Key Engineering Materials Vol. 1045

Abstract: This study developed WO₃/WS₂ composites loaded with noble metals to degrade methyl orange under UV light. Pure WO₃/WS₂ and variations loaded with Au, Ag, Pt, Ru, and Rh were among the photocatalysts. To examine the materials' structural, morphological, and optical characteristics, X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectroscopy were used. The highest photocatalytic activity was observed with Au@WO₃/WS₂, degrading MO by 98.59 %. The synergistic interactions between Au nanoparticles and the WO₃/WS₂ heterostructure improved charge separation and light absorption, indicating the composites' potential for effective UV-active photocatalysts for environmental remediation.

Abstract: This work examines the impact of critical operational parameters pH, temperature, initial copper concentration, adsorption duration, and adsorbent dosage on the efficacy of five bio-based adsorbents: pineapple pulp, tissue pulp, chitosan, chitosan-coated pulp, and chitosan-coated pineapple peel. for the removal of cupric ions from aqueous solutions. The results indicated that both pH and temperature significantly enhanced copper removal efficiency (Re) and adsorption capacity (qe) for all materials tested. Conversely, higher initial copper concentrations led to a decrease in Re but an increase in qe, indicating greater metal loading per unit mass of adsorbent. Adsorption time had minimal influence on performance, while increased adsorbent dosage significantly improved Re only for chitosan-coated pulp and caused a general decline in qe due to reduced surface utilization. Pearson correlation analysis supported these findings, revealing significant positive correlations of pH and temperature with both performance indicators and a dual effect of feed concentration. Dosage and contact time showed weak, statistically non-significant correlations. This analysis identifies pH, temperature, and initial metal content as the principal parameters affecting biosorption efficacy and provides essential recommendations for optimizing conditions in the treatment of copper-contaminated wastewater.

Abstract: Adsorbent beads composed of Chitosan (CS), MIL-101 (Fe), and Polyethyleneimine (PEI) were synthesized for Methyl Orange (MO) adsorption. Parametric studies testing the effects of pH and number of adsorption and desorption cycles on percent MO removal showed the beads’ good performance across a wide range of conditions. A percent MO removal of at least 93% was maintained from pH 2 to pH 9 with a maximum percent removal of 98.6% obtained at pH 3. In addition, the beads remained functional for at least 5 cycles of adsorption and desorption with a percent MO removal of 98% across the cycles. Kinetic modeling was performed and a pseudo-second order kinetic model with an R² of 0.981 was obtained implying chemisorption as the rate limiting step. Adsorption equilibrium data for MO were best fitted into the Sips isotherm model which suggests that adsorption occurs on a heterogeneous surface. From the Sips isotherm model, the maximum adsorption capacity was determined to be 1253.44 mg/g, highlighting the viability of CS – MIL-101 (Fe) – PEI beads as an adsorbent for wastewater treatment.

Abstract: Carbon dioxide (CO₂) capture is a significant chemical process that has attracted considerable interest in both academic and industrial sectors. It is essential for mitigating climate change and its related impacts on the environment and human health. Various technologies are implemented for CO₂ capture, with physical adsorption using porous material standing out as one of the most widely employed methods. Gallate-based metal-organic frameworks (MOFs) are reported to offer remarkable CO₂ adsorption capacity values, with Mg-gallate exhibiting the highest capacity, followed by Co-gallate and Ni-gallate. The mechanism of CO₂ adsorption on gallate-based MOFs, however, lacks extensive discussion. A thorough understanding of the adsorption mechanism helps in designing and synthesizing MOFs with enhanced CO₂ capture performance. Therefore, this work aims to discuss the mechanism of CO₂ adsorption on gallate-based MOFs based on the experimental pure isotherms. The experimental isotherms exhibited S-shaped curves that are related to the occurrence of gate-opening effect. These S-shaped isotherms corresponded to multistep adsorption, classifying gallate-based MOFs as flexible MOFs. The flexibility of these frameworks can be controlled by the pressure and temperature, which is important for designing specific gas storage and separation systems. In addition, the intra-particle diffusion model supported that the CO₂ adsorption occurred at the surface and mesopore of gallate-based MOFs. Given these characteristics, gallate-based MOFs can be considered as the promising physisorbent for CO₂ capture.

Abstract: This research presents the green synthesis of gold nanoparticles (AuNPs) utilizing natural Gum Arabic (GA) resin as an environmentally reducing and stabilizing agent. The study addresses pressing water pollution concerns in Oman by developing a sustainable nanotechnology-based approach for the remediation of trace heavy metal ions (Cu²⁺, Pb²⁺, and Zn²⁺) from aqueous environments. GA was employed at concentrations of 5% and 10% (w/v) in reactions with chloroauric acid (HAuCl₄) under systematically varied conditions, including temperature (23.0–80.0 °C), pH (6.00–9.00), and reaction time (0.33–48.00 h). The synthesised AuNPs were characterised using ultraviolet–visible (UV–Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) to assess their optical properties, morphology, and surface chemistry. Optimal synthesis conditions—10% GA, 5 mM HAuCl₄, 55.0 °C, pH 9.00, and 0.67 h—resulted in a stable ruby-red colloidal dispersion exhibiting a distinct surface plasmon resonance (SPR) peak at 518 nm, indicative of monodisperse spherical AuNPs. FTIR analysis confirmed the involvement of hydroxyl, carbonyl, and amine functional groups in nanoparticle formation and stabilization. The biosynthesis AuNPs demonstrated efficient removal of heavy metal ions from aqueous solutions in the order of Pb²⁺ > Cu²⁺ > Zn²⁺.These findings highlight the potential of Gum Arabic as a green, cost-effective, and biocompatible material for fabricating functional AuNPs suitable for environmental sensing and water purification applications.

Abstract: This study investigates the synergistic potential of a novel heterojunction photocatalyst for methyl orange degradation. The photocatalyst comprises iron tungstate (FeWO₄) and graphitic carbon nitride (g-C₃N₄), engineered to exploit the distinct properties of each component for enhanced photocatalytic activity. The research systematically evaluates the performance of the synthesized FeWO₄/g-C₃N₄ composite in degrading methyl orange, with an emphasis on optimizing catalytic efficiency. The photocatalyst was characterized using advanced techniques, including Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) to elucidate its structural and morphological properties. Key parameters such as loading concentrations were optimized to assess their influence on the photodegradation efficiency. Among tested compositions, 1.0 wt% FeWO₄/g-C₃N₄ achieved the highest degradation efficiency of MO at 78.04% within 180 minutes under UV irradiation. The heterojunction structure promoted effective charge separation, and further enhanced visible-light response. These results demonstrate the catalyst’s potential for sustainable water purification applications.

Abstract: This study presents the preliminary characterization of commercial calcium oxide (CaO) and aluminum oxide (Al₂O₃) catalysts intended for application in the catalytic upgrading of biomass-derived bio-oil. The catalysts were characterized using Scanning Electron Microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area analysis, Thermo gravimetric Analysis (TGA), and X-ray Diffraction (XRD). SEM images revealed that both catalysts exhibit irregular, rough-surfaced particles with visible fractures and mesostructured textures conducive to catalytic activity. BET results indicated a specific surface area of 50.301 m²/g for CaO and 129.442 m²/g for Al₂O₃, with corresponding pore diameters of 2.64 nm and 2.647 nm, respectively, confirming their mesoporosity. TGA of CaO showed substantial weight loss associated with moisture, hydroxide, and carbonate decomposition, indicating the need for pre-calcination to restore active oxide phases. In contrast, Al₂O₃ exhibited minor mass loss mainly due to dehydration and dehydroxylation of surface-bound species. XRD analysis confirmed the presence of crystalline γ-Al₂O₃ and highly crystalline CaO with characteristic diffraction planes for their respective phases. These findings demonstrate that both commercial catalysts possess favorable physicochemical properties particularly high surface area, thermal stability, and mesoporous structure that make them promising candidates for vapor-phase upgrading in biomass pyrolysis systems.

Abstract: The toxicity level and environmental impact of traditional chemical propellants like hydrazine has led to an urgent need for safer alternatives such as Hydroxyl Ammonium Nitrate (HAN) in the global space industry. This study investigates HAN as a promising green propellant for satellite propulsion. It reviews HAN's properties, synthesis, and decomposition mechanisms (thermal, catalytic, electrolytic) while comparing its key HAN-based formulations against hydrazine in terms of performance, eco-friendliness and safety. Despite challenges like catalyst degradation and storage stability, HAN emerges as a viable, potential replacement for hydrazine. Its catalytic innovations, standardization, and production infrastructure should be further researched on for future purpose.

Abstract: Hydrogen is a clean and sustainable energy source that has the potential to significantly lower carbon emissions worldwide and facilitate the switch to renewable energy sources. Meanwhile, one of the biggest obstacles to its broad use, is still sufficient hydrogen storage. This article provides a broad overview of hydrogen storage, tracing its historical development, exploring its diverse applications, examining technological advancements, addressing existing limitations, recent progress in reducing costs, and discussing the current state of the art in storage technologies, along with future directions for improvements in all forms of hydrogen storage methods. Therefore, this review highlights recent breakthroughs in hydrogen storage techniques, advances in cost reduction, and offers a step by step guide to designing next-generation functional hydrogen storage materials for improved performance, which are essential for both developed and developing hydrogen economies in cost reduction and better performance for hydrogen storage materials.