 at 5 A g−1. • Both anthracite and lignite can be converted to capacitive carbon in molten salt. [ABSTRACT FROM AUTHOR]

• CDI was applied for nitrate removal from synthetic domestic wastewater. • Concentrated nitrate stream was obtained during CDI regeneration. • CDI operational parameters were investigated. • Effect of PVDF on AC electrode was estimated. Capacitive deionization (CDI), an emerging technology, has attracted attention recently and has been applied for various purposes. Herein, we investigated the application of a CDI system using activated carbon (AC) electrodes for nitrate removal and recovery in the scope of domestic wastewater treatment. The electrochemical behavior and structural parameters of AC electrodes were investigated as a part of this work. CDI electrodes were fabricated from microporous activated carbon, and the specific surface area of the electrode material was 210 m2/g. The negative effect of polymeric binder on the AC electrodes performance was observed as well. The specific capacitance of the fabricated AC electrodes at 40 mV/s scan rate was 0.5 F/g and 19 F/g for 1 and 1000 mM electrolyte (NH 4 NO 3), respectively. The CDI performance was examined as a function of flow rate (2, 4, 9, 14 mL/min), applied voltage (0.6, 0.8, 1.0, 1.2 V), and initial nitrate concentration (10, 25, 50, 70 mg/L) in single-pass (SP) mode. Regeneration performance and recovery efficiency of the CDI cell were observed during 5 subsequent operational cycles. The recovery efficiency of nitrate ions from low salinity water was 21%, while the electrosorption capacity of 5.5 mg/g and removal efficiency of 48% was achieved. Presence of the competitive ions in the tested solution resulted in a slight decrease (~10%) of nitrate removal efficiency. [ABSTRACT FROM AUTHOR]