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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]

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 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 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]

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]

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]

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]

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]

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]

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]

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]