Stacking Of Sheets Research Articles

Thermo-oxidative degradation behavior of vulcanized butadiene rubber under thermal recycling conditions

Thermo-oxidative reclamation of tire rubber has been proven to be an energy-efficient method for upcycling end-of-life tire. As one of the key components, the complicated oxidative degradation behavior of butadiene rubber (BR) has significantly hindered the reclamation efficiency of tire rubber. This study investigated the thermo-oxidative degradation behavior of vulcanized BR in the temperature range (180-240°C) typically used for reclamation. The influence of oxygen diffusion on the degradation evolution of vulcanized BR was investigated using stacked sheet samples, by characterization of their chemical structure, network structure and mechanical properties during the degradation processes. The chemical structure changes indicated that increased surface oxidation led to more pronounced heterogeneous oxidative distribution within the stack. The different layers exhibited distinct degradation changes due to the competition among chain scission and recombination of rubber network structures in degraded BR. The depth profiles monitored by atomic force microscopy (AFM) observed a high-degree oxidized layer with newly crosslinked structures formed at the stacked sample surface, which was the main cause leading to the heterogeneous oxidative degradation. Additionally, the degradation degree of vulcanized BR was analyzed across different temperatures, with the highest degree of degradation was achieved at 210°C in 20 min.

Ectopic reconstitution of a spine-apparatus-like structure provides insight into mechanisms underlying its formation.

The endoplasmic reticulum (ER) is a continuous cellular endomembrane network that displays focal specializations. Most notable examples of such specializations include the spine apparatus of neuronal dendrites and the cisternal organelle of axonal initial segments. Both organelles exhibit stacks of smooth ER sheets with a narrow lumen, interconnected by a dense protein matrix. The actin-binding protein synaptopodin is required for their formation, but the underlying mechanisms remain unknown. Here, we report that the spine apparatus and synaptopodin are conserved from flies to mammals and that a highly conserved region of this protein is necessary, but not sufficient, for its association with ER. We reveal a dual role of synaptopodin in generating actin bundles and in linking them to the ER. Expression of a synaptopodin construct constitutively anchored to the ER in non-neuronal cells is sufficient to generate stacked ER cisterns resembling the spine apparatus. Cisterns within these stacks are molecularly distinct from thesurrounding ER and are connected to each other by an actin-based matrix that contains proteins also found at the spine apparatus of neuronal spines. Our findings shed light on mechanisms governing the biogenesis of this peculiar structure and represent a step toward understanding the elusive properties of this organelle.

Impact of Graphene Nano particles on static and dynamic mechanical properties of basalt-glass fibre reinforced epoxy polymer hybrid composites

ABSTRACT This paper investigates the structure-property relationships in basalt – glass fabric reinforced hybrid polymer composites doped with graphene nanoplatelets. Basalt Glass fabrics were reinforced with 0.2 wt.% − 0.8 wt.% graphene using hand layup and compression moulding to fabricate laminated plates. The mechanical, morphological, and thermomechanical properties were characterised using tensile, flexural, impact, SEM, FTIR, XRD, and DMA testing. Results showed that low graphene loadings of 0.2 wt.% − 0.4 wt.% led to small, isolated graphene platelets decorating the basalt fibres. At 0.8 wt.% loading, extensive wrinkling, folding, and stacking of graphene sheets on the basalt was observed. FTIR revealed increasing sp2 C=C vibrations and XRD showed rising graphene peak intensities with higher loadings. While tensile and flexural strengths improved up to 0.6 wt.% graphene due to efficient stress transfer, impact energy increased consistently until 0.8 wt.% graphene owing to reinforcement effects. DMA exhibited enhanced storage modulus and restricted mobility with more graphene. An optimum graphene loading of 0.6 wt.% was found to maximise the mechanical performance through uniform dispersion and strong interfacial adhesion. The results demonstrate that graphene incorporation can substantially augment the strength, toughness, and thermomechanical properties of the composites at appropriate compositions prior to aggregation.

Feather keratin in Pavo cristatus: A tentative structure

Abstract Background F-keratin forms an evolutionary conserved nanocomposite which allows birds to fly. Structural models for F-keratin are all based on the pioneering X-ray diffraction studies on seagull F-keratin, first published in 1932, confirmed for other species and refined over the years. There is, however, no experimental proof because native F-keratin does not form a perfect molecular crystal as required for structure determination. Methods Peacock’s tail feathers were systematically re-investigated by taking diffraction patterns at different rotation angles. Using the recently developed AlphaFold algorithm, a collection of 3D models of arbitrarily truncated and multiplied Pavo cristatus F-keratin sequences was created. The shape, dimensions, density and interfacial exposure of functionally relevant amino acid side chains of the calculated 3D building blocks were used as the initial selection criteria for filamentous F-keratin precursors. Full reproducibility of in silico folding and agreement with previous results from mechanical testing, biochemical analyses and SAXS experiments was mandatory for suggesting the tentative structure for the novel F-keratin repeating unit. Results The filament of the F-keratin polymer is an alternating arrangement of two units called "N-block" and "C-block": Four strands AA 1–52 form a disulfide-stabilized twisted parallelepiped, with 89° internal rotation within eight levels of β-sandwiches. Four strands AA 81–100 form a two-level “β-sandwich” in which aromatic residues provide resilience, like vertebral discs in a spinal column. The pitch of an N+C-block octamer is 10 nm. Solidification may involve "C-blocks" to temporarily mold into "C-wedges" of 18° tilt, which align F-keratin into laterally amorphous fiber-reinforced composites of 9.5 nm axial periodicity. This experimentally significant distance corresponds to the fully stretched AA 53–80 matrix segment. The deformed “spinal column” unwinds under compression when F-keratin filaments perfectly align horizontally into stacked sheets in the solid state. Conclusions At present, the tentative structure presented here is without alternatives.

Ultrafine Mo2N Quantum Dots Embedded in N-Doped Graphene Sheets Enable Efficient Adsorption-Catalytic Transformation of Polysulfides.

Because of the high theoretical energy density of 2600 Wh kg-1, lithium-sulfur batteries (LSBs) are anticipated to be among the next generation of high-energy-density storage technologies. However, the practical application of LSBs has been severely hampered by the significant shuttle effect and slow redox kinetics of polysulfides (LiPSs). To address the above problems, in this paper, the concept of quantum dots (QDs) was introduced to design and synthesize Mo2N QD-modified N-doped graphene nanosheets (marked as Mo2N-QDs@NG), which were used as separator modification materials for LSBs. The experimental results demonstrated that the introduction of Mo2N QDs avoids stacking of graphene sheets and provides more active sites for the conversion of LiPSs. Moreover, Mo2N enhances the chemical fixation and catalyzes the liquid-solid conversion of soluble LiPSs by forming Mo-S and Li-N bonds with LiPSs. Additionally, establishing Mo-C bonds with Mo2N, N-doped graphene sheets can facilitate the transport of electrons and ions and physically prevent the diffusion of LiPSs, thus creating a highly conducting carbon structure to support electrochemical reactions. Benefiting from the synergistic effect of chemical immobilization and catalysis of Mo2N QDs with the physical confinement of NG, Mo2N-QDs@NG-PP batteries exhibit enhanced electrochemical performance.

Optimizing Hard Carbon Anodes from Agricultural Biomass for Superior Lithium and Sodium Ion Battery Performance.

Biomass-derived carbon materials are gaining attention for their environmental and economic advantages in waste resource recovery, particularly for their potential as high-energy materials for alkali metal ion storage. However, ensuring the reliability of secondary battery anodes remains a significant hurdle. Here, we report Areca Catechu sheath-inner part derived carbon (referred to as ASIC) as a high-performance anode for both rechargeable Li-ion (LIBs) and Na-ion batteries (SIBs). We explore the microstructure and electrochemical performance of ASIC materials synthesized at various pyrolysis temperatures ranging from 700 to 1400 °C. ASIC-9, pyrolyzed at 900 °C, exhibits multilayer stacked sheets with the highest specific surface area, and the least lateral size and stacking height. ASIC-14, pyrolyzed at 1400 °C, demonstrates the most ordered carbon structure with the least defect concentration and the highest stacking height and an increased lateral size. ASIC-9 achieves the highest capacities (676 mAh/g at 0.134 C) and rate performance (94 mAh/g at 13.4 C) for hosting Li+ ions, while ASIC-14 exhibits superior electrochemical performance for hosting Na+ ions, maintaining a high specific capacity after 300 cycles with over 99.5 % Coulombic efficiency. This comprehensive understanding of structure-property relationships paves the way for the practical utilization of biomass-derived carbon in various battery applications.

P-doped MoS2 nanosheets embedded in 3D porous carbon for electrocatalytic hydrogen evolution reaction

Due to its inherent electrochemical catalytic activity, molybdenum sulfide (MoS2) is a potential electrocatalyst for hydrogen evolution reaction (HER). However, the limited exposure of its active sites resulting from the easy stacking of nanosheets and inert basal plane hampered its optimal catalytic activity. Herein, we developed a novel facile hydrothermal method to prepare phosphorus-doped MoS2 nanosheets anchored on agar-derived 3D nitrogen-doped porous carbon (P-MoS2/NC). The synthesized P-MoS2/NC electrocatalyst possesses high HER catalytic activity with a low overpotential of 167 mV at 10 mA cm−2 and a small Tafel slope of 45 mV dec−1. The excellent performance is attributed to the unique 3D network carbon structure, which avoids the stacking of the MoS2 sheets resulting in more exposed active sites. Additionally, the P atom introduced on the surface of MoS2 sheets successfully activated the in-plane inertness. This work provides an efficient strategy for designing and preparing high-quality catalysts with enhanced electrocatalytic HER activity.

Unveiling the surface of carbon black via scanning probe microscopy and chemical state analysis

Carbon black (CB) has wide range of industrial applications, including in the manufacturing of automobile tires, rubber products, inks, and plastics. To improve the properties of the target products and establish recycling systems, it must be fully characterized. However, characterization of CB is challenging owing to its structural complexity and the limitation of conventionally used experimental techniques, especially for surface structures at the nanoscale. In this study, we characterized the surface structures of two commercial CB via atomic force and scanning tunneling microscopy. Analysis of well-dispersed aggregates on atomically flat solid surfaces revealed primary particles of diverse sizes. The particle surfaces lacked edges, grooves, and steps that should be observed between stacked graphene sheets, which contradicts the widely accepted crystallite model. Observed images suggest that the graphene sheets exhibit a size distribution, inferring that multiple non-uniformly sized small graphene sheets are stacked turbostratically, with each sheet displaying a localized curvature rather than the ideal planar form. Varying size of sheets and curvature indicate the presence of a decent number of edges terminated with hydrogen and oxygen-containing functional groups. This interpretation was corroborated by conventional spectroscopic techniques: Raman spectroscopy, X-ray photoelectron spectroscopy, temperature-programmed desorption, and infrared absorption spectroscopy.

Holey Sheets Enhance the Packing and Osmotic Energy Harvesting of Graphene Oxide Membranes.

Layered membranes assembled from two-dimensional (2D) building blocks such as graphene oxide (GO) are of significant interest in desalination and osmotic power generation because of their ability to selectively transport ions through interconnected 2D nanochannels between stacked layers. However, architectural defects in the final assembled membranes (e.g., wrinkles, voids, and folded layers), which are hard to avoid due to mechanical compliant issues of the sheets during the membrane assembly, disrupt the ionic channel pathways and degrade the stacking geometry of the sheets. This leads to degraded ionic transport performance and the overall structural integrity. In this study, we demonstrate that introducing in-plane nanopores on GO sheets is an effective way to suppress the formation of such architectural imperfections, leading to a more homogeneous membrane. Stacking of porous GO sheets becomes significantly more compact, as the presence of nanopores makes the sheets mechanically softer and more compliant. The resulting membranes exhibit ideal lamellar microstructures with well-aligned and uniform nanochannel pathways. The well-defined nanochannels afford excellent ionic conductivity with an effective transport pathway, resulting in fast, selective ion transport. When applied as a nanofluidic membrane in an osmotic power generation system, the holey GO membrane exhibits higher osmotic power density (13.15 W m-2) and conversion efficiency (46.6%) than the pristine GO membrane under a KCl concentration gradient of 1000-fold.

The magma plumbing system of the Northern Carnarvon Basin, offshore Australia: multiscale controls on basin-wide magma emplacement, and implications for petroleum exploration

Abstract The Northern Carnarvon Basin (NCB) located on Australia's North West Shelf hosts an extensive (∼40 000 km 2 ) intrusive igneous complex related to Mesozoic rifting and break-up. Using an extensive suite of modern 3D seismic reflection surveys, we have mapped this intrusive system across the NCB. We identify three predominant intrusion morphologies: stacked sheets of large interconnected sill intrusions (up to ∼170 km long) and smaller (8–30 km long) isolated, strata concordant intrusions, which often interact with normal faults emplaced into deltaic sedimentary rocks, and variably sized (10–40 km long) saucer-shaped intrusions emplaced into marine shales, spread across seven zones (geographically constrained groups of intrusions of a specific morphology). We consider the zones’ margin-parallel orientation, suggesting control by subcrustal extensional processes during rifting, and the variation in intrusion morphology between these zones, suggesting a dominant control by host rock mechanical properties. We integrate previous work with our observations, constraining emplacement to between the Kimmeridgian and Valanginian, coinciding with key phases of margin evolution. Finally, we assess the impact of this intrusive complex on local petroleum systems. There is likely little to no adverse impact on source rock maturation or reservoir contamination by CO 2 , but there is a spatial dissociation between the location of groups of intrusions and the gas fields, particularly in the Exmouth Plateau. This suggests that migrating hydrocarbons may be blocked, baffled and/or redirected by emplaced igneous rocks.

Staggered structural dynamic-mediated selective adsorption of H2O/D2O on flexible graphene oxide nanosheets

Graphene oxide (GO) is the one of the most promising family of materials as atomically thin membranes for water-related molecular separation technologies due to its amphipathic nature and layered structure. Here, we show important aspects of GO on water adsorption from molecular dynamics (MD) simulations, in-situ X-ray diffraction (XRD) measurements, and ex-situ nuclear magnetic resonance (NMR) measurements. Although the MD simulations for GO and the reduced GO models revealed that the flexibility of the interlayer spacing could be attributed to the oxygen-functional groups of GO, the ultra-large GO model cannot well explain the observed swelling of GO from XRD experiments. Our MD simulations propose a realistic GO interlayer structure constructed by staggered stacking of flexible GO sheets, which can explain very well the swelling nature upon water adsorption. The transmission electron microscopic (TEM) observation also supports the non-regular staggered stacking structure of GO. Furthermore, we demonstrate the existence of the two distinct types of adsorbed water molecules in the staggered stacking: water bonded with hydrophilic functional groups and “free” mobile water. Finally, we show that the staggered stacking of GO plays a crucial role in H/D isotopic recognition in water adsorption, as well as the high mobility of water molecules.

Reduced graphene oxide participation enabling fast nano-homogeneous deposition of sulfur for lithium–sulfur battery cathode

We present a facile, rapid, and gentle approach to synthesize a cathode for lithium-sulfur batteries utilizing reduced graphene oxide (rGO). The rGO sheets are introduced into a supersaturated sulfur solution, resulting in the uniform crystallization of sulfur nanoparticles on the rGO sheets. This process also effectively inhibits the shrinking and stacking of the rGO sheets. Thus, it is possible to achieve adequate utilization of sulfur during the charge/discharge process even when the sulfur mass ratio is high at 70%. Meanwhile, the physical adsorption effect of the host material is fully aroused, resulting in a favorable cycle life of 76.87% capacity retention after 400 cycles at 0.5C. The synthesized material exhibits remarkable homogeneity and electrochemical performance with great potential for practical applications, reaching the forefront of lithium-sulfur (Li–S) battery cathodes utilizing rGO as a host material without metal compounds or heteroatom doping. This approach holds great promise for the loading of sulfur in rGO-based Li–S battery.

Investigation on mechanical, electrical and morphological of high-density polyethylene (HDPE) reinforced with different particle size and composition of graphene nanoplatelets (GNP)

Graphene nanoplatelets (GNP) are just one of the attractive graphene-based nanomaterials that are rapidly emerging and have sparked the interest of many industries. These small stacks of platelet-shaped graphene sheets have a unique size and morphology that quickly disperse into other materials such as polymers, resulting in higher-value composite materials with improved thermal, conductivity, and mechanical capabilities. A detailed analysis of reinforced High-Density Polyethylene (HDPE) using different sizes (2, 15, 25 µm) and compositions (8, 10, 15 wt.%) of Graphene Nanoplatelets (GNP) has been conducted. The microstructure of the HDPE/GNP nanocomposites was extensively examined during the melt blending and injection moulding processes. Based on the results, the nanocomposites with different sizes of GNP exhibited dissimilar behaviour with different compositions. Furthermore, scanning electron microscope (SEM) results indicated a homogeneous dispersion for GNP in melt mixing. Moreover, thermogravimetric (TG) data demonstrate that increasing filler showed a slight increase in the material's thermal stability. The use of GNP improved mechanical properties, as evidenced by the increases in Young's modulus of yield strength from around 100 MPa to over 400 MPa. This study provides a practical reference for the industrial preparation of polymer-based graphene nanocomposites.

High-energy-density zinc ion capacitors based on 3D porous free-standing defect-reduced graphene oxide hydrogel cathodes.

Zinc ion capacitors (ZICs) have shown potential for breaking the energy density ceiling of traditional supercapacitors (SCs) via appropriate device design. Nevertheless, a significant challenge remains in advancing ZIC positive electrode materials with excellent conductivity, high specific capacitance, and reliable cycle stability. A highly attractive option for carbon-based electrode materials is reduced graphene oxide (RGO) due to its vast specific surface area, prominent porosity, and 3D cross-linked frame. However, the tight stacking of RGO sheets driven by van der Waals forces can restrict active sites, decrease specific capacitance, and elevate electrochemical impedance. To overcome these challenges, 3D defective RGO (DRGO) hydrogels were prepared by a metal Co cocatalytic gasification reaction. This method produced mesoporous defects on the surface of RGO hydrogels via a low-temperature hydrothermal self-assembly strategy. The surface of the layer has a wide and uniform distribution, which can offer abundant redox active sites, rich ion transfer channels, and fast reaction kinetics. In this work, 3D DRGO//Zn exhibited a wide operating window (0-1.8 V), high specific capacitance (189.39 F g-1 at 1 A g-1), outstanding energy density (85.23 W h kg-1 at 960.31 W kg-1; 52.36 W h kg-1 at 17454.87 W kg-1), and persistent cycling life (98.86% initial capacitance retention after 10 000 cycles at 10 A g-1). This study emphasizes the device design of ZIC and promising prospects of using 3D DRGO hydrogel as a feasible positive electrode for ZIC.

Terahertz nondestructive stratigraphic reconstruction of paper stacks based on adaptive sparse deconvolution

Characterizing the number of sheets in a stack of paper typically involves mechanical separation of the individual sheets. Here, we explore an nondestructive method that can be applied to the intact paper stack. Namely, terahertz time-of-flight tomography, together with post signal-processing technique sparse deconvolution based on a two-step iterative shrinkage-thresholding algorithm (SD/TWIST), is employed to reconstruct the stratigraphy of stacks of sheets of paper with multilayered structure in a nondestructive and noncontact manner. The double-Gaussian mixture model (DGMM) is also incorporated to suppress dispersion in the reflected THz echoes. The effectiveness and accuracy of the proposed adaptive sparse-deconvolution method are verified experimentally and numerically. Compared with the commonly used frequency wavelet-domain deconvolution (FWDD) method and previous implementations of sparse deconvolution based on an iterative-shrinkage and thresholding algorithm (SD/IST), the proposed sparse-deconvolution approach can provide a clearer and rapid stratigraphic reconstruction of the paper stacks studied, while ensuring accurate thickness information for each paper sheet in the presence of noise, revealing the potential usage of real-time THz tomographic-image processing.

Physics informed neural networks reveal valid models for reactive diffusion of volatiles through paper

Predictive models for the transport of volatile organic compounds in paper need to consider the complex interplay of diffusion, adsorption, desorption, or chemical reactions. The relative importance of each of these processes is determined by the polarity of the volatile. Hence, it is challenging to pick a valid theoretical model that correctly predicts transport regardless of the polarity. Here, physics-informed neural networks (PINNs) assess which of five different models correctly describe transport of DMSO as polar and n-tetradecane as apolar model compound: (i) a pseudo first-order adsorption model for an irreversible sorption process, (ii) a first-order kinetics model allowing reversible sorption, (iii) a second-order model with a reversible process, and an effective diffusion model accounting for a constant (iv) and for a variable effective diffusivity (v). Each tested model is given as set of partial differential equations (PDE). Considering the model under testing and experimentally obtained spatially and temporally resolved concentration profiles through stacks of paper sheets, PINNs predict concentration of the volatiles and associated material constants such as sorption constants and effective diffusion coefficients by solving the inverse problem. Our PINNs revealed two models, pseudo first-order sorption and second-order reversible sorption, that correctly predict concentration profiles and polarity-driven differences in sorption times. While a PINN-based picking of valid transport models has important implications for the development of effective methods for controlling emission of volatiles from paper materials, PINNs represent a versatile mathematical tool to validate or refute the capability of PDE-based theoretical models to describe experimental data.

Sheet-Isolated MoS2 Used for Dispersing Pt Nanoparticles and its Application in Methanol Fuel Cells.

It is highly challenging to activate the basal plane and minimize the π-π stacking of MoS2 sheets, thus enhancing its catalytic performance. Here, we display an approach for making well-dispersed MoS2 . By using the N-doped multi-walled carbon nanotubes (NMWCNTs) as an isolation unit, the aggregation of MoS2 sheets was effectively reduced, favoring the dispersion of Pt nanoparticles (noted as Pt/NMWCNTs-isolated-MoS2 ). Excellent bifunctional catalytic performance for methanol oxidation and oxygen reduction reaction (MOR/ORR) were demonstrated by the produced Pt/NMWCNTs-isolated-MoS2 . In comparison to Pt nanoparticles supported on MoS2 (Pt/MoS2 ), the MOR activity (2314.14 mA mgpt -1 ) and stability (317.69 mA mgpt -1 after 2 h of operation) on Pt/NMWCNTs-isolatedMoS2 were 24 and 232 times higher, respectively. As for ORR, Pt/NMWCNTs-isolated-MoS2 holds large half-wave potential (0.88 V) and high stability (92.71 % after 22 h of operation). This work presents a tactic for activating the basal planes and reducing the π-π stacking of 2D materials to satisfy their applications in electrocatalysis. In addition, the proposed sheet-isolation method can be used for fabricating other 2D materials to promote the dispersion of nanoparticles, which assist its application in other fields of energy as well as the environment.

New local pseudopotential for multilayer carbon materials and its application in wave packet dynamics

Formerly we created a one-electron local pseudopotential which proved to be successful in studying transport phenomena in various sp2 carbon nanosystems, e.g. graphene grain boundaries and nanotube networks. In this work, we present an extended version of the local pseudopotential which correctly describes the electronic structure of van der Waals stacks of carbon sheets, e.g. AA, AB bi-layer graphene, ABC (rhombohedral) tri-layer graphene, as well as AA, AB, and ABC graphite, etc., even in case of external electric fields. We utilize this potential to study the hopping dynamics of wave packets between the graphene sheets in multilayer systems. The frequency of the hopping is proportional to the band splitting, caused by the interlayer coupling. For the case of AB and ABC graphene there is a backscattering near the Fermi level, causing a Zitterbewegung-like phenomenon, an interference between +kBloch and −kBloch states. For the rhombohedral tri-layer graphene the time dependence of the wave packet probability density is an aperiodic function for the first- and third layer (the two outer layers), but a quasi-periodic function for the second (inner) layer.

Multiscale structure of cellulose microfibrils in regenerated cellulose fibers

Cellulose in solution can be assembled into textile fibers by wet-spinning (Viscose etc.) or dry-jet wet spinning (Lyocell, Ioncell etc.), which leads to significant differences in the mechanical properties of fibers. We use scanning X-ray microdiffraction (SXM) to reveal regenerated fibers having a “skin-core” morphology. The “core” region comprises microfibrils (MFs) with ~100 nm in diameter. The cellulose forms elementary fibrils having a ribbon-like cross sectional shape of about 6 × 2 nm, which are packed into MFs. Our SXM studies demonstrate that MFs within Ioncell fibers are composed of elementary fibrils with homogeneous morphologies. Furthermore, the stacking of cellulose molecular sheets within elementary fibrils of Viscose fibers is preferentially along the 010 direction, while those of Ioncell fibers preferably stack in the 1–10 direction. The better structural regularities and distinct morphologies of elementary fibrils give Ioncell fibers enhanced mechanical properties and a wet strength far superior to those of Viscose fibers.

Construction of a magnetic BiOBr-rGO-ZnFe2O4 heterojunction photocatalyst for refinery wastewater treatment under simulated solar light

Considering the importance of sunlight as a free, abundant, and sustainable source of energy, in this paper, first, the removal of phenol from model refinery wastewater under simulated solar light was studied. Then magnetic BiOBr-rGO-ZnFe2O4 photocatalyst with different percentages of BiOBr (0, 30, 45, and 55 %) was synthesized and evaluated in degradation of phenol under simulated solar light. The results showed that the sample containing 45 % wt. of BiOBr was the most active and after 3 h, it succeeded in removing 94 % of the phenol from a 20-ppm phenol solution. The characteristics of the synthesized photocatalysts were analyzed by XRD, BET-BJH, UV–Vis DRS, PL, FESEM, TEM, and EDX analyses. The results showed that by increasing the weight percentage of BiOBr from 30 % to 55 %, the crystal size of BiOBr increased from 22 to 29 nm. FESEM analysis showed that with the increasing amount of BiOBr, more lamellar structures were observed in the sample, and in the sample containing 45 % BiOBr, these structures became flower-like. However, with a further increase in the percentage of BiOBr to 55 %, thick and stacked sheet structures were formed, which resulted in the reduction of porosity and surface area according to BET-BJH analysis. According to PL analysis, the addition of BiOBr to rGO-ZnFe2O4 reduced the rate of recombination of charge carriers. However, increasing the weight percentage of BiOBr declined the light absorption and shifted the absorption edge towards the ultraviolet region. The effect of operational parameters such as pH, amount of photocatalyst, initial concentration of phenol, light intensity, and the presence of oxidant as well as the stability of the selected photocatalytic sample was evaluated. Studying the effect of scavengers also showed that the most active species that degrade phenol are the holes formed on the surface of the BiOBr-rGO-ZnFe2O4 photocatalyst.