Electrosorption Process Research Articles

Flexible beads-on-string hierarchically porous carbon nanofiber/nanotube composites for enhanced capacitive deionization performance in water desalination

Capacitive deionization (CDI) has garnered significant interest for desalinating water and wastewater. However, electrode materials have remained a primary constraint in CDI technology. This study incorporated carbon nanotubes (CNTs) into a polyacrylonitrile (PAN) solution to synthesize a hierarchically porous activated carbon nanofiber (ACNF)/CNT composite. The ACNF/CNT composite possesses a highly flexible structure characterized by a distinctive beads-on-string morphology. It exhibits a specific surface area of 699 m2/g, a specific pore volume of 0.448 cm3/g, and an average pore width of 3.38 nm. The composite is composed of micropores (38 %), mesopores (59 %), and macropores, creating a multi-scale porous architecture. The surface capacitance of the ACNF/CNT composite is six times greater than that of the ACNF alone, and its charge transfer resistance is reduced to one-tenth. Furthermore, the electrosorption capacity of the ACNF/CNT composite as CDI electrodes was found to be 17.3 mg/g for a 500 mg/L NaCl solution, demonstrating stability over 30 cycles. Kinetic studies suggest that the mesopore-rich beads-on-string structure enhances intraparticle diffusion and the electrosorption process. The ACNF/CNT composite also demonstrates exceptional flexibility and mechanical stability, which are crucial for its application at a pilot scale. This study introduces a novel hierarchically porous electrode material for CDI desalination.

Cobalt sulfide derived from metal organic framework for selective treatment of low concentration copper wastewater: Catalytic ability, reaction efficacy, and mechanism

Here, cobalt sulfide derived from metal organic frameworks (S-Co/MOF) was synthesized and applied in capacitive deionization (CDI) for the selective removal of Cu2+. A series of characterizations confirmed the successful preparation of S-Co/MOF. Under an applied voltage of 1 V and an initial concentration of 25 mg L−1, the electro-sorption capacity of the S-Co/MOF electrode can reach 57.39 mg g−1, which is much higher than that of the Co/MOF electrode. Moreover, the S-Co/MOF electrode exhibits excellent cycling stability under continuous operations. The S-Co/MOF shows effective selectivity for Cu2+ when removing copper-plating wastewater with coexisting ions such as Pb2+, Mn2+, Zn2+, and Cd2+. Density functional theory calculations also confirm that the Co/MOF with high binding energy is beneficial to the electro-sorption process. Consequently, the CDI with the S-Co/MOF electrode provides an effective method for the selective removal of copper-plating wastewater, paving the way for innovative electrochemical systems in water treatment applications.

Efficient removal and separation of cationic dyes by microbubbles for electroflotation coupling membrane electrosorption

In order to enhance the treatment efficiency of cationic dyes wastewater, a dual chamber reactor was ingeniously designed to combine electroflotation and electrosorption technologies. The electrochemical system effectively removed representative single and mixed cationic dyes within 64 min at 150 mA. The observable reaction process phenomena, microbubble photos, clear Tyndall effect phenomena, and electrochemical experimental results all indicated the crucial role of electroflotation in removing cations dyes. Furthermore, changes in surface color, morphology, and functional groups of the anion exchange membrane before and after electrolysis suggested that the electrosorption process also contributed significantly to the removal process. Analysis using UV–vis absorption spectrum and high-resolution mass spectroscopy indicated that no significant chemical reaction occurred with the cationic dye during this process; thus, confirming that the separation of the cationic dye was a physical removal process. This study provides valuable theoretical guidance for efficient removal and separation of cationic dyes in wastewaters.

Removal of Sodium Isopropyl Xanthate by Capacitive Deionization Process

This study investigated the removal of sodium isopropyl xanthate (SIPX) by capacitive deionization using ion exchange resin/PVDF electrode. The electrode was prepared by coating a layer of ion exchange resin (Amberlite FPA54) and polyvinylidene fluoride (PVDF) on the carbon electrode. Batch experiments showed that 96% of SIPX was removed via the electrosorption and electrochemical advanced oxidation processes at 1 V. Carbon disulfide (CS2) was generated as a by-product of the xanthate oxidation. Adsorption/desorption cycle tests revealed that the ion exchange resin/PVDF electrode has high adsorption capacity, and the maximum adsorption could not be achieved within 60 min of adsorption times. The total xanthate removed in the final adsorption stage of eight cycles was 323 mg/m2, corresponding to 34.1% of xanthate from a 20 mg/L xanthate solution that flowed 0.4 mL per min at 1 V for 60 min of adsorption. In the desorption stage, some of the adsorbed xanthate was released back into the solution and oxidized to CS2, which was adsorbed by the electrodes in the following adsorption stage.

Single modular flow-electrode capacitive deionization using modified Prussian blue analogues as cation intercalation electrode for continuous water desalination.

Ion back-diffusion hinders the practical application of conventional flow-electrode capacitive deionization (FCDI) under long-term operational conditions. To address this challenge, the present study integrated cation intercalation deionization (CID) with FCDI. A novel PFCDI-CID system was developed by utilizing a modified Prussian blue analogues owing to their enhanced rheological and electrochemical properties. The PFCDI-CID system achieved a high charge efficiency of 89.77% and an energy-normalized removal salt of 0.69 mol kJ-1 in single-cycle (SC) mode with the flow electrodes mass fraction of 2% and a desalinized water chamber-to-concentrated saline water chamber ratio of 2:1. Furthermore, under continuous operation for 12 h in SC mode, the PFCDI-CID system maintained stable desalination performance within the first 2 h. Over an extended duration, the average charge efficiency of the PFCDI-CID system was maintained at 88.44%, with an average energy-normalized removal salt of 0.65 mol kJ-1. The mechanism revealed that the desalination process involving the Prussian blue analogues primarily involves Na+ intercalation, accompanied by a small amount of electro-sorption process. This system exhibits the characteristics of conventional FCDI while enabling desalination and concentration of simulated saline water during brine discharge, thereby mitigating the impact of ion back-diffusion and broadening the application scope of FCDI.

Enhancement of Co(II) removal via coupling of electrosorption and electrodeposition using asymmetric electrode from wastewater

The growing demand for nuclear energy and the promotion of nuclear technology applications will generate large quantities of cobalt-containing wastewater. The efficient removal of cobalt from radioactive wastewater is of great significance for the resource regeneration and environmental protection. However, conventional removal methods are constrained by the poor removal efficiency and slow removal kinetics. Herein, the sulfonated polyether ether ketone coated activated carbon fibers (anode)/activated carbon fibers (cathode) asymmetric electrodes was proposed to boost the Co(II) electrosorption performance. The experimental results showed that compared to traditional symmetric electrodes, the theoretical maximum electrosorption capacity (116.19 mg·g−1) had an exceptional enhancement of 69 %. The voltage and initial pH of the solution had an undeniable impact on the efficiency of cobalt electrosorption. Furthermore, more than 75 % of Co(II) was rapidly immobilized within 3 h. The kinetic fitting indicated that the electrosorption process was more appropriately described by pseudo-second-order kinetic model. The Co(II) removal efficiency was up to 80 % under the conditions of coexistence with Na+, Mn2+, Ni2+, Zn2+, Sr2+, and Cs+. More importantly, it combines two synthetic mechanisms of electrosorption and electrodeposition to realize the purification of cobalt-containing wastewater. Overall, considering the fast and highly-efficient cobalt removal performance and innate economy, the asymmetric electrosorption for cobalt removal provides new insights into the treatment of cobalt-containing wastewater.

Synergistic effect of Fe and Ni on carbon aerogel for enhanced oxygen reduction and H2O2 activation in electro-Fenton process

A novel cathode, iron-nickel alloy modified carbon aerogel (FeNi-CA), was successfully synthesized and utilized as the cathode in an electro-Fenton process for acetaminophen degradation. The incorporation of Fe and Ni in the carbon matrix resulted in superior electrochemical characteristics and catalytic performance compared to Fe-CA and Ni-CA. The unique microstructure of FeNi-CA, including the presence of alloy nanoparticles, carbon defects, and abundant oxygen functional groups, enhanced 2e− oxygen reduction activity and electrocatalytic performance. This enabled FeNi-CA to exhibit a dual functionality of H2O2 electro-generation and in situ activation. FeNi-CA demonstrated good performance over a wide pH range at a low current density of 4.44 mA/cm2. Under optimal conditions, 99.9 % of acetaminophen was removed with a reaction rate constant (kobs) of 0.054 min−1 through electro-sorption and oxidation processes. Importantly, a satisfactory degradation effect was achieved in the absence of external aeration. This work provides a potential wastewater treatment solution without the need for external aeration or additional chemical input by simultaneously achieving oxygen evolution reaction at the anode and oxygen reduction reaction at the cathode. Furthermore, FeNi-CA demonstrated good reusability performance with controlled metal leaching after five consecutive runs, suggesting its potential for sustained use in electro-Fenton processes over the long term.

Construction of three-dimensional polyethyleneimine incorporated graphene oxide aerogels as high-capacity electrode for enhanced uranium(VI) electrosorption performance

Electrosorption technique is paid more attention in recovery of uranium(VI) due to its low energy consumption, green process and easy regeneration, but still is hindered by the limited accessible active sites on the electrode material, poor surface wettability and inherent ion exclusion effects. Herein, novel there dimensional porous polyethyleneimine/graphene oxide aerogel (PEI/GOA) electrode was constructed by incorporating polyethyleneimine into graphene oxide and using chitosan as binder for uranium(VI) electrosorption. The synthesized PEI/GOA had a stable three-dimensional porous structure, high specific capacitance (54.06F/G) and good charge–discharge stability. The electrosorption process of uranium(VI) by PEI/GOA electrode was affected by applied voltage and pH, fitted by the pesuo-second-order kinetics and Langmuir model. The maximum theoretical electrosorption capacity of uranium(VI) by PEI/GOA electrode at − 1.2 V was 419.71 mg/g, which was 2.2 times higher than that of pure graphene oxide electrode. PEI/GOA electrode exhibited less than 20 % loss after five cycles using 0.1 M NaHCO3 as the eluent. The efficient U(VI) electrosorption by PEI/GOA electrode was not only attributed to the formation of the electric double layer, but also due to the interaction and synergy of the –NH2, –CONH- and –OH on the PEI/GOA electrode. This research offers a new approach for the efficient removal of uranium (VI) from uranium-containing wastewater.

Effective electro-removal of glyphosate and glufosinate from aqueous solutions via capacitive deionization

Both glyphosate (Gly) and glufosinate (Glu) are commonly used as herbicides, which has caused rising concerns about their impact on the environment and human health. Capacitive deionization (CDI) is a newly developed energy-efficient water treatment technique that effectively removes inorganic and small organic molecules under the electric field. In this work, a carbon electrode-based CDI device was used in the electro-removal of Gly and Glu in an aqueous solution with an excellent removal rate of up to 95 % under various conditions. Furthermore, maximum electro-removal rates of 1.99 μmol∙cm−2∙min−1 for Gly and 1.33 μmol∙cm−2∙min−1 for Glu were also achieved, except with super-high removal rates of 100 % (Gly) and 97.6 % (Glu) in actual Gly and Glu-containing lake water, demonstrating the feasibility of the CDI device in real aqueous systems. In-situ electro-oxidation that occurred during the electrosorption process was confirmed by analyzing the three-electrode system-based electrochemical behaviors and tracing the time-dependent changes of the suspicious degradation products. Transition state (TS) search and molecular dynamics (MD) simulations were employed to study the microscopic processes theoretically, revealing the degradation pathways and thermodynamic characteristics of Gly and Glu. This research presents a novel avenue for the decomposition and removal of herbicides from water, leveraging the inherent side reactions of CDI systems as an advantage to decontaminate organic pollutants.

High-performance electrosorption of lanthanum ion by Mn3O4-loaded phosphorus-doped porous carbon electrodes via capacitive deionization

Transition-metal-oxide@heteroatom doped porous carbon composites have attracted considerable research interest because of their large theoretical adsorption capacity, excellent electrical conductivity and well-developed pore structure. Herein, Mn3O4-loaded phosphorus-doped porous carbon composites (Mn3O4@PC-900) were designed and fabricated for the electrosorption of La3+ in aqueous solutions. Due to the synergistic effect between Mn3O4 and PC-900, and the active sites provided by Mn–O–Mn, C/PO, C–P–O and Mn–OH, Mn3O4@PC-900 exhibits high electrosorption performance. The electrosorption value of Mn3O4@PC-900 was 45.34% higher than that of PC-900, reaching 93.02 mg g−1. Moreover, the adsorption selectivity reached 87.93% and 89.27% in La3+/Ca2+ and La3+/Na+ coexistence system, respectively. After 15 adsorption-desorption cycles, its adsorption capacity and retention rate were 50.34 mg g−1 and 54.12%, respectively. The electrosorption process is that La3+ first accesses the pores of Mn3O4@PC-900 to generate an electric double layer (EDL), and then undergoes further Faradaic reaction with Mn3O4 and phosphorus-containing functional groups through intercalation, surface adsorption and complexation. This work is hoped to offer a new idea for exploring transition-metal-oxide @ heteroatom doped porous carbon composites for separation and recovery of rare earth elements (REEs) by capacitive deionization.

Regulating Chemisorption and Electrosorption Activity for Efficient Uptake of Rare Earth Elements in Low Concentration on Oxygen-Doped Molybdenum Disulfide.

Recovery of rare earth elements (REEs) with trace amount in environmental applications and nuclear energy is becoming an increasingly urgent issue due to their genotoxicity and important role in society. Here, highly efficient recovery of low-concentration REEs from aqueous solutions by an enhanced chemisorption and electrosorption process of oxygen-doped molybdenum disulfide (O-doped MoS2) electrodes is performed. All REEs could be extremely recovered through a chemisorption and electrosorption coupling (CEC) method, and sorption behaviors were related with their outer-shell electrons. Light, medium, and heavy ((La(III), Gd(III), and Y(III)) rare earth elements were chosen for further investigating the adsorption and recovery performances under low-concentration conditions. Recovery of REEs could approach 100% under a low initial concentration condition where different recovery behaviors occurred with variable chemisorption interactions between REEs and O-doped MoS2. Experimental and theoretical results proved that doping O in MoS2 not only reduced the transfer resistance and improved the electrical double layer thickness of ion storage but also enhanced the chemical interaction of REEs and MoS2. Various outer-shell electrons of REEs performed different surficial chemisorption interactions with exposed sulfur and oxygen atoms of O-doped MoS2. Effects of variants including environmental conditions and operating parameters, such as applied voltage, initial concentration, pH condition, and electrode distance on adsorption capacity and recovery of REEs were examined to optimize the recovery process in order to achieve an ideal selective recovery of REEs. The total desorption of REEs from the O-doped MoS2 electrode was realized within 120 min while the electrode demonstrated a good cycling performance. This work presented a prospective way in establishing a CEC process with a two-dimensional metal sulfide electrode through structure engineering for efficient recovery of REEs within a low concentration range.

Enhanced Cu(II) Adsorption Capacity of Recyclable Activated Carbon Fibers for Flexible Self‐Supporting Electrodes in Capacitive Deionization

AbstractAs the cardinal part of capacitive deionization apparatus, the performance of electrode directly determines the capacitive deionization's adsorption rate, adsorption capacity and selectivity. However, the adsorptivity and reusability of electrode material for special adsorbate need to be developed urgently for the application of capacitive deionization in wastewater purification. In this research, we successfully enhanced the Cu(II) adsorptivity of activated carbon fiber felt (ACFF) to 23 mg/g (4.47 times of ACFF0) by the sonication‐assisted chemical reactivation process with the solution of 20 wt % NaOH used as activator (ACFF‐N20). As ACFF‐N20 used as cathode, the Cu(II) electro‐adsorptivity of ACFF‐N20 under a current of 0.15 A is 84 mg/g for 130 mg/L Cu(II) standard working fluid. For the Cu(II) wastewater with a concentration of 50 mg/L, it can be purified to 0.14 mg/L by one step of capacitive deionization, which below the drinking standard of World Health Organization. By the technology of low‐temperature pickling regeneration, the regeneration rates of ACFF‐N20 are 102 %–106 % for five recycling times of Cu(II) electrosorption process. Based on fitting analysis of adsorption processes using different kinetic models, it was found that Langmuir model is more convergent than Freundlich model to the adsorption isotherms. Additionally, Bangham adsorption kinetic model and pseudo‐first order adsorption kinetic model have the best fitting correlation for the Cu(II) static adsorption and electrosorption of ACFFs.

Electrodeposition of Manganese Dioxide under Different Conditions: Application of MnO2/Carbon Fibers in the Electrosorption Process

AbstractAnodic electrodeposition was used to synthesize a composite electrode of nanostructured manganese dioxide/carbon fiber (CF) galvanostatically. Different characterization results of the nanostructured MnO2 were obtained by varying the H2SO4 concentration and the current density. Field emission scanning electron microscopy, X‐ray diffraction, and atomic force microscopy were utilized to characterize the prepared composite electrodes. The best conditions were: 0.3 mA cm−2 current density and 0.64 M H2SO4 concentration. The electrosorption performance of the MnO2/CF electrode prepared under the best conditions was tested by way of its chromium(VI) ion adsorption from a simulated solution. The applied voltage, pH, and ionic strength affect the efficiency of Cr(VI) ion removal. The highest chromium removal efficiency was 99.98 %, achieved at pH 2, a cell voltage of 4.6 V, and a NaCl concentration of 1 g L−1.

Fabrication of an efficient hierarchical mesoporous 2D-MoS2/CNT/polypyrrole based composite electrodes for competitive and selective U6+ removal using capacitive deionization: Mechanistic evaluation through cyclic voltammetry

In this work, efficient and selective carbonaceous electrode materials based on hierarchical mesoporous functionalized carbon nanotubes, 2D-MoS2 nanosheets electrodeposited with variable content of polypyrrole (PPy) were prepared. The simple etching reaction between HNO3 and carbon nanotubes did not only modify the surface but also improved its hydrophilicity. The annealing of carbon nanotubes and electrodeposition of PPy increased the mesopore volume to total volume ratio (Vmeso/Vt) from 0.42 to 0.86. The composite materials were characterized wisely using different characterization techniques and employed for efficient U6+ electro-assisted sorption through capacitive deionization. Electrode material with PPy content (0.3 M) exhibited good specific capacitance Csp (100.2 F/g), improved Vmeso (0.61 cm3/g), superb Vmeso/Vt ratio (0.86) and large specific surface area SBET (149.7 m2/g). The stated electrode showed fast sorption kinetics (teq=30 min), admirable selectivity and exhibited the experimental sorption capacity of 274.50 mg/g at − 0.90 V. Electrochemical impendence spectroscopic study revealed that the resulting material exhibited relatively small charge transfer resistance (1.19 Ωcm2), minute electrolytic resistance (0.91 Ωcm2) and large double layer constant phase element (0.0368 S sn/ cm2). These significant characteristics promoted U6+ ions diffusion inside the hierarchical porous electrode surface for better performance of electrosorption process. This new class of hierarchical mesoporous composite electrodes may be used as potential supercapacitor materials not only for removal of uranium but also for other potent desalination applications.

Electrosorption of uranium (VI) by sulfonic acid‑decorated FeOOH nanorods

The capacitive deionization (CDI) technology for the removal of U(VI) has been the focus of attention because of its superiorities in operation cost, energy consumption, and environmental friendliness. In this report, electrode materials based on sulfonic acid‑decorated FeOOH were applied to CDI and flow electrode capacitive deionization (FCDI) for the first time. The sulfonic acid‑decorated FeOOH nanorods presented a high electrosorption capability of U(VI) in the CDI system (709.4 mg g−1 at 1.2 V and pH = 4.0, based on Langmuir model), which may result from the coordinative surfaces as well as the mesoporous structures of FeOOH. The thermodynamic and kinetic behaviors of the electrosorption process can be well-fitted using the Freundlich and pseudo-second-order model. The effective electrosorption in the presence of Na+ competitive ions and recycling of adsorbents in the CDI system further demonstrated the potential application of sulfonic acid‑decorated FeOOH nanorods for the electrosorptive removal of U(VI) from radioactive wastewater. The electrosorption mechanism was determined to be a combined process that is composed of diffusion of the uranyl ions into the EDL and adsorption onto the surface of FeOOH via the coordination interaction from Fe-OH and sulfonic acid groups (-SO3H). Further, continuous FCDI batch experiments in low concentration of feed water (60 mg L− 1 U) show that removal efficiency of U remained over 99% in 10 times continuous cycles, endowing it more possibilities for capacitive deionization from research to practical application.

Innovative g-C3N4/AX composite electrode for effective thorium elimination from aqueous solutions

Electrosorption is a technique that combines electrical and adsorption processes and has been established to displace Th(IV) from aqueous solutions. The present study successfully synthesised a novel electrode, where graphitic carbon nitride was modified with amidoxime amidoxime groups (g-C3N4/AX) via the hydrothermal method. The batch experiments conducted in this study revealed that the g-C3N4/AX electrode possessed a favourable thorium adsorption capacity of 275.74 mg.g−1 and a swift elimination equilibrium of within 30 min. Furthermore, the removal efficiency at − 1.0 V (84.46 %) of the electrode was almost threefold greater than the removal efficiency at open circuit potential (24.09 %). The results were due to the free electrical charges on the g-C3N4/AX electrode, which induced the electrical driving force and facilitated the adsorption of Th(IV) ions onto the g-C3N4/AX surface. The shifted bands from the Fourier transform-infrared (FT-IR) spectrum post-electrosorption demonstrated a substantial complexation of Th(IV) with the amine groups of amidoxime and g-C3N4. A significant transference in energy band peaks was also observed during the XPS assessment, indicating that the electrosorption process included oxygen (O), carbon (C), and nitrogen (N) species. In the practical real wastewater involving rare earth residue, which contains Ce, La, Nd and Pr ions, g-C3N4/AX exhibited good capabilities in selectively adsorbing Th(IV). The electrode synthesised in this study also exhibited the ability to regenerate with a reasonable ∼ 80 % removal ratio after five runs. The results indicated that the amidoxime-modified graphitic carbon nitride electrode demonstrated a good potential in removing thorium from aqueous solutions via electrosorption applications.

Novel malonamide-amidoxime bifunctional polymers decorated graphene oxide/chitosan electrode for enhancing electrosorptive removal of uranium(VI)

Developing the best electrode and exploring its electrosorption process are key to promoting the industrialization of uranium(VI) electrosorption. Herein, malonamide-amidoxime bifunctional polymers (MAFP) was incorporated into graphene oxide/chitosan (GO/CS) to prepare a high-performance composite electrode (MAFP/GO/CS) for U(VI) electrosorption. The as-prepared MAFP/GO/CS electrode displayed a more obvious porous structure, a larger specific surface area, an abundant amide and amidoxime group, as well as better hydrophilicity and electrochemical characteristics. This electrosorption experiment systematically examined the effects of voltage, electrosorption time, pH, and initial U(VI) concentration. According to the results, MAFP/GO/CS electrode had the maximum U(VI) electrosorption capacity of 260.58 mg/g at pH 6 and −1.2 V. It was found that Langmuir’s and pseudo-second-order kinetic models of electrosorption were well suitable for simulating the U(VI) electrosorption kinetics and isotherms. A major contribution to enhanced electrosorptive U(VI) by MAFP/GO/CS electrode could be attributed to the synergetic coordination of U(VI) by amide and amidoxime groups in MAFP moieties. This work served as a good guideline for incorporating MAFP with GO/CS to fabricate a novel electrode for U(VI) electrosorption.

Waste Camellia oleifera shell-derived hierarchically porous carbon modified by Fe3O4 nanoparticles for capacitive removal of heavy metal ions

Capacitive deionization is an efficient technology for water purification and treatment. The electrode material is crucial to improving the performance of capacitive deionization. Herein, Fe3O4 nanoparticles-modified hierarchically porous carbon (Fe3O4 NPs/HPC) was successfully synthesized by the pyrolysis of waste Camellia oleifera shell coupling with the post-modification. Owing to its unique structure and composition, the as-prepared Fe3O4 NPs/HPC delivered great potential in capacitive deionization and heavy metal removal. Under the current density of 0.5 A g-1, the Fe3O4 NPs/HPC electrode showed a high specific capacitance of 134.5 F g−1 in 1 M NaCl solution, much more than the bare HPC electrode of 99.9 F g−1. In addition, the Fe3O4 NPs/HPC electrode exhibited excellent cycle stability with negligible loss of capacitance after 1000 cycles at 2 A g-1. At an operating voltage of 1.2 V, the Fe3O4 NPs/HPC electrode released high uptake capacity of 34.22 and 39.52 mg g−1 for Cd(II) and Pb(II) ions, respectively. XPS spectra and competitive adsorption demonstrated that Cd(II) was mainly removed by the oxygen-containing groups of HPC through an electrosorption coupling with an electrodeposition multilayer process, but Pb(II) was uniformly adsorbed on the active sites including the oxygen-containing groups of HPC and the modified Fe3O4 NPs by a monolayer electrosorption process. The impressive results indicate that the as-prepared Fe3O4 NPs/HPC composites possess potential for the selective removal of heavy metal ions from saline wastewater.

Study on electrosorption behavior of weak metal cyanide complex ions based on coal-based electrode

Using the electrosorption technology treatment the cyanide wastewater has a good treatment effect, but the mechanism is not completely clear. In this paper, we conducted electrosorption experiments using simulated cyanide solutions to study the adsorption kinetics, thermodynamics, adsorption isotherms and analyze the reaction mechanism of zinc-cyanide and copper–cyanide complex ions. The results show that the electrosorption process of weak metals cyanide complexes treated by coal-based (CB) electrode conforms to the second-order kinetic model and follow the Langmuir model, affected by the dipole force and exchange of coordination groups. The equilibrium adsorption amounts of the two species at 2 V were 1.53 and 1.74 times higher than those at open circuit, respectively. During the electrosorption process, affected by the pseudo-capacitance, pore structure of CB electrodes and the charges of complex ions, the zinc-cyanide complex is bound in the double electric layer on the anode surface by the electric field, but partly decomposed to produce zinc ions and forms Zn(OH)2 in alkaline solution then generates ZnO precipitates, a small amount of Zn2+ were electrostatically adsorbed on the cathode surface for reduction deposition. However, the majority of the copper–cyanide complexes were purified by electrostatic adsorption to the double layer near the anode, while a small amount of decomposition occurred to produce Cu(OH)2 in the alkaline system, and almost no copper was deposited by reduction. This research results can enable us to better understand the removal characteristics of the weak metal cyanide complex ions in the process of electrosorption by CB electrode, and have great significance for the application of electrosorption technology to the treatment of cyanide wastewater.

Nanoscale Adsorption, Assembly, and Deionization Dynamics Recorded by Optical Fiber Sensors.

Capacitive deionization in environmental decontamination has been widely studied and now requires intensive development to support large-scale deployment. Porous nanomaterials have been demonstrated to play pivotal roles in determining decontamination efficiency and manipulating nanomaterials to form functional architecture has been one of the most exciting challenges. Such nanostructure engineering and environmental applications highlight the importance of observing, recording, and studying basically electrical-assisted charge/ion/particle adsorption and assembly behaviors localized at charged interfaces. In addition, it is generally desirable to increase the sorption capacity and reduce the energy cost, which increase the requirement for recording collective dynamic and performance properties that stem from nanoscale deionization dynamics. Herein, we show how a single optical fiber can serve as an in situ and multifunctional opto-electrochemical platform for addressing these issues. The surface plasmon resonance signals allow the in situ spectral observation of nanoscale dynamic behaviors at the electrode-electrolyte interface. The parallel and complementary optical-electrical sensing signals enable the single probe but multifunctional recording of electrokinetic phenomena and electrosorption processes. As a proof of concept, we experimentally decipher the interfacial adsorption and assembly behaviors of anisotropic metal-organic framework nanoparticles at a charged surface and decouple the interfacial capacitive deionization within an assembled metal-organic framework nanocoating by visualizing its dynamic and energy consumption properties, including the adsorptive capacity, removal efficiency, kinetic properties, charge, specific energy consumption, and charge efficiency. This simple "all-in-fiber" opto-electrochemical platform offers intriguing opportunities to provide in situ and multidimensional insights into interfacial adsorption, assembly, and deionization dynamics information, which may contribute to understanding the underlying assembly rules and the exploring structure-deionization performance correlations for the development of tailor-made nanohybrid electrode coatings for deionization applications.