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1.
J Hazard Mater ; 384: 121491, 2020 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-31690504

RESUMO

Persistent perfluorinated compounds (PFCs) have been recognized as a global environmental issue. Developing methods without leading to additional burden in nature will be essential for PFCs removal. Herein, we functionalized iron nanoparticles on living diatom (Dt) to efficiently enable the Fenton reaction and reactive oxygen species (ROS) production. Iron nanoparticles at the surface of living diatom act as promising catalytic agents to trigger OH radical generation from H2O2. Dt plays dual roles: i) as solid support for effective adsorption, and ii) it supplies oxygen and inherently produces ROS under stress conditions, which improves removal efficiency of PFCs. We also demonstrated its reusability by simple magnetic separation and 85% of decomposition efficiency could still be achieved. This newly developed diatom-assisted bioremediation strategy enables green and efficient PFC decomposition and shall be readily applicable to other persistent pollutants.

2.
Adv Mater ; 32(6): e1906877, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31793695

RESUMO

Advanced redox-polymer materials offer a powerful platform for integrating electroseparations and electrocatalysis, especially for water purification and environmental remediation applications. The selective capture and remediation of trivalent arsenic (As(III)) is a central challenge for water purification due to its high toxicity and difficulty to remove at ultra-dilute concentrations. Current methods present low ion selectivity, and require multistep processes to transform arsenic to the less harmful As(V) state. The tandem selective capture and conversion of As(III) to As(V) is achieved using an asymmetric design of two redox-active polymers, poly(vinyl)ferrocene (PVF) and poly-TEMPO-methacrylate (PTMA). During capture, PVF selectively removes As(III) with exceptional uptake (>100 mg As/g adsorbent), and during release, synergistic electrocatalytic oxidation of As(III) to As(V) with >90% efficiency can be achieved by PTMA, a radical-based redox polymer. The system demonstrates >90% removal efficiencies with real wastewater and concentrations of arsenic as low as 10 ppb. By integrating electron-transfer through the judicious design of asymmetric redox-materials, an order-of-magnitude energy efficiency increase can be achieved compared to non-faradaic, carbon-based materials. The study demonstrates for the first time the effectiveness of asymmetric redox-active polymers for integrated reactive separations and electrochemically mediated process intensification for environmental remediation.

3.
Sci Total Environ ; 692: 844-853, 2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31539990

RESUMO

High-quality meso/micropore-controlled hierarchical porous carbon (HPC) was synthesized by a hard template method utilizing rice husk biochar and then used to adsorb copper ions from an aqueous solution. The preparation procedure included two main steps: base leaching and physicochemical activation. During the activation process, the porosity characteristics (i.e., specific surface area and meso/micropore ratio) were controlled by altering the KOH impregnation ratio, activation time, and temperature under the CO2 atmosphere. In addition, a copper adsorption study was performed using three HPC samples with different pore structures and characteristics. The results of this study indicate that the adsorption capacity of HPC material derived from rice husk biochar is strongly influenced by its meso/micropore ratio. As evidenced, HPC 3-0.5-800, which was impregnated by a KOH:biochar ratio of 3 and activated at 800°C for 0.5h under a CO2 atmosphere, has a very high specific surface area of 2330 m2g-1 with an 81% mesopore to total specific surface area. Importantly, it exhibited a superior adsorption capacity of 265mgg-1 and rapid adsorption kinetics for copper ions. The improvement is ascribed to the high specific surface area and favorable hierarchical structure. The findings demonstrate the feasibility of controlling the hierarchical pore structure of rice husk biochar-derived carbons as high-performance adsorbents for copper ion removal from water.


Assuntos
Carvão Vegetal/química , Cobre/análise , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Hidróxidos/química , Cinética , Oryza/química , Porosidade , Compostos de Potássio/química , Eliminação de Resíduos Líquidos/instrumentação , Purificação da Água/instrumentação
4.
Chemosphere ; 235: 413-422, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31272001

RESUMO

This study aims to investigate the feasibility of desalinating secondary effluent from a domestic wastewater treatment plant (DWTP) using membrane capacitive deionization (MCDI) for reclamation purposes. The desalination performance of a MCDI stack with 10 pairs of 20 cm × 20 cm activated carbon electrodes was evaluated in single-pass mode. As evidenced, the MCDI stack outperformed the capacitive deionization stack. The water quality characteristics of the inflows and product water were also analyzed. Our results revealed that MCDI can effectively remove undesired ions such as calcium and nitrate from the DWTP effluent for water reclamation. In particular, the solution conductivity of the product water was observed to be as low as 1.27 µS/cm. Removal of the ions was easily performed by the electrostatic field-assisted deionization process. The use of MCDI for low-salinity wastewater reclamation demonstrated favorable energy performance with a low volumetric energy input and a molar energy input of 0.12 kWh/m3 and 0.03 kWh/mole, respectively; and the energy efficiency of this system is expected to be further improved by energy recovery or incorporation of energy-producing processes. These results are indicative of the benefits of using MCDI as part of the treatment processes for the reclamation of wastewater with low salinity.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Carbono , Carvão Vegetal , Condutividade Elétrica , Eletrodos , Membranas Artificiais , Nitratos , Salinidade , Cloreto de Sódio , Água , Purificação da Água/métodos
5.
Sci Total Environ ; 675: 41-50, 2019 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-31026642

RESUMO

Microbial desalination cells (MDCs) are promising bioelectrochemical systems that are being investigated for simultaneous seawater desalination, electricity generation, and wastewater treatment. Anode materials play an important role in determining the performance of MDCs. In this study, a three-dimensional (3D) macroporous sponge was coated with compatible and conductive carbon nanotube-chitosan (CNT-CS) as a composite electrode for MDCs. Experimental results showed that the flexible CNT-CS sponge exhibited a high capacitance (159.4F/g at 20mVs-1), good cycling stability (96% specific capacitance retention after 1000 cyclic voltammetry cycles) and low resistance. Moreover, the MDC with a CNT-CS sponge anode generated a high power density of 1776.6mW/m2 (per electrode area) and desalination rate of 16.5mgh-1, which are significantly higher than those of commercial carbon felt electrodes under the same conditions. The improved MDC performance can be attributed to the continuous 3D macroporous structure of the sponge anode promoting the bacterial loading capacity on the electrode surface. Moreover, the presence of CNTs also further enhances extracellular electron transfer. Our results demonstrate that an MDC operating with a 3D CNT-CS sponge anode offers an effective means for manufacturing high-performance MDCs with wide applicability to bioelectrochemical systems.


Assuntos
Fontes de Energia Bioelétrica , Quitosana , Nanotubos de Carbono/química , Purificação da Água/métodos , Condutividade Elétrica , Eletricidade
6.
J Hazard Mater ; 364: 682-690, 2019 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-30399551

RESUMO

Bauxite residue, a major by-product of the alumina-producing Bayer process, is a serious environmental pollutant due to its high alkalinity. Here, we reported an operation system designed in our laboratory that included washing and electrodialysis dealkalization systems with aeration pipes. Washing with aeration releases a substantial amount of free alkali and attached alkali into water and increases the dealkalization efficiency. The washing liquid was treated with five steps of batch-mode electrodialysis. The average removal of total dissolved solids (TDS) after the aeration and non-aeration electrodialysis processes were 61.30% and 39.61%, respectively. The average removal of OH- under aeration conditions was 76.62%, a value that was greater than the value produced under non-aeration conditions (68.48%). This efficiency was also higher than that of some other reports (64.90-68.50%). Aeration decreased the energy consumption to a greater extent than the non-aeration condition. NaOH was recovered in terms of the concentration chamber, and the NaAl(OH)4 present in the dilution chamber was separated for the electrodialysis treatment. Membrane scaling was generated to a lesser amount under aeration conditions than that of non-aeration conditions, which would improve the dealkalization efficiency. The high repeatability of the experiments was indicated by the intraclass correlation coefficient (P < 0.05).

7.
Chemosphere ; 208: 285-293, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-29883863

RESUMO

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


Assuntos
Carvão Vegetal/química , Capacitância Elétrica , Eletrodos , Luffa/química , Águas Salinas/química , Eletroquímica , Porosidade
8.
Nanoscale ; 10(31): 14852-14859, 2018 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-29869671

RESUMO

Zeolitic imidazolate framework (ZIF) composite-derived carbon exhibiting large surface area and high micropore volume is demonstrated to be a promising electrode material for the capacitive deionization (CDI) application. However, some inherent serious issues (e.g., low electrical conductivity, narrow pore size, relatively low pore volume, etc.) are still observed for nitrogen-doped porous carbon particles, which restrict their CDI performance. To solve the above-mentioned problems, herein, we prepared gold-nanoparticle-embedded ZIF-8-derived nitrogen-doped carbon calcined at 800 °C (Au@NC800) and PEDOT doped-NC-800 (NC800-PEDOT). The newly generated NC800-PEDOT and Au@NC800 electrodes exhibited notably increased conductivity, and they also achieved high electrosorption capacities of 16.18 mg g-1 and 14.31 mg g-1, respectively, which were much higher than that of NC800 (8.36 mg g-1). Au@NC800 and NC800-PEDOT can be promisingly applicable as highly efficient CDI electrode materials.

9.
Small ; 14(27): e1702054, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29845726

RESUMO

An approach to assemble hierarchically ordered 3D arrangements of curved graphenic nanofragments for energy storage devices is described. Assembling them into well-defined interconnected macroporous networks, followed by removal of the template, results in spherical macroporous, mesoporous, and microporous carbon microball (3MCM) architectures with controllable features spanning nanometer to micrometer length scales. These structures are ideal porous electrodes and can serve as lithium-ion battery (LIB) anodes as well as capacitive deionization (CDI) devices. The LIBs exhibit high reversible capacity (up to 1335 mAh g-1 ), with great rate capability (248 mAh g-1 at 20 C) and a long cycle life (60 cycles). For CDI, the curved graphenic networks have superior electrosorption capacity (i.e., 5.17 mg g-1 in 0.5 × 10-3 m NaCl) over conventional carbon materials. The performance of these materials is attributed to the hierarchical structure of the graphenic electrode, which enables faster ion diffusion and low transport resistance.

10.
ACS Appl Mater Interfaces ; 9(49): 42425-42429, 2017 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-29182314

RESUMO

Mixed metal oxide nanoparticles have interesting physical and chemical properties, but synthesizing them with colloidal methods is still challenging and often results in very heterogeneous structures. Here, we describe a simple method to synthesize mesoporous titania nanoparticles implanted with a uniform distribution of copper oxide nanocrystals (CuO@MTs). By calcining a titanium-based metal-organic framework (MIL-125) in the presence of Cu ions, we can trap the Cu in the TiO2 matrix. Removal of the organic ligand creates mesoporosity and limits phase separation so that tiny CuO nanocrystals form in the interstices of the TiO2. The CuO@MTs exhibits superior performance for photocatalytic hydrogen evolution (4760 µmol h-1) that is >90 times larger than pristine titania.

11.
Chemosphere ; 184: 924-931, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28655111

RESUMO

A single-pass-mode capacitive deionization (CDI) reactor was used to remove arsenic from groundwater in the presence of multiple ions. The CDI reactor involved an applied voltage of 1.2 V and six cell pairs of activated carbon electrodes, each of which was 20 × 30 cm2. The results indicate that this method achieved an effluent arsenic concentration of 0.03 mg L-1, which is lower than the arsenic concentration standard for drinking water and irrigation sources in Taiwan, during the charging stage. Additionally, the ability of the CDI to remove other coexisting ions was studied. The presence of other ions has a significant influence on the removal of arsenic from groundwater. From the analysis of the electrosorption selectivity, the preference for anion removal could be ordered as follows: NO3- > SO42- > F- > Cl- >As. The electrosorption selectivity for cations could be ordered as follows: Ca2+ > Mg2+ > Na+ âˆ¼ K+. Moreover, monovalent cations can be replaced by divalent cations at the electrode surface in the later period of the electrosorption stage. Consequently, activated carbon-based capacitive deionization is demonstrated to be a high-potential technology for remediation of arsenic-contaminated groundwater.


Assuntos
Arsênico/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Cátions Bivalentes , Cátions Monovalentes , Carvão Vegetal , Eletrodos , Água Subterrânea , Íons , Taiwan
12.
Sci Rep ; 6: 28847, 2016 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-27404086

RESUMO

Three-dimensional (3-D) ZIF-8 derived carbon polyhedrons with high nitrogen (N) content, (denoted as NC-800) are synthesized for their application as high-performance electrodes in electrosorption of salt ions. The results showed a high specific capacitance of 160.8 F·g(-1) in 1 M NaCl at a scan rate of 5 mV·s(-1). Notably, integration of 3-D mesopores and micropores in NC-800 achieves an excellent capacitive deionization (CDI) performance. The electrosorption of salt ions at the electrical double layer is enhanced by N-doping at the edges of a hexagonal lattice of NC-800. As evidenced, when the initial NaCl solution concentration is 1 mM, the resultant NC-800 exhibits a remarkable CDI potential with a promising salt electrosorption capacity of 8.52 mg·g(-1).

13.
J Hazard Mater ; 312: 208-215, 2016 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-27037475

RESUMO

The feasibility of the electro-removal of arsenate (As(V)) and arsenite (As(III)) from aqueous solutions via capacitive deionization was investigated. The effects of applied voltage (0.0-1.2V) and initial concentration (0.1-200mgL(-1)) on arsenic removal were examined. As evidenced, an enhancement of arsenic removal can be achieved by capacitive deionization. The capacity to remove As(V) at an initial concentration of 0.2mgL(-1) on the activated carbon electrode at 1.2V was determined to be 2.47×10(-2)mgg(-1), which is 1.8-fold higher than that of As(III) (1.37×10(-2)mgg(-1)). Notably, the possible transformation of arsenic species was further characterized. The higher effectiveness of As(V) removal via electrosorption at 1.2V was attributed to the formation of an electrical double layer at the electrode/solution interface. The removal of As(III) could be achieved by the oxidation of As(III) to As(V) and subsequent electrosorption of the As(V) onto the electrode surface of the anode. The presence of sodium chloride or natural organic matter was found to considerably decrease arsenic removal. Single-pass electrosorption-desorption experiments conducted at 1.2V further demonstrated that capacitive deionization is a potential means of effectively removing arsenic from aqueous solutions.

14.
Chemosphere ; 146: 113-20, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26714293

RESUMO

In this study, a multiwalled carbon nanotubes-chitosan (CNTs-CS) composite electrode was fabricated to enable water purification by electrosorption. The CNTs-CS composite electrode was shown to possess excellent capacitive behaviors and good pore accessibility by electrochemical impedance spectroscopy, galvanostatic charge-discharge, and cyclic voltammetry measurements in 1 M H2SO4 electrolyte. Moreover, the CNTs-CS composite electrode showed promising performance for capacitive water desalination. At an electric potential of 1.2 V, the electrosorption capacity and electrosorption rate of NaCl ions on the CNTs-CS composite electrode were determined to be 10.7 mg g(-1) and 0.051 min(-1), respectively, which were considerably higher than those of conventional activated electrodes. The improved electrosorption performance could be ascribed to the existence of mesopores. Additionally, the feasibility of electrosorptive removal of aniline from an aqueous solution has been demonstrated. Upon polarization at 0.6 V, the CNTs-CS composite electrode had a larger electrosorption capacity of 26.4 mg g(-1) and a higher electrosorption rate of 0.006 min(-1) for aniline compared with the open circuit condition. The enhanced adsorption resulted from the improved affinity between aniline and the electrode under electrochemical assistance involving a nonfaradic process. Consequently, the CNT-CS composite electrode, exhibiting typical double-layer capacitor behavior and a sufficient potential range, can be a potential electrode material for application in the electrosorption process.


Assuntos
Quitosana/química , Nanotubos de Carbono/química , Cloreto de Sódio/química , Purificação da Água/métodos , Adsorção , Técnicas Eletroquímicas , Eletrodos
15.
Chemosphere ; 141: 71-9, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26135977

RESUMO

Highly porous activated carbons were resource-recovered from Leucaena leucocephala (Lam.) de Wit. wood through combined chemical and physical activation (i.e., KOH etching followed by CO2 activation). This invasive species, which has severely damaged the ecological economics of Taiwan, was used as the precursor for producing high-quality carbonaceous electrodes for capacitive deionization (CDI). Carbonization and activation conditions strongly influenced the structure of chars and activated carbons. The total surface area and pore volume of activated carbons increased with increasing KOH/char ratio and activation time. Overgasification induced a substantial amount of mesopores in the activated carbons. In addition, the electrochemical properties and CDI electrosorptive performance of the activated carbons were evaluated; cyclic voltammetry and galvanostatic charge/discharge measurements revealed a typical capacitive behavior and electrical double layer formation, confirming ion electrosorption in the porous structure. The activated-carbon electrode, which possessed high surface area and both mesopores and micropores, exhibited improved capacitor characteristics and high electrosorptive performance. Highly porous activated carbons derived from waste L. leucocephala were demonstrated to be suitable CDI electrode materials.


Assuntos
Carvão Vegetal/química , Técnicas Eletroquímicas/instrumentação , Fabaceae/química , Madeira/química , Capacitância Elétrica , Eletrodos , Fabaceae/crescimento & desenvolvimento , Modelos Químicos , Porosidade , Salinidade , Água do Mar/química , Propriedades de Superfície , Taiwan
16.
J Hazard Mater ; 278: 8-15, 2014 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-24937658

RESUMO

This study was performed to determine the feasibility of electrosorptive removal of copper ions from aqueous solutions using a capacitive deionization process. The electrosorptive potential of copper ions was determined using cyclic voltammetry measurements, and copper electrodeposition could be suppressed at a voltage less than 0.8 V. Importantly, the experimental results demonstrated a significant enhancement of electrosorption capability of copper ions using the activated carbon electrodes under electro-assistance, associated with electrical double-layer charging. At 0.8 V, the equilibrium electrosorption capacity was enhanced to 24.57 mg/g based on the Langmuir model, and the electrosorption constant rate was increased to 0.038 min(-1) simulated by a first-order kinetics model. Moreover, the activated carbon electrode showed great regeneration performance for the removal of low level copper ions. Additional experiments regarding electrosorption selectivity were performed in the presence of sodium chloride, natural organic matter, or dissolved silica. Copper ions that were preferentially electroadsorbed on the electrode surface can be effectively removed in a competitive environment. Therefore, the electrosorption process using activated carbon electrodes can be recommended to treat copper solutions at low concentrations for wastewater treatment and water purification.


Assuntos
Cobre/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Carbono/química , Capacitância Elétrica , Eletroquímica , Eletrodos , Soluções
17.
Chemosphere ; 91(5): 623-8, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23375820

RESUMO

The microbial fuel cell (MFC) is an emerging technology, which uses exoelectrogenic microorganisms to oxidize organic matter in the wastewater to produce electricity. However, the low energy output limits its application in practice. Capacitive deionization (CDI), an electrochemically controlled method for deionization by the adsorption of ions in the electrical double layer region at an electrode-solution interface, requires a low external power supply. Therefore, in this study, we investigated the MFC driven CDI (MFC-CDI) technology to integrate deionization with wastewater treatment and electricity production. Taking advantage of the low potential requirement of CDI, voltage generated from a continuous flow MFC could be used to drive the CDI to achieve removal of the electrolyte to a stable status. The results indicated that among the three connection types of MFCs including single-, series-, and parallel-configuration, the parallel connection of two MFCs resulted in the highest potential (0.63V) applied to CDI and the conductivity removal of NaCl solution was more than 60%. The electrosorption capacities under different electrolyte concentrations of 50, 100 and 150 mg L(-1) were 150, 346 and 295 µg g(-1), respectively. These results suggest that the new MFC-CDI technology, which utilizes energy recovery from the wastewater, has great potential to be an energy saving technology to remove low level dissolved ions from aqueous solutions for the water and wastewater treatment processes.


Assuntos
Fontes de Energia Bioelétrica , Eletricidade , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Purificação da Água/métodos , Águas Residuárias/microbiologia
18.
Appl Opt ; 50(2): 227-30, 2011 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-21221149

RESUMO

In this paper, we describe a theoretical and experimental study of a wavelength-selective filter derived from hollow optical waveguides composed of Bragg reflectors with defect layers on a silicon substrate. The defect states of the transmission filter at wavelengths of 1519 and 1571 nm were realized using one-dimensional photonic crystals (1D PCs) formed from a-Si and SiO(2). The transmission spectra of the filter waveguides and the band structure of the defect 1D PCs were calculated using the two-dimensional finite-difference time-domain and transfer matrix methods, respectively. The device exhibited the narrow bandwidths of 0.5 and 1.1 nm for wavelengths of 1571 and 1519 nm, respectively.

19.
Inorg Chem ; 48(4): 1519-23, 2009 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-19159316

RESUMO

Four isostructural organically templated lanthanide oxalatophosphates, (H(4)APPIP)[Ln(3)(C(2)O(4))(5.5)(H(2)PO(4))(2)].5H(2)O (Ln = Er-Lu and APPIP = 1,4-bis(3-aminopropyl)piperazine), have been synthesized under hydrothermal conditions and characterized by single-crystal and powder X-ray diffraction. Their structures contain LnO(8) trigonal dodecahedra linked by three bis-bidentate oxalates to form layers in the (102) plane, which are connected by dihydrogen phosphate and bis-monodentate oxalate ligands to form a 3D framework. The charge-compensating tetraprotonated 1,4-bis(3-aminopropyl)piperazinium cations and lattice water molecules are located in the 12-membered ring straight channels. They are the first examples of organically templated lanthanide oxalatophosphates. The thermal stability, guest desorption-sorption properties, variable-temperature in situ powder X-ray diffraction, magnetic susceptibility, and photoluminescence spectrum of the Er compound and catalytic activity of the Yb compound for the Biginelli reaction have also been studied.

20.
J Chem Phys ; 129(22): 224703, 2008 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-19071935

RESUMO

Grand canonical Monte Carlo (GCMC) simulations are employed to study the selective electrosorption of ions from a mixture of symmetric and asymmetric electrolytes confined in pores and results are compared to experimental observations obtained via cyclic voltammetry and batch electrosorption equilibrium experiments. GCMC simulations have the advantage over other Monte Carlo methods to unambiguously quantify the total number of ions in the pore solution. The exclusion parameter and selectivity factor are used to evaluate the selective capacity of pores toward different ionic species under various conditions. The number of coions inside the pore solution is determined by the proportion of different counterions present in the double-layer region. Because of the competitive effects resulting from asymmetries in charge and size associated with different ions, the electrosorption selectivity of small monovalent over large divalent counterions first decreases with increasing surface charge, passes through a minimum, and then increases with further increase in surface charge. At low and moderate surface charge densities, the fact that large divalent counterions preferentially screen the surface charge has a strong effect on pore occupancy; whereas at a very high surface charge density, size-exclusion effects dominate and determine the accessibility of different ions into the pores. Therefore, electrosorption selectivity of ions from a mixture of electrolytes could, in principle, be achieved via tuning the electrical double-layer formation inside the pores through the regulation of surface charge tailored for different ion characteristics. The findings of this work provide important information relevant to ion selectivity during separation processes and energy storage in supercapacitors.


Assuntos
Misturas Complexas/química , Eletrólitos/química , Nanoestruturas/química , Nanotecnologia , Absorção , Adsorção , Eletroquímica , Elétrons , Íons/química , Método de Monte Carlo , Porosidade
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