Confinement in nanopores at the oxide/water interface: modification of alumina adsorption properties

There is limited knowledge on the influence of the pore size on surface phenomena (adsorption, dissolution, precipitation, etc.) at the oxide/water interface and a better understanding of the space confinement in nanoscale pores should have practical implications in different areas, such as transport of contaminants in the environment or heterogeneous catalyst preparation, to name a few. To investigate the modifications of the oxide adsorption properties at the oxide/water interface in a confined environment, the surface acidobasic and ion adsorption properties of six different aluminas (5 porous commercial aluminas with pore diameters ranging from 25 to 200 A and 1 non-porous alumina) were determined by means of acid-base titration and Ni(II) adsorption. It is shown that the confinement has a moderate impact on the alumina adsorption capacity because all materials have similar surface charging behaviours and ion saturation coverages. However, a confined geometry has a much larger impact on the ion adsorption constants, which decrease drastically when the average pore diameter decreases below 200 A. These results are discussed in terms of nanoscale pore space confinement.     

氨基酸在固/液界面的吸附作用

本文介绍了氨基酸在固/液界面吸附等温线的特点,氨基酸液相吸附热力学和活性炭、硅胶、二氧化钛、氧化铝、蒙脱土等自水中吸附氨基酸的机制。     

Surface studies of gas sensing metal oxides

The relation of surface science studies of single crystal metal oxides to gas sensing applications is reviewed. Most metal oxide gas sensors are used to detect oxidizing or reducing gases and therefore this article focuses on surface reduction processes and the interaction of oxygen with these surfaces. The systems that are discussed are: (i) the oxygen vacancy formation on the surface of the ion conductor CeO(2)(111); (ii) interaction of oxygen with TiO(2) (both adsorption processes and the incorporation of oxygen into the TiO(2)(110) lattice are discussed); (iii) the varying surface composition of SnO(2)(101) and its consequence for the adsorption of water; and (iv) Cu modified ZnO(0001)-Zn surfaces and its interaction with oxygen. These examples are chosen to give a comprehensive overview of surface science studies of different kinds of gas sensing materials and to illustrate the potential that surface science studies have to give fundamental insight into gas sensing phenomena.     

二维炭基多孔材料的合成及应用

Two-dimensional (2D) materials possess nanoscale thickness with large aspect ratios on the other two dimensions. The ultrahigh surface-to-volume ratio of 2D materials is the most important property different from their bulk counterparts, and is beneficial for mass and heat transport, and ion diffusion. Among the various 2D materials, carbon-based materials have attracted tremendous attentions since the first explosive research on graphene. Therefore, they provide opportunities for applications in adsorption, catalysis, and electrical energy storage. The porous structure of such carbon materials is a key influence on the properties of these 2D materials. This review focuses on recent developments in synthesis strategies for 2D carbon-based materials, especially the preparation of carbon nanosheets and carbon-inorganic hybrids/composites nanosheets. The main factors influencing the porous structure of the material are discussed for each method. Applications of the materials are introduced, mainly in the fields of adsorption, heterogeneous catalysis, and electrical energy storage. Finally, the leading-edge issues of novel 2D carbon-based materials for the future are discussed.     

Energetics of methane adsorption on microporous activated carbons

The influence of microporous carbon surface oxidation on energetics of methane adsorption at 308 K is discussed. Obtained adsorption heats and integral molar entropies of the adsorbate show that microporous carbon surface oxidation changes the methane adsorption process. This is probably resulted by the existence of an endothermic effect during adsorption in oxidized carbon micropores.     

FT-IR Study of Carbon Nanotube Supported Co-Mo Catalysts

In this paper, adsorption properties of dibenzothiophene (DBT) on carbon nanotube, carbonnanotube supported oxide state and sulfide state CoMo catalysts are studied by using thermal gravi-metric analysis (TGA) technique and FT-IR spectroscopy. Activated carbon support, 7-A1203 supportand supported CoMo catalysts are also subjected to studies for comparison. It was found that sulfidestate CoMoS/MWCNT, CoMoS/AC and CoMoS/γ-A12O3 catalysts adsorbed much more DBT moleculesthan their corresponding oxide state catalysts, as well as their corresponding supports. The chemicallyadsorbed DBT aromatic molecules did not undergo decomposition on the surface of supports, supportedoxide state CoMo catalysts and sulfide state CoMo catalysts when out-gassing at 373 K. FT-IR results indicated that DBT molecules mainly stand upright on the active sites (acid sites and/or transition active phases) of CoMoS/MWCNT catalyst. However, DBT aromatic molecules mainly lie flat on MWCNT and CoMoO/MWCNT.     

介孔气体吸附剂

介孔二氧化硅经过表面修饰,赋予介孔材料不同的特性,具有很多的潜在用途,是无机材料研究的热点之一。本文综述了近年来以介孔二氧化硅（M41S 和 SBA）为载体设计的气体吸附剂的研究进展。详细讨论了二氧化碳和可挥发性有机物(VOCs)在介孔吸附剂上的吸附过程;介绍了二氧化碳介孔吸附剂的不同制备方法和影响二氧化碳在介孔吸附剂上吸附的因素,以及介孔吸附剂的结构对可挥发性有机物吸附过程的影响。最后,对介孔气体吸附剂的发展进行了展望。     

Quantum-Chemical Investigation of the Interaction of Water and Methanol Molecules with Surface Carboxyl Groups on Graphite

A quantum-chemical investigation made of the adsorption of water and methanol at hydrophilic centers (carboxyl groups) on the partly oxidized surface of graphite was undertaken. The enthalpy of adsorption of water and methanol at such centers was determined. It was shown that water is adsorbed at the surface carboxyl groups in the form of dimers, while methanol is adsorbed in the form of single molecules. It was confirmed that the formation of clusters of water molecules in the vicinity of the hydrophilic center is a characteristic feature of the adsorption of water on the surface of graphite and other adsorbents.     

Glycine‐functionalized reduced graphene oxide for methylene blue removal

Glycine‐functionalized reduced graphene oxide (GRGO) was prepared through the reaction of glycine and chlorine‐functionalized reduced graphene oxide. The product was characterized by SEM, HRTEM, IR, Raman, and XPS. The nitrogen content (8.28%) was high in product, peak at 285.8 eV was assigned to the C–N bond, which implied that the chlorine residues in raw material were substituted by amine group of glycine. The intensity ratio of D and G peak was about 1.5, which also implied that more saturated carbon atoms were present in the product. Results of SEM, IR, and XPS confirmed that glycine molecules were attached to graphene sheets. Compared with reduced graphene oxide (61.5 mg/g) and active carbon (45.2 mg/g), GRGO had a good adsorption capacity (98.9 mg/g) for methylene blue. The adsorption process was fitted to three kinetic models and three adsorption isotherm models. The adsorption process complied with pseudo‐second order kinetic model and Langmuir model.     

Gas-Sensing Activity of Amorphous Copper Oxide Porous Nanosheets

In this paper, the gas-sensing properties of copper oxide porous nanosheets in amorphous and highly crystalline states were comparatively investigated on the premise of almost the same specific surface area, morphology and size. Unexpectedly, the results show that amorphous copper oxide porous nanosheets have much better gas sensing properties than highly crystalline copper oxide to a serious of volatile organic compounds, and the lowest detection limit (LOD) of the amorphous copper oxide porous nanosheets to methanal is even up to 10 ppb. By contrast, the LOD of the highly crystalline copper oxide porous nanosheets to methanal is 95 ppb. Experiments prove that the oxygen vacancies contained in the amorphous copper oxide porous nanosheets play a key role in improving gas sensitivity, which greatly improve the chemical activity of the materials, especially for the adsorption of molecules containing oxygen-groups such as methanal and oxygen.     

Features of the adsorption of hydrogen by various types of microporous materials

A comparative investigation was made of the adsorption of N₂ and H₂ by silicate and phosphate zeolites (Zt) and carbon materials with micropores of various dimensions, shapes, and volumes. It was found that the adsorption of hydrogen has significant sensitivity to the shape of the pores, the chemical composition of the zeolite framework, and the nature of the surface of the adsorbents. In particular, the adsorption is increased in the presence of constrictions (the cationic forms of zeolite LTA) or channels (MFI) with sizes close to hydrogen molecules in the micropores and the ions of divalent metals included isomorphously in the framework of the aluminophosphates. There is also increased affinity to the carbon surface. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 2, pp. 67–73, March–April, 2008.     

Review on recent advances of carbon based adsorbent for methylene blue removal from waste water

The growth in textile and printing industries proven detrimental to the aquatic environment as the industrial waste containing dye seeped into the ecosystem. A high concentration of dye in water possess negative impacts on water ecosystem and harmful to human health. Removal of methylene blue (MB) dye from industrial waste via adsorption pathway has been widely investigated that promised high efficiency of MB removal. This review will summarize researches published from 2008 to 2019 on the removal of MB using carbon adsorbent with focus will be given on the synthesis and modification of carbon-based materials, and the structural properties influencing the performance of MB adsorption. Summary on the type of material used for the synthesis of carbon materials (activated carbon and biochar) will be included from utilization of the naturally occurring carbon sources such as polymers, biomasses and biowastes, and also sucrose and hydrocarbon gases. Modification of carbon materials such as chemical activation and physical activation; surface grafting to form functionalized surfaces; deposition with metal and magnetic nanoparticles via impregnation; and manufacturing of carbon composites will be discussed on the effects to promote MB adsorption and desorption. Another type of carbon adsorbents such as porous carbon; graphitic carbons including graphite, graphene, graphene oxide, and carbon nitride (g-C₃N₄); and finally nanocarbon in the form of nanotube, nanorod and nanofiber; will be included in the review with details on the synthesis method and the correlation between structural properties and adsorption activity. The regeneration process to increase the life cycle of carbon adsorbent will also be discussed based on two regeneration pathway i.e. a thermal degradation and desorption on MB. Finally the thermodynamics, kinetics, and the adsorption models of MB on carbon adsorbent will be discussed in this review.     

Simple fabrication of a phosphorus-doped hierarchical porous carbon via soft-template method for efficient CO2capture

Hierarchical porous carbons are widely used as adsorbents, catalyst supports, electrode materials, and other applications because of their high specific surface area (SSA), varied pore structure, adjustable porosity, and excellent physicochemical stability. Introducing heteroatoms such as N, P, or S, with electronegativities different from that of carbon, into the carbon skeleton can change the chemical properties of the surface and the density of the electron cloud around the carbon matrix, thus altering interactions of CO₂molecules with the surface and improving CO₂adsorption capacity. Therefore, doping heteroatoms in carbon materials has attracted a great amount of attention. In this paper, the template method was used with F108 (polyethylene glycol–polypropylene glycolpolyethylene glycol) as the template, resorcinol and formaldehyde solutions as the carbon sources, phosphoric acid as the phosphorus source, and KOH as the activator to prepare phosphorus-doped hierarchical porous carbons. Through a series of characterization and CO₂adsorption experiments, the influence of the amount of KOH and template agent on the pore structure of carbon materials was studied. We conclude that these phosphorus-doped hierarchical porous carbon materials are promising CO₂adsorbents.     

Water treatment: functional nanomaterials and applications from adsorption to photodegradation

Global efforts for engineering desired materials which are able to treat the water sources still are ongoing in the bench level methods. Considering adsorbent and photocatalytic materials as the main reliable candidates still are encountering with struggles because of many challenges that restrict their large-scale application. This review comprehensively considered the recent advanced materials water treatment methods which involve to magnetic, activated carbon, carbon nanotubes (CNTs), graphene (G), graphene oxide (GO), (Graphene) quantum dots, carbon nanorods, carbon nano-onions, and reduced graphene oxide (RGO), zeolite, silica and clay-based nanomaterials. The adsorption and photocatalytic properties of these nanomaterials introduced them as highly potent option for heavy metal ions and organic dyes removal and photocatalytic degradation. High specific surface area in conjugation with presenting higher kinetics of adsorption and decomposition are the main characteristics of these materials which make them appropriate to treat wastewater even in ultralow concentration of the pollutants. Considering the mechanistic aspects of the adsorption and photocatalytic decomposition process, challenges and opportunities were other subjects that have been highlighted for the discussed nanomaterials. In term of the adsorption approaches, the mechanism of adsorptions and their influence on the maximum adsorption capacity were discussed and also for photocatalyst approach the radical active spices and their role in kinetic and efficiency of the organic pollutant decomposition were provided a deep discussion.     

Adsorption of Carbon Dioxide on Activated Carbon

The adsorption of CO2 on a raw activated carbon A and three modified activated carbon samples B, C, and D at temperatures ranging from 303 to 333 K and the thermodynamics of adsorption have been investigated using a vacuum adsorption apparatus in order to obtain more information about the effect of CO2 on removal of organic sulfur-containing compounds in industrial gases. The active ingredients impregnated in the carbon samples show significant influence on the adsorption for CO2 and its volumes adsorbed on modified carbon samples B, C, and D are all larger than that on the raw carbon sample A. On the other hand, the physical parameters such as surface area, pore volume, and micropore volume of carbon samples show no influence on the adsorbed amount of CO2. The Dubinin-Radushkevich (D-R) equation was the best model for fitting the adsorption data on carbon samples A and B, while the Preundlich equation was the best fit for the adsorption on carbon samples C and D. The isosteric heats of adsorption on carbon samples A, B, C, and D derived from the adsorption isotherms using the Clapeyron equation decreased slightly increasing surface loading. The heat of adsorption lay between 10.5 and 28.4 kJ/mol, with the carbon sample D having the highest value at all surface coverages that were studied. The observed entropy change associated with the adsorption for the carbon samples A, B, and C (above the surface coverage of 7 ml/g) was lower than the theoretical value for mobile adsorption. However, it was higher than the theoretical value for mobile adsorption but lower than the theoretical value for localized adsorption for carbon sample D.     

Cluster-Mediated Water Adsorption on Carbon Nanopores

The adsorption isotherms of water at 303 K and N2 at 77 K on various kinds of porous carbons were compared with each other. The saturated amounts of water adsorbed on carbons almost coincided with amounts of N2 adsorption in micropores. Although carbon aerogel samples have mesopores of the great pore volume, the saturated amount of adsorbed water was close to the micropore volume which is much small than the mesopore volume. These adsorption data on carbon aerogels indicated that the water molecules are not adsorbed in mesopores, but in micropores only. The adsorption isotherms of water on activated carbon having micropores of smaller than 0.7 nm in width had no clear adsorption hysteresis, while the water adsorption isotherms on micropores of greater than 0.7 nm had a remarkable adsorption hysteresis above P/P0 = 0.5. The disappearance of the clear hysteresis for smaller micropores suggested that the cluster of water molecules of about 0.7 nm in size gives rise to the water adsorption on the hydrophobic micropores; the formation and the structure of clusters of water molecules were associated with the adsorption mechanism. The cluster-mediated pore filling mechanism was proposed with a special relevance to the evidence on the formation of the ordered water molecular assembly in the carbon micropores by in situ X-ray diffraction.     

改性纤维素的制备及分光光度法对Cu~(2+)吸附研究

针对日益严重的铜离子污染问题,以化学浆纤维素为原料,通过氨基酸接枝修饰2,2,6,6-四甲基哌啶氧自由基(TEMPO)氧化体系氧化的纤维素,制备出一种新型吸附剂,并采用灵敏简便的分光光度法研究改性对铜离子的吸附效果。结果表明,氨基酸修饰纤维素(AMC)与TEMPO氧化纤维素(TOC)相比,对铜离子的吸附效果有不同程度的提升,其中组氨酸改性的吸附效果最好,低浓度时吸附率可以高达97%。随着浓度增大,吸附率下降,但是吸附量增大,当吸附200 mg/L的Cu2+溶液时,吸附量可达47 mg/g。此外,研究了不同条件下AMC对Cu2+的吸附情况,包括AMC投加量、初始浓度、pH值等。结果表明,吸附过程的吸附模型符合Langmuir等温模型,吸附动力学可以用准二级吸附动力学方程拟合。     

The Effect of the Nature and Structure of Adsorbents on Interaction with Ibuprofen

The interaction of ibuprofen [2-(4-isobutylphenyl)propionic acid] with the surface of carbon and oxide adsorbents was investigated. The significant role of wide pores during the adsorption of ibuprofen on carbon adsorbents in the presence of protein molecules was demonstrated. At low concentrations ibuprofen is adsorbed on the surface of hydrophilic and hydrophobic adsorbents in the form of a monomer, but the contribution from the adsorbed dimer increases with increase in its concentration.     

Kinetic isotope effect for H2 and D2 quantum molecular sieving in adsorption/desorption on porous carbon materials

Adsorption and desorption of H(2) and D(2) from porous carbon materials, such as activated carbon at 77 K, are usually fully reversible with very rapid adsorption/desorption kinetics. The adsorption and desorption of H(2) and D(2) at 77 K on a carbon molecular sieve (Takeda 3A), where the kinetic selectivity was incorporated by carbon deposition, and a carbon, where the pore structure was modified by thermal annealing to give similar pore structure characteristics to the carbon molecular sieve substrate, were studied. The D(2) adsorption and desorption kinetics were significantly faster (up to x1.9) than the corresponding H(2) kinetics for specific pressure increments/decrements. This represents the first experimental observation of kinetic isotope quantum molecular sieving in porous materials due to the larger zero-point energy for the lighter H(2), resulting in slower adsorption/desorption kinetics compared with the heavier D(2). The results are discussed in terms of the adsorption mechanism.     

Vapor Adsorption Measurements with Two-Dimensional Membranes

Two-dimensional (2D) membranes display extraordinary mass transfer properties, in particular for the permeation of gaseous substances. Their ultimate thickness not only ensures the shortest diffusion pathways, but also makes the membrane surface play a significant role in accommodating and guiding the permeating molecules. As saturated vapors of water and organic solvents are often observed to pass 2D membranes faster than inert gases, condensation is believed to be responsible for surface-mediated transport. Here, we present a spectroscopic experiment to probe adsorption of condensable species on 2D membranes under realistic conditions. Polarization-modulation infrared reflection absorption spectroscopy (PM IRAS) is coupled with a reaction chamber and a vacuum system to control the vaporous environments. The measurements are demonstrated to yield quantitative information on the amount of adsorbates onto supported 2D layers. As a case study, the azeotropic mixture of water and propanol is revealed to maintain its molar composition upon interaction with carbon nanomembranes.