Formation Of Silica Research Articles

POLYSILICATE BINDER FOR SILICATE PAINTS

Information is given on the structure and properties of a polysilicate binder obtained by mixing a silicic acid sol with a liquid glass. It was found that the introduction of a silicic acid sol in a liquid glass promotes an increase in the fraction of high-polymer fractions of silicic anions. An increase in the sol content promotes an increase in the fraction of high-polymer fractions of silicic anions. The results of the kinetics of the change in the silica content in the monomeric form in the potassium and sodium polysilicate solution are given. It was found that the dependence of the silica content in the monomeric form in the early stages of the interaction of the silicic acid sol with liquid glass is extremely extreme. It has been shown that when the potassium liquid glass is mixed with silica sol, the formation of silica in the monomeric form proceeds more slowly at the initial stage than in the sodium liquid glass. The results of studying the structure of polysilicate solutions by the method of violation of total internal reflection are presented. IR-spectroscopy revealed a shift in the band corresponding to Si-O-Si vibrations to the region of higher frequencies compared to liquid glass, which indicates a higher degree of polymerization of silica. The presence of silica in the polysilicate binder polymeric species is established, which ensures an increase in the stability of silicate coatings. Information on the properties of silicate composition with the use of polysilicate film-forming and coatings based on it is given. The composition is intended for interior and exterior walls of buildings.

Shaping Silica Rods by Tuning Hydrolysis and Condensation of Silica Precursors.

We present the synthesis of colloidal silica particles with new shapes by manipulating the growth conditions of rods that are growing from polyvinylpyrrolidone-loaded water-rich droplets containing ammonia and ethanol. The silica rods grow by ammonia-catalyzed hydrolysis and condensation of tetraethoxysilane (TEOS). The lengthwise growth of these silica rods gives us the opportunity to change the conditions at any time during the reaction. In this work, we vary the availability of hydrolyzed monomers as a function of time and study how the change in balance between the hydrolysis and condensation reactions affects a typical synthesis (as described in more detail by our group earlier1). First, we show that in a “standard” synthesis, there are two silica growth processes occurring; one in the oil phase and one in the droplet. The growth process in the water droplet causes the lengthwise growth of the rods. The growth process in the oil phase produces a thin silica layer around the rods, but also causes the nucleation of 70 nm silica spheres. During a typical rod growth, silica formation mainly takes place in the droplet. The addition of partially hydrolyzed TEOS or tetramethoxysilane (TMOS) to the growth mixture results in a change in balance between the hydrolysis and condensation reaction. As a result, the growth also starts to take place on the surface of the water droplet and thus from the oil phase, not only from inside the droplet onto a silica rod sticking out of the droplet. Carefully tuning the growth from the droplet and the growth from the oil phase allowed us to create nanospheres, hollow silica rods, hollow sphere rod systems (colloidal matchsticks), and bent silica rods.

In situ study of the oxidation of ZrB2 and ZrB2-SiC materials by monitoring the LIF signal of BO2 radicals

In this study, the Laser Induced Fluorescence (LIF) technique is used to detect BO2 radicals in the gas phase above heated ZrB2 and ZrB2-20 vol. % SiC samples in air, in order to provide an in situ and real-time monitoring of their thermal oxidation. Samples are heated up to 1923 K in air flow with a 2 kW CO2 laser. The BO2 fluorescence and the laser transmission signals are monitored throughout the temperature ramp. This technique allows to detect the key steps of the oxidation (silica formation,...) and to propose more precise oxidation mechanisms as a function of temperature.

Effect of silica on the ZnS nanoparticles for stable and sustainable antibacterial application

AbstractSilica‐capped Zinc Sulfide (ZnS) nanoparticles were synthesized for the use as stable and long‐term antibacterial agents because silica is a very important component in food packaging applications for moisture absorption in tune with its property of biocompatibility and water solubility. The variation in morphological and optical properties of core‐shell nanostructures was studied by changing the concentration of silica in a core‐shell combination. The structural and morphological properties of silica‐capped ZnS have been observed by powder X‐ray diffraction (PXRD) and transmission electron microscopic (TEM) studies, respectively. Uncapped ZnS nanoparticles with particle size of 2‐4 nm in a highly agglomerated state have been observed from TEM, which shows that they can be used only for short‐term antibacterial action despite its excellent zone of inhibition (antibiotic sensitivity). However, ZnS/SiO2 core‐shell nanostructures are highly monodisperse in nature and the particle size increases up to 5‐8 nm with increase in silica concentration. Fourier‐transform infrared spectroscopy (FTIR) analysis confirms the formation of silica capping on the ZnS surface. The inhibition of defect‐related emission by silica capping in energy‐resolved photoluminescence studies also shows the formation of very stable ZnS nanoparticles. To study the antibacterial properties of the pure and silica‐capped ZnS nanostructure the agar‐well diffusion method was employed against both gram‐positive and gram‐negative bacteria. The obtained results indicate that pure ZnS shows excellent antibacterial action but it can last only for few days.

Towards viable CO2 sequestration: Production of high specific surface area silica by olivine dissolution in concentrated acidic solutions

CO2 sequestration by reaction with ultramafic minerals such as olivine has been considered for decades. However, the moderate leaching yield of olivine by CO2 even at high temperature and pressure, led to consider an alternative. For this purpose, indirect sequestration process has been investigated with acidic dissolution of olivine for the formation of valuable silica. The remaining concentrated solutions of magnesium, iron and nickel salts could be used for production of the separate carbonates. Numerous dissolution tests of industry-grade 120 μm olivine were carried out in a 250 mL stirred reactor under non-oxidant atmosphere with concentrated acidic solutions. Two solid fractions (“Upper” and “Bottom”) and a metal-rich liquor were recovered, then thoroughly characterized. Results are discussed in terms of quality of the silica nanoparticles produced (BET specific area, pore size distribution, purity) as well as of dissolution yields, depending on operating conditions. BET surface area of the silica over 500 m2/g and nearly complete dissolution could be obtained for 3 h at 80 °C, however with appreciable excess of acid. A final test was conducted with an acid excess fixed at 12%, a solid/liquid ratio at 180 g/L, for 2 h at 95 °C: olivine was converted at 72% to silica. The “Upper” solid fraction recovered consisted of regular 15–20 nm particles in agglomerates with an overall BET area near 400 m2/g.

Extraction and Characterization of Silicon Dioxide from Rice Straw

Study of silicon dioxide (silica) extraction from biomass has been successfully done. The biomass used in this study is rice straw. That is one of the rice production waste. Rice straw burning method at initial temperature of 400°C to 900°C with heating rate of 1.7s for 2 hours. Then rice straw ash washed by hydrochloric acid (HCl) with a concentration of 3% to remove the impurities. Last, that was burned at 900°C at a rate of 1.7 for 1 hour to obtain silica in crystalline form. The resulting silica samples were compared by commercial silica with purity of 99.95%. Based on FTIR characterization data of rice straw silica has a functional group representing the formation of SiO2 compound, that is at 483.39cm−1, 789.41cm−1, and 1095.65cm−1 wavenumber. According to the XRD results also have shown the pattern of crystalline diffraction with crystallinity percentage of 80.40%. The result of the characterization is similar to the pattern shown by the commercial silica used as the comparison. Although this method has succeeded in forming silicon dioxide, but the final result is very dense powder, so it difficult to crush. Therefore, further study is needed to find the most optimal temperature. The characterization also necessary to determine the purity of rice straw silicon dioxide.

Reaction pathways in the oxidation and pesting of molybdenum disilicide MoSi2 studied with scanning tunneling microscopy and spectroscopy

The oxidation and pesting of Molybdenum Disilicide is a critical limiter in its technical use. The materials disintegration during the pesting reaction in cracks and at grain boundaries prevents direct observation of the process. A model system consisting of silicide crystallites on a Si(001) surface was developed to study the progression of the oxidation reaction in-situ with Scanning Tunneling Microscopy and Spectroscopy. Deposition and annealing of Mo thin films is used to synthesize crystallites in a size range between 10 and 100 nm, and atomic resolution is achieved on several facets. The MoSi2 is oxidized in the temperature range 400–800°C bracketing the pesting regime and beyond, combined with molecular oxygen exposure from 2 to 100 Langmuir. The oxidation process can be subdivided in three distinct regimes defined by their respective oxidation conditions: regime 1 (incubation) where only subtle changes in the electronic structure of the crystallites occurs, to regime 2 with a rapid increase in the crystallite density due to the volume gain of the pesting reaction transforming silicide to oxide, and regime 3 where a silica layer starts to form. The incubation time is attributed to oxygen dissolution and/or formation of a ternary Mo-Si-O phase, which is followed by the release of MoOx molecules. The diffusion of MoOx triggers secondary nucleation events, and contributes to the accelerated oxidation of the surface. Increasing the surface temperature > 650°C promotes desorption and sublimation over diffusion and supports silica formation. This study unraveled the intermediate reaction steps of silicide oxidation, and specifically underscores the critical role of reactant diffusion in the rapid progression of the pesting reaction.

Oxidation of Epitaxial Silicene on Ag(111)

The high chemical reactivity of epitaxial silicene on Ag(111) still remains a debated subject in the literature. In particular results on the oxidation of epitaxial silicene and its related lifetime under ambient conditions are controversially discussed. Here, a detailed investigation of the oxygen exposure to epitaxial silicene layers investigated by means of X‐ray photoemission and in situ Raman spectroscopy is reported. The results should clearly cease the discussion on the stability of epitaxial silicene against oxygen as it becomes completely oxidized after an exposure to only 100 L of oxygen. Such a small dose sets strict limits for ex situ studies of epitaxial silicene. Besides the formation of silicon oxide also the silver substrate surface oxidizes, suggesting that the silicene layer can hardly protect it, probably owing to the high number of domain boundaries within the silicene layer.

Synthesis and characterization of hierarchical porous clay heterostructure from Al, Fe -pillared nano-bentonite using microwave and ultrasonic techniques

Abstract The present research is focused on the textural, structural and surface properties of Al, Fe and Si hierarchical porous nano-bentonite heterostructure (PBH) derivated from Al, Fe pillared nano-bentonite (Al, Fe-PILB). The application of Al, Fe-PILB as a precursor to prepare porous clay minimized the use of cationic surfactant, water consumption, synthetic time and organic wastes. Furthermore, the incorporation of Al and Fe species from Al, Fe-PILB in the silica framework was performed in one step reaction compared to the conventional method required the continuous control for hydrolysis and condensation in the synthesize of PBH. Besides using Al, Fe-PILB as a precursor, the ultrasonic and microwave techniques were firstly assisted to the synthesis of PBH for opening bentonite layers with breaking pillars resulted in the increasing basal spacing and improving mesoporous silica formation in interlayer space of Al, Fe-PILB in little synthetic time. The LPSD, XRD, UV–Vis spectra, N2 adsorption-desorption, FESEM-EDS, TEM, and FTIR analyses allowed for a better understanding of PBH behaviors under different synthetic conditions. The results showed that the use of pillared clays in the conventional method did not lead to the formation of PBH due to the strong interaction between the Al, Fe species and the clay layers. The synergism effect of ultrasonic waves and microwave irradiation reduced the structural damage of nano-bentonite and improved BET surface area (867 m2/g), micropore and mesopore volume (0.62 cm3/g) compared to the only application of ultrasonic or microwave techniques. These properties make PBH as an attractive candidate for catalysis and adsorption applications.

Efficient silica synthesis from tetra(glycerol)orthosilicate with cathepsin- and silicatein-like proteins

Silicateins play a key role in biosynthesis of spicules in marine sponges; they are also capable to catalyze formation of amorphous silica in vitro. Silicateins are highly homologous to cathepsins L – a family of cysteine proteases. Molecular mechanisms of silicatein activity remain controversial. Here site-directed mutagenesis was used to clarify significance of selected residues in silica polymerization. A number of mutations were introduced into two sponge proteins – silicatein A1 and cathepsin L from Latrunculia oparinae, as well as into human cathepsin L. First direction was alanine scanning of the proposed catalytic residues. Also, reciprocal mutations were introduced at selected positions that differ between cathepsins L and silicateins. Surprisingly, all the wild type and mutant proteins were capable to catalyze amorphous silica formation with a water-soluble silica precursor tetra(glycerol)orthosilicate. Some mutants possessed several-fold enhanced silica-forming activity and can potentially be useful for nanomaterial synthesis applications. Our findings contradict to the previously suggested mechanisms of silicatein action via a catalytic triad analogous to that in cathepsins L. Instead, a surface-templated biosilification by silicateins and related proteins can be proposed.

Kinetic Modeling of the Silicothermic Reduction of Manganese Oxide from Slag

A model was developed to describe the mixed rate control kinetics in systems with MnO-SiO2-CaO-Al2O3 slags and Fe-Si metal droplets. During the reaction of Fe-Si droplets and slag, Mn2+ transport was found to be part of controlling the system but could not sufficiently describe all initial conditions (chiefly, changes to initial silicon content). The current model describes the kinetics of the stated system and offers answers to the question of rate control; the model has been fitted to nine datasets of varying initial conditions including initial [Si], initial (MnO), initial droplet size, and reaction temperature. The fitted mass transfer coefficients for metal and slag were 2.3 × 10−4 and 6.7 × 10−4 m/s, respectively; these values are constant across the nine datasets. Previous claims about the efficiency of silicon usage in reducing manganese have been modified; it appears that the formation of silica is favored throughout the reaction, but that the formation of a silicon monoxide gas layer on the metal surface dramatically impacts the rate of reaction. As a measure of overall fit of the model, the average of the root-mean-square errors for all datasets is 14 pct. Mass transport in slag is twice as influential on rate control as the metal phase. The simultaneous transport of both Mn2+ and silicate dimers controls mass transport in the slag. Both [Si] and [Mn] can control from the metal side but are dependent on the initial conditions.

Could Mesophases Play a Role in the Nucleation and Polymorph Selection of Zeolites?

Zeolites and mesoporous silicas are porous materials with important applications in catalysis, gas storage, and separation. Zeolite crystals form in the presence of cationic surfactants that act as structure directing agents (SDAs). The way SDAs control the nucleation and polymorphs selection in zeolites is not fully understood. The formation of mesoporous silica is templated by liquid crystalline mesophases that result from frustrated attraction between silicates and long-chain SDAs. Experiments indicate that surfactants C nH2 n+1(CH3)3N+ with n > 6 yield mesoporous silicas, and the one with n = 6 produces a zeolite. This suggests that the driving force toward mesophase formation is also present for small organocations, but is overcome by the ability of silica to wrap a crystal lattice around them. Here we use molecular dynamics simulations to investigate whether the existence of metastable mesophases can play a role in the nucleation and polymorph selection of zeolitic crystals. As a proof of concept, we investigate the phase behavior of simple mesogenic mixtures of SDAs and a network former T that favors tetracoordinated crystals. We represent the network-former T by Stillinger-Weber models of water and silicon, in lieu of silica, because a computationally efficient silica potential that would allow for the spontaneous nucleation of zeolites in molecular dynamics simulations is not yet available. The mixtures of T and SDA produce a rich phase diagram that encompasses the sII clathrate and at least six zeolites, including sigma-2 (SGT). We find that the nucleation of SGT is not assisted by a mesophase. The nucleation of the other five zeolites of this study, however, is facilitated by the existence of metastable mesophases that decrease the nucleation barriers and direct the selection of the crystal polymorph. Together with the experimental support for mesophases in mixtures of silicates and SDAs, our results for model systems suggest that metastable mesophases could play a prominent role in promoting the nucleation and polymorph selection of some zeolites.

Solid‐Solution Effects on the High‐Temperature Oxidation Behavior of Polymer‐Derived (Hf,Ta)C/SiC and (Hf,Ti)C/SiC Ceramic Nanocomposites

In the present study, two concepts to improve the oxidation resistance at high‐temperatures of ceramic nanocomposites consisting of 85–90 vol% SiC, 5–8 vol% group IV metal carbides (i.e., HfC, TaC), and 5–7 vol% carbon are introduced and discussed. First improvement concept relates to the passivation of the samples upon short‐term oxidation at 1400 °C (30 min). This is a critical step, especially with respect to silica formation, which is relatively sluggish at temperatures lower than 1000–1200 °C. Moreover, solid‐solution metal carbides (Hf,Ta)C and (Hf,Ti)C are shown to be clearly more oxidation resistant than the binary HfC and TaC phases. Whereas, the solid‐solution effect contributes to a significant improvement of the short‐term oxidation resistance of the studied nanocomposites, the passivation of the materials prior exposure of high‐temperature oxidation conditions provides a remarkably improved long‐term behavior thereof. Possible mechanisms involved in the oxidation processes of (Hf,Ta)C/SiC and (Hf,Ti)/SiC ceramic nanocomposites are highlighted and critically assessed.

Effect of silicone resin as precursor and binder on the properties of alumina-based ceramic cores using ball-shaped powders

Al2O3-based ceramic cores with uniform microstructure were fabricated by sintering ball-shaped Al2O3 powders as the matrix and silicone resin as the precursor and binder in air atmosphere. Effects of silicone resin content and sintering temperature on phase composition, microstructure and properties of the Al2O3-based ceramic cores were investigated. Results showed that a low sintering rate was beneficial for preparing high-quality Al2O3-based ceramic cores with no defects and cracks. Silicone resin was uniformly adhered on the surface of the ball-shaped Al2O3 particles, playing a well role in connecting Al2O3 particles. Sintering process made the organic-inorganic transformation process of silicone resin happen, leading to the formation of amorphous silica at 1300 °C, followed by cristobalite appeared by the crystallization of amorphous silica as the temperature was higher than 1400 °C. The sintering necks between ball-shaped Al2O3 grains were formed by the pyrolyzed products of silicone resin. As the temperature was lower than 1500 °C, the phase composition consisted of Al2O3 and silica. However, at 1600 °C, new mullite phases were in situ formed on the surface of ball-shaped Al2O3 particles. The increasing silicone resin content promoted the formation of more mullite phase. Al2O3-based ceramic cores prepared had well dimensional stability during sintering, and the linear shrinkage rate reached the minimum value of 0.23% in the ceramic cores with silicone resin content of 20 wt% at 1400 °C. The open porosities of Al2O3-based ceramic cores prepared were 24.2~30.0% and relative densities were 63.9~70.2%. The bending strength increased with the increase in the sintering temperature, and the maximum value was obtained in the ceramic cores with silicone resin content of 15 wt% at the same sintering temperature. In our research, the highest bending strength reached to 77.06 MPa in the ceramic cores with silicone resin content of 15 wt% at 1500 °C.

АНАЛІЗ ВПЛИВУ ВХІДНИХ КОМПОНЕНТІВ НА ТЕПЛОФІЗИЧНІ ВЛАСТИВОСТІ ПОКРИТТЯ ПРИ ВОГНЕВОМУ ВПЛИВІ

Purpose. Development of fire protection composition and study of its properties: definition of fire protection group of the proposed coating. Methodology. In the course of the research, an analytical review of the main groups of fire retardants, which increase the fire resistance of wooden construction constructions, gave an assessment of their technical characteristics, as well as in accordance with DSTU B V.1.1-4-98 "Fire protection. Building constructions. Test methods for fire resistance. General requirements "defines the fire-protective properties of the developed fire protection coating. Findings. The authors developed a composition of flame retardant coating that forms on the surface, which "protects" a thin non-transparent layer that prevents inflammation and spread of flame on a wooden structure. The selection of composition of fire protection composition was carried out according to the scheme "compound - the additive that is flowing -the filler". The basis of the coating is liquid glass, because it has such positive characteristics as accessibility, due to the manifestation of liquid glass adhesive properties - the ability to spontaneous hardening with the formation of artificial silica. An increase in the content of fillers can increase the use interval of the composition to 900-9200С, and the maximum temperature at which provides the swelling of the coating 540-6800С. According to studies, the highest fire-retardant coating efficiency is achieved with content in the composition of asbestos-cement waste from 15.0 to 22.5%, aluminum-calcium slag from 7.5 to 10.0%. An increase in the content of fillers and technical drill for a rational area reduces the heat-shielding ability of the coating and reduces the fire-retardant effectiveness of the coating. Adding to the flame retardant composition sulfite-alcoholic membrane greatly improves the adhesion of the coating from the protected surface, which also affects the fire-protective ability of the coating, it grows to 76.0-81.0 minutes. Originality. Taking into account the theoretical preconditions, the choice of output components for a new fire protection composition has been carried out. Practical value. A new nonflammable spillway structure is developed, which allows the transfer of combustible materials into a group of heavier and increase fire resistance of building structures. On the developed fireproof composition the Ukrainian patent for utility model was obtained.

ВИБІР МАТЕРІАЛІВ ДЛЯ РОЗРОБКИ ЗАХИСНИХ ПОКРИТТІВ ВІД ВПЛИВУ ВИСОКИХ ТЕМПЕРАТУР

Purpose. When developing protective coatings to protect building structures when exposed to high temperatures, it is necessary to determine the necessary materials, which together solve the main task of ensuring the safe operation of building structures. Method. In carrying out the research conducted an analytical review of major groups of protective agents that reduce the combustibility of wooden construction structures, gave an assessment of their technical characteristics, as well as in accordance with GOST 12.1.044-89 "OHSAS. Fire and explosion of substances and materials. Nomenclature of indicators and methods for their determination", fire protection and sanitary-technical indicators of the developed protection coating are determined. Results. The authors have conducted studies of raw materials: liquid glass, epoxy resin, graphite, perlite, fly ash. The selection of composition of fire protection composition was carried out according to the scheme "compound - the additivethat is flowing - the filler". The basis of the coating is liquid glass, because it has such positive characteristics as accessibility, due to the manifestation of liquid glass adhesive properties - the ability to spontaneous hardening with the formation of artificial silica. Adding to the liquid glass such components as perlite, graphite and epoxy resin, taking into account their positive characteristics regarding the effect of high temperatures, allowed to obtain a new flame retardant composition. For firing tests, an installation was used to determine the coefficient of smoke formation of substances and materials. The essence of the test me thod was to determine the optical density of smoke that occurs during flame combustion or corrosion of the sample. Tests are conducted in two modes. In the mode of decay, for example, there is a heat flux with a surface density of 35 kW/m2, and in th e mode of flame combustion - the heat flow and the flame of the gas burner. The conducted studies on determining the smoke forming ability have shown that the samples provided by the material "Mixture for the production of fireproof coating VPE -1", belong to materials with moderate smoke-forming ability D2. According to the results of the testing of the toxicity of combustionproducts, it turns out that the object of testing is a little dangerous to the class. Scientific novelty. Taking into account the theoretical preconditions, the choice of output components for a new fire protection composition has been carried out. Practical meaningfulness. The selection of input components that allow a targeted selection of protective coatings under high temperatures. Practical significance. A new non-flammable composition has been developed, which is expanded, which allows to transfer combustible materials to a group of slow-burning and to increase the protection of building structures from high temperatures. The developed protective composition received the patent of Ukraine for a useful model.

Influence of the initial chemical conditions on the rational design of silica particles

The influence of the water content in the initial composition on the size of silica particles produced using the Stöber process is well known. We have shown that there are three morphological regimes defined by compositional boundaries. At low water levels (below stoichiometric ratio of water:tetraethoxysilane), very high surface area and aggregated structures are formed; at high water content (>40 wt%) similar structures are also seen. Between these two boundary conditions, discrete particles are formed whose size are dictated by the water content. Within the compositional regime that enables the classical Stöber silica, the structural evolution shows a more rapid attainment of final particle size than the rate of formation of silica supporting the monomer addition hypothesis. The clearer understanding of the role of the initial composition on the output of this synthesis method will be of considerable use for the establishment of reliable reproducible silica production for future industrial adoption.

Front Cover: A Possible Path to Prebiotic Peptides Involving Silica and Hydroxy Acid-Mediated Amide Bond Formation (ChemBioChem 18/2018)

Front Cover: A Possible Path to Prebiotic Peptides Involving Silica and Hydroxy Acid-Mediated Amide Bond Formation (ChemBioChem 18/2018)

Influence of the Structure and Experimental Surfaces Modifications of 2:1 Clay Minerals on the Adsorption Properties of Methylene Blue

In this work the adsorption capacities of methylene blue on Mg-smectite and sepiolite and its derived material obtained after acid treatment and/or the addition of Fe at its surfaces are studied. Natural smectite with high Mg-content in its octahedral sheet (Mg-smectite) displays higher adsorption capacity than the sepiolite due to the ability of Mg-smectite to expand the basal spacing to accommodate methylene blue cations between adjacent layers and the inability of sepiolite to adsorb these cations within the structural channels. The acid-activation of Mg-smectite causes a clear decrease in the adsorption capacity attributed to the partial loss of the interlayer positions by the loss of the octahedral sheet and subsequent formation of amorphous silica. Moreover, the adsorption of the Mg-smectite decreases even more when iron oxohydroxides species are incorporated in its interlayer spacing making inaccessible the interlayer active sites for the adsorption of methylene blue cations. On the contrary, the microwave-assisted acid treatment of sepiolite causes a slight increase in the adsorption capacity related with the dispersion of fibers. Nevertheless, contrary to that observed with Mg-smectite, higher increasing of adsorption capacities are obtained after the formation of new adsorption centers due to the incorporation of iron oxohydroxides species at the external surfaces of sepiolite.

Formation of Silica–Organic Hybrid Nanoparticles by Cross-linking of Ultra-small Silica Nanoparticles

A new type of silica–organic hybrid nanoparticle (HNPs) ∼30 nm in size, consisting of vinylsilylated silica nanoparticles (SNPs) of size ∼2 nm and 1,6-hexanedithiol as the organic linker, were prep...