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The present study manufactured and utilized the chitosan-coated fumed silica composite (CS@silica) for simultaneous adsorption of rare earth elements (REEs) of Ce(III), La(III), and Nd(III) cations in an aqueous solution. The CS@silica composite underwent characterization using a CHNOS analyzer, Brunauer-Emmett-Teller (BET) surface area analyzer, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrophotometer, scanning electron microscope coupled with energy-dispersive X-ray (SEM-EDX) spectrophotometer, and X-ray diffraction (XRD) analyzer. The findings indicated that the CS@silica composite exhibited a lack of pores and possessed a specific surface area of 1.27 m2/g. Additionally, it was observed that the composite contained a significant amount of oxygen and nitrogen atoms, which serve as the active sites for the adsorption of REEs. The maximum adsorption capacities of Ce(III), La(III), and Nd(III) cations were determined under optimal experimental conditions. These parameters included a pH of 4, an adsorbent dose of 0.01 g, and an equilibrium duration of 20 min. The maximum adsorption capacities for Ce(III), La(III), and Nd(III) cations were found to be 341, 241, and 299 mg/g, respectively. The adsorption kinetics followed the pseudo-second-order kinetic model. The desorption percentage of REEs-loaded CS@silica composite was significantly low when exposed to deionized water and hydrochloric acid (0.01 and 0.02 M). This suggests that there is a chemical interaction between the REEs and the active site on the surface of the composite. The predominant adsorption process proposed was complexation, with ion exchange and electrostatic contact playing a minor role. The CS@silica composite is highly promising for the recovery of REEs because of its rapid adsorption and high adsorption capacities. [ABSTRACT FROM AUTHOR]

[Display omitted] The utilization of Na 2 MnSiO 4 as a Faraday electrode in hybrid capacitive deionization (HCDI) is investigated to achieve efficient desalination. The Na 2 MnSiO 4 /C (NMSO) materials were fabricated via a simple sol–gel method, in which the synthesis process was modulated by adjusting the volume ratio of ethanol to water. When maintaining the volume ratio of water to ethanol at 3:1, the resultant NMSO-3/1 exhibited expected salt adsorption capacity of 31.06 mg g−1 and salt adsorption rate of 20.43 mg g−1 min−1. This distinguished desalination performance was mainly attributed to its inherent multiple redox pairs, as well as the integration of ethanol, which enhanced both specific capacitance and hydrophilicity of the material. This study opens a new perspective for the development of highly efficient materials in HCDI. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient CuHCF/C electrode was prepared for Cu2+ removal by CDI. • CuHCF/C achieved high Cu2+ adsorption capacity of 134.47 mg g−1 at low applied voltage of 0.8 V. • CuHCF/C manifested excellent Cu2+ selectivity in multi-ion coexisting solution. • The mechanism of removing Cu2+ by Faradaic pseudocapacitance was explained. The efficient capture of copper ions (Cu2+) in wastewater has dual significance in pollution control and resource recovery. Prussian blue analog (PBA)-based pseudocapacitive materials with open frameworks and abundant metal sites have attracted considerable attention as capacitive deionization (CDI) electrodes for copper removal. In this study, the efficiency of copper hexacyanoferrate (CuHCF) as CDI electrode for Cu2+ treating was evaluated for the first time upon the successful synthesis of copper hexacyanoferrate/carbon sheet combination (CuHCF/C) by introducing carbon sheet as conductive substrate. CuHCF/C exhibited significant pseudocapacitance and high specific capacitance (52.92 F g−1) through the intercalation, deintercalation, and coupling of Cu+/Cu2+ and Fe2+/Fe3+ redox pairs. At 0.8 an applied voltage and CuSO 4 feed liquid concentration of 100 mg L−1, the salt adsorption capacity was 134.47 mg g−1 higher than those of most reported electrodes. Moreover, CuHCF/C demonstrated excellent Cu2+ selectivity in multi-ion coexisting solutions and in actual wastewater experiments. Density functional theory (DFT) calculations were employed to elucidate the mechanism. This study not only reveals the essence of Cu2+ deionization by PBAs pseudocapacitance with promising potential applications but also provides a new strategy for selecting efficient CDI electrodes for Cu2+ removal. [ABSTRACT FROM AUTHOR]

A commercial carbon cloth (CC) was oxidized by HNO3 acid and the features of the plain and oxidized CC were evaluated. The results of characterization illustrated that HNO3 oxidization duplicated the oxygen-containing functional groups and the surface area of the CC. The adsorption performance of the plain and oxidized CC (Oxi-CC) toward benzotriazole (BTR) was compared. The results disclosed that the uptake of BTR by oxidized CC was greater than the plain CC. Thence, the affinity of oxidized CC toward BTR was assessed at different conditions. It was found that the adsorption was quick, occurred at pH 9 and improved by adding NaCl or CaCl2 to the BTR solution. The kinetic and isotherm studies revealed that the surface of Oxi-CC is heterogeneous and the adsorption of BTR follows a physical process and forms multilayer over the Oxi-CC surface. The regenerability and reusability study illustrated that only deionized water can completely regenerate the Oxi-CC and that the Oxi-CC can be reused for five cycles without any loss of performance. The high maximum adsorption capacity of Dubinin–Radushkevich isotherm model (252 mg/g), ease of separation and regeneration, and maintaining the adsorption capacity for several cycles revealed the high efficiency and economical and environmental feasibility of Oxi-CC as an adsorbent for BTR. [ABSTRACT FROM AUTHOR]

The scarcity of freshwater has attracted the attention of countries around the world. Capacitive deionization (CDI) is a burgeoning green desalination technology with low price and high efficiency. The properties of the CDI electrodes directly affect the deionization efficiency. It is a hot spot of CDI technology research to develop electrode materials with higher adsorption capacity, better sustainability and lower cost. On this purpose, porous carbon materials derived from corncobs, cornstalks and waste cigarette butts have been firstly used as electrodes for CDI desalination in this paper. Eight derived materials have been successfully prepared through carbonization and activation. The morphology characteristics and electrochemical performance of the materials have been examined. Their desalination performance has been investigated. The results show corncobs activated at 800°C (CBC-800) have the best properties with a specific surface area of 1,201.9 m²·g-1 and pore size of 1.7268 nm. The CBC-800 electrode also possesses a high specific capacitance of 141.4 F·g-1 and low inner resistance. The salt adsorption capacity is 19.2 mg·g-1 and the charge efficiency is 60.3% in a 3,000 mg·L-1 NaCl solution at 1.2 V. CBC-800 is expected to be an efficient electrode material for CDI applications. [ABSTRACT FROM AUTHOR]

The current study evaluated the use of pumice, a volcanic mineral and common sand, in treating reverse osmosis membrane reject water (ROR) using a novel combined adsorption distillation (CAD) method. The CAD method is developed to separate the dissolved solids through adsorption distillation, i.e., leaving the vaporized distillate as freshwater and concentrated brine. The adsorption potential of pumice and sand was investigated at different adsorbent doses, i.e., 2, 5, and 10 g, and consecutive CAD adsorbent backwashing cycles. The improved results were achieved at a 10 g pumice dose. However, its adsorption efficiency declined in longer CAD cycles, i.e., due to the separated deposition of solids. After backwashing, the adsorbed and accumulated salts were slightly removed, and pumice adsorption capacity was maintained for up to 20 cycles of CAD. The properties of the pumice, i.e., before and after five CAD cycles and after backwashing, were characterized with scanning electron microscopic (SEM), elemental disruptive spectroscopy (EDS), and X-ray diffraction (XRD), which revealed that the porous structure of the pumice was completely accumulated with deposits of ionic salts, which were slightly washed away after backwashing, but accumulation remained continued in post-CAD cycles. The explored method revealed a high potential of pumice in water filtration. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks with RHO, qtz and ANA topologies were synthesized at room temperature under aqueous conditions. An excess of unreacted ligand acted as a structure directing agent to nucleate the porous RHO framework. [Display omitted] Here we report the synthesis of a zeolitic imidazolate framework with RHO topology (RHO-Zn(eim) 2 ; eim is the deprotonated anion of 2-ethylimidazole (Heim)) in the aqueous phase. Zn(eim) 2 crystals were prepared by the reaction between Heim and zinc acetate in deionized water. The products prepared at relatively high Heim/Zn molar ratios were Zn(eim) 2 whose structure assigned to RHO, qtz and ANA topologies. Zn(eim) 2 obtained under static condition had porous RHO structure, while under stirred condition, nonporous dense qtz and ANA structures were formed. This study revealed that the formation of RHO porous structure requires the template effect of excess Heim. The RHO-Zn(eim) 2 crystals possessed high surface area and micropore volume, whose morphology consisted of a rhombic dodecahedron. RHO-Zn(eim) 2 exhibited high adsorption capacity (4 mmol/g) for hexane and cyclohexane. Due to the hydrophobic nature of RHO-Zn(eim) 2 , water vapor was hardly adsorbed. Although RHO-Zn(eim) 2 was stable in the presence of water vapor, it became nonporous upon hydrolysis in aqueous solution. In contrast, partial carbonization of topmost surface improved the structural stability against hydrolysis by water, while maintaining the adsorption capacity and increasing the adsorption rate. [ABSTRACT FROM AUTHOR]

Birnessite has been widely used for electrochemical removal of heavy metals due to its high pseudocapacitance. Incorporation of carbon-based materials into birnessite can enhance its conductivity and stability, and synergistically improve the electrochemical adsorption capacity due to the double-layer capacitor reaction derived from carbon-based materials. In this study, biochar was successfully incorporated with birnessite at various ratios to synthesize composites (BC-Mn) for effective electrochemical removal of cadmium (Cd(II)) from water. The effects of cell voltage, initial pH, and recycling performance of BC-Mn were evaluated. As a result, the electrosorption capacity of BC-Mn for Cd(II) exhibited gradual increases with increasing birnessite content and reached equilibrium at a Mn content of 20% (BC-Mn20). The Cd(II) adsorption capacity of BC-Mn20 rose at higher cell voltage, and reached the maximum at 1.2 V. At pH 3.0–6.0, the electrosorption capacity initially rose until pH 5.0 and then approached equilibrium with a further increase in pH value. The Cd(II) electrochemical adsorption capacity of BC-Mn20 in the solution could reach 104.5 mg g−1 at pH 5.0 for 8 h at 1.2 V. Moreover, BC-Mn20 exhibited excellent reusability with a stability of 95.4% (99.7 mg g−1) after five cycles of reuse. Due to its superior heavy metal adsorption capacity and reusability, BC-Mn20 may have a promising prospect in the remediation of heavy metal polluted water. [ABSTRACT FROM AUTHOR]

The low capacity, poor rate capability and sluggish kinetics limit the practical application of carbonaceous materials. Heteroatom doping is an effective method to regulate the intrinsic property and improve electrochemical reactivity of carbon-based materials. Herein, we prepare N/O co-doped porous carbon nanofibers (N/O–PCNF) with large surface area and high heteroatom doping for sodium ion batteries. The excellent electrochemical performance of optimized N/O–PCNF sample is due to high diffusion coefficient and low charge transfer resistance during the sodiation/desodiation process. Kinetic analysis reveals that the capacitive behaviors play an important role in sodium storage performance of N/O–PCNF sample. Moreover, density functional theory calculations further demonstrate that N/O co-doping can promote the adsorption capacity of sodium ions, and provide theoretical guidance for the excellent sodium storage performance of the electrode. [ABSTRACT FROM AUTHOR]

• Structure evolution features of LDHs precursors with pH was investigated. • Role of pH on activating the performance of LDHs type adsorbents was concluded. • Precipitative formation mechanism of LDHs adsorbents was firstly proposed. Aluminum-based adsorbents, simply prepared by eluting the lithium-aluminum layered double hydroxide precursors with deionized water, is the only industrialized adsorbents for selectively separating Li+ from saline brines. Taking the roles of lattice and surface Li+ active sites on its performances into consideration, influence of ending pH modulating on prominently improving the adsorbing capacity and stability of aluminum-based adsorbents prepared by precipitation method is initially investigated. As experimentally evidenced that, the maximum desorption amount of Li+ at the eluting stage should be controlled to around 20 mg/g Li+ rather than thoroughly removed to effectively avoid the topotactic solid-phase transformation from adsorbent to α-Al(OH) 3. As-prepared adsorbents not only has high adsorption capacity up to 8.4 mg/g in 400 ppm LiCl solution, but also owns unique self-healing ability, thus promising the excellent cycling stability. It is firstly proposed that the formation of the layer-structured precursor by precipitation method is well in accordance with the three-step formation mechanism and pH modulating mainly contributes to the anions exchange between solution Cl- and interlayer OH–. This study experimentally proves the importance of pH adjusting for preparing high performance lithium adsorbents by precipitation method, which is very significant and important for effectively extracting lithium resources from the complicated multi-component liquid minerals. [ABSTRACT FROM AUTHOR]

• K 2 FeO 4 is first utilized for the solid-phase oxidation of pitch by a high-energy ball mill. • The solid-phase reaction mechanism involving in oxidation and condensation was revealed. • Advanced pitch-based porous carbon (H-CBPF) was prepared by a solid–liquid synergistic strategy. • The synergistic effect improves both the porous geometric configuration and O content of H-CBPF. • H-CBPF delivers an excellent salt adsorption capacity and a superior charge efficiency. To address limited desalination capacity and insufficient charge efficiency for carbon materials in capacitive deionization (CDI), a solid–liquid synergistic oxidation strategy of potassium pertechnetate (VI) for pitch was proposed to construct porous carbon with a reasonable pore structure and high reactive surface. On the one hand, K 2 FeO 4 is first utilized for the solid-phase oxidation (SPO) of pitch by a high-energy ball mill, introducing rich oxygen-containing groups such as ether bonds. Meanwhile, dehydro-condensation reactions occurred during SPO, resulting in the formation of the oxidized pitch with a high degree of condensation. Importantly, the pyrolysis yield of the oxidized pitch is as high as 46.9 % at 800 °C, almost twice that of the pristine pitch, meaning that the oxidized pitch with high polymer degree and rich C-O bridge bonds facilitates the carbon fixation and emission reduction during carbonization. On the other hand, the self-oxidation of K 2 FeO 4 in aqueous solution forms bifunctional activators (KOH and Fe(OH) 3) for the preparation of pitch-based porous carbon. Benefiting from the crosslinking structure of oxidized pitch and the multi-effective activation, the prepared porous carbon (H-CBPF) exhibits a robust layered stacking topology with a high surface area and oxygen content. Thereby, it can deliver an excellent salt adsorption capacity (SAC) of 22.1 mg g−1 with an average desalination rate of 1.89 mg g−1 min−1 and a high charge efficiency of 85 % at 1.2 V in 500 mg L-1 NaCl solution. This work opens up a green and economical route for the preparation of pitch-derived porous carbon for high-performance CDI. [ABSTRACT FROM AUTHOR]

In this work, a new strategy by in situ combining slag-based geopolymer microsphere (SGS) with dithiocarbamate (DTC) was employed to synthesize in situ the composite adsorbent of the SGS and DTC (SGS-DTC). The differences of material properties, performance, and mechanisms in adsorption and immobilization of toxic Cd(II) in water between the SGS and SGS-DTC were investigated. For the static adsorption, the adsorption rate of SGS-DTC(1.5h) was faster than that of SGS(6h); the Cd(II) adsorption capacity of the SGS-DTC (211.2 mg/g) was almost twice that of the SGS (116.7 mg/g), corresponding to the removal rate of the SGS-DTC (99.75%) was nearly twice that of the SGS (53.2%). For the dynamic adsorption, the adsorption capacity of the SGS-DTC is higher than that of the SGS in the Cd(II) solution prepared by the deionized water or the river water from Yongjiang, Nanning, Guangxi, China. The mechanism of the difference of the Cd(II) adsorption between SGS and SGS-DTC was analyzed in dept. [Display omitted] In this study, slag-based geopolymer microspheres (SGS) were combined with dithiocarbamate (DTC) to synthesize the composite adsorbent of SGS and DTC in situ (SGS-DTC). Synthesis was carried out with optimal dosages of 10 mL of EDA, 1.0 g of SGS, and 20 mL of CS 2. The differences in material properties, performance, and mechanisms in the adsorption and immobilization of toxic Cd(II) in water between SGS and SGS-DTC were investigated. SGS-DTC showed better adsorption performance than SGS, irrespective of adsorbent dosage, pH, original content, and contact duration. Although after the Cd(II) adsorption, the immobilization performance at a different pH was better in the SGS-DTC than in the SGS, the immobilization performance was unaffected by changes in the other factors. For static adsorption, the adsorption rate of SGS-DTC (1.5 h) was faster than that of SGS (6 h); the Cd(II) adsorption capacity of SGS-DTC (211.2 mg/g) was almost twice that of SGS (116.7 mg/g), and correspondingly, the removal rate of SGS-DTC (99.75%) was nearly twice that of SGS (53.2%). For dynamic adsorption, the adsorption capacity of SGS-DTC was 389.78 mg/g, which is considerably higher than that of SGS (293.38 mg/g) in the Cd(II) solution prepared with deionized water. Furthermore, the adsorption capacity of the SGS-DTC was 299.26 mg/g, which is significantly higher than that of SGS (150.03 mg/g) in the Cd(II) solution prepared by the river water from Yongjiang, Nanning, Guangxi, China. One reason is that DTC was able to activate Si-O-Si without adsorption performance within SGS, thereby improving its adsorption and purification properties significantly. The other reason is that, after anchoring DTC on SGS, the specific surface area varied from 34.05–146.47 m2/g, the morphology was smooth-leaf-like, the pore volume was 0.13–0.20 cm3/g, and the pore size in SGS, was 14.75–5.60 nm. The high potential of SGS-DTC in removing and immobilizing heavy metal materials in wastewater is demonstrated in the results. [ABSTRACT FROM AUTHOR]

Recently, the rational design and development of efficient faradaic deionization electrodes with high theoretical capacitance, natural abundance, and attractive conductivity have shown great promise for outstanding capacitive deionization (CDI)‐based desalination applications. Herein, the construction of novel FeOOH hybrid heterostructures with Na and Cl dopants (e.g., Na‐FeOOH and Cl‐FeOOH) via a robust hydrothermal strategy is reported, and an asymmetric CDI cell (Na‐FeOOH//Cl‐FeOOH) comprising Na‐FeOOH and Cl‐FeOOH working as the cathode and anode, respectively, is assembled. The multiple coupling effects of the specific structural features (e.g., enriched porosity, hierarchical pore alignment, and highly open crystalline framework), enhanced electrochemical conductivity, and optimized ion‐transfer property endow the FeOOH hybrid electrode with improved electrochemical performance. Impressively, the Na‐FeOOH//Cl‐FeOOH cell demonstrates a superior salt adsorption capacity (SACNaCl) of 35.12 mg g−1 in a 500 mg L−1 NaCl solution, a faster removal rate, and remarkable cycling stability. Moreover, the pseudocapacitive removal mechanism from the synergetic contribution of the Na‐FeOOH cathode and Cl‐FeOOH anode account for the significant desalination promotion of the Na‐FeOOH//Cl‐FeOOH cell. [ABSTRACT FROM AUTHOR]

• A novel capacitive deionization with a three-phase architecture (T-CDI) was proposed. • Cathodic oxygen reduction was enhanced in T-CDI without affecting desalination. • SAC value and H 2 O 2 generation were 14.91 mg/g and 25.55 mg/L, respectively. • Simultaneous desalination and organics control was achieved by T-CDI/UV. • Applicability of T-CDI in long-term operation was investigated. Cathodic oxygen reduction, as a Faradaic side reaction, has been proven to be thermodynamically favorable for H 2 O 2 generation in capacitive deionization (CDI), which may provide a greener manner for organics control alongside desalination. However, the low levels of dissolved oxygen (DO) in saline water and its potential Faradaic degradation of carbon-based electrodes limit the H 2 O 2 generation in the conventional CDI (C-CDI). Herein, a novel three-phase CDI architecture (T-CDI) was proposed to simultaneously achieve stable desalination and supplementary H 2 O 2 generation. Unlike C-CDI architecture, T-CDI was open-ended at the cathode side, where porous nickel foam was used as current collector and air diffusion layer. Accordingly, a stable gas–liquid-solid three-phase interface was created inside the cathode, thus enhancing the diffusion and utilization of atmospheric air and preventing the damaging effects of excessive DO on the electrode. A stable electrosorption and electrocatalysis performance for T-CDI was obtained by regulating electrode hydrophilic-hydrophobic properties, comparing with other CDI configurations, and altering operating conditions. The salt adsorption capacity and H 2 O 2 accumulative concentration were 14.91 mg/g and 25.55 mg/L, respectively. Furthermore, the simultaneous desalination and organics control in T-CDI were investigated with the assistance of UV irradiation (T-CDI/UV). When treating NaCl and sulfamethazine (SMR) mixture solution, T-CDI/UV significantly reduced the irreversible electrode organic fouling and improved the desalination stability. Additionally, the potentially hazardous SMR was effectively removed alongside desalination. Finally, the long-term operation of T-CDI demonstrated that the generated H 2 O 2 cannot induce an additional substantial deterioration in desalination stability. The techno-economic assessment showed T-CDI was economically competitive compared with C-CDI. This study provides insights into the synergy of non-Faradaic and Faradaic processes and further diversifies the application of CDI in water treatment. [ABSTRACT FROM AUTHOR]

Efficient recovery of rare scattered metal Re(VII) from various resources is a prerequisite due to its important application. Herein, a type of novel nanofibrous membrane, 0.4P(Ph-3MVIm-Br)-3PVP/2TPU, is successfully prepared by electrospinning, where poly(ionic liquid) P(Ph-3MVIm-Br) is incorporated and could supply more adsorption sites. Meanwhile, PVP (polyvinyl pyrrolidone) and TPU (thermoplastic polyurethane) ensured the water flux and the structural stability of the membrane. The nanofibrous membrane exhibited a high adsorption capacity for ReO 4 −, which can reach 128 mg g−1 at pH 5. Its water flux is as high as 433 L m−2 h−1 at 0.4 g of poly(ionic liquid) addition, membrane thickness of 20 μm, and pressure of 1 bar. Furthermore, 0.4P(Ph-3MVIm-Br)-3PVP/2TPU nanofibrous membrane can remove 91.7% of ReO 4 − within 30 min. After 9 times recycling, the adsorption efficiency of the membrane can still maintain more than 90%. Dynamic ReO 4 − removal with 0.4P(Ph-3MVIm-Br)-3PVP/2TPU after one cycle was accomplished with a breakthrough volume of 24 mL ReO 4 − solution (feed 10 mg L−1, 100 mg membrane). The exchange of ReO 4 − and Br− of poly(ionic liquid) mostly promote the adsorption of ReO 4 −. Moreover, the structure of the membrane has excellent selectivity, mechanical performance, strong acid and alkali resistance stability, which endow the membrane easy to operate in practical applications. [Display omitted] • Nanofibrous membrane can remove 91.7 % of ReO 4 − within 30 min. • It has a great adsorption capacity of 128 mg g−1 for ReO 4 − at pH 5. • It has a good selectivity for ReO 4 − in the presence of SO 4 2− or NO 3 −. • It unfolds prominent regeneration ability after nine consecutive cycles. • It can achieve a water flux of 433 L m−2 h−1. [ABSTRACT FROM AUTHOR]

The zirconium-based MOF/graphene oxide (UiO-66-NH2/GO) composites were prepared by ultrasonic dispersing different amounts of graphene oxide (GO) in a well-dissolved zirconium tetrachloride/H2BDC-NH2 mixture, obtaining 2 wt% (UiO-66-NH2/GO-1), 5 wt% (UiO-66-NH2/GO-2), and 10 wt% (UiO-66-NH2/GO-3) GO composites. The products were characterized by XRD, FTIR, SEM, BET, Raman, UV, XPS, and Zeta potential. Adsorption experiments on simulated Eriochrome Black T (EBT) printing and dyeing wastewater were carried out using UiO-66-NH2/GO, and the optimal conditions for adsorption were obtained by exploring the effects of initial EBT concentration, time, pH, and salt ionic strength. Adsorption isotherms, kinetics, mechanism, and regeneration were also researched. The adsorption behavior was consistent with the Langmuir isotherm and fully compliant with pseudo secondary dynamics model. The adsorption capacity of UiO-66-NH2/GO-2 was found to be the highest of the three products, which was 263.158 mg/g. Therefore, the UiO-66-NH2/GO-2 composite was considered to be an excellent adsorbent for the adsorption of EBT from organic dye wastewater. [ABSTRACT FROM AUTHOR]

Membrane capacitive deionization (MCDI) is a modification of capacitive deionization (CDI) using ion-exchange membranes (IEM) in front of the electrodes. Electrode properties, especially the specific surface area, are known to be strongly related with desalination performance in CDI, but the effects of other properties in MCDI are not fully understood. The objective of this study was to investigate the effect of hydrophilicity in activated carbon electrodes on desalination performance in MCDI. Two types of activated carbon (P60 and YS-2) whose specific surface areas were similar were used as electrode materials, but they had different hydrophilicity (i.e., P60 was originally hydrophobic and YS-2 was relatively hydrophilic due to its nitrogen-containing surface chemistry). These hydrophilic electrodes (either the electrode itself or modified with polydopamine (PDA)) led to an increase in the salt adsorption capacity (SAC) in MCDI because they facilitated the access of both ions and water molecules into the electrode pores. In particular, the SAC of the P60 electrode displayed a large increase to almost reach that of the YS-2 electrode due to the improved hydrophilicity with PDA modification and the insignificant effects of PDA modification on an already hydrophilic YS-2 electrode. Additionally, PDA-modified IEM in MCDI reduced the SAC as a result of the additional insulating PDA layer with little changes in hydrophilicity. [ABSTRACT FROM AUTHOR]

Cathode materials with high capacity and cyclic durability are urgently needed for capacitive deionization. Na 3 V 2 (PO 4) 3 is an emerging pseudocapacitive candidate for this process on account of its high capacity and Na+ reversible insertion, while it suffers from the intrinsic low electrical conductivity and small electrolyte-accessible surface area. Herein, a sea urchin-like Na 3 V 2 (PO 4) 3 @carbon (NVP@C) compound material was synthesized from MXene-V 2 C via hydrothermal method followed by annealing treatment, and then assembled as capacitive deionization (CDI) electrode material. Benefiting from three-dimensional sea urchin-like structure, where the nanoneedles of NVP@C serve as fast transport channel for Na+, NVP@C performed high specific capacity (437 F g−1 at 5 mV s−1) and fast ionic diffusion kinetics. Moreover, the NVP@C showed attractive desalination performance as cathode material for CDI, achieving a remarkable adsorption capacity of 74.0 mg g−1 in a NaCl salt solution (1000 mg L−1) and long life cycle stability. The present work provides a novel perspective to construct practical redox-active and stable CDI electrode with 3D structure from MXene for highly capacitive and durable desalination application. [Display omitted] • An urchin-like NVP@C derived from V 2 C MXene was used for capacitive deionization. • The NVP@C showed superior electrochemical performance with high capacity of 437 F g−1. • The NVP@C exhibited an outstanding salt (Na+) adsorption capacity of 74.0 mg g−1. • The unique structure provides fast ion transfer channels and ensures the stability. [ABSTRACT FROM AUTHOR]

Heteroatom doping, involving the introduction of atoms with distinct electronegativity into carbon materials, has emerged as an effective approach to optimize their charge distribution. In this study, we designed a strategy to synthesize in-situ Mn, N co-doped carbon nanospheres (Mn-NC) through the polycondensation of 2,6-diaminopyridine and formaldehyde in synchronization with Mn2+ chelation to form Mn-polytriazine precursor, followed by calcination to form carbonaceous solid. Then Mn-NC was fabricated into a capacitive deionization (CDI) electrode for the selective removal of uranium ions (U (VI)), which is commonly found in radioactive water. Interestingly, Mn-NC exhibited good selectivity for UO 2 2+ capture with a demonstrated adsorption capacity of approximately 194 mg/g @1.8 V. The systematic analysis of the adsorption mechanism of UO 2 2+ revealed that N dopants within Mn-NC can coordinate with the U (VI) ions, thereby facilitating the removal process. Our study presents a straightforward and convenient strategy for removing UO 2 2+ ions by harnessing the coordination effect, eliminating the requirement for pore size control. [Display omitted] • Trace Mn in N doped carbon can boost charge density and adsorption energy. • Mn–N–C adsorbs UO 2 2+ ions by coordination interaction with high selectivity. • This material has a good adsorption capacity of 194 mg/g @1.8 V. [ABSTRACT FROM AUTHOR]

Bioelectrochemical system is a prospective strategy in organic-contaminated groundwater treatment, while few studies clearly distinguish the mechanisms of adsorption or biodegradation in this process, especially when dense biofilm is formed. This study employed a single chamber microbial electrolysis cell (MEC) with two three-dimensional electrodes for removing a typical organic contaminant, 2,4-dichlorophenol (DCP) from groundwater, which inoculated with anaerobic bacteria derived from sewage treatment plant. Compared with the single biodegradation system without electrodes, the three-dimensional electrodes with a high surface enabled an increase of alpha diversity of the microbial community (increased by 52.6% in Shannon index), and provided adaptive ecological niche for more bacteria. The application of weak voltage (0.6 V) furtherly optimized the microbial community structure, and promoted the aggregation of microorganisms with the formation of dense biofilm. Desorption experiment proved that the contaminants were removed from the groundwater mainly via adsorption by the biofilm rather than biodegradation, and compared with the reactor without electricity, the bioelectrochemical system increased the adsorption capacity from 50.0% to 74.5%. The aggregated bacteria on the surface of electrodes were mainly dominated by Delftia tsuruhatensis (85.0%), which could secrete extracellular polymers and has a high adsorption capacity (0.30 mg/g electrode material) for the contaminants. We found that a bioelectrochemical system with a three-dimensional electrode could stimulate the formation of dense biofilm and remove the organic contaminants as well as their possible more toxic degradation intermediates via adsorption. This study provides important guidance for applying bioelectrochemical system in groundwater or wastewater treatment. [Display omitted] • Bioelectrochemical system was used to treat chlorophenol-contaminated groundwater • External electricity led to the aggregated biofilm on three-dimensional electrode • The dense biofilm enhanced the adsorption of chlorophenols from 50% to 74.5% • The aggregations on electrode were dominated by Delftia tsuruhatensis (85%) • Delftia tsuruhatensis was enriched for the first time in bioelectrochemical system [ABSTRACT FROM AUTHOR]

With the continuous development of society, industrialization, and human activities have been producing more and more pollutants. Fluoride discharge is one of the main causes of water pollution. This review summarizes various commonly used and effective fluoride removal technologies, including ion exchange technology, electrochemical technology, coagulation technology, membrane treatment, and adsorption technology, and points out the outstanding advantages of adsorption technology. Various commonly used fluoride removal techniques as well as typical adsorbent materials have been discussed in published papers, however, the relationship between different adsorbent materials and adsorption models has rarely been explored, therefore, this paper categorizes and summarizes the various models involved in static adsorption, dynamic adsorption, and electrosorption fluoride removal processes, such as pseudo-first-order and pseudo-second-order kinetic models, Langmuir and Freundlich isotherm models, Thomas and Clark dynamic adsorption models, including the mathematical equations of the corresponding models and the significance of the models are also comprehensively summarized. Furthermore, this comprehensive discussion delves into the fundamental adsorption mechanisms, quantification of maximum adsorption capacity, evaluation of resistance to anion interference, and assessment of adsorption regeneration performance exhibited by diverse adsorption materials. The selection of the best adsorption model not only predicts the adsorption performance of the adsorbent but also provides a better description and understanding of the details of each part of the adsorption process, which facilitates the adjustment of experimental conditions to optimize the adsorption process. This review may provide some guidance for the development of more cost-effective adsorbent materials and adsorption processes in the future. [Display omitted] • Overview of commonly used effective fluoride removal technologies. • The various models involved in different fluoride removal modes by adsorption are classified and summarized. • Combining models to describe the adsorption process and mechanism of different materials. • The adsorption capacity, anion resistance, and adsorption regeneration performance of different materials are discussed. [ABSTRACT FROM AUTHOR]

• A system based on membrane rejection and electrochemical technique was developed. • MIL-101 endowed the mixed matrix membranes (MMMs) with phosphate adsorption capacity. • MMMs of capacitive deionization capacity was prepared with porous carbon cloth. • The conductive MMM performed both high selectivity and permeability. The great potential of ultrafiltration (UF) membranes for phosphate rejection has been challenged by the selectivity-permeability trade-off. Here, we propose a filtration system based on a novel dual-layer UF mixed matrix membrane (MMM) with a capacity for capacitive deionization (CDI), which was fabricated by incorporating NH 2 -MIL-101 into a polyethersulfone (PES) polymer matrix and the in-situ combination of carbon cloth (CC). The MMM exhibited an improved porosity of 85.52%, a declined water contact angle of 53.25°, and a 5.7% increase in water permeability in comparison to those of the PES membrane due to the hydrophilic and mesoporous NH 2 -MIL-101 particles. While incorporating the CC provided the non-conductive PES polymer with high electroconductivity. As an electrode, the CC/MMM exhibited a relatively high permeance of 424.63 L/h MPa m2, good antifouling performance, and remarkable phosphate rejection that reached 100% during the 2-h filtration period in the electrically-enhanced dead-end filtration cell. The removal capacity of the cell exceeded 22.51% and 74.0% for the energized CC/PES membrane and uncharged CC/MMM, respectively, due to the superior phosphate adsorption ability of NH 2 -MIL-101 and enhanced deionization capacity due to the electric field. UF MMM separation coupled with the electrochemical technique exhibited great potential to enhance the selective rejection of phosphate ions at low levels, while maintaining high membrane permeability and shortening the treatment time required by the CDI technique. [ABSTRACT FROM AUTHOR]

A polypyrrole/chitosan composite material was obtained by chemical polymerization. The adsorption performance of a hot-molded polypyrrole/chitosan composite electrode was tested by adsorption/desorption experiments. Scanning electron microscopy and Fourier-transform infrared spectroscopy both showed the deposition of polypyrrole on the chitosan surface. The specific capacitance of the polypyrrole/chitosan composite was determined by cyclic voltammetry in 1.0 M KCl at 0.01 V/s as 102.96 F/g. The adsorption/desorption experiments indicated that the specific adsorption capacity of the composite for Cu2+ was 99.67 mg/g, while the removal performance for other metal ions, such as Ag+, Pb2+, and Cd2+, was good. The results of multicycle adsorption/desorption tests showed that the adsorption rate of the polypyrrole/chitosan composite electrode for Cu2+ was decreased from 56.4 to 51.4% over 10 cycles, demonstrating the stable metal-ion adsorption/desorption behavior of the composite electrode. The obtained performances show that the prepared polypyrrole/chitosan composite material is an ideal electrode material for the removal of heavy metal ions. [ABSTRACT FROM AUTHOR]

Abstract Hexavalent chromium is highly toxic and elaborate technology is necessary for ensured removal during drinking water production. The present study aimed at estimating the potential of a micro-sized iron hydroxide (μGFH] adsorbent for chromate removal in competition to ions presents in drinking water. Freundlich and Langmuir models were applied to describe the adsorption behaviour. The results show a high dependency on the pH value with increasing adsorption for decreasing pH values. The adsorption capacity in deionized water (DI) at pH 7 was 5.8 mg/g Cr(VI) while it decreased to 1.9 mg/g Cr(VI) in Berlin drinking water (DW) at initial concentrations of 1.2 mg/L. Desorption experiments showed reversible adsorption indicating ion exchange and outer sphere complexes as main removal mechanisms. Competing ions present in DW were tested for interfering effects on chromate adsorption. Bicarbonate was identified as main inhibitor of chromate adsorption. Sulfate, silicate and phosphate also decreased chromate loadings, while calcium enhanced chromate adsorption. Adsorption kinetics were highly dependent on particle size and adsorbent dose. Adsorption equilibrium was reached after 60 min for particles smaller than 63 μm, while 240 min were required for particles from 125 μm to 300 μm. Adsorption kinetics in single solute systems could be modelled using the homogeneous surface diffusion model (HSDM) with a surface diffusion coefficient of 4∙10 −14 m2/s. Competitive adsorption could be modelled using simple equations dependent on time, adsorption capacity and concentrations only. Graphical abstract Image 1 Highlights • Micro-seized ferric hydroxide (μGFH) useful as adsorbent for chromate. • Decreased capacities in drinking water due to the competition by carbonate species. • Improved kinetics in contrast to conventional GFH due to small particle size. • Modelling of chromate adsorption onto μGFH with the homogeneous surface diffusion model in single solute systems. • Modelling of competitive adsorption using a model dependent only on time, adsorption capacity and concentrations. [ABSTRACT FROM AUTHOR]

The resin-activated carbon composite (RAC) electrodes were fabricated and applied in capacitive deionization for recovery of V(V) from complex vanadium solution. The adsorption capacity of the RAC electrode for V(V) is extremely low and the reduction of V(V) is significant in low pH solution, but the adsorbed V(V) on the electrode increases obviously and the reduction of V(V) gradually diminishes with the rise of pH. However, as the pH is increased to 10, the adsorbed V(V) on the RAC electrode declines. The higher applied potential is beneficial to the adsorption of V(V) and 1.0 V is appropriate for the adsorption. The impurities ions (Al, P and Si) are mainly adsorbed in the electric double layers on the RAC electrode and V(V) is dominantly adsorbed by the resins in the electrode. The adsorbed impurity ions can be easily removed by diluted H 2 SO 4 and V(V) can be effectively eluted by 10% NaOH solution. The vanadium-bearing eluent can be recycled to recover and enrich vanadium from the complex solution. The performance of the RAC electrode keeps stable during the cyclic operation. This study may provide a promising and novel method for the recovery and separation of metals from aqueous solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • Charging time plays a decisive role in CDI performance improvement. • UQ analysis quantitively provides guidance for CDI optimization. • The pore distribution and connectivity are highlighted. Capacitive deionization (CDI) is considered to be one of the most promising technologies to deionize water with low/medium concentration. Great attention has been paid to improve its performance by optimizing electrode architectures and operation conditions. However, no guidelines are built for developing such strategies due to the nonlinear impact of the parameters concerning electrodes and operations. Therefore, our work quantitatively reveals the influence of some key parameters involving electrode characteristics, operation conditions and ion properties using the statistical analysis based on uncertainty quantification. We find the porosity solely has a small influence on all the performance metrics. But the pore might play a significant role by the pore size distribution and connectivity that greatly determine the effective diffusion coefficient of salt ions. The high diffusion coefficient obviously raises the salt adsorption by facilitating ion transport, which also reduces the energy consumption while most of the consumed energy could even be recovered. The current exerts an opposite influence by shortening the charging period in the constant current (CC) mode. The salt concentration in the inflow water increases the adsorption capacity but decreases the removal efficiency. The decreased removal efficiency requires less external energy, enabling the usage of CDI as an economic pre-treatment unit. We highlight the ion transport resistance and its influence on CDI performance by acting upon charging time in the CC mode. We also suggest the application of the constant voltage mode to the low-salinity wastewater instead of the CC mode due to the high resistance. Our work addressed the importance of proper electrode and operation condition for high desalination performance and energy efficiency. [ABSTRACT FROM AUTHOR]

Polyethersulfone (PES) is a widely used polymer for ultrafiltration (UF) membrane fabrication. In the current study, carbide-derived carbon (CDC) oxidized by acid treatment was utilized as a filler to fabricate a novel PES composites UF membranes. The successful oxidation of CDC was validated from presence of oxygen containing functional groups and improved oxygen content, from 5.08 at.% for CDC to 26.22 at.% for oxidized CDC (OCDC). The OCDC PES UF membranes were prepared at different loadings of OCDC between 0.5 and 3.0 wt%. The membrane porosity, pore size and surface free energy found to be improved while a noticeable reduction in water contact angle was observed with OCDC loading implying the improved hydrophilicity of PES membranes. Consequently, the pure water flux found to improve from 151.6 to 569.6 (L/(m2. h)) for the 3.0 wt% modified OCDC membrane (M−3) which is 3.8 folds of the bare PES membrane. The antifouling characteristics were evaluated by humic acid (HA) filtration. The results revealed a significant enhancement in HA rejection with OCDC loading, the highest rejection was 96.8% for M−3 membrane. Additionally, the adsorption capacity of OCDC modified membranes found to decrease with OCDC loading indicating improved rejection of HA from the membrane surface. Moreover, M−3 demonstrated the maximum flux recovery ratio (FRR) of 92.3%. Reusability of the fabricated membranes was evaluated by deionized water/humic acid cycling filtration. The FRR was higher than 86.7% over three cycles of pure water/HA filtration for 140 min, indicated the excellent stability and reusability of the membranes. Overall, the OCDC was an effective filler for enhancing the PES UF membranes antifouling and permeability properties. [Display omitted] • Oxidized carbide-derived carbon (OCDC) was synthesized by acid treatment. • PES UF membrane porosity, contact angle and hydrophilicity were improved with OCDC addition. • Humic acid rejection and antifouling properties were improved with OCDC loading. • Long term filtration experiments of pure water and humic acid were considered. • The OCDC found to be an effective and compatible filler for PES UF membranes. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nitrogen-doped porous carbon is synthesized via a dual-salt template approach. • The carbon exhibits high ion adsorption capacity and ultrafast adsorption rate. • Ion adsorption proceeds via electrocapacitive and pseudocapacitive mechanisms. • The electrocapacitive mechanism plays a dominant role in the ion adsorption. Porous carbon materials hold tremendous potential for capacitive deionization (CDI). However, realizing high specific surface area (SSA), suitable pore size distribution, and hierarchical porosity in carbons with facile and sustainable techniques is still challenging. In this work, we prepare hierarchical porous carbons (HPCs) with high SSA, abundant pore structures, and N-self doping via a versatile and sustainable modified salt-template approach. The optimized electrode gives a high SSA of 1639.9 m2/g, a large pore volume (2.7 cm3/g), and hierarchical porous structures (micro-meso-macro pores). For applications, the symmetric CDI electrode assembly delivers a salt adsorption capacity (SAC) of up to 17.67 mg/g in a 500 mg/L NaCl at 1.2 V together with ultrafast salt adsorption kinetics. We systematically study their associated desalination mechanism by combining several electrochemical experiments with the in-situ Raman spectroscopy technique, which revealed that the total salt storage is from the synergistic effect of both electrical double-layer (EDL) storage and pseudocapacitive mechanisms, with the EDL storage being dominant. This work paves the way to design economical and eco-friendly porous carbon materials for high-performance CDI desalination. [ABSTRACT FROM AUTHOR]

Integration of membrane and nanomaterial is a forward-looking research orientation, which can effectively overcome the permeability-selectivity trade-off relationship and improve anti-fouling performance. However, the current combination methods usually suffer from defects due to the aggregation and embedding of nanomaterials, resulting in serious performance deterioration of membrane during continuous operation process. Herein, "graphdiyne-like" Tetrabromobisphenol A molecularly imprinted membranes with uniform and dense SiO 2 layer, namely TB-MIMs, are successfully prepared by delayed phase inversion method (DPIM). We found that the membrane prepared by DPIM exhibits both promoted pure water flux (405 L m−2 h−1) and enhanced adsorption capacity (83.476 mg g−1) by comparing with the membranes prepared by blending and grafting methods. The role of molecularly imprinting technique contributes to improving the selectivity of TB-MIMs toward TBBPA, leading to a high selectivity factor of 3.39, 3.27 and 3.05 for bisphenol A, paratert-butyl phenol and 4, 4'-dihydroxybiphenyl, respectively. Moreover, the flux of TB-MIMs is nearly recovered to an original level after washing the bovine serum albumin fouled membrane surface with deionized water. Notably, the TB-MIMs presents a high rejection rate for bovine serum albumin (94%), humic acid (92%) and alginic acid (91%) in natural water, indicating its bright actual application value. These superior performances highlight the advantage of DPIM strategy over traditional methods in terms of combination between membrane and nanomaterials. A "graphdiyne-like" molecularly imprinted membrane with high selectivity and lasting anti-fouling performance was first proposed and developed by delayed phase inversion method for selective recognition and separation of Tetrabromobisphenol A. [Display omitted] • A"graphdiyne-like" membrane was synthesized by delayed phase inversion method. • The SiO 2 sphere had a dense and uniform distribution on the membrane surface. • The TB-MIMs possessed a superior selectivity and water permeability. • A lasting anti-fouling stability was realized. [ABSTRACT FROM AUTHOR]

[Display omitted] • S-doped ultra-microporous wood carbon (SUMW) composite was prepared by one-step chemical activation. • We proposed E pzc -based ion-selective electro-adsorption mechanism. • The selective coefficient of SUMW electrode of NO 3 – over SO 4 2− was reached 32, • The adsorption capacity of the designed material reached up to 637 μmol/g. Capacitive deionization (CDI) technology is promising for selective removal of target ions from various sewages. However, the low electro-adsorption capacity and poor selectivity in the complex sewage system highly restrict its practical application. Potential of zero charge (E pzc) is the external circuit applied potential as the electrode material exhibiting no ion electro-adsorption from the electrolyte. Although E pzc shows a great prospect for regulating the electro-adsorption performance of the electrode, how to use it to achieve selective electro-sorption remains challenging. Herein, we demonstrate a Sulphur (S) doped ultra-microporous (∼0.7 nm) free-standing wood carbon electrode by one step chemical activation, which exhibits different E pzc values in nitrate or sulphate solution due to the unique S-doped ultra-microporous structure. Accordingly, a fantastic selectivity for NO 3 – over SO 4 2− (S N O 3 - / SO 4 2 - =32) was achieved as the applied voltage window ranges from 0.12 V (E pzc -NO 3 –) to 0.43 V (E pzc -SO 4 2−). In addition, the adsorption capacity of the designed material reached up to 637 μmol/g, which is much higher than the maximum value ever reported (∼200 μmol/g). 2000 mL Yellow River water was treated by our tandem CDI cell device through recycling charge and discharge ten times. As expected, the concentrations of NO 3 – ions in the Yellow River water were dramatically reduced from 152 mg/L to about ∼ 35 mg/L after treated with the tandem CDI cell device, which demonstrates the excellent practical application prospect. [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]

• The presence of coordinated water was beneficial for ion diffusion within CuHCF. • Chelators and Na+ in precursors reduced zeolitic and/or coordinated water in CuHCF. • Lower water content increased Na+ removal capacity but sacrificed stability. • CuII/CuI redox couple activation increases when controlling chelators in precursors. • Activation of reversible CuII/CuI redox couple contributed to BDI cycling stability. Prussian blue analogues are being explored as electrode materials for electrochemical desalination of saline water in battery-type electrode deionization systems and hybrid capacitive deionization systems due to their open framework crystal structure that provides selective adsorption of multiple cations, high theoretical sodium adsorption capacities, and low costs. However, poor electronic conductivity and instability (dissolution) prevents the use of these materials for long-term desalination applications. To understand how synthesis conditions might improve the properties of copper hexacyanoferrate (CuHCF) powders relative to sodium ion adsorption capacity and cycle life, the co-precipitation process was investigated using multiple common synthesis strategies that included addition of chelators and sodium salts as well as different concentrations and oxidation states of precursors. Smaller crystallite sizes (<35 nm) and lower structural water contents increased the initial sodium removal capacity to 53.2 mAh/g from 40.4 mAh/g (control), but also reduced cycling stability in long-term operation (20–55% retention over 100 cycles). The trade-off in stability is thought to be a consequence of structural water facilitating ion diffusion within the material. Adding chelators as precursors led to a highly reversible CuII/CuI redox couple that increased the stability of the FeIII/FeII redox couple in BDI cycling performance (79.4% retention over 100 cycles). [ABSTRACT FROM AUTHOR]

• A porous nanofiber membrane with dense distribution of La nanorods was prepared. • Exceptional high utilization ratio of La (0.98). • LPS was easily separated from solution. • The LPS can reduce total phosphorus to less than 10 μg/L in natural lake water. • Phosphate was effectively captured in a wide pH range of 4–10. As phosphate is one of the key causes of water eutrophication, its removal from aquatic ecosystems is essential. Adsorption methods have been widely used to remove phosphate from water bodies. However, most of the adsorbents are unstable and difficult to separate from solution. In this paper, we used a simple electrospinning method to prepare a new, well-dispersed, lanthanum (La)-based porous polyacrylonitrile nanofiber (LPS) with more active sites, which improve its phosphate removal efficiency. The maximum phosphate adsorption capacity on LPS was 218.5 mg P/g (La) (50.4 mg P/g). After complete adsorption, the P/La molar ratio on LPS was 0.98. After 48 h of oscillation, the leakage of La from LPS in deionized water was only 74 μg/L, effectively ruling out secondary pollution of the water-body. Moreover, unlike most adsorbents, LPS has the advantage that it can be readily isolated from water. After treatment with LPS, the total phosphorus (TP) of a water sample from Yangzonghai Lake (Yunnan, China) was reduced to 4.2 μg/L, a value lower than the concentration threshold of eutrophication (10 μg/L) set by the United States Environmental Protection Agency (USEPA) and the first category of the surface water environmental quality standard (10 μg/L) set by China for lakes and reservoirs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Developed a carbonized MIP-202/MXene (CMM) for selective electrosorption of U(VI). • MXene provides pseudocapacitance/intercalation effect and conductive base. • Two composite structures were observed during preparation of CMMs. • The CMM electrode exhibited excellent adsorption capacity and selectivity for U(Ⅵ). As the key element in the nuclear industry, uranium (U) has been widely concerned for its stable acquisition and efficient recycling. Capacitive deionization (CDI), which known as a seawater desalination technology, has shown great potential for uranium-adsorption. However, the poor selectivity restricts the application of CDI in uranium extraction. In this work, a carbonized MIP-202/MXene (CMM) composite was developed for highly efficient selective electrosorption of U(VI) from multi-ionic water. The uniformly decorated MIP-202 can prevent MXene from aggregation and provide rich pore structures, large specific surface area and additional nitrogen source for the efficient electrosorption of U(VI). With the addition of MXene nanosheets, a conductive network was introduced into the CMM and improved mechanical robustness of material to facilitate rapid charge transfer at the interface. As a result, the CMM electrode exhibited a maximum adsorption capacity of 582.46 mg g−1 calculated from Langmuir model and a removal ratio of 89.1% at 1.2 V in UO 2 2+ solution. The selectivity adsorption of CMM for UO 2 2+ can reach 92.3% when treated with multi-ionic solution. Besides, there is an interesting fact that the decreased ratio of added MXene can got a higher adsorption capacity, which may cause by the two composite structures formed when the mixing ratio changed. Overall, the excellent conductivity, high adsorption capacity and selectivity make CMM a promising electrode in CDI for efficient extraction of uranium from water. [ABSTRACT FROM AUTHOR]

A self-supported MoS 2 /CoS 2 @TiO 2 nanotube (TNT) hybrid electrode was fabricated by an in-situ hydrothermal process-assisted growth strategy, which achieved a significantly high gravimetric Na+ adsorption capacity and excellent regeneration performance. It also demonstrated amazing removal efficiencies close to 90% for various heavy metal ions (i.e., Fe3+, Cr3+, Cd2+, Pb2+, Cu2+ and Ni2+), revealing its great potential for wastewater purification. [Display omitted] • A self-supported MoS 2 /CoS 2 @TNT hybrid electrode was constructed. • The electrode achieved a gravimetric Na+ adsorption capacity of 44.22 mg g−1. • The electrode exhibited excellent regeneration performance and removal rates. • The electrode also realized removal efficiencies up to 90% for heavy metal ions. Recently, the rational design and construction of graphene-like layered transition-metal disulfides (TMDs) with chemical and physical superiorities to act as capacitive desalination (CDI) electrodes for water purification have attracted increasing interest worldwide. Herein, an advanced self-supported MoS 2 /CoS 2 @TiO 2 nanotube (TNT) hybrid electrode was grown on a TNT scaffold by a hydrothermal process-assisted in-situ growth strategy, and an asymmetric CDI cell was constructed with the as-fabricated MoS 2 /CoS 2 @TNT and commercial AC electrodes as cathode and anode, respectively. Benefiting from the effective structural feature (i.e., fully open nanosheet-assembled flowers and hierarchical pore alignment) and synergy effect of metal-like CoS 2 , state-of-the-art MoS 2 and TNTs with an efficient charge "superhighway", the MoS 2 /CoS 2 @TNT electrode achieved a significantly high gravimetric Na+ adsorption capacity of 44.22 mg g−1 in a 600 mg L−1 NaCl solution at 1.2 V. Moreover, the hybrid electrode possessed excellent regeneration performance with a capacity retention of nearly 100% even after 20 cycles. Most notably, such electrode also demonstrated amazing removal efficiencies close to 90% for various heavy metal ions (i.e., Fe3+, Cr3+, Cd2+, Pb2+, Cu2+ and Ni2+), revealing its great potential for wastewater purification. [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]

• Methyl Red (MR) was adsorbed from wastewater and the residual amount of MR was detected simultaneously. • The synthesized MR-MIP has a specific adsorption capacity for MR. • The MR-MIP has a large adsorption capacity (C p = 264.20 mg g−1). • Graphite in the normal carbon paste electrode was replaced by Co-FeC for improved conductivity. In this paper, an integrated system for specific adsorption of methyl red (MR) and sensitive detection of the residual amount of this dye in printing and dyeing wastewater is proposed. A molecularly imprinted polymer using MR as the template molecule (MR-MIP) was prepared for specific adsorption of MR from printing and dyeing wastewater. A solid-phase extraction column was filled with a paste of MR-MIP and cobalt-doped iron carbide nanoparticles as the working electrode to construct a highly sensitive sensor for MR detection. The distillation–precipitation approach was used to fabricate microspheres with molecularly imprinted surfaces using cellulose as the carbon source and methyl red (MR) as the template. Not only do the molecularly imprinted microspheres have a satisfactory adsorption performance for the template molecule MR, with a dynamic adsorption capacity up to 264.2 mg g−1, but also the electrochemical sensor built from the molecularly imprinted polymer and iron paste electrode, co-modified with nitrogen-doped carbonized iron nanoparticles, has great sensitivity for MR detection. It is very important to develop an integrated platform for dye treatment and residue detection in wastewater. This technique has a low detection limit and a broad linear range compared to other approaches. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemical capture and release of Cd2+ were conducted using Cu-MOF-74. • Selective removal of Cd2+ (>95%) was feasible under Na/Cd ~ 2 × 104 in molar ratio. • Redox of Cu within the MOF enables energy-efficient electrosorption/regeneration. • Excellent electrosorption (>100 mg/g) and regeneration (>90%) were achieved. An electrochemically-assisted wastewater treatment using Faradaic materials offers a promising technique for the selective removal of hazardous substances. Here, we demonstrate the reversible capture and release of cadmium ions in aqueous solutions, using a redox-active metal-organic framework (MOF) electrode. As-synthesized copper-based MOF (Cu-MOF-74; copper 2,5-dihydroxyterephthalate) is a highly attractive candidate for Faradaic electrosorption due to its large surface area, water stability, and redox-active metal nodes. Our work demonstrates the reversible capture and release of Cd2+ ions assisted by the electrochemical redox reaction of Cu2+/Cu+ within the MOF structure. Combined material characterization and electrosorption tests were carried out to determine the operational conditions for maximizing adsorption capacity, energy efficiency, and material stability, thus leading to excellent electrosorption (>100 mg g−1) and regeneration efficiency (>90%). This study demonstrates the feasibility of leveraging MOFs containing redox-active metal nodes for the selective separation of toxic cations, and paves the way for promising future applications of these 3-D porous structures for wastewater treatment and environmental remediation. [ABSTRACT FROM AUTHOR]

The performance of the membrane capacitive deionization (MCDI) system was evaluated during the removal of three selected pharmaceuticals, neutral acetaminophen (APAP), cationic atenolol (ATN), and anionic sulfamethoxazole (SMX), in batch experiments (feed solution: 2 mM NaCl and 0.01 mM of each pharmaceutical). Upon charging, the cationic ATN showed the highest removal rate of 97.65 ± 1.71%, followed by anionic SMX (93.22 ± 1.66%) and neutral APAP (68.08 ± 5.24%) due to the difference in electrostatic charge and hydrophobicity. The performance parameters (salt adsorption capacity, specific capacity, and cycling efficiency) and energy factors (specific energy consumption and recoverable energy) were further evaluated over ten consecutive cycles depending on the pharmaceutical addition. A significant decrease in the specific adsorption capacity (from 24.6 to ∼3 mg−NaCl g−1) and specific capacity (from 17.6 to ∼2.5 mAh g−1) were observed mainly due to the shortened charging and discharging time by pharmaceutical adsorption onto the electrode. This shortened charging time also led to an immediate drop in specific energy consumption from 0.41 to 0.04 Wh L−1. Collectively, these findings suggest that MCDI can efficiently remove pharmaceuticals at a low energy demand; however, its performance changes dramatically as the pharmaceuticals are present in the target water. [Display omitted] • The performances of the MCDI system were evaluated during pharmaceutical removal. • Neutral APAP, cationic ATN, and anionic SMX were tested. • Neutral APAP was removed ∼68% while ionic ATN and SMX were removed >93%. • A significant decrease in SAC and SC were observed. • The shorter operation time of the pharmaceutical addition led to lower SEC and E R. [ABSTRACT FROM AUTHOR]

• A novel core-shell LiX@ZIF-8 composite has been constructed. • Single layer showed the highest CO 2 adsorption capacity in highly humid flue gas. • The whole synthesis is conducted in a green, energy-saving and economical way. • LiX@ZIF-8-I could maintain excellent cycle hydrothermal stability in humid flue gas. Decreased adsorption capacity and complicated synthetic procedures with expensive or toxic raw chemicals are two major challenges faced by physical adsorbents for carbon capture in highly humid flue gas. In this study, a novel core-shell composite using LiX with high CO 2 adsorption capacity as core and superior hydrophobic ZIF-8 as shell is proposed. The overall synthesis process is conducted under ambient temperature and pressure by adopting deionized water as green solvent. Experimental results show that the adsorption performance of the core-shell structure is enhanced along with the improvement of hydrophobic performance in highly humid flue gas. The performance of ZIF-8 shells from monolayer to multilayers (up to three layers) are investigated. In particular, LiX@ZIF-8-I with single layer of ZIF-8 exhibit the highest CO 2 adsorption capacity of 1.73 mmol/g in humid flue gas. The monolayered adsorbent not only exhibit superior hydrophobicity and CO 2 adsorption capacity but also maintain excellent hydrothermal stability in humid flue gas over 50 adsorption/desorption cycles, which promote its application to practical in a green, energy-saving and economical way. [ABSTRACT FROM AUTHOR]

Here a strategy by designing a series of hyper-cross-linked polystyrene resins ( HCLR s) with highly selective adsorption ability toward hazardous 2,4-dinitrotoluene from nitrophenol sodium salt-rich real industrial wastewater was reported. Macroporous cross-linked chloromethylated polystyrene was self-crosslinked or crosslinked with ligands, i.e. toluene, aniline, and phenol to produce 2,4-dinitrotoluene affinitic HCLR-0 , HCLR-T , HCLR-A and HCLR-P , respectively. The ultrahigh affinity through the like dissolves like mechanism toward 2,4-dinitrotoluene was validated by adsorption experiments, i.e. isotherm, kinetics, thermodynamics, effect of pH & 2-nitrophenol sodium salt and dynamic column adsorption-desorption investigations. They showed ultrahigh adsorption capacities toward 2,4-dinitrotoluene, reaching 628.9, 621.1, 657.9 and 641.0 mg/g for HCLR-0 , HCLR-T , HCLR-A and HCLR-P at 303 K, outperforming their matrix cross-linked chloromethylated polystyrene of 79.2 mg/g and XAD-4 of 286 mg/g very much. This advantage was also reflected in the dynamic adsorption study with promising breakthrough and saturated capacities of 195.8 and 334.4 mg/mL wet HCLR-A s, respectively. The HCLR s also featured interesting impurity affectless properties, in which 2-nitrophenol sodium salt showed no influence on the 2,4-dinitrotoluene capture even in high concentration. With the interesting properties shown above, the HCLR-A column worked very well in the large-scale real industrial wastewater, and could also be fully recycling used through simple low-cost treatment. Image 1 • HCLR s with highly selective adsorption affinity toward DNT were synthesized. • Ultrahigh adsorption capacity of 657.9 mg/g for DNT was reached by HCLR-A. • 2-nitrophenol sodium salt showed no influence on the adsorption of DNT onto HCLR s. • HCLR-A column shows stable adsorption in large-scale real industrial wastewater. • HCLR column could be fully recycling used through simple treatment of toluene. [ABSTRACT FROM AUTHOR]

A novel amino-functionalized magnetic adsorbent (Fe 3 O 4 @C@DETA) was developed for adsorption of Cr(III) and Cr(III)-EDTA from wastewater. Fe 3 O 4 @C@DETA were successfully prepared by modification of Fe 3 O 4 @C with diethylenediamine (DETA), which exhibits a core-shell structure and sufficient saturation magnetization. Fe 3 O 4 @C@DETA exhibits much better adsorption performance for Cr(III) and its chelates than the Fe 3 O 4 @C because of newly introduced amino active sites. The enhanced adsorption capacity of Fe 3 O 4 @C@DETA for Cr(III) is 44.74 mg g−1 (at 25 °C and pH 3.0), which is due to the surface coordination with the newly introduced amino functional sites. The Cr(III)-EDTA anions as a whole was adsorbed through the electrostatic interaction with protonated amino species of the Fe 3 O 4 @C@DETA and have maximum adsorption capacity of 47.27 mg g−1 (at 25 °C and pH 3.0). The adsorption data of free and EDTA coordinated Cr(III) were followed the Langmuir equation, while the adsorption dynamics was well explained by pseudo second order model indicating the chemical nature of adsorption process. The higher concentration of Ca2+ ions in the wastewater compete for adsorption sites and inhibit the Cr(III) removal, while on other hand Ca2+ ions promotes the adsorption of Cr(III)-EDTA, because of electrostatic interaction with adsorbent active sits. Furthermore, the adsorbent can be easily separated by external magnetic field and regenerated in acidic solution. The adsorbent is stable, recyclable and have more than 75% regeneration efficiency and can be repeatedly used in the adsorption process. ga1 • DETA functionalized magnetic carbon-based adsorbent was developed. • Fe 3 O 4 @C@DETA exhibits higher adsorption capacity for Cr(III)-EDTA than Cr(III). • High salt reduced Cr(III) adsorption but improved Cr(III)-EDTA adsorption. • Ternary complex formation contributed to the enhanced Cr(III)-EDTA adsorption. • Fe 3 O 4 @C@DETA could be regenerated and the adsorbent can be reused. [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]

A new Electrocoagulation (EC) technique, sinusoidal AC coagulation (SACC), is creatively put forward for Cu2+ removal in the wastewater from the printed circuit board (PCB) production in this paper. The removal efficiency of Cu2+ from PCB wastewater and energy consumption are compared by SACC and conventional direct current coagulation (DCC). The optimal process parameters were established through analysis of response surface methodology (RSM). The coagulations containing Cu2+ was characterized by SEM, EDS, TEM，BET, XRD and FTIR. The nano-ferrum collosol, mainly composed of goethite (α-FeOOH) and magnetite (γ-Fe 2 O 3), absorbs the Cu2+ and coagulates to remove Cu2+. The results show that the removal rates of Cu2+ by SACC and DCC are 99.86％ and 98.21％, respectively, and the energy consumption is 2.76 × 10−2 kWh⋅m−3 for SACC and 4.42 × 10−2 kWh⋅m−3 for DCC under the optimal process conditions of c 0 (Cu2+) = 41.99 mg⋅dm−3, pH = 7.14, j = 0.293 A⋅m−2, t = 16.7 min. The pilot tests indicate that the SACC technique is feasible in industrial application. Cu2+ removal were completed through electrodeposition of Cu2+ on iron electrode, the deposition of Cu(OH) 2 and the adsorption of Cu2+ by ferrum collosol. The adsorption follows the pseudo-second order kinetics model well. The maximum saturated adsorption capacity (q max) of Cu2+ on ferrum collosol produced by SACC is larger than that by DCC. The adsorption of Cu2+ on the ferrum collosol prepared by SACC and DCC are in accordance with Langmuir's adsorption isotherms. The novel SACC technique is a promising technique for the highly-efficient treatment of Cu2+ from PCB wastewater. • Innovated a sinusoidal AC coagulation technique for Cu 2+ removal. • Detailed study on effect of Cu 2+ removal by AC and DC coagulation. • Explained the mechanism of Cu 2+ removal by AC coagulation. • Show the practicability and feasibility of AC coagulation through pilot tests. [ABSTRACT FROM AUTHOR]

Manganese-zinc chloride waste liquor (MZCWL) produced during cobalt smelting is a significant source for the preparation of high-purity manganese sulfate. The key to recover manganese from MZCWL is the separation of Zn(II). Conventional methods for zinc removal are unsatisfactory due to similar physicochemical properties of zinc and manganese. In this study, a complexation ion-exchange approach was developed to selectively extract and separate zinc from MZCWL. Theoretical analysis suggested that zinc existed as non-cationic chloride complexes (ZnCl 2 0, ZnCl 3 −, and ZnCl 4 2−) under a high chloride concentration. They can be adsorbed by an anion-exchange resin, while manganese still existed in the form of divalent cation. Herein, D201 resin was used to selectively adsorb zinc from MZCWL. The adsorption was significantly affected by chloride concentration, contact time, resin dosage, and temperature. Moreover, the Langmuir isotherm model fitted the adsorption best with a maximum zinc adsorption capacity of 158.98 mg·g−1 at room temperature. In addition, SEM-EDS and Raman analysis further revealed that Zn(II) was adsorbed by D201 resin in the form of zinc chloride complexes. This work provides an alternative and feasible approach for the separation of zinc from chloride medium. Unlabelled Image • The species of Zn(II) under varying chloride concentrations were clarified. • Zn(II) adsorption by D201 resin was related to monolayer uniform adsorption and controlled by chemisorption. • The adsorption efficiency of Zn(II) by D201 resin reached 99.93% under the optimal condition. • Zn(II) was adsorbed on the D201 resin in the form of ZnCl 4 2−. • Zn(II) could be readily eluted from the loaded resin by deionized water. [ABSTRACT FROM AUTHOR]

Due to various ecological problems, it is required to remove the ammonia nitrogen from wastewater. Industrial wastewater that was not subjected to any purification was used in this study, while most processes described in the literature were carried out using synthetically prepared solutions. The study investigated the removal of ammonium ions using ion exchange on various commercial minerals, in 3 h long batch ion-exchange experiments. Furthermore, research on the sodium chloride activation of the selected mineral was conducted. The screening of the mineral with the highest removal potential was conducted taking into account the adsorption capacity (q) and maximal removal efficiency (E), based on the NH4+ ions changes determined using the selective electrode and spectrophotometric cuvette tests. The highest adsorption capacity (q = 4.92 mg/g) of ammonium ions with the maximum removal efficiency (52.3%) was obtained for bentonite, with a 0–0.05 mm particle size. After pretreatment with a 1 mol/L NaCl solution, maximum efficiency increments were observed (55.7%). The Langmuir adsorption isotherm corresponds well with the equilibrium adsorption data (R2 from 0.97 to 0.98), while the Freundlich model was found to be mismatched (R2 = 0.77). Based on these results it was concluded that natural sorbents may be effectively applied in wastewater treatment. It can be observed that as the size of sorbent particles gets lower, the adsorption capacity, as well as the removal efficiency, gets higher. The bentonite pretreatment with the NaCl solution did not result in the expected efficiency improvement. The 2 mol/L solution affected about 3.5% of the removal efficiency yield. [ABSTRACT FROM AUTHOR]