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In this work, the objective is to utilize avocado seed extract as a cheap alternative source of active compounds and was successfully encapsulated using gum arabic by spray drying as an antioxidant and antimicrobial agent. First, the active compounds were extracted from avocado seed using solvent n-hexane and followed by solvent separation using rotary vacuum evaporator. Next, gum arabic as the encapsulation agent was added to avocado seed extract to form an emulsion, then spray-dried with drying air at a temperature of 140 °C. The mass ratio of avocado seed was varied at extract: gum arabic of 5:5, 5:10, 5:15, and 5:20. Then, the particle morphology, yield, moisture content, encapsulation efficiency, loading capacity, chemical groups, antioxidant activity, and antibacterial ability were analyzed to investigate the performance of the encapsulation particles. Among the ranges studied, the extract–gum arabic with a mass ratio of 5:10 exhibited the best properties of yield powder, loading capacity, and encapsulation efficiency at 49.78%, 3.43%, and 7.33%, respectively. The encapsulated particles have smooth surface, crackless, lower indentation, and a single-core encapsulation structure with an average diameter of 4.60 μm. Besides, the stability of antioxidant activity decreased by 2.36%, from 94.82% to 92.46% for four weeks of storage. They also performed antimicrobial activity against E. coli and S. aureus, which were maintained after seven days. Meanwhile for avocado seed extract only, the unencapsulated stability of antioxidant activity has continually decrease from 91.58% to 84.05% and performed no antimicrobial activity against E. coli after seven days.

This study reported the effect of sodium lauryl sulfate (SLS) as a template on silica morphology and its properties. The precursor was prepared by producing silica nanofluid by the sol-gel method and mixed with various SLS concentrations. After that, the precursor was spray-dried to generate silica powder. An increase in SLS concentration up to 2 critical micelle concentration (CMC) indicates an increase in the silica particle size from 2.12 μm in untemplated silica particles to 2.58 μm. On the other hand, when the SLS concentration increases to 3 CMC, the particle size decreases to 2.19 μm. A significant increase in total pore volume and surface area is obtained for silica particles synthesized at least at the SLS concentration of 2 CMC, around eight higher volumes than without SLS addition. In addition, they have a macropore compared to silica particles synthesized without SLS addition that only exhibits mesopore. The surface area was 1,011 m2/g for the SLS concentration at 3 CMC, whereas the silica without SLS has only a surface area of 131 m2/g. The SLS concentration at 2 CMC or higher leads to a significant increase in its physical properties because the micelle formation is enough for sacrificed template formation. Methylene blue solution was used as an adsorbate for evaluating the dye adsorption capacity that followed the Langmuir isothermal adsorption model. The highest theoretical maximum monolayer adsorption capacity was 142.9 mg/g, obtained by silica adsorbent with the SLS concentration at 3 CMC.

Solid acid catalyst is a promising alternative to the counterpart homogeneous acid for esterification reaction from the viewpoint of reusability and environmental concerns. This work aims to develop sulfonated mesoporous silica-carbon composite as solid acid catalyst for the esterification. The catalyst was synthesized from sodium silicate as the silica precursor and polyethylene glycol (PEG) as both carbon precursor and template via a sol-gel route in an aqueous system. Then, it was carbonized to produce mesoporous silica-carbon composite. Using the proposed method, the surface area of the silica-carbon composite could reach as high as 1074.21 m2/g. Although the surface area decreased to 614.02 m²/g when it was functionalized with sulfonate groups, the composite had a high ionic capacity of 5.3 mEq/g and exhibited high catalytic activity for esterification reaction of acetic acid with ethanol. At a reaction temperature of 80 °C, the acetic acid conversion reached 76.55% in 4 h. In addition, the catalyst had good reusability, which can be comparable with the commercial catalyst Foltrol F-007. It appears that the sulfonated silica-carbon composite prepared from sodium silicate using PEG as the carbon source a promising candidate as catalyst for esterification and the related area. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

The composite restorations in posterior teeth have recently received an increasing interest due to the improvement of their physical and mechanical properties. However, compositing by the most common polymerization procedure tends to deform the tooth structure that may cause some damage in the marginal seal due to the imperfect interfacial attachment. Several techniques have been used to overcome this problem, one of them is using a flowable composites on the bottom of the cavity as the first layer. The purpose of this study is to develop fiber-reinforced composite (FRC) material made of coir fiber (Cocos nucifera) with matrix (Bis-GMA, TEGDMA, DGEBA, and camphorquinone). Cellulose fiber was formed by an anti-solvent method from an aqueous NaOH-urea cellulose solution dropped into ethanol-water mixture. The resulting cellulose fibers were then mixed with the matrix using a magnetic stirrer. The composition of nanocellulose in the matrix was varied 10:90 and their characteristics were compared with the commercial nanofiller composite (Z 350 and 3M) as control. The sample was tested for cross-linked using a scanning electron microscope (SEM) and Fourier transform infrared (FTIR). The morphology of nanocellulose look like a fiber as cross-linked with matrix. Therefore, the formation of a crosslink bond between cellulose and matrix C-O-C with a new wavenumber in 890 cm-1. The nanocellulose composite also form fibers that binds the matrix, while flowable composites from manufacturers from fibers and particulates. From this experimental method it can be suggested coconut fiber has high potential as raw material to be filler in a dental flowable composite.

Amine functionalized silica has been successfully prepared using a direct co-condensation method in spray-assisted with sodium silicate as silica source and γ-aminopropyltriethoxysilane (APTS) as amine source. This study aims to synthesize amine grafted silica in one step process which includes particle formation and surface modification. Silica-amine nanofluids were prepared in stable colloidal phase as precursor solution for spray drying system. Amine sourced from APTS was condensed separately with silica nanofluids. The process of controlling the condensation rate of APTS can prevent the occurrence of silica precipitates in the precursor. The silica-amine precursor solution was then processed by spray drying at a temperature of 200°C. Silica particles that have been modified by amine groups were characterized using FT-IR, TG-DTA, and Adsorption-desorption N2. The silica-amine showed the presence of an amine group that was successfully grafted. This is indicated by the presence of characteristic amine peaks on FT-IR and mass changes due to amine decomposition in TG-DTA. The number of amines that were successfully grafted was 0.5 mmol/g sample. The washing of amine-modified silica particles with ethanol showed that the type of bond that occurred between silica and the amine functional group was a physical bond. The surface area of amine-modified silica is 169 m2/g with the pore size distribution in the micro-mesopore regime. The average pore size of amine-modified silica was 0.1288 nm.

Boehmite (g-AlOOH) has demonstrated to have superior performance as coating material for battery separator, especially lithium-ion battery, due to its excellent wetting ability and thermal stability. The products of Bayer process from bauxite are typically in the form of aluminum trihydrate (ATH). Observing the phase diagram of Al2O3-H2O, it was assumed that the ATH might be converted into boehmite by controlling the pressure and temperature under hydrothermal condition. Therefore, the purpose of this work is to investigate the effect of operating conditions on the conversion of ATH to boehmite in a hydrothermal reactor. The experiments were carried out in a 100-mL hydrothermal reactor with a liquid filling volume of 30% and 50%. The reaction time was varied from 2 to 8 h. The hydrothermally treated ATH particles were characterized by an X-ray diffraction (XRD) and a scanning electron microscopy (SEM). The XRD patterns exhibited that the ATH has not been converted yet into boehmite at a reaction time of 2 h for all conditions. When the reaction time was prolonged to 4 h, ATH was transformed into boehmite at filling volume of 30% and 50%. It appears that liquid filling volume influences the transformation of ATH into boehmite. As observed by the SEM images, the morphology of particles also changed by the change of the crystalline phase. The particles changed from nearly spherical-shaped to cube and the particle size was typically larger