Coprecipitation and hydrothermal synthesis of CaO from dolomite in the presence of Sapindus rarak extract for biodiesel production: catalysts characterization and optimization.

High-purity CaO cubic crystallites extracted from limestone exhibited excellent activity as base catalysts for waste cooking oil (WCO) conversion into biodiesel. Saponin from Sapindus rarak extract acted as a surfactant in CaO extraction and transformation into well-defined cubic microcrystallites. The application of saponin from Sapindus rarak extract as a surfactant for CaO production results in a high level of CaO purity and particle size reduction compared to directly calcined limestone (CaO-MgO). The catalytic activity was evaluated on CaO from hydrothermal and co-precipitation synthesis, MgO and CaO-MgO derived from limestone, giving hydrothermal CaO catalysts enhanced biodiesel yield. Optimization of transesterification conditions using Box Behnken Design response surface methodology achieved 92.40% biodiesel yield at 65 °C, 3 h reaction time and when using 5% of CaO catalysts.

Innovative surfactant-free synthesis of core-shell SiO2/ZnO particles: rapid ultrasonication and photocatalytic inhibition.

This study demonstrates the preparation of SiO2/ZnO core-shell nanoparticles with controllable shell size and their optical properties. A facile ultrasonication method was utilized to prepare the core-shell particles in the absence of surfactant materials. The synthesis duration was 75% shorter than that required for the common sol-gel method, which favours its potential applicability in the future for mass production. Tetraethyl orthosilicate (TEOS) was used as the silica source, while the core material was prepared using zinc acetate dihydrate. The outer shell size could easily be controlled by changing the molar ratio of silica from 0.25 to 1.00. The experimental results show that increasing the silica ratio was effective in suppressing the self-agglomeration of ZnO and, further, in obtaining agglomeration-free particles. The investigation of the photoluminescence (PL) properties of nanometre-sized ZnO revealed several emission peaks in the ultraviolet (UV) wavelength range, indicating variations in bandgap energy. This did not appear in the spectrum of micrometre-sized ZnO particles. The core-shell particles produced with higher amounts of silica showed higher UV-A and UV-B absorption. In addition, the presence of silica reduced the photocatalytic activity of ZnO by 65% and reduced the PL intensity. The obtained emission peaks, intensity changes, and spectral characteristics open new avenues for further research on tailoring the properties of SiO2/ZnO core-shell structures for specific technological advancements. These advancements hold promising applications in UV attenuation materials, LED technologies, lenses, and solar cells within the realm of optical devices.

The role of pH-induced tautomerism of polyvinylpyrrolidone on the size, stability, and antioxidant and antibacterial activities of silver nanoparticles synthesized using microwave radiation.

Tautomerism alters the structure and properties of materials, which can be exploited to control their chemical and biological activities. The role of pH-induced tautomerism of polyvinylpyrrolidone (PVP) was determined by measuring the size, stability, and antioxidant and antibacterial properties of microwave synthesized-silver nanoparticles (AgNPs). TEM and XRD analyses confirmed the formation of face-centered cubic silver nanoparticles. PVP stabilized the AgNPs by interaction with the carbonyl or hydroxyl groups depending on the tautomerization under different pH conditions. At pH 4, PVP was stable in the keto tautomer, stabilizing Ag through electron donation of oxygen atoms in the carbonyl group, producing smaller AgNPs with a higher zeta potential. At pH 7 and 9, the enol tautomer PVP stabilized the AgNPs via oxygen atoms in the hydroxyl group, forming large nanoparticles. The keto form of PVP improved the stability and antioxidant and antibacterial properties of AgNPs compared with the enol form. This study also excluded the antioxidant contribution of PVP via hydrogen donation to free radicals. A facile method for controlling the size of AgNPs by adapting the pH-induced tautomerism of PVP that affects their stability and antioxidant and antibacterial activities is thus reported.

Microwave-assisted synthesis of silver nanoparticles as a colorimetric sensor for hydrogen peroxide.

To consider silver nanoparticles (AgNPs) as a colorimetric sensor for H2O2 we require investigation of the effects of the homogeneity of the nanoparticle size and morphology on the sensor parameters. Uniformly-sized Ag nanoparticles with diameters of ∼18.8 ± 2.8 nm were produced using microwave irradiation (AgNP1) but non-uniform particles with diameters of ∼71.2 ± 19.4 nm (AgNP2) were formed without microwave irradiation. Microwave synthesis produced AgNP1 with superiority in terms of repeatability, selectivity and sensor stability for up to eight months of storage over AgNP2. AgNP1 exhibited higher sensitivity and detection limits in the working range of 0.01-40000 µM as compared to AgNP2. The application of the AgNP sensor to milk samples provided recovery values of 99.09-100.56% for AgNP1 and 98.18-101.90% for AgNP2. Microwave irradiation resulted in strong and uniform PVP-Ag interactions for isotropic growth into small nanoparticles. Size and morphology uniformity determined the characteristics of the AgNP sensor that can be applied for H2O2 detection in a wide range of concentrations and real-time evaluation, with the potential for industrial applications.

Direct synthesis of Fe-aluminosilicates from red mud for catalytic deoxygenation of waste cooking oil.

Conversion of red mud (RM) that contains a high level of silica, alumina and iron minerals into heterogenous catalysts, offers a route for the utilization of abundant toxic by-products of bauxite refining. In this study, the conversion of red mud into mesoporous Fe-aluminosilicate produced selective catalysts for the deoxygenation of waste cooking oil to green diesel hydrocarbons. Direct conversion of red mud in the presence cetyltrimethylammonium bromide into Fe-aluminosilicate (RM-CTA) produced a highly mesoporous structure with oligomeric Fe2O3 clusters within the pores. When red mud was treated with citric acid (RM-CA-CTA), a wide distribution of Fe2O3 particles was obtained on the aluminosilicate external surface. TEM analysis showed a well-defined hexagonal mesoporosity of Fe-aluminosilicate obtained from untreated red mud, while the treated red mud produced lower regularity mesopores. RM-CTA exhibits 60% WCO conversion and 83.72% selectivity towards liquid products with 80.44% diesel hydrocarbon (C11-C18) yield. The high selectivity was due to the high acidity of Fe-aluminosilicate to dissociate the C-O bond and the regularity of mesostructure for efficient hydrocarbon diffusion, preventing a cracking reaction.

Synthesis of mesoporous zeolite Y using Sapindus rarak extract as natural organic surfactant for deoxygenation of Reutealis trisperma oil to biofuel.

Saponin is a plant-derived chemical with an amphiphilic glycoconjugate structure extracted from sapindaceae plants like Sapindus rarak. This study investigated saponin extract of Sapindus rarak as a natural template for formation of mesoporous zeolite Y. Surface area and mesoporosity of zeolite Y were improved with optimization of Sapindus rarak extract (SRE) concentration (Y-Ln; n = 2, 5, 10 or 15 mL), reaching 216.26 m2 mesoporous area and 0.214 cm3 g-1 mesoporous volume for Y-L10 samples. A different loading of Ni was impregnated onto Y-L10 zeolite to improve Lewis/Brønsted acidity as catalysts in the deoxygenation of Reutealis trisperma oil (RTO) into hydrocarbon fuels. Impregnating 15% Ni on NaY zeolite enhanced Lewis acidity to 0.4556 mmol g-1, producing 48.8% liquid oil with 85.43% degree of deoxygenation. A high selectivity towards C15 and C17 hydrocarbon was analyzed from liquid yield, indicating the contributing factor from Lewis acidity and mesoporosity to enhance deoxygenation and prevent the hydrocracking reaction.

The application of silica gel synthesized from chemical bottle waste for zinc (II) adsorption using Response Surface Methodology (RSM).

The application of silica gel adsorbent synthesized from chemical bottle waste to remove zinc ions in the solution has been carried out. The synthesis of silica gel was carried out using alkaline fusion followed by sol-gel reactions. The chemical glass bottle container was made from borosilicate glass which was different from glass bottles for food and beverage that has been studied in previous studies. The Zn2+ adsorption was optimized using Box-Behnken Design (BBD). Box-Behnken Design was applied to study the optimum zinc ion removal and the input variables interaction. The input variables optimized were adsorbent dosage (1.0 - 2.0 g), initial zinc ion concentration in the solution (25 - 100 ppm), contact time (15 - 45 min), and pH (4 - 9). Response Surface Methodology (RSM) was applied to visualize the input variables' correlation to zinc ion removal. The optimum zinc ion removal was achieved at an adsorbent dosage of 2 g, initial concentration of 35 ppm, contact time of 45 min, and pH 8, which was 99.56%. The optimization of adsorption isotherm obtained that the adsorption follows the Langmuir isotherm model. The silica gel obtained was characterized using SEM-EDX and BET to obtain silica gel properties. The SEM-EDX showed a spherical shape of silica gel. Silica gel containing zinc (Zn) was observed from SEM-EDX after the adsorption process. A pore diameter of 42.098 nm and surface area of 297.083 m2/g were obtained from BET analysis of synthesized silica gel.

The Fabrication of Solid Polymer Electrolyte from CS/PEO/NaClO4/Fly Ash Composite.

Solid polymer electrolytes (SPEs) have been successfully fabricated from CS/PEO/NaClO4/Fly ash composite. Chitosan (CS), an organic polymer, was blended with polyethylene oxide (PEO) to enhance its electrochemical properties. However, SPEs based on CS/PEO composites have low conductivity. Fly ash (FA) has been studied to be used as a filler to increase the ionic conductivity of SPEs. In this study, polymer composites based on CS and PEO were developed with the addition of FA as a filler using the solution casting method. The interactions between CS, PEO, NaClO4, and fly ash were observed using FTIR. The SPE characterization using XRD and DSC showed a decrease in crystallinity after the addition of NaClO4 and FA. The SPE composite morphology and elemental distribution were investigated using SEM. SPE conductivity analysis using EIS showed the optimum results for SPE fabricated with a ratio of CS:PEO:NaClO4 = 3:2:7.5, which was 1.02 × 10-4 S cm-1 at 30 °C and increased to 2.13 × 10-3 S cm-1 at 60 °C. The addition of FA (5 wt.%) increased the conductivity to 3.20 × 10-4 S cm-1 at 30 °C and increased to 4.34 × 10-3 S cm-1 at 60 °C.

Controlling the Size and Porosity of Sodalite Nanoparticles from Indonesian Kaolin for Pb2+ Removal.

Mesoporous sodalite nanoparticles were directly synthesized from Indonesian kaolin with the addition of CTABr as a mesopore template. The studies highlighted the importance of aging time (3-12 h) and temperature (50-80 °C) on increasing surface area and mesoporosity of sodalite. Indonesian kaolin was used without pre-treatment and transformed to sodalite following the initial molar composition of 10 Na2O: 2 SiO2: Al2O3: 128 H2O. Characterization data revealed the formation of high surface area sodalite with mesoporosity at increasing aging temperatures and times. The presence of CTABr as templates produced sodalites nanoparticles with smaller aggregates than the non-template sodalite. The sodalite sample obtained at 80 °C of crystallization temperature for 9 h (S80H9) displayed the highest mesopore volume (0.07612 cm3/g) and the highest adsorption capacity of Pb2+ (212.24 mg/g). Pb2+ was suggested to adsorb via ion exchange with the Na+ counter cation and physical adsorption.

Increase of Solid Polymer Electrolyte Ionic Conductivity Using Nano-SiO2 Synthesized from Sugarcane Bagasse as Filler.

The synthesize of solid polymer electrolyte (SPE) based on polyethylene oxide (PEO), NaClO4 and nano-SiO2 was carried out by solution cast technique. Nano-SiO2 was synthesized from sugarcane bagasse using sol-gel method. FTIR analysis was carried out to investigate the bonding between nano-SiO2 and PEO/NaClO4. The morphology of the SPE was characterized using SEM. XRD and DSC analysis showed that SPE crystallinity decreased as nano-SiO2 concentration was increased. Mechanical analyses were conducted to characterize the SPE tensile strength and elongation at break. EIS analysis was conducted to measure SPE ionic conductivity. The PEO/NaClO4 SPE with the addition of 5% nano-SiO2 from sugarcane bagasse at 60 °C produced SPE with the highest ionic conductivity, 1.18 × 10-6 S/cm. It was concluded that the addition of nano-SiO2 increased ionic conductivity and interface stability at the solid polymer electrolyte-PEO/NaClO4.

Lewis acid Ni/Al-MCM-41 catalysts for H2-free deoxygenation of Reutealis trisperma oil to biofuels.

The activity of mesoporous Al-MCM-41 for deoxygenation of Reutealis trisperma oil (RTO) was enhanced via modification with NiO nanoparticles. Deoxygenation at atmospheric pressure and under H2 free conditions required acid catalysts to ensure the removal of the oxygenated fragments in triglycerides to form liquid hydrocarbons. NiO at different weight loadings was impregnated onto Al-MCM-41 and the changes of Lewis/Brønsted acidity and mesoporosity of the catalysts were investigated. The activity of Al-MCM-41 was enhanced when impregnated with NiO due to the increase of Lewis acidity originating from NiO nanoparticles and the mesoporosity of Al-MCM-41. Increasing the NiO loading enhanced the Lewis acidity but not Brønsted acidity, leading to a higher conversion towards liquid hydrocarbon yield. Impregnation with 10% of NiO on Al-MCM-41 increased the conversion of RTO to hydrocarbons via the deoxygenation pathway and reduced the products from cracking reaction, consequently enhancing the green diesel (C11-C18) hydrocarbon products.