Small- and Large-angle X-ray Scattering Studies of Nanometer-order Sulfuric Acid Solution in Carbon Micropores

Futamura, Ryusuke; Iiyama, Taku; Hamasaki, Atom; Ozeki, Sumio

doi:10.1246/cl.2012.159

Cited by 5 publications

(3 citation statements)

References 28 publications

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“…We reported that a benzylammonium (BA)-modified (Scheme b) smectite was found to be the most effective adsorbent for the caffeine adsorption in aqueous solution among commercially available organoclays containing organoammonium ions as quaternary long-chain alkylammonium and BA . Transmission XRD with an angle-dispersion diffractometer , and small-angle X-ray scattering have been recently adopted to investigate the interlayer expansion of organically functionalized smectites in water , and in aqueous solutions of caffeine . BA-exchanged smectites swelled in liquid water by ∼0.2 nm and expanded further by 0.1 nm in an aqueous caffeine solution.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Interlayer Expansion of a Layered Silicate Driven by Caffeine Intercalation in the Water Phase Using Transmission X-ray Diffraction

Okada¹,

Yoshida

Iiyama

2017

J. Phys. Chem. B

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The kinetics of caffeine uptake into the interlayer nanospace of silicate nanosheets modified with benzylammonium (BA) was evaluated by in situ monitoring the basal spacing in aqueous media using transmission X-ray diffraction. An interlayer spacing of 0.58 nm in water before caffeine uptake indicates a monomolecular layer of BA and a few water layers in each interlayer. The interlayer space expanded by 0.10 nm upon caffeine uptake (intercalation) and saturated even in the presence of excess caffeine. Time-course profiles of the interlayer spacing and the uptake amount after injection of caffeine into the water slurry were obtained. At the initial period, the plot for the basal spacing was located above that for the adsorbed amount, suggesting that the rate of the interlayer spacing change was faster than that to attain the adsorption equilibrium. A first-order kinetic simulation fitted to the profile also indicates that the basal spacing included a rapid expansion of 0.08 nm within a few minutes and a slow expansion of 0.02 nm over several hours. Regarding the slow component, the rate constant for the basal spacing was lower than that for the amount of caffeine adsorbed, meaning that a steady-state basal spacing is reached after the adsorption equilibrium.

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Section: Introductionmentioning

confidence: 99%

Kinetics of Interlayer Expansion of a Layered Silicate Driven by Caffeine Intercalation in the Water Phase Using Transmission X-ray Diffraction

Okada¹,

Yoshida

Iiyama

2017

J. Phys. Chem. B

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“…Thus, we have paid attention to organic cations containing aromatic ring for using organically modified smectites (a natural montmorillonite and synthetic saponite) through cation-exchange reactions with BA and neostigmine (CONH, which has been reported for effective adsorption of phenylphenol; Scheme e). Transmission X-ray diffraction (XRD) using an angle-dispersion diffractometer was used for pursuing the nanostructural change in the aromatic ammonium–smectites upon the adsorption in aqueous media. We will discuss a role of the nanostructures, which correlate the adsorption behavior of caffeine.…”

Section: Introductionmentioning

confidence: 99%

Organoclays in Water Cause Expansion That Facilitates Caffeine Adsorption

Okada¹,

Oguchi²,

Yamamoto

et al. 2014

Langmuir

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This study investigates the adsorption of caffeine in water on organically modified clays (a natural montmorillonite and synthetic saponite, which are smectite group of layered clay minerals). The organoclays were prepared by cation-exchange reactions of benzylammonium and neostigmine with interlayer exchangeable cations in the clay minerals. Although less caffeine was uptaken on neostigmine-modified clays than on raw clay minerals, uptake was increased by adding benzylammonium to the clays. The adsorption equilibrium constant was considerably higher on benzylammonium-modified saponite (containing small quantities of intercalated benzylammonium) than on its montmorillonite counterpart. These observations suggest that decreasing the size and number of intercalated cations enlarges the siloxane surface area available for caffeine adsorption. When the benzylammonium-smectite powders were immersed in water, the intercalated water molecules expanded the interlayer space. Addition of caffeine to the aqueous dispersion further expanded the benzylammonium-montmorillonite system but showed no effect on benzylammonium-saponite. We assume that intercalated water molecules were exchanged with caffeine molecules. By intercalating benzylammonium into smectites, we have potentially created an adaptable two-dimensional nanospace that sequesters caffeine from aqueous media.

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“…Microscopic measurement methods such as X-ray diffraction (XRD) 1 and extended X-ray absorption fine structure (EXAFS) 2 enable the study of the behavior of adsorbed molecules. New porous materials such as metalorganic frameworks (MOFs) 3 and porous organosilicates 4 have designable nanostructures.…”

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Study of Water Adsorption on Hydrophobic Na-ZSM-5 and H-ZSM-5 by Directly Measuring Adsorption Isobars and Isotherms

et al. 2012

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The effects of different cation species on water adsorption on hydrophobic ZSM-5 zeolite are investigated through adsorption isotherm and isobar measurements. The adsorption isobars clearly show that sodium cations behave as stronger water adsorption sites than do protons. Furthermore, the adsorption isotherms of Na-and H-zeolites show such differences at part of the hysteresis loop. This suggests that the cation species in ZSM-5 affect the formation of the first, second, and third hydration shells in the hydrophobic space.Recently, there has been much focus on making improvements to microscopic measurement techniques and developing new methods for synthesizing porous materials. Microscopic measurement methods such as X-ray diffraction (XRD) 1 and extended X-ray absorption fine structure (EXAFS) 2 enable the study of the behavior of adsorbed molecules. New porous materials such as metalorganic frameworks (MOFs) 3 and porous organosilicates 4 have designable nanostructures. Using these new techniques and materials, we developed a method for controlling the pore structure and elucidating the molecular behavior in nanospaces. However, macroscopic measurements of the adsorbed amount, heat of adsorption, etc., are also important for the development of porous materials with new properties and functions.In adsorption studies, the adsorbed amount, which can be determined from adsorption isotherms by conventional gravimetric or volumetric analyses, is considered the most important macroscopic property. Adsorption isotherms have been frequently used to investigate the microscopic properties of porous materials since suitable measurement methods and the isothermal adsorption theory 57 have been well established. However, the information obtained by adsorption isotherm measurements is inadequate because the isotherms do not include the effects of temperature changes. Therefore, isobaric adsorption measurements are necessary. Adsorption isobars are typically measured using an indirect method that involves the measurement of many adsorption isotherms. However, this method cannot be applied to investigate the hysteresis during adsorbate loading. Therefore, we have developed a direct method for measuring adsorption isobars, using a high-speed feedback electrical circuit that helps in maintaining a constant pressure.In this study, we investigated the water adsorption on hydrophobic ZSM-5, a well-known microporous adsorbent and catalyst that finds numerous applications in different industrial fields.8,9 Although ZSM-5 is hydrophobic, its micropore structure contains adsorption sites that show strong interactions with polar molecules: an interesting advantage of ZSM-5.There are many reports on the behavior of water molecules inside hydrophobic nanospaces (e.g., in activated carbon). On the basis of XRD data, Kaneko, Iiyama, et al. suggested that water molecules confined in activated carbon form cluster-like assemblies.10 Gubbins et al. investigated the importance of hydrophilic adsorption sites in the formation of such assemblies ...

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Small- and Large-angle X-ray Scattering Studies of Nanometer-order Sulfuric Acid Solution in Carbon Micropores

Cited by 5 publications

References 28 publications

Kinetics of Interlayer Expansion of a Layered Silicate Driven by Caffeine Intercalation in the Water Phase Using Transmission X-ray Diffraction

Kinetics of Interlayer Expansion of a Layered Silicate Driven by Caffeine Intercalation in the Water Phase Using Transmission X-ray Diffraction

Organoclays in Water Cause Expansion That Facilitates Caffeine Adsorption

Study of Water Adsorption on Hydrophobic Na-ZSM-5 and H-ZSM-5 by Directly Measuring Adsorption Isobars and Isotherms

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