Search Results (7)

The advancement of optical materials has garnered significant interest from the global scientific community in the pursuit of efficient photocatalysts for the purification of water using light. This challenge, which cannot be addressed using traditional methods, is tackled in the present study utilizing unconventional approaches. This study presents the fabrication of an effective photocatalyst using an unconventional approach that employs explosive reactions. This method successfully produces 3D nanostructures composed of carbon nanotubes (CNTs), carbon nanofibers (CNFs), and silica–alumina nanoparticles at temperatures below 270 °C. Gold-supported silica–alumina–CNT–CNF nanostructures were synthesized and characterized using XRD, TEM, SEM, and EDX, in addition to mapping images. To study and determine the photoactivity of these produced nanostructures, two well-known photocatalysts—titanium dioxide and zinc oxide—were synthesized at the nanoscale for comparison. The results showed that the presence of CNTs and CNFs significantly reduced the band gap energy from 5.5 eV to 1.65 eV and 3.65 eV, respectively, after modifying the silica–alumina structure. In addition, complete degradation of green dye was achieved after 35 min of light exposure using the modified silica–alumina structure. Additionally, the surface properties of the modified silica–alumina had a positive role in accelerating the photocatalytic decomposition of the green dye NGB. A kinetic study confirmed that the modified silica–alumina functions as a promising additive for optical applications, accelerating the photocatalytic degradation of NGB to a rate three times faster than that of the prepared titanium dioxide and six times that of the prepared zinc oxide. Full article

Hydrogen has emerged as a promising energy carrier, offering a viable solution to meet our current global energy demands. Solar energy is recognised as a primary source of renewable power, capable of producing hydrogen using solar cells. The pursuit of efficient, durable, and cost-effective photocatalysts is essential for the advancement of solar-driven hydrogen generation. Copper slag, a by-product of copper smelting and refining processes, primarily consists of metal oxides such as hematite, silica, and alumina. This composition makes it an attractive secondary resource for use as a photocatalyst, thereby diverting copper slag from landfills and generating 0.113 μmol/g h of hydrogen, as noted by Montoya. This review aims to thoroughly examine copper slag as a photocatalytic material, exploring its chemical, physical, photocatalytic, and electrochemical properties. Additionally, it evaluates its suitability for water treatment and its potential as an emerging material for large-scale solar hydrogen production. Full article

In the present work, rock dust was evaluated as an adsorbent and heterogeneous photocatalyst in the discoloration of Basazol Yellow 46 L dye, which is widely used in the dyeing of molded pulp packages. Although rock dust is produced in large quantities in quarries as a byproduct of rock exploration, little is known about its application as a photocatalyst. Rock dust was characterized by XRD, SEM/EDS, photoacoustic spectroscopy, and N₂ physisorption and had its photocatalytic activity assessed through phenol and salicylic acid degradation tests. The characterization results showed that the rock dust is mainly composed of silica and alumina in a triclinic structure, has a bandgap energy of 2.36 eV, and has a specific area of 1.5 m²/g. Rock dust was proven to be photocatalytically active in phenol and salicylic acid degradation tests and also presented the adsorptive and photocatalytic capacity for the discoloration of effluent containing Basazol Yellow 46 L dye. Full article

Although they are of significant importance for environmental applications, the industrialization of photocatalytic techniques still faces many difficulties, and the most urgent concern is cost control. Natural minerals possess abundant chemical inertia and cost-efficiency, which is suitable for hybridizing with various effective photocatalysts. The use of natural minerals in photocatalytic systems can not only significantly decrease the pure photocatalyst dosage but can also produce a favorable synergistic effect between photocatalyst and mineral substrate. This review article discusses the current progress regarding the use of various mineral classes in photocatalytic applications. Owing to their unique structures, large surface area, and negatively charged surface, silicate minerals could enhance the adsorption capacity, reduce particle aggregation, and promote photogenerated electron-hole pair separation for hybrid photocatalysts. Moreover, controlling the morphology and structure properties of these materials could have a great influence on their light-harvesting ability and photocatalytic activity. Composed of silica and alumina or magnesia, some silicate minerals possess unique orderly organized porous or layered structures, which are proper templates to modify the photocatalyst framework. The non-silicate minerals (referred to carbonate and carbon-based minerals, sulfate, and sulfide minerals and other special minerals) can function not only as catalyst supports but also as photocatalysts after special modification due to their unique chemical formula and impurities. The dye-sensitized minerals, as another natural mineral application in photocatalysis, are proved to be superior photocatalysts for hydrogen evolution and wastewater treatment. This work aims to provide a complete research overview of the mineral-supported photocatalysts and summarizes the common synergistic effects between different mineral substrates and photocatalysts as well as to inspire more possibilities for natural mineral application in photocatalysis. Full article

In this investigation, a hybrid-biocomposite “ZnO-Bentonite/Chitosan” was synthesized using inexpensive and environmentally friendly materials (Bentonitechitosan) and (ZnO). It was used as a photocatalyst for water remediation. The structural, optical, thermal, and morphological properties of the synthesized hybrid-biocomposite were investigated using XRD, FTIR spectroscopy, UV-vis diffuse reflectance spectroscopy, TGA, XPS, and SEM-EDS. The thermal measurements showed that the decomposition of CS was postponed progressively by adding PB and ZnO, and the thermal stability of the synthesized hybrid-biocomposite was improved. The characterization results highlighted strong interactions between the C–O, C=O, -NH₂, and OH groups of chitosan and the alumina-silica sheets of bentonite on the one side, and between the functional groups of chitosan (-NH₂, OH) and ZnO on the other side. The photocatalytic efficiency of the prepared hybrid-biocomposite was assessed in the presence of Methyl Orange (MO). The experiments carried out in the dark showed that the MO removal increased in the presence of Zn-PB/CS hybrid-biocomposite (86.1%) by comparison with PB (75.8%) and CS (65.4%) materials. The photocatalytic experiments carried out under visible light showed that the MO removal increased 268 times in the presence of Zn-PB/CS by comparison withZnO.The holes trapping experiments indicated that they are the main oxidative active species involved in the MO degradation under both UV-A and visible light irradiations. Full article

In spite of the progress achieved on the photo-catalytic treatment of water streams, there is still a gap of knowledge on the optimization of the performance of continuous-flow photo-reactors. Zinc-oxide (ZnO) nanoparticles were immobilized on Duranit (80% silica + 20% alumina) inert balls with dip-coating and thermal annealing. The immobilized ZnO nanoparticles were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), ultraviolet-visible (UV-Vis) spectroscopy, and Raman spectroscopy. To assess the stability and photocatalytic capacity of immobilized ZnO, degradation tests of phenol were performed in batch mode in a 22 W UV-oven with an emission peak at 375 nm by varying the temperature, the initial phenol concentration, and the ratio of photocatalyst mass to initial phenol mass. Continuous flow tests were conducted on two types of annular photo-reactors, made of poly(methyl)methacrylate (PMMA) and stainless steel (STST), equipped with a 6 W UV-lamp with emission at 375 nm, packed with ZnO-coated Duranit beads. Experiments were conducted by recirculating the phenol solution between the annular space of reactor and an external tank and varying the flow rate and the liquid volume in the tank. A one-dimensional dynamic mathematical model was developed by combining reactive with mass-transfer processes and used to estimate the overall reaction kinetic constant with inverse modeling. The results revealed that the ZnO losses might be discernible in batch mode due to the intense stirring caused by the bubbles of injected air, while an insignificant loss of ZnO mass occurs under continuous flow conditions, even after several cycles of reuse; the order of the overall phenol photodegradation reaction is lower than unity; the pseudo-1st order kinetic constant scales positively with the ratio of photocatalyst mass to the initial phenol mass and Peclet number. Full article

TiO₂-based photocatalysts synthesized by the microwave-assisted sol-gel method was tested in the photocatalytic glucose conversion. Modifications of TiO₂ with type-Y zeolite (ZeY) and metals (Ag, Cu, and Ag-Cu) were developed for increasing the dispersion of TiO₂ nanoparticles and increasing the photocatalytic activity. Effects of the TiO₂ dosage to zeolite ratio (i.e., TiO₂/ZeY of 10, 20, 40, and 50 mol %) and the silica to alumina ratio in ZeY (i.e., SiO₂:Al₂O₃ of 10, 100, and 500) were firstly studied. It was found that the specific surface area of TiO₂/ZeY was 400–590 m²g⁻¹, which was higher than that of pristine TiO₂ (34.38 m²g⁻¹). The good properties of 20%TiO₂/ZeY photocatalyst, including smaller particles (13.27 nm) and high surface area, could achieve the highest photocatalytic glucose conversion (75%). Yields of gluconic acid, arabinose, xylitol, and formic acid obtained from 20%TiO₂/ZeY were 9%, 26%, 4%, and 35%, respectively. For the effect of the silica to alumina ratio, the highest glucose conversion was obtained from SiO₂:Al₂O₃ ratio of 100. Interestingly, it was found that the SiO₂:Al₂O₃ ratio affected the selectivity of carboxylic products (gluconic acid and formic acid). At a low ratio of silica to alumina (SiO₂:Al₂O₃ = 10), higher selectivity of the carboxylic products (gluconic acid = 29% and formic acid = 32%) was obtained (compared with other higher ratios). TiO₂/ZeY was further loaded by metals using the microwave-assisted incipient wetness impregnation technique. The highest glucose conversion of 96.9 % was obtained from 1 wt. % Ag-TiO₂ (40%)/ZeY. Furthermore, the bimetallic Ag-Cu-loaded TiO₂/ZeY presented the highest xylitol yield of 12.93%. Full article