绿茶对水溶液中Pb2+和Cd2+吸附性能初步研究

研究了绿茶对溶液中Pb2 和Cd2 离子的吸附和解吸性质。考察了pH、温度、吸附时间对绿茶吸附性能的影响,得到吸附动力学曲线和吸附等温线。结果表明,茶叶在pH为4~6的弱酸性范围内对两种金属离子的吸附效果最佳,在30℃时,茶叶对Pb2 和Cd2 的饱和吸附量分别为46.66 mg/g和33.29mg/g,吸附符合Langmuir吸附等温方程,并对吸附机理进行了初步的探讨。对解吸条件研究发现,用0.1 mol/L HCl和EDTA作为解吸剂,对Pb2 和Cd2 的解吸效果较好,解吸率达80%以上,可有效回收重金属Pb2 和Cd2 。     

Influence of PZC (Point of Zero Charge) on the Static Adsorption of Anionic Surfactants on a Malaysian Sandstone

Static adsorption studies of two anionic surfactants produced in our lab are reported. The adsorption of surfactants on the rock samples was investigated with and without the presence of alkali. The point of zero charge (PZC) values were determined for the sandstone samples employing three titrimetric methods and it was found to be at pH 7.98. The relationship between the adsorption degree and pH value of brine below and above the PZC is discussed. It was found that at the pH of solution exceeds the PZC of the rock, the adsorption was 0.43 and 0.86mg/g of rock for the two surfactants. However, at pH values below PZC, the adsorption as high as 3.66 and 4.49mg/g for the two surfactants. The synthesized surfactants are found to be suitable for the EOR applications at pH values higher than the PZC of the rock sample.     

Physical adsorption of gases on energetically heterogeneous solids II. Theoretical extension of a generalizedLangmuir equation and its application for analysing adsorption data

The generalizedLangmuir equation proposed in part I is extended to monolayer adsorption with lateral interactions and to multilayer adsorption on heterogeneous surfaces with random distribution of adsorption sites. New differential functions, useful for interpreting the adsorption data, are introduced to study the mathematical and physical properties of this equation. These functions are applied to study three gas adsorption systems available from the literature.

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Gasadsorption auf energetisch heterogenen Feststoffen, 2. Mitt.: Die theoretische Erweiterung einer generalisierten Langmuir-Gleichung und ihre Anwendung zur Analyse von Adsorptionsdaten

Zusammenfassung Die generalisierteLangmuir-Gleichung, die in der 1. Mitt. beschrieben wurde, wird für die einlagige Adsorption mit lateralen Wechselwirkungen und für die viellagige Adsorption auf heterogenen Oberflächen mit einer Zufallsverteilung von Adsorptionsplätzen erweitert. Es werden neue Differentialfunktionen zur Untersuchung der mathematischen und physikalischen Eigenschaften dieser Gleichung eingeführt, die sich als fruchtbringend zur Interpretation von Adsorptionsdaten erweisen. Diese Funktionen werden zur Untersuchung von drei Gasadsorptionssystemen aus der Literatur herangezogen.

     

Theoretical study of the adsorption of oxygen on a Cu(100) surface and the coadsorption with alkali atoms

We performed a theoretical study of the adsorption of oxygen on a cluster model of the Cu(100) surface and also the surface coadsorbed with lithium and potassium atoms. The study showed that alkali coadsorption facilitates in a significant way the process of molecular adsorption, whereas the adsorption of atomic oxygen is only slightly modified. The alkali atoms on the copper surface produce an increase in the charge transfer toward the oxygen molecule, favoring the oxygen dissociation. The effect is greater for the potassium coadsorption. In addition, we found that the potassium coadsorption favored the dissociation and recombination processes by about 60 and 15%, respectively. In turn, the lithium coadsorption favored only the recombination process by about 50%. These results could be an important aspect for catalytic processes.From the Proceedings of the 28th Congreso de Quimicos Teóricos de Expression Latina (QUITEL 2002)     

Kinetics of adsorption and desorption of Pb(II) in aqueous solution on activated carbon by two-site adsorption model

The adsorption and desorption equilibrium and kinetics of lead ions from aqueous solutions on a granular activated carbon (GAC) were examined. Rapid increase followed by slow increase in Pb(II) amount on the GAC was observed as a function of time for the adsorption, while rapid decrease and consecutive very slow decrease was observed in desorption. Based on the experimental results, a two-site adsorption model was proposed for the adsorption and the desorption of Pb(II) under the study conditions. The Pb(II) adsorption on the GAC was estimated to have simultaneously occurred on the strong and the weak adsorption sites. Conventional Langmuir-type kinetic equations were introduced to quantitatively predict the adsorption and desorption with the two-site model by optimizing the parameters to fit the equilibrium and the kinetic experimental results. The equilibrium and kinetic experimental results could be represented by the equations by using one set of the common Langmuir parameters. Resultant kinetic parameters revealed that the adsorption equilibrium constant was two orders of magnitude greater for strong adsorption site than for weak adsorption site, though the maximum number of weak adsorption site was 1.5 times as great as that of strong adsorption site. The strong adsorption equilibrium constant resulted from a small desorption rate constant for the site. The equations were demonstrated to be applicable for predicting other desorption performances as well.     

Application of surface plasmon resonance spectroscopy for adsorption studies of different types of components on poly(dimethylsiloxane)

Surface plasmon resonance (SPR) spectroscopy is utilized to study in real-time and, by label-free means, the reversible and quasi-irreversible adsorption of small ionic or neutral molecules, pharmaceuticals, and proteins on poly(dimethylsiloxane) (PDMS) surfaces. The SPR sensor is covered with 0.2% (w/v) PDMS in octane. During the timescale of a typical lab-on-a-chip analysis or an electrophoretic separation, it was found that small neutral components containing a hydrophobic part do not adsorb or absorb onto PDMS, while larger, water-soluble polymer-like materials like proteins generally irreversibly adsorb to PDMS. The technique can be used to monitor the kinetics of adsorption and desorption of the molecules. For the non-specific adsorption of teicoplanin to PDMS, a Langmuir-like adsorption isotherm was obtained (K_d = 32 ± 2 μmol L⁻¹).     

Comparative Adsorption of Lead(II) on Flake and Bead‐Types of Chitosan

The adsorption of Pb(II) ions from aqueous solutions by chitosan flakes and beads was studied. The chitosan beads were prepared by casting an acidic chitosan solution into alkaline solution. Experiments were carried out as a function of pH, agitation period and initial concentration of Pb²⁺ ions. The uptake of Pb²⁺ ions from aqueous solution was determined from changes in concentration as measured by atomic absorption spectroscopy. The maximum uptake of Pb²⁺ ions on chitosan beads was greater than that on chitosan flakes. Adsorption isothermal data could be interpreted by the Langmuir equation. The experimental data of the adsorption equilibrium from Pb²⁺ ion solutions correlated well with the Langmuir isotherm equation. SEM analyses were also conducted for visual examination of the chitosan flakes and beads. Physical properties including surface area and average pore diameter were characterized by N₂ adsorption experiment.     

A comparison between dual polarization interferometry (DPI) and surface plasmon resonance (SPR) for protein adsorption studies

This work was performed with the aim of comparing protein adsorption results obtained from the recently developed dual polarization interferometry (DPI) with the well-established surface plasmon resonance (SPR) technique. Both techniques use an evanescent field as the sensing element but completely different methods to calculate the adsorbed mass. As a test system we used adsorption of the lipase from Thermomyces lanuginosus (TLL) on C18 surfaces. The adsorbed amount calculated with both techniques is in good agreement, with both adsorption isotherms saturating at 1.30–1.35 mg/m² at TLL concentrations of 1000 nM and above. Therefore, this supports the use of both SPR and DPI as tools for studying protein adsorption, which is very important when comparing adsorption data obtained from the use different techniques. Due to the spot sensing in SPR, this technique is recommended for initial kinetic studies, whereas DPI is more accurate when the refractive index and thickness of the adsorbed layer is of more interest.     

The effect of surface microtopography of poly(dimethylsiloxane) on protein adsorption, platelet and cell adhesion

Chemical homogeneous poly(dimethylsiloxane) (PDMS) surface with dot-like protrusion pattern was used to investigate the individual effect of surface microtopography on protein adsorption and subsequent biological responses. Fibrinogen (Fg) and fibronectin (Fn) were chosen as model proteins due to their effect on platelet and cell adhesion, respectively. Fg labeled with ¹²⁵I and fluorescein isothiocyanate (FITC) was used to study its adsorption on flat and patterned surfaces. Patterned surface has a 46% increase in the adsorption of Fg when compared with flat surface. However, the surface area of the patterned surface was only 8% larger than that of the flat surface. Therefore, the increase in the surface area was not the only factor responsible for the increase in protein adsorption. Clear fluorescent pattern was visualized on patterned surface, indicating that adsorbed Fg regularly distributed and adsorbed most on the flanks and valleys of the protrusions. Such distribution and local enrichment of Fg presumably caused the specific location of platelets adhered from platelet-rich plasma (PRP) and flowing whole blood (FWB) on patterned surface. Furthermore, the different combination of surface topography and pre-adsorbed Fn could influence the adhesion of L929 cells. The flat surface with pre-adsorbed Fn was the optimum substrate while the virgin patterned surface was the poor substrate in terms of L929 cells spread.     

Removal of Cd(II), Cu(II), and Pb(II) by adsorption onto natural clay: a kinetic and thermodynamic study

In this work, we study the elimination of three bivalent metal ions (Cd²⁺, Cu²⁺, and Pb²⁺) by adsorption onto natural illitic clay (AM) collected from Marrakech region in Morocco. The characterization of the adsorbent was carried out by X-ray fluorescence, Fourier transform infrared spectroscopy and X-ray diffraction. The influence of physicochemical parameters on the clay adsorption capacity for ions Cd²⁺, Cu²⁺, and Pb²⁺, namely the adsorbent dose, the contact time, the initial pH imposed on the aqueous solution, the initial concentration of the metal solution and the temperature, was studied. The adsorption process is evaluated by different kinetic models such as the pseudo-first-order, pseudo-second-order, and Elovich. The adsorption mechanism was determined by the use of adsorption isotherms such as Langmuir, Freundlich, and Temkin models. Experiments have shown that heavy metals adsorption kinetics onto clay follows the same order, the pseudo-second order. The isotherms of adsorption of metal cations by AM clay are satisfactorily described by the Langmuir model and the maximum adsorption capacities obtained from the natural clay, using the Langmuir isotherm model equation, are 5.25, 13.41, and 15.90 mg/g, respectively for Cd(II), Cu(II), and Pb(II) ions. Adsorption of heavy metals on clay is a spontaneous and endothermic process characterized by a disorder of the medium. The values of ΔH are greater than 40 kJ/mol, which means that the interactions between clay and heavy metals are chemical in nature.     

Quantitative Studies of Metal Ion Adsorption on a Chemically Modified Carbon Surface: Adsorption of Cd(II) and Hg(II) on Glutathione Modified Carbon

The adsorption behavior of model toxic metal cations namely Cd(II) and Hg(II) on carbon surfaces chemically modified by glutathione was investigated as a function of the concentration of Cd²⁺ and Hg²⁺ ions, time and the amount of modified carbon used. Square wave and linear sweep anodic stripping voltammetry was used to monitor the uptake of Cd(II) and Hg(II) ions respectively. Kinetic and adsorption isotherm studies reveal that both Cd(II) and Hg(II) ions undergo similar large adsorption with the modified glutathione carbon material (Glu‐carbon).     

NO adsorption on the stoichiometric and reduced SnO2(110) surface

The adsorption of NO molecules on the perfect and defective (110) surfaces of SnO₂ was studied with first-principles methods at the density-functional theory level. It was found that NO mainly interacts via the nitrogen atom with the bridging oxygens of the stoichiometric surface while the coordinatively unsaturated surface Sn atoms are less reactive. On the oxygen-deficient surface, NO is preferentially adsorbed at the vacancy positions, with the nitrogen atom close to the former surface oxygen site. Regardless of the adsorption site, the unpaired electron is located mainly on the NO molecule and only partly on surface Sn atoms. The results for the SnO₂ surface are compared to literature results on the isostructural TiO₂ rutile (110) surface. Dedicated to Professor Karl Jug on the occasion of his 65th birthday     

Nanosized centers for mercury(II) ions adsorption on a surface of modified silica

The present work investigates the adsorptive interactions of Hg(II) ions in aqueous medium with hydroxylated silica, aminopropylsilica and silica chemically modified by β-cyclodextrin. Batch adsorption studies were carried out with various agitation times and mercury(II) concentrations. The maximum adsorption was observed within 15–30 min of agitation. The kinetics of the interactions, tested with the model of Lagergren for pseudo-first and pseudo-second order equations, showed better agreement with first order kinetics (k₁ = 3.4 ± 0.2 to 5.9 ± 0.3 min⁻¹). The adsorption data gave good fits with Langmuir isotherms. The results have shown that β-cyclodextrin-containing adsorbent has the largest adsorption specificity to Hg(II): K _L = 4125 ± 205 mmol⁻¹. “β-cyclodextrin-NO3-” inclusion complexes with ratio 1: 1 and super molecules with composition C₄₂H₇₀O₃₅ ⊎ 3 Hg(NO₃)₂ are formed on the surface of β-cyclodextrin-containing silica.      

Pt adsorption on the PbTiO3(110) polar surface: a density functional theory study

The monolayer (ML) and submonolayer Pt on both terminations of PbTiO₃(110) polar surface have been studied by using density functional theory (DFT) with projector‐augmented wave(PAW) potential and a supercell approach. The most favored ML Pt arrangements on PbTiO and O₂ terminations are the hollow site and the short‐bridge site, respectively. By examining the geometries of different ML arrangements, we know that the dominant impetus for stability of the favored adsorption site for PbTiO termination is the Pt–Ti interaction (mainly from covalent bonding), while that for O₂ termination is the Pt–O interaction (mainly from ionic bonding). In addition, the appearance of the gap electronic states in the outermost layers of each termination indicates that a channel for charge transfer between adsorbed layer and substrate is formed. Moreover, the interface hybridization between Pt 5d and O 2p orbitals is also observed, especially for ML Pt on O₂ termination. The stability sequences for various arrangements of 1/2 ML Pt adsorption conform well with those of ML Pt adsorption, and the most stable arrangement is energetically more favorable than the corresponding ML coverage in the view of adsorption energy maximization. The behavior, i.e. the increase in adsorption energy with decrease in coverage, indicates that Pt? Pt interactions weaken those between Pt and the substrate. Copyright © 2009 John Wiley & Sons, Ltd.     

CO2在Fe3O4(111)表面的吸附结构及能量研究

利用密度泛函理论研究了CO₂在Fe₃O₄（111）表面Fe_tet1和Fe_oct2两种终结的吸附行为。在Fe_tet1终结表面,当覆盖度为1/5 ML时,CO₂倾向于线性吸附;而在高覆盖度下,弯曲的CO₂与表面O作用形成CO₃^2-结构。在Fe_oct2终结表面,CO₂倾向于弯曲吸附,在1/6 ML和1/3 ML覆盖度时都可以形成CO₃^2-和-COO结构。覆盖度对Fe_tet1终结的表面影响很弱,但是对Fe_oct2终结的表面影响很大。从热力学上来说,CO₂在Fe_oct2终结表面的吸附要比Fe_tet1终结表面更有利。     

The adsorption of CaOH+ on (001) basal and (010) edge surface of Na‐montmorillonite: a DFT study

Ca²⁺ cations were generally added to facilitate the coagulation of stable fine clay mineral dispersion due to the specific adsorption of their first hydrolysis CaOH⁺ species at pH near 10. The adsorption of CaOH⁺ on dry and hydrated (001) basal surface and (010) surface of Na‐montmorillonite was investigated by using density functional theory method combined with the periodic slab model method. The adsorption energies and geometries, Mulliken charge, electron density difference, and density of state were presented and discussed. It was found that the adsorption energy of CaOH⁺ on (010) edge surface of Na‐montmorillonite (?328.8 kJ/mol) was much larger than that (?126.9 kJ/mol) on (001) basal surface. The presence of waters could increase the adsorption energy of CaOH⁺ on (001) surface but affect that on (010) surface slightly. The protons in Si–OH and Al–OH₂ groups as well as the OH₂ ligands in Al–OH₂ group on (010) edge surface were easily dissociated and coordinated to CaOH⁺ to form new waters. CaOH⁺ was the most steady adsorption species among CaOH⁺, Ca²⁺ cation, and H₂O molecule on both (001) and (010) surfaces. Copyright © 2016 John Wiley & Sons, Ltd.     

Characterization of an unusual adsorption behavior of racemic methyl-mandelate on a tris-(3,5-dimethylphenyl) carbamoyl cellulose chiral stationary phase

An interesting adsorption behavior of racemic methyl mandelate on a tris-(3,5-dimethylphenyl)carbamoyl cellulose chiral stationary phase was theoretically and experimentally investigated. The overloaded band of the more retained enantiomer had a peculiar shape indicating a type V adsorption isotherm whereas the overloaded band of the less retained enantiomer had a normal shape indicating a type I adsorption behavior. For a closer characterization of this separation, adsorption isotherms were determined and analyzed using an approach were Scatchard plots and adsorption energy distribution (AED) calculations are combined for a deeper analysis. It was found that the less retained enantiomer was best described by a Tóth adsorption isotherm while the second one was best described with a bi-Moreau adsorption isotherm. The latter model comprises non-ideal adsorbate-adsorbate interactions, providing an explanation to the non-ideal adsorption of the more retained enantiomer. Furthermore, the possibility of using the Moreau model as a local model for adsorption in AED calculations was evaluated using synthetically generated raw adsorption slope data. It was found that the AED accurately could predict the number of adsorption sites for the generated data. The adsorption behavior of both enantiomers was also studied at several different temperatures and found to be exothermic; i.e. the adsorbate-adsorbate interaction strength decreases with increasing temperature. Stochastic analysis of the adsorption process revealed that the average amount of adsorption/desorption events increases and the sojourn time decreases with increasing temperature.     

A DFT study of acetonitrile adsorption and decomposition on the TiO2 (110) surface

The adsorption and decomposition of acetonitrile on the TiO₂ (110) surface have been investigated with first principles calculations. Our results reveal that both C?N and C? C bonds of acetonitrile become weakened after adsorption. Acetonitrile behaves as an electron donor, and electrons transfer from acetonitrile to substrate is obvious. The reaction mechanism of further decomposition of acetonitrile on TiO₂ (110) surface is also investigated, and the result shows that acetonitrile can decompose into CH₃ and CN fragments and form OCH₃ and NCO groups on the TiO₂ (110) surface, which consists with the experimental results. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011