Surface OH Groups Research Articles

Long‐Range Interaction Between NO2 Molecules, Impurity Boron Atoms and Si Atoms with Dangling Bonds in Porous Silicon

Density functional theory (DFT) simulation show that in p‐doped porous silicon (PS), boron (B) atoms are passivated by surface dangling bonds of Si atoms (pb‐centers) at distances up to 25 Å. A positive charge of the pb‐centers leads to the appearance of an increased potential region and a Coulomb blockade (CB) of free holes. When a NO2 molecule is adsorbed on a surface OH group near the pb‐center, a shallow acceptor state arises. This state is related to the NO2 molecule and not to the B atom. When an electron is captured from the valence band by the NO2 molecule, the potential around it and the pb‐center decreases, which removes CB.

Hydrogen-Bond Relations for Surface OH Species

This paper concerns thin water films and their hydrogen-bond patterns on ionic surfaces. As far as we are aware, this is the first time H-bond correlations for surface water and hydroxide species are presented in the literature while hydrogen-bond relations in the solid state have been scrutinized for at least five decades. Our data set, which was derived using density functional theory, consists of 116 unique surface OH groups–intact water molecules as well as hydroxides–on MgO(001), CaO(001) and NaCl(001), covering the whole range from strong to weak to no H-bonds. The intact surface water molecules are found to always be redshifted with respect to the gas-phase water OH vibrational frequency, whereas the surface hydroxide groups are either redshifted (OsH) or blueshifted (OHf) compared to the gas-phase OH– frequency. The surface H-bond relations are compared with the traditional relations for bulk crystals. We find that the “ν(OH) vs R(H···O)” correlation curve for surface water does not coincide with ...

Hydroxyl-rich ceria hydrate nanoparticles enhancing the alcohol electrooxidation performance of Pt catalysts

CeO2·xH2O nanoparticles with abundant surface OH groups can remarkably promote the alcohol electrooxidation activity of Pt/CNT catalysts.

Adsorption and characterization of palygorskite-isoniazid nanohybrids

Abstract Studies of the equilibrium and thermodynamic aspects of the adsorption of isoniazid onto a pharmaceutical-grade palygorskite and features of the resultant clay drug nanohybrid systems were carried out. Equilibrium studies were performed in aqueous medium at different times and temperatures. The overall adsorption process was explained as the result of two simple processes: drug adsorption on the activated sites of palygorskite and a slight precipitation phase of drug molecules over the adsorbed monolayer. Formation of the nanohybrid was spontaneous, exothermic and exoentropic, obtaining an increase in the thermodynamic stability of the system (ΔH = − 48,82 kJ/mol; ΔS = − 0.14 kJ/mol K). A full and comprehensive study of the solid state characterization corroborated the effective interaction between the components. Total amount of INH loaded was about 20% w/w. FTIR spectra revealed the interaction via water bridges between the endocyclic N of the drug and surface OH groups of palygorskite. Surface charge studies confirmed the non-electrostatic nature of the interactions.

Distinguishing Surface versus Bulk Hydroxyl Groups of Cellulose Nanocrystals Using Vibrational Sum Frequency Generation Spectroscopy.

In plant cell walls and cellulose-containing composites, nanocrystalline cellulose interacts with water molecules or matrix polymers through hydrogen bonding of the hydroxyl groups at the cellulose surface. These interactions play key roles in cellulose assembly in plant cell walls and mechanical properties of cellulose composites; however, they could not be studied properly due to the spectroscopic difficulty of selectively detecting the surface hydroxyl groups of nanocrystalline domains. This study employed the sum frequency scattering principle to distinguish the hydroxyl groups inside of the crystalline nanodomain of cellulose and those exposed at the surface of crystalline domains. The comparison of the spectra at various scattering angles revealed that the OH peak near ∼3450 cm-1 comes from the weakly hydrogen-bonded OH groups at the surface of crystalline cellulose. Also, a time delay measurement found that the sharp vibrational features observed near 3700 cm-1 can be attributed to isolated OH groups not accessible by ambient water molecules. These findings allow the distinction of surface versus bulk OH groups in sum frequency generation vibrational spectroscopy.

Impact of crystalline and amorphous iron- and aluminum hydroxides on mechanisms of phosphate adsorption and desorption

Fourier-transform infrared (FT-IR) spectroscopic experiments were carried out during phosphate adsorption on highly crystalline gibbsite, poorly crystalline 2-line-ferrihydrite and amorphous iron–aluminum–hydroxide mixtures in the molar ratio 1:0, 10:1, 5:1, 1:1, 1:5, 1:10 and 0:1. The OH stretching vibrational bands were utilized to analyze changes in structural and surface OH groups during adsorption, because the position of characteristic PO vibrational bands can shift depending on reaction conditions, pH or adsorbed phosphate content. Adsorption and desorption kinetics were studied at pH6 and different initial phosphate concentrations to achieve varying phosphate coverage on the mineral surfaces. For gibbsite the formation of AlHPO4 and Al2HPO4 can be assumed, while for ferrihydrite, a FeHPO4 or Fe2PO4 complex and the precipitation of FePO4 with longer equilibration time were proposed. Fe2HPO4 or a Fe2PO4 surface complex was deduced for Fe-hydroxides, an AlH2PO4 surface complex was identified for Al-hydroxide, and both displayed either hydrogen bonds to neighboring hydroxyl groups or hydrogen bonds to outer-sphere complexes. Fe:Al-hydroxide mixtures with high Al ratios showed a low phosphate desorption rate, while ferrihydrite and the Fe:Al-hydroxide mixtures with high Fe ratios had almost negligible desorption rates. It was concluded that within the weakly associated amorphous FeO(OH) materials, FePO4 precipitated, which was bound by outer-sphere hydrogen bonds. With high Al ratios, desorption increased, which indicated weaker phosphate binding of both inner-sphere and outer-sphere complexes and hence, either no or minor quantities of precipitate. Ferrihydrite showed a more rigid structure and a lower extent of precipitation compared to amorphous Fe-hydroxide.

Associating low crystallinity with peroxo groups for enhanced visible light active photocatalysts

In the present study hydrogen peroxide was applied during the synthesis of titanium dioxide (TiO2) photocatalysts to anchor peroxo groups onto the surface to enhance visible light excitability. The effect of changes in the pH value and crystallization temperature was investigated. As-prepared peroxo-titania were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), infrared spectroscopy (IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was investigated using phenol as model contaminant under visible light irradiation. IR and XPS measurements confirmed the presence of peroxo groups in the samples, moreover Raman and XPS measurements showed the formation of amorphous sodium titanate. Photocatalytic activity measurements pointed out, that most efficient as-prepared photocatalyst exceeded the photocatalytic performance of all reference materials. The cause of the enhanced photocatalytic activity was attributed to the enhanced visible light excitability and considerable amount of peroxo groups, which were not stable after the reusability experiments of the photocatalysts, suffering a redox reaction with the relatively high amount of Ti3+, resulting Ti4+ and surface OH groups. Therefore, the loss of peroxo groups and concomitantly photocatalytic activity was observed.

VOx/Zr–SBA-15 catalysts for selective oxidation of ethanol to acetaldehyde

Effect of zirconium presence in the silica framework and content and speciation of vanadium surface oxo-complexes on the catalytic behavior of VOx/Zr–SBA-15 catalysts in oxidative dehydrogenation of ethanol was investigated. Experimental results bring evidence of successful incorporation of zirconium into ordered mesoporous silica framework with the preservation of ordered mesoporosity by hydrothermal template base synthesis method. The presence of zirconium in the SBA-15 framework increases reducibility of vanadium species and acidity of the catalysts. It is reflected in higher activity of vanadium species expressed as turn-over frequency (e.g., TOF of 20 h−1 for 5%VOx/Zr–SBA-15 sample in comparison with TOF of 12 h−1 for 5%VOx/SBA-15 sample) and also in significant decrease of selectivity to acetaldehyde (65% in comparison with 90% for mentioned samples) followed by increase in selectivity to ethylene (25% in comparison with 5%). This change in distribution of reaction products is related to stronger acidity character of surface OH groups and inhibition effect of formed water vapours on the oxidative dehydrogenation products (acetaldehyde). Catalytic data also reveal that oligomeric/polymeric tetrahedrally coordinated vanadium species exhibit higher activity in ethanol oxidative dehydrogenation than monomeric complexes. In addition, comparison of the catalytic performance of VOx/Zr–SBA-15 catalysts with VOx/SBA-15 catalysts showed that catalytic properties of VOx/Zr–SBA-15 catalysts can be tuned by incorporation of controlled amount of zirconium into silica framework.

Computational study on the structural and surface properties of amorphous hydroxylated TiO2 spherical nanoparticles

Monte Carlo simulations were carried out on amorphous titanium dioxide (TiO2) for both bulk and hydroxylated nanoparticles with particle sizes ranging from 1 to 10 nm. The potential developed by the Matsui and Akaogi (MA) was used to model the interatomic interactions of TiO2 in both cases (bulk and nanoparticles). Besides, Angular and Morse potentials proposed by the Tether, Cormack, Du et. al. (TCD) were introduced to model the interactions of hydroxyl groups on the TiO2 surfaces, i.e., the Ti-O-H groups with an experimental and theoretical angles of 125 o . The bulk system was developed using periodic boundary conditions. The TiO2 nanoparticles were extracted by applying a spherical cut section in the bulk TiO2 melt structure to obtain the required size. Free valences on the nanoparticle surfaces were saturated via additional hydroxyl groups and then quenched to 300 K under free boundary conditions. The bulk and surface properties of the nanoparticles were calculated at 300 K and zero pressure and characterized via radial distribution functions, bond angle distributions, bond distances, coordination numbers, OH group concentrations and radial density profiles. In addition, to understand the difference in properties of amorphous hydroxylated TiO2 nanoparticles and bulk amorphous TiO2, a comparative study was done at the same thermodynamic conditions. The study shows that the bulk properties of amorphous hydroxylated TiO2 nanoparticles are strongly size-dependent and different from those of the bulk TiO2. As expected, increasing the particle size leads to an approach of the particle’s bulk properties to the bulk properties of the (quasi) infinite system. The size effects show that decreasing the particle size results in increasing the surface effects and surface OH group concentrations. Accordingly, small-sized TiO2 nanoparticles have higher surface OH group concentrations and larger surface effects than large-sized TiO2 nanoparticles. Larger surface effects result significant changes in their bond angles, bond distances, and coordination numbers. The simulation results of the surface properties reveal that the surface titanium atoms in the TiO2 nanoparticles have the capability of accommodating up to 5 hydroxyl groups. The mean surface hydroxyl group density of the amorphous TiO2 spherical nanoparticles is estimated to be around 8.1/nm 2, which lies in the range of 8–16/nm 2, found by experimental and other simulation studies. Details of the modelling, simulations results and the study are presented in this paper.

Impact of fiberizing method on physical properties of glass wool fibers

The physical properties of the glass fibers and their woven and non-woven products are affected by many factors, such as glass composition, thermal history, melting conditions, and fiberizing method. In this work, we have investigated the impact of fiberizing method on dynamic properties and relaxation behavior of the glass wool fibers, and inferred its effect on the mechanical properties of the filtration mats consisting of glass wool fibers. We have fabricated the glass wool fibers using the rotary (R) and flame (F) attenuation processes, which are denominated as R- and F- fibers, respectively. Both fibers have the same chemical composition and hence similar structural features, surface quality, glass transition temperature (Tg), and sub-Tg enthalpy relaxation behaviors. However, two fibers show striking differences in the surface hydroxyl (OH) content, fictive temperature (Tf) and cooling rate (qc). F-fibers have weakly hydrogen-bonded surface hydroxy (OH) groups, while R-fibers have free OH groups and strongly hydrogen-bonded OH groups. F-fibers have higher Tf and qc than R-fibers. We argue that the higher tensile strength of the F-fiber mat (compared to the R-fiber mat) could be attributed to both the weaker hydrogen-bonded surface OH groups, and the higher Tf and qc values that may increase the tensile strength of fiber itself. This work gives guidance for designing the fiber mat products with high tensile strength.

Low-temperature CO oxidation over Ag/SiO2 catalysts: Effect of OH/Ag ratio

Combined application of TPx methods, H2‐O2 titration, UV–vis DRS, TGA‐DSC‐MS, TEM, XRD, N2 adsorption at −196 oC allowed proving the OH/Ag molar ratio as the key parameter defining the catalytic properties of silica-supported silver (Ag/SiO2) in low‐temperature CO oxidation. A new insight into the formation of active species on the catalyst surface is presented. In this study, Ag/SiO2 catalysts with Ag loading of 5 and 8 wt.% were prepared by incipient wetness impregnation method on the basis of commercial silicas preliminary calcined at 500, 700 and 900°C. Detailed characterization of catalysts by physicochemical methods revealed that molar ratio between the concentration of surface OH groups (normalized to support mass) and silver amount in the prepared catalysts (OH/Ag ratio) affects the silver dispersion, structure of silver nanoparticles (NPs) and their catalytic properties. Only at optimal value of OH/Ag ratio the silver NPs are stated to possess both high dispersion and defective multidomain structure (that consists of several nanodomains) providing the adsorption of weakly bound oxygen species responsible for high catalytic activity in CO oxidation at low‐temperature. Additionally, the co-existence of two types of active sites reacting with CO at room temperature with and without formation of adsorbed carbonate species is discussed. The first type of active sites was catalytically active in low-temperature CO oxidation with CO2 release at room temperature (RT). The second type may retain surface carbonate species up to ∼40–50°C. The balance between these species shifts towards the first type for the active catalyst.

Pressurized calcium looping in the presence of steam in a spout-fluidized-bed reactor with DFT analysis

Calcium looping is a high-temperature solid-looping process for CO2 capture, exploiting cyclical carbonation of CaO. Previous work investigating the effects of steam on the carbonation reaction has produced conflicting results, with the majority of work conducted using thermogravimetric analyzers (TGA). Here, pressurized carbonation kinetics in the presence of steam in a 3kWe pressurized spout-fluidized bed reactor, gives a rigorous insight into the effects of steam. Pseudo-intrinsic kinetics were determined using an effectiveness factor model along with activation energies and kinetic expressions. The mechanism in which steam promotes CO2 adsorption on the surface of CaO was investigated using density functional theory (DFT). The molecular-scale changes on the CaO surface owing to the presence of steam compared to the base case of CO2 adsorption on a ‘clean’ (without steam) surface were simulated with the Cambridge Serial Total Energy Package (CASTEP) software. The results suggest that steam promotes CO2 adsorption via the formation of surface OH groups on the CaO surface.

Aqueous speciation is likely to control the stable isotopic fractionation of cerium at varying pH

Cerium (Ce) can be used as a plaeoredox proxy as shown by a recent study of stable isotopic fractionation of Ce during adsorption and precipitation. However, the experiments in that study were performed at pH conditions lower than that of natural seawater. In the current study, adsorption and precipitation experiments were performed at pH 6.80, 8.20, and 11.00 with 2.25mM dissolved carbonate to simulate Ce isotopic fractionation in the natural environment and examine the relationship between isotopic fractionation and Ce speciation in the liquid phase. Mean isotopic fractionation factors between liquid and solid phases (αLq-So) of Ce adsorbed on ferrihydrite did not depend on pH conditions or dissolved Ce species. In the Ce/δ-MnO2 system,αLq-So values decreased from 1.000411 (±0.000079) to 1.000194 (±0.000067) with increasing pH or number of carbonate ions, from Ce3+ to Ce(CO3)2−. In the Ce/precipitation system at pH 8.20 and 11.00 where Ce(CO3)2− is present in solution, the αLq-So values were 0.999821 (±0.000071) and 0.999589 (±0.000074), respectively, meaning that lighter isotope enrichment was observed in the liquid phase, which is the contrary to those of the other systems.Extended X-ray absorption fine structure (EXAFS) analyses were also performed to investigate the coordination structure of the adsorbed or precipitated Ce species that control the isotopic fractionation during adsorption. Even at higher pH, where Ce(CO3)+ or Ce(CO3)2− are the dominant dissolved species, the first coordination sphere of Ce in the solid phase in the Ce/ferrihydrite and Ce/precipitation systems was similar to that observed at pH 5.00 where Ce3+ was the main species in solution. A slight elongation in the CeO bond length in the solid phase at pH 11.00, where negatively charged dissolved species are dominant in the liquid phase, may cause a decrease in isotopic fractionation in the Ce/δ-MnO2 system. The coordination environment of Ce may not change significantly during the adsorption onto ferrihydrite, because Ce binds to the neutral surface OH group on ferrihydrite at pH below 8.5–8.8 (i.e. the pH of the point of zero charge (PZC) for ferrihydrite), similar to other cations when the metal–O distance was similar in hydrated and adsorbed species. At pH above PZC, Ce bonds to the negatively charged surface OH group, while Ce also bonds with CO32− in dissolved species. The reduced partition functions (ln β) for dissolved species (ln βLq) and adsorbed species (ln βSo) with the same trends canceled each other, because ln β of hydrated cation was reduced by the binding anion, resulting in small isotope fractionations. Thus, isotope fractionations for Ce/ferrihydrite may be quite small at the entire pH conditions in this study. The direction of the isotopic fractionation was estimated based on density functional theory (DFT) calculations, which confirmed that lighter Ce is enriched in the liquid phase when Ce forms a complex with carbonate ions. Therefore, this study indicates that the dissolved species can control stable Ce isotopic fractionation during precipitation reactions.

Lignosulfonate-based macro/mesoporous solid protonic acids for acetalization of glycerol to bio-additives

The enclosed paper introduces a novel, scalable and environmentally benign process for making strongly acidic solid meso/macroporous carbon catalysts from Na-lignosulfonate (LS), a byproduct from sulfite pulping. Ice-templated LS was converted to strongly acidic macro/mesoporous solid protonic acids via mild pyrolysis (350–450°C) and ion/H+ exchanging technique. The synthesized materials were extensively characterized by FT-IR, Raman, XRD, XPS, TGA, FE-SEM, TEM and N2-physisorption methods. These LS derived materials exhibited a macro/mesoporous and highly functionalized heteroatom doped (O, S) carbon structure with large amounts of surface OH, COOH and SO3H groups similar to the sulfonated carbon materials. Further, these carbon materials showed excellent potential as solid acid catalysts upon acetalization of glycerol with various bio-based aldehydes and ketones (acetone, methyl levulinate and furfural), easily outperforming the commercial acid exchange resins (Amberlite® IR120 and Amberlyst® 70). Most importantly, the optimum LS catalyst exhibiting a large specific surface area demonstrated exceptional potential for continuous solketal production (liquid phase atmospheric pressure operation) maintaining its activity (glycerol conversion≥91%) and structural features even after 90h time on stream.

One step hydrothermal synthesis of TiO2 with variable HCl concentration: Detailed characterization and photocatalytic activity in propene oxidation

TiO2 materials have been prepared by a novel one-step hydrothermal synthesis method at mild conditions (low temperature and time) using titanium tetraisopropoxide as precursor and HCl solutions of different concentration, ranging from 0.5 to 12M. A detailed physico-chemical characterization has been done, putting especial attention to the quantification of crystallinity and surface OH content. All the obtained samples have high surface areas (100–135m2/g), small anatase crystal size (8–11nm) and high crystallinity (around 80%). The concentration of the HCl used in the synthesis has a significant effect on the two first mentioned parameters and on the proportion of crystalline phases (anatase-brookite-rutile) developed. There is a good correlation between the amount of hydroxyl surface groups and the specific surface area (SBET), but regarding surface density of OH groups there are, as well, some differences between samples (the samples with higher OH surface densities are those prepared with less concentrated HCl solutions).Most of the prepared photocatalysts are more active than commercial TiO2-P25 in the gas phase oxidation of propene at low concentration. The best photocatalytic performance is found for samples prepared with 0.5 and 0.8M HCl, what can be explained by a suitable combination of properties: high surface area and developed porosity, high surface OH groups’ content and density and large proportion of anatase with small crystal size.

Revisiting the growth mechanism of atomic layer deposition of Al2O3: A vibrational sum-frequency generation study

The growth mechanism of the prototypical atomic layer deposition (ALD) process of Al2O3 using Al(CH3)3 (TMA) and H2O has been revisited on the basis of insights obtained with the nonlinear optical analysis technique of broadband sum-frequency generation (BB-SFG). With BB-SFG spectroscopy, both the –CH3 and –OH surface groups ruling the growth of Al2O3 by ALD were detected and could be monitored during the ALD process with submonolayer sensitivity. Several remaining questions pertaining to the growth mechanism of Al2O3 were addressed. The reaction kinetics of the H2O half-cycle were studied for ALD between 100 and 300 °C, and the reaction cross section σ was determined. The cross section at 300 °C was fairly large (σ = 3 × 10−19 cm2) and it decreased with decreasing temperature. Below 200 °C, the cross section also clearly varied with the surface coverage. For example, at 100 °C, the cross section started at σ = 1 × 10−20 cm2 for a full –CH3 coverage and decreased to σ = 3 × 10−21 cm2 for a 60% coverage. This coverage dependence of the reaction kinetics also explains the presence of the persistent –CH3 groups at low temperatures which are no longer reactive toward H2O. By a dedicated study using x-ray photo-emission spectroscopy, it was demonstrated that the persistent –CH3 groups were not incorporated into the film as a contaminant species. The absolute –CH3 coverage was measured for ALD between 100 and 450 °C. With this data, steric hindrance was ruled out as the cause of the self-limiting behavior in the TMA half-cycle on basis of the decrease observed in the –CH3 coverage with temperature. The self-limiting behavior was attributed to the depletion of under coordinated O during the TMA half-cycle. Moreover, the chemisorption of TMA on the -OH surface groups during the TMA half-cycle was investigated. On average, 1.5 –CH3 ligands remained on the surface per deposited Al atom after the TMA half-cycle at 300 °C, and this number decreased to 0.8 at 100 °C. These insights into the underlying growth mechanism augment the understanding of Al2O3 ALD and reveal several nuances in this well-studied ALD process.

An impedance model for the low-frequency noise originating from the dynamic hydrogen ion reactivity at the solid/liquid interface

Understanding the dynamics of hydrogen ion reactivity at the solid/liquid interface is of paramount importance for applications involving ion sensing in electrolytes. However, the correlation of this interfacial process to noise generation is poorly characterized. Here, the relationship is unveiled by characterizing the interfacial process with impedance spectroscopy assisted by a dedicated electrochemical impedance model. The model incorporates both thermodynamic and kinetic properties of the amphoteric hydrogen ion site-binding reactions with the surface OH groups. It further takes into consideration the distributed nature of the characteristic energy of the binding sites. The simulated impedance matches the experimental data better with an energy distribution of the kinetic parameters than with that of the thermodynamic ones. Since the potentiometric low-frequency noise (LFN) originating from the solid/liquid interface correlates excellently with the real part of its electrochemical impedance spectrum, this work establishes a method for evaluating sensing surface quality aimed at mitigating LFN.

Illuminate the active sites of γ-FeOOH for low-temperature desulfurization

FeOOH has been explored as a promising adsorbent for low-temperature H2S adsorption. However, the nature of the active sites toward the desulfurization has remained elusive. Here, a series of γ-FeOOH is prepared with well-defined lath-like and rod-like shapes by adjusting the pH value of the reaction system. The two shapes of γ-FeOOH have identical bulk structures but expose different distributions of surface OH groups, namely singly (FeOH, OH), doubly (Fe2OH, μOH), and triply coordinated (Fe3OH, μ3OH) hydroxyls, allowing us to investigate the geometrical-site-dependent desulfurization activity of γ-FeOOH at molecular-scale level. Following a thorough analysis by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and in situ Fourier transform infrared spectroscopy (In situ FT-IR), we demonstrate that singly hydroxyl (FeOH, OH) site is responsible for H2S adsorption, which acts as the active site for low-temperature desulfurization.

A novel method for the preparation of inorganic and organo-modified montmorillonite essential oil hybrids

In this study, a novel method which can be easily applied in industry for the modification of sodium exchanged montmorillonite (NaMt) and commercial organically modified montmorillonite (OrgMt) with essential oils (EO) such as oregano oil, thyme oil and basil oil was presented. The obtained clays-essential oils powders were promising nanostructures for controlled release applications. The presence of EO molecules in the interlayer space was studied with X-ray diffraction (XRD) analysis. Thermogravimetric Analysis (TG) was used to calculate the adsorbed amount of EO into NaMt and OrgMt clay layers and to determine the temperature region where EO release took place. Fourier-Transform Infrared (FTIR) spectroscopy was used to study the adsorption mechanism. The interlayer space of NaMt was found not to be affected by the adsorption of EO molecules while a significant increase of OrgMt interlayer space was recorded. EO amount released from NaMt surface above 220°C and between 100°C to 220°C in OrgMt. A hydrogen bond between OH groups of EO and external surface OH groups of NaMt in the case of NaMt/EO hybrids and a weak interaction between aromatic EO groups and amino chains in interlayer space of OrgMt in the case of OrgMt/EO hybrids were suggested.

Chemically Treated Rice Husk Blends as Green Desiccant Materials for Industrial Application

AbstractThe use of rice husks (RHs), treated RHs, and blends thereof as desiccants was studied. Bare RHs, treated RHs, and blends were characterized, and their water absorbances compared. Acid‐treated RHs showed better moisture absorbance than alkali‐treated RHs and hence were used to prepare blends. Moisture absorption of RH materials and silica gel were compared. Blends with a higher content of acid‐treated RHs showed higher water and moisture absorbency. The moisture absorbency of the blends was enhanced, and they exceeded the silica‐gel limit at 48 h of exposure time. The higher absorbency in blends with higher contents of acid‐treated RHs is likely due to higher porosity and improved adhesion properties owing to surface OH groups. Moreover, RH blends require shorter regeneration times than silica gel.