Search

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).

In this paper, a new method using an ammonia–urea system was proposed to prepare cellulose aerogels from coir fibers as the starting material for non-ordered porous nitrogen-doped carbon aerogels. ...

Activated carbon nanofibers (ACNF) have been successfully prepared using an electrospinning method with coconut shell charcoal (CSC) as a carbon source and poly(vinyl alcohol) (PVA) as a spinning polymer agent. The high voltage of 10 kV was applied for the electrospinning system. The positive electrode of the high voltage power supply was connected to the needle tip, and the grounded electrode was connected to the metallic collector wrapped with an aluminum foil. The dry fibers in the form of a fibrous mat were collected in the aluminum foil. The average pore diameters of the generated fibers for all variables ranging from 2.23 to 3.73 nm corresponding to mesoporous carbon nanofibers. The total pore volumes were ranging from 0.50 to 0.92 cm3/g. IACNF-60 had the largest surface area of 1,277 m2/g obtained from the use of PVA 12 w/v %, 60 wt% CSC, and the use of iodine treatment before thermal stabilization, carbonization, and activation stages. Methylene blue solution was used as a model for the dye adsorption capacity that followed the Langmuir adsorption model. IACNF-60 also indicated the highest theoretical maximum monolayer adsorption capacity in the amount of 166.7 mg/g. Furthermore, the methylene blue removal ability of IACNF-60 for the third cycle was maintained relatively constant at 96%.

Here, we reported the utilization of coconut shell charcoal used for solid acid catalysts and its performance in the esterification reaction of acetic acid and methanol. The graphitization of coconut shell charcoal was carried out by the calcination and KOH activation at the temperature of 400 °C for an hour and continued at the temperature of 800 °C for an hour under nitrogen flow resulted in graphitic carbon. The effect of the addition of KOH activation was observed by varied the weight ratio of coconut shell charcoal as raw material (RM) and KOH. The selected weight ratio of RM:KOH was 1:1, 1:2, and 1:4. The resulted graphitic carbon was sulfonated by heating with the sulfuric acid to obtain a solid acid catalyst. The sulfonic time was evaluated for 5 and 10 hours. The generated particles were characterized to examine the morphology, the crystallinity, the specific surface area, the chemical bonding, and the ionic capacity using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), nitrogen gas absorption-desorption, Fourier Transform Infrared Spectroscopy (FTIR), and titration method, respectively. The best condition for graphitization of raw material is the use of RM:KOH = 1:4, resulting in the highest surface area reaching 1259.67 m2/g and the most dominant of the sulfonic group of −SO3 bond. Furthermore, increasing the sulfonating time from 5 to 10 hours led to the increase of the yield of esterification reaction from 85% to 96.57% for graphite synthesized using RM:KOH = 1:4. Copyright © 2020 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).

Lignin as a by-product of the pulping process is less widely used for worth materials. In this study, the utilization of lignin by-product of the soda delignification process of coconut coir converted to the activated carbon by a simple precipitation method followed by the carbonization at various temperatures is presented. The by-product liquor of the soda delignification process having a pH of 13.4 was neutralized by dropping of hydrochloric acid solution to achieve the pH solution of 4 resulting in the lignin precipitation. The precipitated was washed, filtered, and dried. The dried lignin was then carbonized under a nitrogen atmosphere at various temperatures of 500, 700, and 900 °C. The dried lignin and carbonized samples were characterized using SEM, XRD, FTIR, and nitrogen adsorption-desorption analyzer, to examine their morphology, X-Ray diffraction pattern, chemical bonding interaction, and surface area-pore size distribution, respectively. The characterization results showed that the functional groups of lignin mostly disappeared gradually with the increase of temperature approached the graphite spectrum. The XRD patterns confirmed that the carbonized lignin particles were amorphous and assigned as graphitic. All samples had a pore size of 3–4 nm classified as mesoporous particles. This study has shown that the carbonization lignin at a temperature of 700 °C had the highest surface area (i.e. 642.5 m2/g) in which corresponds to the highest specific capacitance (i.e. 28.84 F/g).

A heterogeneous solid acid catalyst was successfully derived from coir fiber, which is a cheap and abundantly available waste material. The coir fiber was first transformed into carbon aerogel to enhance the surface area and pore volume using a sol-gel method. H2SO4 immersion was then used to graft the SO3H functional group onto the produced carbon aerogel. Surprisingly, the NH4OH-urea system could maintain the honeycomb-like internal pore structure of the cellulose fiber in the resulting carbon aerogel, while the NaOH-urea system could not. Good physical properties, including a high surface area and large pore volume, could be achieved in the catalyst at a sulfonation temperature of 100 °C. The obtained sulfonated carbon catalyst also had excellent performances, with an ionic capacity of 4.45 meq/g, a conversion of 81–83% in a short time reaction, and good recyclability, with a slight decrease and then a constant value of 60–62% after the fourth cycle.

High-purity magnetite nanoparticles with a mixed quasi-spherical and cubic morphology have been successfully synthesized using a new alternating monopolar arrangement of multiple iron electrodes in water. The magnetite nanoparticles have a narrow size distribution with a mean size ranging from 20 to 30 nm, depending on the applied voltage and pH. The formation of magnetite nanoparticles is favored only in the pH range of 7–10; outside this range, magnetite nanoparticles cannot be produced. The magnetite nanoparticles exhibit ferromagnetic properties with saturation magnetization ranging from 16 to 75 emu/g. They demonstrated to be a promising electrocatalyst for oxygen reduction reactions in basic media. This facile method is a promising production route for magnetite nanoparticles and can be easily scaled up for large production.

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

Textile waste is produced in the starch process, a starch removal process, coloring, and printing. The use of banana peel (Musa Paradisiaca) was an alternative that was being developed as an absorbent to remove the color content and metal ions in textile waste. The purpose of this study was to analyze the workings and effectiveness of heavy metal adsorption and textile dyes with banana peel waste. Banana peel particles that were ready to be used as adsorbents were characterized using Scanning Electron Microscopy (SEM) to obtain particle morphology. Absorbance curve of Cu2+ dan Cr6+ can be obtained using spectrophotometric UV-Vis analysis with a wavelength of 635 nm for copper (Cu) and 469 nm for chromium (Cr). The activated carbon of banana peel was applied to 50 ml industrial waste solution and observed changes in absorbance for 120 minutes. The activated carbon was directly in contact with the solution of metal ions but the adsorption power was still not seen effectively so that the Atomic Absorption Spectroscopy (AAS) test was performed. The results of AAS analysis, namely activated carbon can reduce copper and chromium ion content respectively by 55.5% and 61%. If this activated carbon was used as an adsorbent for dyes in textile waste, the average absorption capacity of dye ion was 12.21% during the contact time of adsorption 120 minutes.

Agroindustry waste containing cellulose compound, Sorghum stem, was utilized to become cellulose aerogel which was then used as dye absorbent in textile dye wastewater. Cellulose was prepared by sorghum stem powder delignification using 6%w of NaOH solution. The ratio of powder and NaOH was varied in 1:12, 1:15, and 1:20. After this process, the powder was synthesized with NaOH/Urea to produce an aerogel by the freeze-drying method. The result shows that a higher amount of NaOH in the delignification process could increase aerogel density and decrease the porosity. Thermal stability and sorption efficiency of the aerogel was analyzed in this study. Higher porosity of aerogel tends to raise % removal in methylene blue absorption. This study reveals that aerogel three times more effective than activated carbon in dye removal.

Magnetite (Fe3O4) is one of the most important iron oxides due to its extensive range of application in various fields. The characteristics of magnetite can be considerably enhanced by reducing the particle size to the nanometer scale. When novel functions of nanoparticles are desired, it is necessary to have monodispersed or nearly monodispersed nanoparticles. Many synthesis methods have been proposed to produce monodispersed magnetite nanoparticles, including co-precipitation, sol-gel, hydrothermal and electrochemical methods. In this review, progress in the preparation of magnetite nanoparticles and their composites through the electrochemical method and the scale-up method are discussed.

The use of solid adsorbents such as amine-modified silica aerogels to capture CO2 has been commonly used but poses several obstacles, including expensive raw materials, production complexity, and considerations for adsorbent regeneration. This research develops sodium silicate solution as a carbon scrubber in a packed column. Besides being able to capture CO2, the amorphous silica which has economic value can also be produced. The packing size and CO2 flow rate were studied to prevent the deposition of silica inside of the packed column. The precipitated product analysis using XRF, XRD, FTIR, and SEM Image observed that CO2 was well absorbed by sodium silicate solution. The amorphous silica precipitated concentration reaches 98.6%.

Lignin waste that comes from various biomass processing has caused an environmental problem which is undegradable under anaerobic condition. One way to use lignin waste is to utilize as an alternative carbon material precursor that applied for electrocatalyst on metal-air batteries. The purpose of this research was to convert Na-Lignin into carbon at carbonization temperature of 500, 700, and 900 °C then combined with MnO2 by soaking KMnO4 and carbon at 1:1 and 1:2 mass ratio. Na-Lignin carbonization produced r-GO (reduced Graphene oxide) particles with surface area and pore diameter of 261.584 m2/g and 3.82 nm at 700 °C. The best electrocatalytic performance was obtained from a composite sample of 1:2 mass ratio and a carbonization temperature of 900 °C, which had 3.39 electrons transfer for oxygen reduction reaction.

Surfactants have been proposed as solutions of liquid loading problems. This research is a preliminary study which is to obtain a stable surfactant by adding nanosilica. Mixing of sodium lauryl sulfate (SLS) as anionic surfactant and polysorbate-20 as non-ionic surfactants conducted to obtain the composition that produces the highest foaming. Then added to the best mixture composition a number of nanosilica sol to enhance the foam stability. The nanosilica sol that synthesized from water glass was added to the surfactant with varying concentration of 10ppm to 50ppm. The nanosilica sol added to the surfactant is stable with a zeta potential of 39.7mV and size around 4nm. The results of surfactant mixing showed that the composition of 90% SLS and 10% polysorbate-20 were the highest foaming. The addition of nanosilica sol increases foam stability and the 30ppm concentration greatly enhance the foam stability.

High-surface area carbon with porous structure can provide a large electrical-double layer as energy storage in supercapacitors. Herein, porous graphene-like materials with high-surface area were prepared from renewable coconut shell charcoal via KOH activation followed by oxidation in a harsh environment using a modified-Hummer method. Using the method, the surface area of the treated coconut shell charcoal increased significantly from about 189.97 m2/g to 642.45 m2/g with a pore diameter of approximately 5 nm. As expected, the increase in surface area increased the capacitance significantly, by up to 46-fold, from 3.22 to 148.20 F/g. These results demonstrated that the low cost renewable porous graphene-like material prepared from coconut shell charcoals is promising for use as electrode material for supercapacitor.

Many types of research related to battery currently being developed to answer the increasing need for energy. One of the most exciting topics is about a metal-air battery that has low oxygen reduction reaction (ORR) in the cathode side as main problem. This research used a composite between MnO2 and carbon to increase the oxygen reduction reaction. MnO2 was synthesized from KMnO4 solution through electrochemistry method using multi-electrode at various temperatures. Carbon was synthesized from coconut charcoal through calcination and modified hummer method. Furthermore, The composite of MnO2/carbon was carried out using physical treatment. Sample analysis consists of characterization and electrocatalytic analysis. The characterization itself consists of morphological analysis using Scanning Electron Microscopy (SEM), and particle surface area analysis using Brunauer Emmet Teller (BET). While the electrocatalyst consists of Cyclic Voltammetry (CV) analysis to determine the occurrence of oxygen reduction reaction (ORR), and Linear Sweep Voltammetry (LSV) to determine the amount of electron transfer. According to the X-Ray Diffraction pattern and specific surface area, a higher temperature of potassium permanganate electrolysis indicated the lower performance of MnO2 produced. Also, after composited with carbon, the electrocatalytic analysis showed that both samples could initiate the oxygen reduction reaction with the number of electrons transferred are 1.52 for MnO2 30°C-Graphene and 2.28 for MnO2 60°C-Graphene which conclude that MnO2-carbon composite is quite promising to be researched further as electrocatalyst in the metal-air battery.