Search Results (45)

Due to its persistence and potential negative effects on ecosystems and human health, microplastic pollution in aquatic environments has become a major worldwide concern. Photocatalytic degradation is a sustainable manner to degrade microplastics to non-toxic by-products. In this review, comprehensive discussion focuses on the synergistic effects of various photocatalytic materials including TiO₂, ZnO, WO₃, graphene oxide, and metal–organic frameworks for producing heterojunctions and involving multidimensional nanostructures. Such mechanisms can include the generation of reactive oxygen species and polymer chain scission, which can lead to microplastic breakdown and mineralization. The advancements of material modifications in the (nano)structure of photocatalysts, doping, and heterojunction formation methods to promote UV and visible light-driven photocatalytic activity is discussed in this paper. Reactor designs, operational parameters, and scalability for practical applications are also reviewed. Photocatalytic systems have shown a lot of development but are hampered by shortcomings which include a lack of complete mineralization and production of intermediary secondary products; variability in performance due to the fluctuation in the intensity of solar light, limited UV light, and environmental conditions such as weather and the diurnal cycle. Future research involving multifunctional, environmentally benign photocatalytic techniques—e.g., doped composites or composite-based catalysts that involve adsorption, photocatalysis, and magnetic retrieval—are proposed to focus on the mechanism of utilizing light effectively and the environmental safety, which are necessary for successful operational and industrial-scale remediation. Full article

WO₃ has attracted great attention in the field of catalysts due to its excellent photocatalytic performance. However, the difficulty in recycling and low reuse percentage of nano WO₃ limit its application. This paper used the hydrothermal method to prepare an Fe₃O₄@SiO₂@WO₃ core–shell nanocatalyst. Its composition and structure were characterized by various techniques including XRD, FT-IR, and Raman analyses, which confirmed the successful preparation of a core–shell-structured catalyst with a strong response to an external magnetic field. In the degradation experiment of rhodamine B solution (RhB), the composite catalyst with a WO₃ doping amount of 0.8 g and catalyst dosage amount of 30 mg had the best catalytic degradation effect on 10 ppm RhB, with a degradation efficiency of 99.80%. Due to its high transparency and ion conductivity, SiO₂ did not affect the performance of the composite catalyst, but could effectively reduce the corrosion of WO₃ by the reaction solution. The presence of a SiO₂ interlayer prevented any deterioration in the catalytic efficiency of WO₃ nanocrystal shells and the chemical and thermal stability of Fe₃O₄ nuclei. By applying an external magnetic field, this nanocatalyst can be easily recovered from the solution. These features not only maximize the value of this new material, but also provide sustainable solutions for environmental protection, energy crises, and health issues. Full article

A magnetic shell-structured nano-catalyst was prepared by self-polymerization of dopamine wrapped by ferric oxide as the carrier, which was loaded with palladium nanoparticles (Pd/PDA@Fe₃O₄). The presence of magnetic Fe₃O₄ made it easy for nanoscale palladium particles to recover and prevent the loss of palladium nanoparticles that is unavoidable in traditional usage and preparation procedures. The catalyst was characterized by X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy, thermal weight loss analysis, Raman spectroscopy, X-ray photo-electron spectroscopy, and magnetic properties analysis. The catalytic performance of the prepared catalyst was investigated taking 4-nitrophenol (10 mg/L) and rhodamine B (15 mg/L) as the target pollutants. The results showed that under the conditions of 35 °C, pH = 7 and a catalyst dosage of 3 mg, the catalytic reduction efficiency of 4-nitrophenol, rhodamine B, and the mixture of them all can reach 99%. The catalytic efficiency of Pd/PDA@Fe₃O₄ remained above 90% after being used 10 times. The shell structure of Fe₃O₄ made it possible and easy to recover and recycle the nanoscale palladium, which was a real problem in the usage of nano-catalysts. At the same time, the problem of separation and recovery of palladium nano-catalyst is solved by magnetism, which provides research ideas for the recycling and utilization of nano-materials. Full article

Biodiesel is a mixture of fatty acid alkyl esters (FAAEs) mainly produced via transesterification reactions among triglycerides and short-chain alcohols catalyzed by chemical catalysts (e.g., KOH, NaOH). Lipase-assisted enzymatic transesterification has been proposed to overcome the drawbacks of chemical synthesis, such as high energy consumption, expensive separation of the catalyst from the reaction mixture and production of large amounts of wastewater during product separation and purification. However, one of the main drawbacks of this process is the enzyme cost. In recent years, nano-immobilized lipases have received extensive attention in the design of robust industrial biocatalysts for biodiesel production. To improve lipase catalytic efficiency, magnetic nanoparticles (MNPs) have attracted growing interest as versatile lipase carriers, owing to their unique properties, such as high surface-to-volume ratio and high enzyme loading capacity, low cost and inertness against chemical and microbial degradation, biocompatibility and eco-friendliness, standard synthetic methods for large-scale production and, most importantly, magnetic properties, which provide the possibility for the immobilized lipase to be easily separated at the end of the process by applying an external magnetic field. For the preparation of such effective magnetic nano-supports, various surface functionalization approaches have been developed to immobilize a broad range of industrially important lipases. Immobilization generally improves lipase chemical-thermal stability in a wide pH and temperature range and may also modify its catalytic performance. Additionally, different lipases can be co-immobilized onto the same nano-carrier, which is a highly effective strategy to enhance biodiesel yield, specifically for those feedstocks containing heterogeneous free fatty acids (FFAs). This review will present an update on the use of magnetic iron oxide nanostructures (MNPs) for lipase immobilization to catalyze transesterification reactions for biodiesel production. The following aspects will be covered: (1) common organic modifiers for magnetic nanoparticle support and (2) recent studies on modified MNPs-lipase catalysts for biodiesel production. Aspects concerning immobilization procedures and surface functionalization of the nano-supports will be highlighted. Additionally, the main features that characterize these nano-biocatalysts, such as enzymatic activity, reusability, resistance to heat and pH, will be discussed. Perspectives and key considerations for optimizing biodiesel production in terms of sustainability are also provided for future studies. Full article

The development of a catalyst for the conversion of CO₂ and epoxides to the corresponding cyclic carbonates is still a very attractive topic. Magnetic nano-catalysts are widely used in various organic reactions due to their magnetic separation and recycling properties. Here, a magnetic nano-catalyst containing a Schiff base unit was designed, synthesized and used as a heterogeneous catalyst to catalyze CO₂ and epoxides to form cyclic carbonates without solvents and co-catalysts. The catalyst was characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), thermogravimetric (TG), VSM, SEM, TEM and BET. The results show that the magnetic nano-catalyst containing the Schiff base unit has a high activity in the solvent-free cycloaddition reaction of CO₂ with epoxide under mild conditions, and is easily separated from the reaction mixture driven by external magnetic force. The recovered catalyst maintains a high performance after five cycles. Full article

A magnetite chlorodeoxycellulose/ferroferric oxide (CDC@Fe₃O₄) heterogeneous photocatalyst was synthesised via treated and modified cotton in two steps. The designed nanocomposites were characterised by FTIR, TGA, XRD, SEM, and VSM analyses. The Fenton-photocatalytic decomposition efficiency of the synthesised magnetic catalyst was evaluated under visible sunlight using Methyl Orange (MO) as a model organic pollutant. The impacts of several degradation parameters, including the light source, catalyst load, irradiation temperature, oxidant dose, and pH of the dye aqueous solution and its corresponding concentration on the Fenton photodegradation performance, were methodically investigated. The (CDC@Fe₃O₄) heterogeneous catalyst showed a remarkable MO removal rate of 97.9% at 10 min under visible-light irradiation. (CDC@Fe₃O₄) nanomaterials were also used in a heterogeneous catalytic optimised protocol for a multicomponent reaction procedure to obtain nine tetra-substituted imidazole derivatives. The green protocol afforded imidazole derivatives in 30 min with good yields (91–97%) at room temperature and under ultrasound irradiation. Generally, a synthesised recyclable heterogeneous nano-catalyst is a good example and is suitable for wastewater treatment and organic synthesis. Full article

Nano/micromotors are artificial robots at the nano/microscale that are capable of transforming energy into mechanical movement. In cancer diagnosis or therapy, such “tiny robots” show great promise for targeted drug delivery, cell removal/killing, and even related biomarker sensing. Yet biocompatibility is still the most critical challenge that restricts such techniques from transitioning from the laboratory to clinical applications. In this review, we emphasize the biocompatibility aspect of nano/micromotors to show the great efforts made by researchers to promote their clinical application, mainly including non-toxic fuel propulsion (inorganic catalysts, enzyme, etc.), bio-hybrid designs, ultrasound propulsion, light-triggered propulsion, magnetic propulsion, dual propulsion, and, in particular, the cooperative swarm-based strategy for increasing therapeutic effects. Future challenges in translating nano/micromotors into real applications and the potential directions for increasing biocompatibility are also described. Full article

As heterogeneous catalysis is a practical method for activating Oxone, the immobilization of transition metals (e.g., Co, Fe) on carbonaceous supports is a promising platform. Thus, this study attempts to develop a carbon-supported metallic catalyst by growing Co/Fe on carbon foam (CF) via adopting melamine foam as a readily available template which could be transferred to nitrogen-doped CF with marcoporous structures. Specifically, a unique adornment of Co/Fe species on this CF is facilely fabricated through a complexation of Co/Fe with a plant extract, tannic acid, on melamine foam, followed by carbonization to produce nano-needle-like Co/Fe on N-doped CF, forming a magnetic CF (MCF). This resultant MCF exhibits a much higher surface area of 54.6 m²/g than CF (9.5 m²/g), and possesses a much larger specific capacitance of 9.7 F/g, than that of CF as 4.0 F/g. These superior features of MCF enable it to accelerate Oxone activation in order to degrade an emerging contaminant, bis(4-hydroxyphenyl)methanone (BHPM). Furthermore, MCF + Oxone exhibits a lower activation energy as 18.6 kJ/mol for BHPM elimination and retains its effectiveness in eliminating BHPM over multiple rounds. More importantly, the CF is also prepared and directly compared with the MCF to study the composition-structure-property relationship to provide valuable insights for further understanding of catalytic behaviors, surficial characteristics, and application of such a functional carbon material. Full article

Ferrites have excellent magnetic, electric, and optical properties that make them an indispensable choice of material for a plethora of applications, such as in various biomedical fields, magneto–optical displays, rechargeable lithium batteries, microwave devices, internet technology, transformer cores, humidity sensors, high-frequency media, magnetic recordings, solar energy devices, and magnetic fluids. Recently, magnetically recoverable nanocatalysts are one of the most prominent fields of research as they can act both as homogeneous and heterogenous catalysts. Nano-ferrites provide a large surface area for organic groups to anchor, increase the product and decrease reaction time, providing a cost-effective method of transformation. Various organic reactions were reported, such as the photocatalytic decomposition of a different dye, alkylation, dehydrogenation, oxidation, C–C coupling, etc., with nano-ferrites as a catalyst. Metal-doped ferrites with Co, Ni, Mn, Cu, and Zn, along with the metal ferrites doped with Mn, Cr, Cd, Ag, Au, Pt, Pd, or lanthanides and surface modified with silica and titania, are used as catalysts in various organic reactions. Metal ferrites (MFe₂O₄) act as a Lewis acid and increase the electrophilicity of specific groups of the reactants by accepting electrons in order to form covalent bonds. Ferrite nanocatalysts are easily recoverable by applying an external magnetic field for their reuse without significantly losing their catalytic activities. The use of different metal ferrites in different organic transformations reduces the catalyst overloading and, at the same time, reduces the use of harmful solvents and the production of poisonous byproducts, hence, serving as a green method of chemical synthesis. This review provides insight into the application of different ferrites as magnetically recoverable nanocatalysts in different organic reactions and transformations. Full article

Production of biodiesel from edible vegetable oils using homogenous catalysts negatively impacts food availability and cost while generating significant amounts of caustic wastewater during purification. Thus, there is an urgent need to utilize low-cost, non-food feedstocks for the production of biodiesel using sustainable heterogeneous catalysis. The objective of this study was to synthesize a novel supported nano-magnetic catalyst (CaO/Fe₂O₃/feldspar) for the production of biodiesel (fatty acid methyl esters) from waste and low-cost plant seed oils, including Sinapis arvensis (wild mustard), Carthamus oxyacantha (wild safflower) and Pongamia pinnata (karanja). The structure, morphology, surface area, porosity, crystallinity, and magnetization of the nano-magnetic catalyst was confirmed using XRD, FESEM/EDX, BET, and VSM. The maximum biodiesel yield (93.6–99.9%) was achieved at 1.0 or 1.5 wt.% catalyst with methanol-to-oil molar ratios of 5:1 or 10:1 at 40 °C for 2 h. The CaO/Fe₂O₃/feldspar catalyst retained high activity for four consecutive cycles for conversion of karanja, wild mustard, and wild safflower oils. The effective separation of the catalyst from biodiesel was achieved using an external magnet. Various different physico-chemical parameters, such as pour point, density, cloud point, iodine value, acid value, and cetane number, were also determined for the optimized fuels and found to be within the ranges specified in ASTM D6751 and EN 14214, where applicable. Full article

Many areas of electronics, engineering and manufacturing rely on ferromagnetic materials, including iron, nickel and cobalt. Very few other materials have an innate magnetic moment rather than induced magnetic properties, which are more common. However, in a previous study of ruthenium nanoparticles, the smallest nano-dots showed significant magnetic moments. Furthermore, ruthenium nanoparticles with a face-centred cubic (fcc) packing structure exhibit high catalytic activity towards several reactions and such catalysts are of special interest for the electrocatalytic production of hydrogen. Previous calculations have shown that the energy per atom resembles that of the bulk energy per atom when the surface-to-bulk ratio < 1, but in its smallest form, nano-dots exhibit a range of other properties. Therefore, in this study, we have carried out calculations based on the density functional theory (DFT) with long-range dispersion corrections DFT-D3 and DFT-D3-(BJ) to systematically investigate the magnetic moments of two different morphologies and various sizes of Ru nano-dots in the fcc phase. To confirm the results obtained by the plane-wave DFT methodologies, additional atom-centred DFT calculations were carried out on the smallest nano-dots to establish accurate spin-splitting energetics. Surprisingly, we found that in most cases, the high spin electronic structures had the most favourable energies and were hence the most stable. Full article

In this paper, we describe the creation of a moderate band gap Nd-substituted Ni-Zn ferrite as a nano photo catalyst via a simple and cost-effective process of solution combustion. Nd substitution alters the crystallite size, shape, band gap, and magnetic characteristics of Ni-Zn ferrite significantly. Investigations using X-ray diffraction revealed that all samples display a pure phase. The average crystallite size was determined to be between 31.34 and 38.67 nm. On Nd doping, morphology investigations indicated that the shape of nanoparticles changed from approximately spherical to stacked grains. Band gap experiments confirmed the red shift in optical band gap on Nd doping. The synthesized catalysts Ni_0.5Zn_0.5Fe₂O₄ (Nd0), Ni_0.5Zn_0.45Nd_0.05Fe₂O₄ (Nd1), and Ni_0.5Zn_0.5Nd_0.05Fe_1.95O₄ (Nd2) have been effectively used for the degradation of methylene blue dye under the solar light irradiation. The sample with Nd substitution on Fe sites had the highest methylene blue degradation efficiency. Nd2 photo catalyst degrades the methylene blue dye with a degradation efficiency of 98% in 90 min of solar light irradiation. The photocatalytic activity is triggered by the existence of oxygen vacancies and a mixed valence state of Ni, Fe, and Nd, as confirmed by the XPS investigation. In addition, the investigations on scavenging reveal that the hydroxyl radical is a reactive component in the degradation process. The degradation route has been investigated in relation to the many potential reactions and discovered reactive substances. Full article

In this work, we report a new facile method for the preparation of myrcene-limonene copolymers and nanocomposites using a Lewis acid as a catalyst (AlCl₃) and organo-modified clay as a nano-reinforcing filler. The copolymer (myr-co-lim) was prepared by cationic copolymerization using AlCl₃ as a catalyst. The structure of the obtained copolymer is studied and confirmed by Fourier Transform Infrared spectroscopy, Nuclear Magnetic Resonance spectroscopy, and Differential Scanning Calorimetry. By improving the dispersion of the matrix polymer in sheets of the organoclay, Maghnite-CTA⁺ (Mag-CTA⁺), an Algerian natural organophilic clay, was used to preparenanocomposites of linear copolymer (myr-co-lim). In order to identify and assess their structural, morphological, and thermal properties, the effect of the organoclay, used in varyingamounts (1, 4, 7, and 10% by weight), and the preparation process were investigated. The Mag-CTA⁺ is an organophylic montmorillonite silicate clay prepared through a direct exchange process in which they were used as green nano-reinforcing filler. The X-ray diffraction of the resulting nanocomposites revealed a considerable alteration in the interlayer spacing of Mag-CTA⁺. As a result, interlayer expansion and myr-co-lim exfoliation between layers of Mag-CTA⁺ were observed. Thermogravimetric analysis provided information on the synthesized nanocomposites’ thermal properties. Fourier transform infrared spectroscopy and scanning electronic microscopy, respectively, were used to determine the structure and morphology of the produced nanocomposites (myr-co-lim/Mag). The intercalation of myr-co-lim in the Mag-CTA⁺ sheets has been supported by the results, and the optimum amount of organoclay needed to create a nanocomposite with high thermal stability is 10% by weight. Finally, a new method for the preparation of copolymer and nanocomposites from myrcene and limonene in a short reaction time was developed. Full article

Biodiesel is an alternative fuel in many developing and developed countries worldwide. Biodiesel has significant and numerous economic, environmental, and social benefits. However, the problem with conventional biodiesel production is the high industrial production cost, mainly contributed by the raw materials. Therefore, catalysts and feedstock are essential in increasing total biodiesel production rates and minimizing production costs. Magnetic nano-catalysts play a crucial role in heterogeneous catalysis due to their easy recovery, recyclability, excellent selectivity, and fast reaction rates, owing to their larger surface area. This research activity used heterogeneous magnetic nano-catalysts of ICdO, ISnO, and their modified form, to produce biodiesel. The synthesized nano-catalysts were made through co-precipitation and found quite efficient for transesterifying Pongamia pinnata oil. The effect of various parameters on biodiesel yield in the presence of prepared magnetic nano-catalysts has been studied. In the transesterification supported by ISnO, high yield, i.e., 99%, was achieved after 2 h of reaction time at 60 °C. The nano-catalysts were magnetically recovered and reused 4–5 times without any change in their activity. All the synthesized magnetic nano-catalysts performed SEM analysis. Each fraction of the produced biodiesel was assessed for different quality parameters, and the results were per ASTM standards. The components present in biodiesel produced from Pongamia pinnata oil were determined by GCMS. Full article

In the current study, a novel green nano-catalyst from Tragacanth gum (TG) was synthesized and used for sustainable biodiesel production from Brassica juncea (L.) Czern. seed oil. Brassica juncea (L.) Czern contains 30% oil on dry basis and free fatty acid content of 0.43 mg KOH/g. Physiochemical characterization of a newly synthesized nano-catalyst was performed by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX), Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. The XRD results showed an average crystalline size of 39.29 nm. TEM analysis showed the cluster form of NiSO₄ nanoparticles with a size range from 30–50.5 nm. SEM analysis of the catalyst showed semispherical and ovoid shapes with surface agglomeration. The synthesized catalyst was recovered and re-used in four repeated transesterification cycles. Maximum biodiesel yield (93%) was accomplished at 6:1 methanol to oil molar ratio, catalyst concentration of 0.3 wt%, at 90 °C for 120 min at 600 rpm using Response Surface Methodology (RSM) coupled with central composite design (CCD). Brassica juncea (L.) Czern. biodiesel was characterized by Thin Layer Chromatography (TLC), FT-IR, Nuclear Magnetic Resonance (NMR) (¹H, ¹³C), and Gas Chromatography-Mass Spectroscopy (GCMS) analytical techniques. The major fatty acid methyl esters were 16-Octadecenoic acid and 9-Octadecenoic acid methyl ester. The fuel properties, i.e., flash point (97 °C), density (825 kg/m³ at 40 °C), kinematic viscosity (4.66 mm²/s), pour point (–10 °C), cloud point (–14 °C), sulfur content (66 wt.%), and total acid number (182 mg KOH/g) were according to the International biodiesel standards. The reaction kinetic parameters were determined, and all the reactions followed Pseudo first-order kinetics. It was concluded that non-edible Brassica juncea (L.) Czern. seed oil is one of the sustainable candidates for the future biofuel industry using a cleaner, reusable, and highly active Ni-modified TG nano-catalyst. Full article