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3 pages, 191 KiB

Open AccessEditorial

Silica and Silica-Based Materials for Biotechnology, Polymer Composites, and Environmental Protection

by Jakub Zdarta and Teofil Jesionowski

Materials 2022, 15(21), 7703; https://doi.org/10.3390/ma15217703 - 2 Nov 2022

Cited by 5 | Viewed by 1664

Abstract

Over recent years, silica and silica-based materials have become some of the most frequently used materials worldwide [...] Full article

(This article belongs to the Special Issue Silica and Silica-based Materials for Biotechnology, Polymer Composites and Environmental Protection)

Research

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15 pages, 3882 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of the Effects of Cement and Lime with Rice Husk Ash as an Additive on Strength Behavior of Coastal Soil

by Zahraalsadat Eliaslankaran, Nik Norsyahariati Nik Daud, Zainuddin Md. Yusoff and Vahid Rostami

Materials 2021, 14(5), 1140; https://doi.org/10.3390/ma14051140 - 28 Feb 2021

Cited by 22 | Viewed by 3162

Abstract

Coastal accretion and erosion are unavoidable processes as some coastal sediments undergo modification and stabilization. This study was conducted to investigate the geotechnical behavior of soil collected from Bagan Lalang coast and treated with lime, cement, and rice husk ash (RHA) to design [...] Read more.

Coastal accretion and erosion are unavoidable processes as some coastal sediments undergo modification and stabilization. This study was conducted to investigate the geotechnical behavior of soil collected from Bagan Lalang coast and treated with lime, cement, and rice husk ash (RHA) to design a low-cost alternative mixture with environmentally friendly characteristics. Laboratory tests were carried out to analyze the physical properties of the soil (Atterberg limits and compaction properties), together with mechanical characteristics (direct shear and unconfined compressive strength (UCS) tests) to determine the effect of different ratios of stabilizer/pozzolan on the coastal soil and the optimum conditions for each mixture. Part of the purpose of this study was also to analyze the shear behavior of the coastal soil and monitor the maximum axial compressive stress that the treated specimens can bear under zero confining pressure. Compared to the natural soil, the soil treated with lime and rice husk ash (LRHA) in the ratio of 1:2 (8% lime content) showed a tremendous increase in shear stress under the normal stress of 200 kPa. The strength parameters such as the cohesion (c) and internal friction angle (ϕ) values showed a significant increase. Cohesion values increased considerably in samples cured for 90 days compared to specimens cured for 7 days with additional LRHA in the ratio of 1:2 (28%). Full article

(This article belongs to the Special Issue Silica and Silica-based Materials for Biotechnology, Polymer Composites and Environmental Protection)

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15 pages, 5431 KiB

Open AccessEditor’s ChoiceArticle

Stress-Dependent Particle Interactions of Magnesium Aluminometasilicates as Their Performance Factor in Powder Flow and Compaction Applications

by Pavlína Komínová, Lukáš Kulaviak and Petr Zámostný

Materials 2021, 14(4), 900; https://doi.org/10.3390/ma14040900 - 14 Feb 2021

Cited by 6 | Viewed by 2782

Abstract

In the pharmaceutical industry, silicates are commonly used excipients with different application possibilities. They are especially utilized as glidants in low concentrations, but they can be used in high concentrations as porous carriers and coating materials in oral solid drug delivery systems. The [...] Read more.

In the pharmaceutical industry, silicates are commonly used excipients with different application possibilities. They are especially utilized as glidants in low concentrations, but they can be used in high concentrations as porous carriers and coating materials in oral solid drug delivery systems. The desirable formulations of such systems must exhibit good powder flow but also good compactibility, which brings opposing requirements on inter-particle interactions. Since magnesium aluminometasilicates (MAS) are known for their interesting flow behavior reported as “negative cohesivity” yet they can be used as binders for tablet compression, the objective of this experimental study was to investigate their particle interactions within a broad range of mechanical stress from several kPa to hundreds of MPa. Magnesium aluminometasilicate (Neusilin^® US2 and Neusilin^® S2)-microcrystalline cellulose (Avicel^® PH102) physical powder mixtures with varying silicate concentrations were prepared and examined during their exposure to different pressures using powder rheology and compaction analysis. The results revealed that MAS particles retain their repulsive character and small contact surface area under normal conditions. If threshold pressure is applied, the destruction of MAS particles and formation of new surfaces leading to particle interactions are observed. The ability of MAS particles to form interactions intensifies with increasing pressure and their amount in a mixture. This “function switching” makes MAS suitable for use as multifunctional excipients since they can act as a glidant or a binder depending on the applied pressure. Full article

(This article belongs to the Special Issue Silica and Silica-based Materials for Biotechnology, Polymer Composites and Environmental Protection)

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14 pages, 1700 KiB

Open AccessArticle

Particle Size Distribution of Bimodal Silica Nanoparticles: A Comparison of Different Measurement Techniques

by Mohammed A. Al-Khafaji, Anikó Gaál, András Wacha, Attila Bóta and Zoltán Varga

Materials 2020, 13(14), 3101; https://doi.org/10.3390/ma13143101 - 11 Jul 2020

Cited by 17 | Viewed by 5635

Abstract

Silica nanoparticles (SNPs) belong to the most widely produced nanomaterials nowadays. Particle size distribution (PSD) is a key property of SNPs that needs to be accurately determined for a successful application. Many single particle and ensemble characterization methods are available for the determination [...] Read more.

Silica nanoparticles (SNPs) belong to the most widely produced nanomaterials nowadays. Particle size distribution (PSD) is a key property of SNPs that needs to be accurately determined for a successful application. Many single particle and ensemble characterization methods are available for the determination of the PSD of SNPs, each having different advantages and limitations. Since most preparation protocols for SNPs can yield bimodal or heterogeneous PSDs, the capability of a given method to resolve bimodal PSD is of great importance. In this work, four different methods, namely transmission electron microscopy (TEM), dynamic light scattering (DLS), microfluidic resistive pulse sensing (MRPS) and small-angle X-ray scattering (SAXS) were used to characterize three different, inherently bimodal SNP samples. We found that DLS is unsuitable to resolve bimodal PSDs, while MRPS has proven to be an accurate single-particle size and concentration characterization method, although it is limited to sizes above 50 nm. SAXS was found to be the only method which provided statistically significant description of the bimodal PSDs. However, the analysis of SAXS curves becomes an ill-posed inverse mathematical problem for broad size distributions, therefore the use of orthogonal techniques is required for the reliable description of the PSD of SNPs. Full article

(This article belongs to the Special Issue Silica and Silica-based Materials for Biotechnology, Polymer Composites and Environmental Protection)

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12 pages, 2676 KiB

Open AccessArticle

“DIY” Silica Nanoparticles: Exploring the Scope of a Simplified Synthetic Procedure and Absorbance-Based Diameter Measurements

by Łukasz Tabisz, Jerzy Stanek and Bogusława Łęska

Materials 2020, 13(14), 3088; https://doi.org/10.3390/ma13143088 - 10 Jul 2020

Cited by 6 | Viewed by 2914

Abstract

In this study, the classical Stöber silica synthesis protocol was used to test the limits of simplification in the preparation and size determination of nanoparticles. The scope of three-ingredient, one-pot synthesis was established in conditions of regular 96% and 99.8% ethanol as solvent, [...] Read more.

In this study, the classical Stöber silica synthesis protocol was used to test the limits of simplification in the preparation and size determination of nanoparticles. The scope of three-ingredient, one-pot synthesis was established in conditions of regular 96% and 99.8% ethanol as solvent, with aqueous ammonia as the only source of base and water. Particles with diameters in the 15–400 nm range can be reliably obtained with this straightforward approach, and the direct relationship between the size and the product of concentrations of water and ammonia is evidenced. Furthermore, the idea of a linear approximation for Mie scattering in particular conditions is discussed, using experimental data and theoretical calculations. A simple, fast method for particle size determination utilizing a UV-Vis spectrophotometer—an easily accessible instrument—is explained, and shows a level of error (<0.5 SD) that can be acceptable for less rigorous laboratory use of nanoparticles or serve as a quick means for testing the influence of minor alterations to known synthetic protocols. This work aims to show that nanoparticle synthesis can (and should) become a regular occurrence, even in non-specialized labs, facilitating research into their new applications and inspiring outside-the-box solutions, while discussing the drawbacks of a more relaxed synthetic regimen. Full article

(This article belongs to the Special Issue Silica and Silica-based Materials for Biotechnology, Polymer Composites and Environmental Protection)

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11 pages, 2644 KiB

Open AccessArticle

Preparation of Cu-Al/SiO₂ Porous Material and Its Effect on NO Decomposition in a Cement Kiln

by Yanling Gan, Suping Cui, Xiaoyu Ma, Hongxia Guo and Yali Wang

Materials 2020, 13(1), 145; https://doi.org/10.3390/ma13010145 - 30 Dec 2019

Cited by 14 | Viewed by 2798

Abstract

Nitrogen oxide (NOx) emissions have attracted much attention for increasing concern on the quality of the atmospheric environment. In view of NO decomposition in the cement production process, the preparation of Cu-Al/SiO₂ porous material and its effect on NO decomposition were studied, [...] Read more.

Nitrogen oxide (NOx) emissions have attracted much attention for increasing concern on the quality of the atmospheric environment. In view of NO decomposition in the cement production process, the preparation of Cu-Al/SiO₂ porous material and its effect on NO decomposition were studied, and the denitrification mechanism was proposed in this paper. The NO decomposition performance of the Cu-Al/SiO₂ porous material was tested via the experimental setup and infrared spectrometer and micro gas chromatography (GC). The result shows that the Cu-Al/SiO₂ porous material with the template of cetyltrimethylammonium bromide (CTAB) had a better NO decomposition rate than materials with other templates when the temperature was above 500 °C, and NO decomposition rate could approach 100% at high temperatures above 750 °C. Structure analysis indicates that the prepared Cu-Al/SiO₂ material structure was a mesoporous structure. The X-Ray Diffraction (XRD) and Ultraviolet–visible spectrophotometry (UV–Vis) results of the denitrification product show that the Cu-Al/SiO₂ material mainly decomposed to Cu₂O and Si₂O, and the CuO decomposed to Cu₂O and O₂ at high temperature. The Cu(I)O was considered as the active phase. The redox process between Cu(II)O and Cu(I)O was thought to be the denitrification mechanism of the Cu-Al/SiO₂ porous material. Full article

(This article belongs to the Special Issue Silica and Silica-based Materials for Biotechnology, Polymer Composites and Environmental Protection)

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16 pages, 2497 KiB

Open AccessArticle

Co-Immobilization of Glucose Dehydrogenase and Xylose Dehydrogenase as a New Approach for Simultaneous Production of Gluconic and Xylonic Acid

by Jakub Zdarta, Karolina Bachosz, Oliwia Degórska, Agata Zdarta, Ewa Kaczorek, Manuel Pinelo, Anne S. Meyer and Teofil Jesionowski

Materials 2019, 12(19), 3167; https://doi.org/10.3390/ma12193167 - 27 Sep 2019

Cited by 12 | Viewed by 3096

Abstract

The conversion of biomass components catalyzed via immobilized enzymes is a promising way of obtaining valuable compounds with high efficiency under mild conditions. However, simultaneous transformation of glucose and xylose into gluconic acid and xylonic acid, respectively, is an overlooked research area. Therefore, [...] Read more.

The conversion of biomass components catalyzed via immobilized enzymes is a promising way of obtaining valuable compounds with high efficiency under mild conditions. However, simultaneous transformation of glucose and xylose into gluconic acid and xylonic acid, respectively, is an overlooked research area. Therefore, in this work we have undertaken a study focused on the co-immobilization of glucose dehydrogenase (GDH, EC 1.1.1.118) and xylose dehydrogenase (XDH, EC 1.1.1.175) using mesoporous Santa Barbara Amorphous silica (SBA 15) for the simultaneous production of gluconic acid and xylonic acid. The effective co-immobilization of enzymes onto the surface and into the pores of the silica support was confirmed. A GDH:XDH ratio equal to 1:5 was the most suitable for the conversion of xylose and glucose, as the reaction yield reached over 90% for both monosaccharides after 45 min of the process. Upon co-immobilization, reaction yields exceeding 80% were noticed over wide pH (7–9) and temperature (40–60 °C) ranges. Additionally, the co-immobilized GDH and XDH exhibited a significant enhancement of their thermal, chemical and storage stability. Furthermore, the co-immobilized enzymes are characterized by good reusability, as they facilitated the reaction yields by over 80%, even after 5 consecutive reaction steps. Full article

(This article belongs to the Special Issue Silica and Silica-based Materials for Biotechnology, Polymer Composites and Environmental Protection)

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Review

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33 pages, 4716 KiB

Open AccessReview

Synthesis, Characterization and Use of Mesoporous Silicas of the Following Types SBA-1, SBA-2, HMM-1 and HMM-2

by Sylwia Jarmolińska, Agnieszka Feliczak-Guzik and Izabela Nowak

Materials 2020, 13(19), 4385; https://doi.org/10.3390/ma13194385 - 1 Oct 2020

Cited by 28 | Viewed by 3680

Abstract

Mesoporous silicas have enjoyed great interest among scientists practically from the moment of their discovery thanks to their unique attractive properties. Many types of mesoporous silicas have been described in literature, the most thoroughly MCM-41 and SBA-15 ones. The focus of this review [...] Read more.

Mesoporous silicas have enjoyed great interest among scientists practically from the moment of their discovery thanks to their unique attractive properties. Many types of mesoporous silicas have been described in literature, the most thoroughly MCM-41 and SBA-15 ones. The focus of this review are the methods of syntheses, characterization and use of mesoporous silicas from SBA (Santa Barbara Amorphous) and HMM (Hybrid Mesoporous Materials) groups. The first group is represented by (i) SBA-1 of three-dimensional cubic structure and Pm

\bar{3}

n symmetry and (ii) SBA-2 of three-dimensional combined hexagonal and cubic structures and P6₃/mmc symmetry. The HMM group is represented by (i) HMM-1 of two-dimensional hexagonal structure and p6mm symmetry and (ii) HMM-2 of three-dimensional structure and P6₃/mmc symmetry. The paper provides comprehensive information on the above-mentioned silica materials available so far, also including the data for the silicas modified with metal ions or/and organic functional groups and examples of the materials applications. Full article

(This article belongs to the Special Issue Silica and Silica-based Materials for Biotechnology, Polymer Composites and Environmental Protection)

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