Ionic Adsorption Research Articles

3D Capacitive Deionization Electrode Supported By Carbon Fiber/Felt Framework with Ordered Macropores for Brackish Water Desalination

Capacitive Deionization (CDI) is an emerging technology for brackish water desalination. To achieve scaling electrodes with a commercial mass loading, carbon fiber/felt was employed as framework to build 3D composite electrode. The highly conductive carbon fiber/felt can serve as electron transfer channel and also provide macrostructure while activated carbon (AC) with microstructure was loaded to furnish ionic adsorption sites. The electrochemical characterization of 3D composite with carbon felt (1 cm2) showed a larger total ion storage capacity (25 F g−1, 40 mg cm−2, 0.79 F) as compared to an AC film electrode (93 F g−1, 1.5 mg cm−2, 0.11 F). It was then tested in a 10 cm2 CDI cell reaching salt adsorption capacity (SAC) values of 5.2–8.7 mg g−1 and 57–67% in charge efficiency. In addition, the 3D composite was scaled to a 300 cm2 stack demonstrating excellent performance (8.7 mg g−1SAC, 2.6gSALT m−2 h−1 and 63% charge efficiency). Similarly, the 3D composite with carbon fiber as the framework and ordered macropores by the introduction and removal of a second fiber showed lower ohmic drop and higher deionization performance than the AC film electrode and also the ones with only carbon fiber. Therefore, these 3D composite electrode supported by carbon fiber/felt framework can be a great promise for large-scale CDI practical applications.

In situ analysis of pore size effect of ionic solvation during the formation of double electric layers

Electrochemical quartz crystal microbalance (EQCM) technique was used to characterize the influence of pore size and ion size and, solvation effect on the formation of electric double-layer capacitors (EDLCs). Based on quantitative calculation and analysis, the apparent molecular mass ( M sx ) was calculated from the slope of the electrode mass change ( Δm ) vs. the charge ( ΔQ ) passed in the electrode during charging/discharge. Comparing M sx with the molar mass of bare ion, the value of specific solvation number( x )was deduced. Findings indicate that the formation of double layers at electrode interface by ionic absorption was accompanied by solvation effect. The solvation effect was weakened as the pore size of the electrode decreased, concluding that the pore size effect exist concurrently with solvation effect during ionic adsorption. The pore size effect was influenced by the size of the counter-ions, polarity of solvent molecules and ionic concentrations.

The Impact of Spatially Correlated Heterogeneity and Adsorption on Modified Salinity Water in Carbonates.

Modified salinity water (MSW) core flooding tests conducted in carbonates often exhibit a delay in the additional oil recovery. It has been suggested that the ionic adsorption process controls this delay. In this study, we examine the adverse effect of the adsorption process on the performance of MSW flooding in various models categorized as layered and heterogeneous reservoirs and a North Sea field sector model. To evaluate the impact of porous media’s heterogeneity on the delay caused by the adsorption, we introduce the net present volumetric value based on which the cost of delay is calculated. This evaluation is achieved by comparing the calculated cost of delay for heterogeneous systems and that of their equivalent homogeneous porous media. It is found that, as the level of reservoir heterogeneity increases, the adverse effect of ionic adsorption on the improved oil production decreases. Further, computational results suggest that the connectivity index, which is defined as the effective permeability between injection and production wells divided by the average permeability, is a better alternative to the vorticity index to describe the impact of the delay of additional oil recovery in heterogeneous reservoirs subjected to MSW flooding.

Characteristics of ionic adsorption on silica nanoparticles and its impact on the long term stability of dye-sensitized solar cells

Quasi-solid electrolytes based on silica nanopowder are well known in literature and these electrolytes are able to match in performance with that of liquid electrolytes. However, contrasting results are observed in literature regarding stability of dye-sensitized solar cells (DSSCs) with most of the reported articles projecting silica-loaded quasi-solid electrolyte-based cells as a stable alternative to liquid electrolyte-based cells, while a few others contradicting the same. The present study demonstrates the effect of ageing under heat (60°C) and illumination on the performance of liquid electrolyte and silica-loaded electrolyte-based DSSCs. It has been observed that DSSC based on silica-loaded electrolyte are less stable than DSSC based on liquid electrolyte even though independent study on both electrolytes by thermal analysis shows silica-loaded electrolyte to be more stable than liquid electrolyte. Segregation of silica in electrolyte has been confirmed through cryo-field emission gun-scanning electron microscopy. Zeta potential measurements show that ions are desorbed from the surface of silica on ageing under heat and illumination.

Ion-specific effects on equilibrium adsorption layers of ionic surfactants

This review article reports the effect of the counter-ions on the ionic surfactant adsorption layer and its relation to the stability of foams and emulsions. The adsorption theory of Davies about the ionic surfactant monolayer was revisited and it is shown how to account for the type of the counter-ions. The experimental validation of this theory on thin liquid films was shown as well, thus explaining the effect of Hofmeister. However, their effect on foams and emulsions is more complex. Furthermore, it is shown how the counter-ions affect in complex way the stability of foams and emulsions via the surfactant adsorption layer in the light of the newest theory. To elucidate the nature of this effect, further investigation is called for.

Synthesis of a New Imidazole Amino Acid Ionic Liquid Polymer and Selective Adsorption Performance for Tea Polyphenols.

A series of imidazolium ionic liquid monomers with L-Proline anions (ViImCn-L-Pro and (ViIm)2Cn(L-Pro)2) were firstly synthesized, after which new copolymer materials were prepared by polymerization of the ionic liquid monomers with N,N′-methylene diacrylamide (MBA). Polymerization conditions, including the ratio of Ils(ViImCn-L-Pro or (ViIm)2Cn(L-Pro)2) and MBA, solvent, ionic liquids and initiator’s amount, were investigated and found to have an important effect on the adsorption capacity. Polymerization conditions were shown to have more significant impacts on adsorption capacities in the following order: the ratio of Ils and MBA > the amount of initiator > ionic liquids > solvent. The polymers were characterized by IR, EA, SEM, particle size distribution and TG. One of the polymers exhibited the highest selective adsorption capacity of tea polyphenols (521 mg/g). which was significantly higher than other adsorption media. The absorbed tea polyphenols could be desorbed readily with 2% hydrochloric acid methanol solution as eluent. The polymer material could maintain a higher adsorption capacity after four reuses. Based on this polymer, a new method for the efficient separation of tea polyphenols from tea water could be developed.

PH-Dependent surface charge at the interfaces between aluminum gallium nitride (AlGaN) and aqueous solution revealed by surfactant adsorption

HypothesisThe net surface charge of AlGaN/GaN structures, where AlGaN is in contact with the solution, is controlled by the pH-dependent protonation and deprotonation of the surface hydroxyl groups and possibly the electron-deficient surface electronic states. We hypothesize that atomic force microscopy (AFM) force measurements of ionic surfactant adsorption can reveal how the AlGaN surface properties vary with pH. ExperimentsAFM force curves and images were used to probe the AlGaN/solution interface in water as a function of pH, and with added cationic surfactant cetyltrimethylammonium bromide (CTAB) or anionic surfactant sodium dodecylsulfate (SDS). FindingsThe AlGaN/solution interface is negatively charged at pH 12, has an isoelectric point near pH 5.5, and is positively charged at pH values less than 5.5. Surfactant adsorption data suggests AlGaN surface is somewhat hydrophobic at acidic pH. Compared to gallium nitride (GaN), at pH 2, AlGaN has a lower charge density and hydrophobicity, but at other values of pH, the surface properties of AlGaN and GaN are similar.

Bi2S3 anchored ZnS/ZnO nanorod arrays photoanode for enhanced visible light driven photo electrochemical properties

We report on the enhanced photoelectrochemical water splitting of hybrid ZnS/ZnO core-shell nanorod arrays functionalized with Bi2S3 nanosheets as photoanode. The ZnO nanorod arrays were prepared by a facile hydrothermal approach and sulphurized to form ZnS shell. Subsequently porous Bi2S3 nanosheets were arbitrarily decorated on the nanorod arrays by ionic adsorption and reaction method. Substantial enhancement in photocurrents with twofold increment is observed for hybrid photoanode compared to pristine counterparts. The structural and morphological properties of nano hybrid Bi2S3/ZnS/ZnO samples were analyzed by field emission scanning electron microscopy and X-ray diffraction. The higher wavelength shift in the absorption edge of Bi2S3/ZnS/ZnO photocatalyst was observed in diffuse reflectance UV–Visible spectra. The low temperature photoluminescence and impedance spectra of Bi2S3/ZnS/ZnO photoanode confirm that Bi2S3 functionalization reduces the recombination of electron–hole pair and facilitates barrier free charge transfer. The Bi2S3/ZnS/ZnO photoanode device exhibits photocurrent density of 220 μA/cm2 at 0.2 V vs. Ag/AgCl under the electrolyte solution at pH ~10.8. The resultant hybrid photoanode withhold good stability and maintain the facile charge carrier generation and separation. Bi2S3 topological nanosheets are responsible for the absorption of complete visible photons while ZnS/Bi2S3 inter-junction provides the robust electron-hole pair separation at their interface due to infiltration pathway. The photoactive hybridization of Bi2S3/ZnS/ZnO provokes the enhanced donor charge density for efficient hydrogen evolution reaction.

Processing Strategies to Obtain Highly Porous Silk Fibroin Structures with Tailored Microstructure and Molecular Characteristics and Their Applicability in Water Remediation

The present work reports on the control of silk fibroin (SF) porous structures performance through various processing methods. The study includes the analysis of two dissolving techniques (CaCl2/H2O/EtOH ternary and LiBr/H2O binary solutions), three regeneration methods (gelation, lyophilization and gas foaming) and one post-processing (EtOH). In all the cases, followed steps lead to SF structures with porosity values above 94% and large surface areas. Also, results about samples microstructure, secondary organization, crystallinity and water behavior, reveal a direct correlation between processing and SF properties.Thanks to the achieved progress, the SF varying porous structures were evaluated for metalloids (As5+ and As3+) and heavy metals (Cr6+ and Cr3+) adsorption, observing a direct relationship between samples processing and ionic species adsorption ability.Thus, it is shown that the control of the properties of SF based porous structures through processing, represents a suitable and ecofriendly approach for the development of bio-based materials for environmental applications.

Photon–phonon interaction of surface ionic adsorption within electric double layer in reservoir sandstone

In solid materials, the interaction of photon comprises ionic and electronic oscillating charges, while phonons are the collection of excitations in arrangement of atoms and molecules in both solid and liquids materials at certain frequencies. The distribution of ions and charges under electric double layer in reservoir sandstone and the kind of electrostatic environments they create are major challenges to the recovery of residual hydrocarbons in depleted and marginal fields. Saturated Berea sandstone was used to investigate interaction of ions on sandstone and crude oil with the aid of Scanning electron microscopy; Energy Dispersive X-Ray mapping (EDX), Fourier Transform Infrared Spectroscopy (FTIR), X-ray fluorescence (XRF), Raman spectral analysis and Core flooding experiment were used to determine the absorption of ions with and without electromagnetic wave intensity. This paper provides insight on surface adsorption of ion within electric double layer and the effect of photon–phonon interaction with reservoir sandstone under EDL mechanisms. Result reveal that the absorption is located between 1–50 μm ranges this is referred to infrared absorption bands, the influx of electrolyte contributes to well dispersion and interaction of both positive and negative ions on the sandstone. It shows that the domination of the repulsive double layer is due to high proportion of NaCl electrolyte which has highest negative zeta potential for the fluid stability. Comparison of the major ions and composition of the ions on the sandstone reacted; indicate fluid mobility due to water-rock interaction.

Influence of solvent on the performance of liquid and silica nanoparticle loaded quasi solid electrolytes based dye sensitized solar cells

ABSTRACT In quasi-solid electrolytes loaded with nanoparticles such as silica and titania, the solvent of the electrolyte has a key role in the separation of ionic species and their adsorption on the surface of nanoparticle. The present article demonstrates the effect of different solvents on the ionic adsorption and its impact on the photoelectrochemical characteristics of dye sensitized solar cells (DSSCs). Ionic adsorption behaviour has been studied by zeta potential measurements and analysis of carbon to nitrogen (C/N) ratio. It has been found out that effective cationic adsorption occurs in 3-methoxypropionitrile (MPN) as solvent in electrolyte, whereas poor adsorption occurs in N-methyl-2-pyrrolidone (NMP)-based electrolyte due to the higher donor number of the latter which results in effective interaction of solvent and nanopowder. Performance of DSSC fabricated with MPN-based solvent in electrolyte was superior to others in both liquid and quasi-solid electrolytes.

Synthesis of 3D Cu(OH)2 nanoflower thin film by room temperature chemical method for high performing positive electrode in supercapacitor

Abstract Herein, we report synthesis of three dimensional (3D) copper hydroxide [Cu(OH)2] nanoflower thin film by room temperature successive ionic layer and adsorption reaction (SILAR) method. The synthesized film is characterized for its structural, chemical, surface morphological properties by means of X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and field emission scanning electron microscopy (FE-SEM), respectively. The XRD analysis shows the deposited film is amorphous in nature, formation of copper compound with hydroxide phase is confirmed by FT-IR study. The FE-SEM analysis reveals the nanoflower morphology of the deposited material. Moreover, FE-SEM micrograph shows the entire surface of the substrate is uniformly covered by Cu(OH)2 nanoflowers. When employed as the positive electrode in supercapacitor device, the Cu(OH)2 nanoflower thin film exhibits highest specific capacitance which exceeds 283 Fg−1 at 10 mVs−1 in 1 M KOH electrolyte, which demonstrates that the hydrous 3D Cu(OH)2 nanoflowers with porous morphology can effectively be used in supercapacitor application.

Electrode materials for capacitive deionization: A review

Abstract Capacitive deionization (CDI) is an emerging technology for energy-efficient water desalination, and attracts more and more attention in recent years. It has been concluded that CDI technology shows competitiveness and perspectives on seawater desalination and wastewater treatment. The ionic adsorption mechanism can be clarified by electric double-layer capacitive adsorption and pseudocapacitive adsorption. The performance of CDI depends on both device and materials. The adsorption capacity and energy efficiency was improved significantly with fast growth of researches on material and novel energy storage techniques. This review summarizes researches on CDI technologies with an emphasis on electrode material design and improved adsorption performance.

Unraveling how nanoscale curvature drives formation of lysozyme protein monolayers on inorganic oxide surfaces

The development of nanostructured material interfaces is critical to various application areas spanning diverse fields such as medicine, energy, and sensing. One of the most promising areas involves nanomedicine and drug delivery and involves the formation of noncovalently adsorbed protein coatings on nanostructured surfaces such as inorganic nanoparticles. The coatings can form naturally as part of the so-called protein corona or be purposely incorporated as functional elements to evade immune recognition or to enable enzymatic function, for example. To date, most relevant studies have examined the underlying adsorption processes on planar surfaces while the effect of nanoscale curvature on protein adsorption is still being unraveled across many dimensions. Herein, we investigated the ionic strength-dependent adsorption of antibacterial lysozyme protein onto planar and nanostructured silicon oxide surfaces by employing the quartz crystal microbalance-dissipation and localized surface plasmon resonance sensing techniques. Our findings revealed that lysozyme undergoes greater adsorption-related denaturation and spreading on planar surfaces which led to multilayer formation, while nanoscale curvature effects suppress protein denaturation on nanostructured surfaces leading to monolayer formation. We discuss these findings within the context of protein-surface and protein-protein interactions and how subtle changes in adsorption pathways can drive the formation of distinct macromolecular assemblies. Looking forward, we also discuss how such measurement strategies can enable mechanistic insights into the formation of protein coatings on nanostructured surfaces with broad implications for nano-bio interface science.

Effect of FSI Based Ionic Liquid on High Voltage Li-Ion Batteries

In this manuscript, a functionalized ionic liquid 1-cyanoethyl-2-methyl-3-allylimidazolium bis (trifluoromethanesulfonimide) salt (CEMAImTFSI) was synthesized and explored as an electrolyte component to improve the oxidation resistance of the electrolyte in high-voltage lithium-ion batteries. Based on the calculation by Gaussian 09, CEMAImTFSI has a higher highest occupied molecular orbital (HOMO) value than the organic solvents ethylene carbonate (EC) and dimethyl carbonate (DMC), suggesting that CEMAImTFSI is more susceptible to oxidation than EC and DMC. Moreover, a low Li+ binding energy value of –3.71 eV and the lower lowest unoccupied molecular orbital (LUMO) enable CEMAImTFSI to migrate easily to the surface of the LiNi0.5Mn1.5O4 cathode and participate in the formation of the SEI (solid electrolyte interphase) film, protecting the electrode materials. Electrochemical studies showed that the LiNi0.5Mn1.5O4/Li cell with 1.0 mol/L LiPF6-EC/DMC/10 vol% has the best cycling stability in the voltage range of 3–5 V. The initial discharge specific capacity of the cells was 131.03 mAh·g−1 at 0.2 C, and even after 50 cycles the discharge specific capacity value of 126.06 mAhg−1 was observed, with the cell showing a capacity retention as high as 96.2%. Even at the rate of 5 C, the average discharge specific capacity of the cell was still 109.30 mAh·g−1, which was 1.95 times higher than the cell without the CEMAImTFSI addition. The ionic liquid molecules adsorption on the cell electrode surface was confirmed by X-ray photoelectron spectroscopic (XPS) analysis after charge–discharge measurements.

Investigation of the CdS quantum dot sensitized solar cells based on a series of zinc titanium mixed metal oxides

In this work, a series of zinc titanium mixed metal oxides obtained from the zinc titanium layered double hydroxides as precursor were prepared as the photoanode material of the CdS quantum dot-sensitized solar cells. CdS quantum dots were deposited on photoanodes by the successive ionic adsorption and reaction method. It was investigated that the effects of photoanode based on different Zn–Ti molar ratios on the photovoltaic performance of solar cells. The essential parameters of samples were investigated by UV–vis absorption spectrum, incident photon-to-current conversion efficiency, photoelectric conversion efficiency and electrochemical impendence spectrum. The varying Zn–Ti ratios influence adsorption properties and charge mobility. As a result, the cells based on Zn–Ti MMOs achieved an optimum power conversion efficiency of 2.71% when the Zn–Ti ratio is 7:1.

Non-linear optical study of hierarchical 3D Al doped ZnO nanosheet arrays deposited by successive ionic adsorption and reaction method

Successive ionic layer adsorption and reaction (SILAR) method is based on the adsorption and reaction of the ions in the cationic solution and the ionic solution, respectively. This method is simple, inexpensive, large-scale deposition, effective way for deposition on 3D substrates, low-temperature process and represents an easy way for the preparation of doped, composite and heterojunction materials. To take advantage of this method and the ZnO nanostructures, various parameters have been optimized.Undoped and Aluminum (Al) doped ZnO nanostructures were prepared by the SILAR technique. The characterization of the nanostructures prepared was carried out using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoemission spectroscopy (XPS), UV–Vis spectrometry and nonlinear optical analysis (NLO). The structural, compositional and optical properties confirm the introduction of Al3+ ions into the ZnO matrix. As a result, an enhancement of the crystallinity, enhancement of the light absorption and a change in the morphology of the nanostructures were observed.The laser stimulated nonlinear optical effects of the second and third harmonic generation were done using a fundamental laser beam. The laser stimulated NLO values obtained are at least 10% higher than the doped ZnO nanomaterials synthesized by other methods using the same set-up.

(Invited) Underpotential Deposition and Alloy Co-Deposition

The interplay between ionic adsorption, underpotential deposition and excess bond enthalpy in the deposition of materials will be discussed based on selections from recent work. Examples of limiting behavior will be presented that range from the deposition of solid-solutions, e.g. Pt-Cu and Pt-Fe group alloys, to intermetallics, e.g. Pt-Pb, to immiscible, e.g. Cu-Pb, systems. In addition, contributions of “parasitic” electrolyte breakdown reactions on the deposition of elements and alloys will also be briefly discussed. Close coupling between electroanalytical, gravimetric, metallurgical and surface science measurements enable the underlying thermodynamic and kinetic influences on co-deposition process to be revealed.

Investigation of adsorption mechanism of phosphate(V) ions on the nanostructured Na-A zeolite surface modified with ionic polyacrylamide with regard to their removal from aqueous solution

The sorption properties of Na-A-type synthetic zeolite, obtained from fly ash with regard to the phosphate(V) ions, were determined. The Na-A zeolite was prepared using hydrothermal conversion of fly ash with aqueous sodium hydroxide. The effects of solution pH and zeolite surface modification by ionic polyacrylamide (PAM) were examined. Both anionic and cationic forms of PAM were applied. The adsorption and electrokinetic data were obtained by means of spectrophotometric measurements, potentiometric titrations and zeta potential determination. It was shown that the presence of ionic polyacrylamide adsorption layers modifies the surface properties of the solid. The resulting composite material (zeolite/polymer) can be applied for effective removal of phosphate(V) ions from the liquid medium. Its regeneration possibilities are also considerable. Additionally, the use of fly ash for zeolite preparation leads to management of hazardous waste material.

Preparation and characterization of tin sulfide films with or without sodium chloride

The successive ionic adsorption and reaction (SILAR) method was used to obtain tin sulfide film on FTO glass. In this work tin sulfide films were prepared with or without the immersion stage in distilled water. As-deposited tin sulfide films consisted of orthorhombic structures SnS and Sn2S3. This multiphase composition of obtained thin films was confirmed by X-ray diffraction and Raman spectroscopy. The estimated average crystallite size was in the range of 14–31 nm and was dependent on the conditions of the film preparation. Energy-dispersive X-ray analysis showed that tin sulfides films prepared without the immersion stage in distilled water formed with sodium chloride. The percentage incorporation of sodium and chlorine in those films was 5.29–8.10 and 8.71–11.22 at. %, respectively. The addition of sodium and chlorine atoms exhibited better crystallinity and effected on the optical properties of tin sulfides films.