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Adsorption of Metal
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Gang Yang – One of the best experts on this subject based on the ideXlab platform.
Charge reversal and anion effects during Adsorption of Metal ions at clay surfaces: Mechanistic aspects and influence factorsChemical Physics, 2020Co-Authors: Xiaoxiao Huang, Gang YangAbstract:
Abstract Charge reversal occurs frequently during Adsorption of Metal ions at clay surfaces, and recent experimental studies manifest the strong anion specificities during Adsorption of Metal ions at clay surfaces. Herein, mechanisms and influence factors of charge reversal and anion specificities have been addressed by DFT calculations. Charge reversal is attributed to the intrinsic electrostatic interactions from clay surfaces, which become more depleted at higher surface charges due to existence of more counterions. The tendency of charge reversal is negatively correlated with the amount of surface charges. Charge reversal can be caused by all Metal ions while has a limited degree, even for high-valent Metal ions. Anions take effects by forming ionic bonds with charge-balancing Metal ions instead of forming direct interactions with clay surfaces, and the experimental observations are finely interpreted, such as anion specificities (Cl−
Adsorption of Metal ions at kaolinite surfaces: Ion-specific effects, and impacts of charge source and hydroxide formationApplied Clay Science, 2020Co-Authors: Xiaoxiao Huang, Qian Wang, Gang YangAbstract:
Abstract Adsorption of Metal ions at clay surfaces plays a critical role in a variety of geochemical, environmental and engineered processes, and p-DFT calculations with dispersion corrections were employed with aim to comprehensively understand the Adsorption of Metal ions at hydrated kaolinite surfaces, considering both (00 1 ¯ ) and (001) surfaces and different Metal ions (Mn+ = Li+, Na+, K+, Mg2+, Ca2+, Al3+, Fe3+). Ion-specific effects resulting from Adsorption also became the focus of this study. For Adsorption of alkali ions, inner-sphere complexes dominated for (00 1 ¯ ) surface while owing to hydroxide formation, outer-sphere complexes dominated for (001) surface. Both charge sources and surface structures can significantly alter Adsorption structures and their relative stabilities, and surface structures can further perturb ion-specific sequences. Hydroxide formation at (00 1 ¯ ) surface was favored for Metal ions (Mn+) of higher oxidation states: Non-existent for M+, geometrically stable but disfavored for M2+ while dominant for M3+. Al3+ Adsorption was likely to form AlOH2+, Al(OH)2+ and Al(OH)3 and released more H+ than base cations, which further caused soil acidification. Hydroxide formation affected significantly the extents of ion-specific effects and may further alter their sequences. Results were also helpful to rationalize and guide experimental studies.
Competitive Adsorption of Metal Ions at Smectite/Water Interfaces: Mechanistic Aspects, and Impacts of Co-Ions, Charge Densities, and Charge LocationsThe Journal of Physical Chemistry, 2019Co-Authors: Sen Yang, Xiantang Liu, Gang YangAbstract:
In natural environments, multiple Metal ions are concomitant, and their Adsorption at clay mineral/water interfaces is competitive and selective. In this study, the competitive mechanisms and impacts of co-ions for binary electrolyte solutions contacting smectite surfaces are probed by molecular dynamics simulations. Different binary Metal ions (Na⁺/Cs⁺, K⁺/Cs⁺ of 1:1 type, Na⁺/Pb²⁺ of 1:2 type, and Pb²⁺/Ca²⁺ of 2:2 type) are considered, and impacts of charge densities and locations that are critical to ion Adsorption are also subject to investigations. Impacts of charge densities and locations onto Adsorption of Metal ions are similar in single and binary systems, and increase of charge densities and shift of charge locations from octahedral to tetrahedral sheets may change the major surface complexes from the outer sphere to the inner sphere and greatly enhance the amounts and stabilities, with the enhancement degrees being Pb²⁺, Ca²⁺ > Na⁺ > K⁺ > Cs⁺. The major surface complexes of Metal ions can be changed by charge densities and locations and are more affected by co-ions than the minor surface complexes. Stronger competition and higher Adsorption selectivity occur (1) at higher charge densities; (2) for beidellite than montmorillonite; and (3) for the inner sphere than the outer sphere. As discussed, all binary systems show peculiarities regarding competition and Adsorption selectivity, and the competition capabilities and Adsorption selectivities may vary with charge densities and locations. These findings are consistent with experimental observations available and provide insights to unravel the complicated Adsorption mechanisms at clay mineral/water interfaces and to manage contaminated soil sites.
Tae Yoon Eom – One of the best experts on this subject based on the ideXlab platform.
Hydrophobic Effects of o-Phenanthroline and 2,2′-Bipyridine on Adsorption of Metal(II) Ions onto Silica Gel SurfaceJournal of Colloid and Interface Science, 1993Co-Authors: Yeong Jae Park, Kyung-hoon Jung, Kyoung Kyun Park, Tae Yoon EomAbstract:
Abstract The effects of o-phenanthroline and 2,2′-bipyridine on the Adsorption of Metal(II) (Fe, Co, Ni and Cu) ions onto silica gel surface have been studied. The Adsorption is expressed in terms of the measured concentrations of both Metal and ligand at equilibrium. Each Adsorption of the four Metal ions is increased with the presence of the ligands. In addition, Adsorption increases slowly with pH at low pH values and then increases rapidly up to near the pKa value of silica gel (≈6.5). The Adsorption of each Metal ion at low pH is increased with increased ligand concentration. However, at high pH the Adsorptions of Fe(II) and Cu(II) are decreased with increased ligand concentration whereas the Adsorptions of Co(II) and Ni(II) are always increased. At low pH values the ligand to Metal ratio adsorbed on the silica gel surface is ca. 3:1 while at high pH values it is 1:1, 2:1, and 3:1, corresponding to the initial ligand to Metal ion concentration ratio. The addition of ethanol to the phenanthroline-SiO2 solution results in a decrease in the Adsorption of phenanthroline. The effect of ethanol is also observed in the Fe(II)-phenanthroline-SiO2 system. The behavior of the Adsorption is interpreted qualitatively by hydrophobic expulsion, the formation of surface complexes, and electrostatic interaction. It is concluded that hydrophobic expulsion plays an important role in the Adsorption of Metal ions in the presence of hydrophobic ligands on silica gel surface.
Clas Persson – One of the best experts on this subject based on the ideXlab platform.
Physical Chemistry Chemical Physics, 2015Co-Authors: Vadym V Kulish, Clas Persson, Oleksandr I MalyiAbstract:
Single- or few-layer phosphorene is a novel two-dimensional direct-bandgap nanomaterial. Based on first-principles calculations, we present a systematic study on the binding energy, geometry, magnetic moment and electronic structure of 20 different adatoms adsorbed on phosphorene. The adatoms cover a wide range of valences, including s and p valence Metals, 3d transition Metals, noble Metals, semiconductors, hydrogen and oxygen. We find that adsorbed adatoms produce a rich diversity of structural, electronic and magnetic properties. Our work demonstrates that phosphorene forms strong bonds with all studied adatoms while still preserving its structural integrity. The Adsorption energies of adatoms on phosphorene are more than twice higher than on graphene, while the largest distortions of phosphorene are only ∼0.1–0.2 A. The charge carrier type in phosphorene can be widely tuned by adatom Adsorption. The unique combination of high reactivity with good structural stability is very promising for potential applications of phosphorene.
Hiroyuki Yoshida – One of the best experts on this subject based on the ideXlab platform.
Industrial & Engineering Chemistry Research, 1993Co-Authors: Yoshihide Kawamura, Masaki Mitsuhashi, Hiroaki Tanibe, Hiroyuki YoshidaAbstract:
Highly porous chelating resin was fabricated from the natural polysaccharide chitosan. The Adsorption capacity was increased by polyamination with poly(ethylene imine) (MW = 10,000). The capacity was about 1-2 times larger than that of commercial chelate resins. The selectivity for Adsorption of Metal ions on the resin, which was determined for a single solute at pH [approx equal] 7, was Hg(II) > UO[sub 2](II) > Cd(II) > Zn(II) > Cu(II) > Ni(II). Mg(II), Ca(II), Ga(III), As(III), and Sr(II) were not adsorbed on the resin at all. The selectivity depended on the pH of each Metal solution. The equilibrium isotherms for Adsorption of HgCl[sub 2] were correlated by the Langmuir equation. The saturation capacities were close to the concentration of amino group fixed on the resin. When HCl or NaCl coexisted in HgCl[sub 2] solution and their concentrations were lower than 100 mol/m[sup 3], the saturation capacity of HgCl[sub 2] was little affected by them. When 500 mol/m[sup 3] H[sub 2]SO[sub 4] coexisted in HgCl[sub 2] solution, extremely low pH inhibited the Adsorption of Hg(II) at all.
Alzira Maria Serpa Lucho – One of the best experts on this subject based on the ideXlab platform.
Journal of Applied Electrochemistry, 2018Co-Authors: Paulo Cesar Mendes Villis, José Costa Sampaio Filho, Wolia Costa Gomes, Rita De Cassia Mendonça Miranda, Gilvanda Silva Nunes, Fábio Luiz Pissetti, Yoshitaka Gushikem, Alzira Maria Serpa LuchoAbstract:
This paper proposes the preparation of a hybrid adsorbent material organically modified with N 1-[3-(trimethoxysilyl)propyl]diethylenetriamine and imprinted ionically with Cu(II) ions. The structure of functionalized silica matrix with an organic group containing electron-donating nitrogen atoms allows several applications such as Adsorption of Metal ions, electrocatalytic studies, and development of electrochemical sensors. The electrochemical behavior of the hybrid material was investigated using a carbon paste electrode in different electrochemical techniques: cyclic voltvoltammetry, differential pulse voltammetry, differential pulse anodic stristripping voltvoltammetry, and chronoamperometry. DPASV yielded the best results and linear response to Cu(II) in the concentration range of 6.0 × 10^−4 to 5.4 × 10^−3 mmol L^−1 ( R ^2 = 0.999; n = 9) using a pre-concentration time ( t _pc) of 1800 s at a reduction potential ( E _red) of − 0.51 V versus SCE and a scan rate of 20 mV s^−1, with a detection limit estimated at 1.82 × 10^−7 mmol L^−1. The samples were evaluated using the proposed sensor and a good recovery of Cu(II) was obtained in the range from 92.88 to 110.89%. The proposed method for DPASV was used for Cu(II) determination in samples of tap water, and the results from literature and that of flame atomic absorption specspectrometry. Graphical Abstract