Search Results (18,468)

This study presents the synthesis and characterization of a series of multiblock copolymers, poly(ethylene 2,5-furandicarboxylate)-poly(ε-caprolactone) (PEF-PCL), created through a combination of the two-step melt polycondensation method and ring opening polymerization, as sustainable alternatives to fossil-based plastics. The structural confirmation of these block copolymers was achieved through Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), ensuring the successful integration of PEF and PCL segments. X-ray Photoelectron Spectroscopy (XPS) was employed for chemical bonding and quantitative analysis, providing insights into the distribution and compatibility of the copolymer components. Differential Scanning Calorimetry (DSC) analysis revealed a single glass transition temperature (T_g), indicating the effective plasticizing effect of PCL on PEF, which enhances the flexibility of the copolymers. X-ray Diffraction (XRD) studies highlight the complex relationship between PCL content and crystallization in PEF-PCL block copolymers, emphasizing the need to balance crystallinity and mechanical properties for optimal material performance. Broadband Dielectric Spectroscopy (BDS) confirmed excellent distribution of PEF-PCL without phase separation, which is vital for maintaining consistent material properties. Mechanical properties were evaluated using Nanoindentation testing, demonstrating the potential of these copolymers as flexible packaging materials due to their enhanced mechanical strength and flexibility. The study concludes that PEF-PCL block copolymers are promising candidates for sustainable packaging solutions, combining environmental benefits with desirable material properties. Full article

Bimetallic (Ta/Ti, V, Co, Nb) mesoporous MCM-41 nanoparticles were obtained by direct synthesis and hydrothermal treatment. The obtained mesoporous materials were characterized by XRD, XRF, N₂ adsorption/desorption, SEM, TEM, XPS, Raman, UV-Vis, and PL spectroscopy. A more significant effect was observed on the mesoporous structure, typically for MCM-41, and on optic properties if the second metal (Ti, Co) did not belong to the same Vb group with Ta as V and Nb. The XPS showed for the TaTi-MCM-41 sample that framework titanium is the major component. The new nanoparticles obtained were used as catalysts for oxidation with hydrogen peroxide of olefinic compounds (1,4 cyclohexadiene, cyclohexene, styrene) and photodegradation of organic pollutants (phenol, methyl orange) from water. The results showed improvementsin activity and selectivity in oxidation reactions by the addition of the second metal to the Ta-MCM-41 catalyst. The slow addition of H₂O₂ was also beneficial for the selectivity of epoxide products and the stability of the catalysts. The band gap energy values decreased in the presence of the second metal, and the band edge diagram evidenced positive potential for all the conduction bands of the bimetallic samples. The highestlevels of photocatalytic degradation were obtained for the samples with TaTi and TaV. Full article

Portugal’s architecture reflects a rich history influenced by Roman, Moorish, Neoclassical and Romantic styles, with the 20th century marked by Art Deco and colonial influences. Regional styles vary, with white-painted buildings commonly experiencing color changes due to biofilm formation. Visually striking are the red-colored biological patinascommon in the coastal areas. A survey of 120 historical buildings affected by bio-colonization helps to understand the reasons for the patinas’ growing, which beyond natural factors, is often linked to construction defects. A characterization of four samples utilizes Next-Generation Sequencing (NGS) to identify the microorganisms composing the red biofilm, while the SEM-EDS, FTIR-ATR and XRD techniques provide further insights into the biofilm and substrate features. The comprehensive data of biochemical characterization indicate a wide variety of microorganisms, including bacteria and fungi, some of which exhibit potential as producers of a UV-tolerant red/yellow pigment (carotenoid) responsible for the macroscopic coloration of bio-colonization. Full article

Strategies followed to improve SBA-15 surface (essentially inert) included modifications by adding acidic or basic (or both) species during or after silica synthesis. Amphoteric properties are especially important, as some reactions (alcohol dehydration, for instance) require both types of sites to efficiently take place. In this work, single Zr (nominal 3, 5, and 10 wt%, as ZrOCl₂•8H₂O) direct addition during SBA-15 synthesis was used to impart amphoteric characteristics (as determined by NH₃ and CO₂ TPD) to mesostructured SiO₂ matrices. Additional materials characterization included textural (N₂ physisorption) and structural (XRD, FTIR, and UV–Vis spectroscopies, and HRTEM as well) studies. Actual solids composition was also determined (EDS). The degree of Zr incorporation into mesoporous silica was enhanced with nominal content in binary formulations, although not necessarily integrated into SBA-15 walls forming Zr-O-Si linkages. It seemed that single ZrO₂ domains (framework and extra-framework) could provide suitable amphoteric properties by significantly increasing the number and strength of both acid and basic sites (especially formulations containing nominal 5 wt% Zr), as to those over mesostructured silica matrices. Also, potentially deleterious strong acid sites were avoided. The binary oxides present great potential to be applied in reactions requiring vicinal acid–base pairs (alcohol dehydration, for instance). Full article

The escalating issue of phenol-containing wastewater necessitates the development of efficient and sustainable treatment methods. In this context, we present a novel composite photocatalyst comprising ZnFe₂O₄ (ZFO) nanoparticles supported on nanocellulose (NC), aimed at addressing this environmental challenge. The synthesis involved a facile hydrothermal method followed by the impregnation of ZFO nanoparticles onto the NC matrix. The morphology and structure of ZFO, NC, and ZFO/NC were investigated by TEM, SEM-EDX, UV–vis, FT-IR, XRD, and XPS analyses. ZFO, as a weakly magnetic semiconductor catalytic material, was utilized in photocatalytic experiments under magnetic field conditions. By controlling the electron spin states through the magnetic field, electron–hole recombination was suppressed, resulting in improved photocatalytic performance. The results demonstrated that 43% and 76% degradation was achieved after 120 min of irradiation due to ZFO and 0.5ZFO/NC treatment. Furthermore, the composite 0.5ZFO/NC demonstrated the highest photocatalytic efficiency, showing promising recyclability by maintaining its activity after three cycles of use. This study underscores the potential of the ZFO/NC composite for sustainable wastewater treatment, offering a promising avenue for environmental remediation. Full article

This study explores the H₂ production performance of CuO/Cu₂O with different morphology (nanocubes) synthesized by different methods using different sacrificial reagent (lactic acid), compared with the other three reported CuO/Cu₂O photocatalysts used for H₂ production. A cubic Cu₂O photocatalyst was prepared using a hydrothermal method. It was then calcined at a certain temperature to form a cubic Cu₂O/CuO composite photocatalyst. XRD, TEM, and XPS spectra confirmed the successful synthesis of cubic Cu₂O/CuO composite photocatalysts by calcination-induced oxidation at a certain temperature. As the calcination temperature increases, the crystal phase of the photocatalyst changes from Cu₂O to Cu₂O/CuO and then to CuO. The effects of calcination-induced oxidation on morphology, light absorption, the separation of photoexcited carriers, and the H₂ production activity of photocatalysts were studied. EPR spectra were monitored to analyze the oxygen vacancies in different samples. Mott–Schottky and Tauc plots were utilized to establish the band structure of the composite photocatalyst. Cu₂O/CuO is a type II photocatalyst with a heterogeneous structure that helps to improve electron–hole separation efficiency. The H₂ production efficiency of Cu₂O/CuO composite photocatalyst reaches 11,888 μmol h⁻¹g⁻¹, 1.6 times that of Cu₂O. The formation of the Cu₂O/CuO heterojunction leads to enhanced light absorption, charge separation, and hydrogen production activity. Full article

Porous activated carbons (AC-AN and AC-AO) for toluene adsorption were prepared starting from brewer’s grain biomass pretreated with microorganisms (Aspergillus niger van Tieghem for AC-AN and Aspergillus oryzae RIB40 for AC-AO). The structures and chemical properties of the three activated carbon materials (AC-AN, AC-AO, and AC that was not pretreated with microorganisms) were characterized by N₂ adsorption–desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The adsorption behavior of the three activated carbons for toluene was studied and correlated with the physical and chemical properties of these materials. The results suggested that the activated carbons prepared by microbial pretreatment had a rougher morphology, higher specific surface area, richer pore structure, fewer oxygen-containing functional groups on the surface, and better adsorption performance for toluene (increased by 31.5% and 18.3% with AC-AN and AC-AO, respectively) compared with the untreated activated carbon (AC). The Thomas model was used to fit the toluene adsorption data, indicating that the rich pore structure accelerated the kinetic process of toluene adsorption. Therefore, appropriate microbial pretreatment of the feedstock that is used to prepare activated carbon can effectively improve its adsorption capacity towards toluene. Full article

To investigate the thermal stability of a shot-peened specimen and ensure the reliability operation under high temperatures, CNT/Al-Cu-Mg composites were treated by shot peening (SP) and the isothermal aging treatment. The heating temperatures were 100, 150, 200, and 250 °C. Changes in surface residual stress and the distribution along the depth were investigated. The microstructure changes were analyzed by XRD and observed by TEM. Changes in mechanical properties were characterized by microhardness. The results show that the compressive residual stress (CRS) release and the microstructure changes mainly occurred at the initial stage of heating treatment. After 128 min of isothermal aging treatment at 250 °C, the surface CRS released 91.9% and the maximum CRS released 80.9%, the surface domain size increased by 222%, and the microstrain and microhardness decreased by 49% and 27.3%, respectively. The reinforcement effect introduced by SP basically disappeared. A large number of second-phase particles, such as CNT, Al₂Cu, and Al₄C₃, were anchored at grain boundaries, hindering dislocation movement and enhancing the thermal stability of the material. Isothermal aging treatment at 100 °C and 150 °C for a duration of 32 min is a reliable circumstance for maintaining SP reinforcement. Full article

To obtain lead-resistant microorganisms as potential strains for bioremediation, in this study, a strain of fungus with high resistance to lead was isolated and domesticated from lead-contaminated soil, which was cultured and molecularly biologically identified as the genus Sarocladium Pb-9 (GenBank No. MK372219). The optimal incubation time of strain Pb-9 was 96 h, the optimal incubation temperature was 25 °C, and the optimal incubation pH was 7. The strain Pb-9 had a good adsorption effect on Pb²⁺ at a lead concentration of 2000 mg/L; scanning electron microscopy (SEM) observed that the spores of the Pb-9 strain appeared to be wrinkled and deformed under Pb²⁺ stress, and XRD analysis showed that the mycelium of Pb-9 adsorbed Pb²⁺; Fourier transform infrared spectroscopy (FTIR) analysis showed that the Pb-9 strain might produce substances such as esters and polysaccharides under the treatment of different Pb²⁺ concentrations. The above results showed that strain Pb-9 has good resistance and adsorption capacity to lead. Therefore, it has potential application value in the bioremediation of environmental heavy metal pollution, and this study provides a fundamental basis for the bioremediation of lead pollution in the environment. Full article

In order to enhance the corrosion resistance of tantalum, the double-glow plasma (DGP) metallurgy technique was used to prepare TaC coatings on the tantalum. The morphology, microstructure, and phase constituents of TaC were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Nano-indentation tests were used to evaluate the mechanical properties of the coatings. The specimens were immersed in NaCl-KCl molten salt at 830 °C to evaluate their corrosion resistance. The results showed that the coating prepared by the DGP technique has a thickness of approximately 5 µm, the diffusion layer has a thickness of 2.5 µm, and the nano-indentation hardness is measured to be 17.27 GPa. The high-temperature stable ceramic phase enhances the high-temperature oxidation resistance of pure tantalum (Ta), while the dense corroded surface and oxidation products improve the anti-corrosion property of TaC coatings. Full article

Weathering products of sphalerite-bearing ores play an important role in controlling the fate of Zn in the environment. In this framework, the relative stability of Zn carbonates is of special relevance for the common case of ore weathering by carbonated groundwater in the presence of calcium carbonates. We investigated the experimental (co)nucleation and growth of Zn and Ca carbonates at 25 °C in finite double diffusion silica hydrogel media with the purpose of deciphering the system’s reactive pathway and unraveling the major governing factors behind the obtained mineral assemblages. The crystallized solids were carefully extracted two months post-nucleation and studied with micro-Raman spectroscopy, micro X-ray diffraction (XRD), scanning electron microscopy, and electron microprobe (EMP) methods. The obtained results indicate that the grown Zn-bearing phases corresponded to smithsonite and/or Zn hydroxyl carbonate, while CaCO₃ polymorphs aragonite and calcite were also crystallized. Moreover, the observed mineral textural relationships reflected the interplay between supersaturation with respect to CaCO₃/pCO₂ and the grown Zn-bearing carbonate. Experiments conducted in more supersaturated conditions with respect to CaCO₃ polymorphs (higher pCO₂) favored the precipitation of smithsonite, while the opposite was true for the obtained Zn hydroxyl carbonate phase. The gathered Raman, XRD, and EMP data indicate that the latter phase corresponded to a non-stoichiometric, poorly crystalline solid. Full article

The effective and safe treatment of red mud has become a pressing global issue in recent years. The purpose of this study is to prepare different systems of low-carbon cementitious materials by combining various solid wastes (slag powder, red brick of construction waste) with different systems of low-carbon cementitious materials and to observe the effects of different cementitious compositions on the construction performance, mechanical properties, freeze–thaw resistance, and heavy metal leaching properties by designing different systems of low-carbon cementitious materials, as well as to analyze the microscopic morphology, mineral composition, and strength-forming mechanisms of the different systems of low-carbon cementitious materials through the use of X-ray fluorescence (XRF), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) techniques. The findings reveal that a ternary cementitious system containing 16% red brick powder exhibits the most favorable overall performance. Compared to a binary system, this mixture improves fluidity by 4.5%, increases compressive strength by 18.27%, reduces drying shrinkage by 39.56%, and lowers the mass loss rate during dry–wet cycling by 11.07%. Furthermore, the leaching levels of heavy metals such as Cr, As, Pb, Ni, and Cu in the red mud-based cementitious materials, combined with multiple solid wastes, are within the safe limits for non-hazardous environmental release, as specified by Chinese regulations, under both freeze–thaw and non-freeze–thaw conditions. This study demonstrates for the first time the potential of combining red mud with construction waste brick dust and provides a scientific basis and theoretical guidance for the synergistic utilization of alkaline solid waste, calcium solid waste, and silica–aluminum solid waste. Full article

Abstract: The photocatalytic reduction of CO₂ to useful products is an area of active research because it shows a potential to be an efficient tool for mitigating climate change. This work investigated the modification of titania with copper(II) nitrate and its impact on improving the CO₂ reduction efficiency in a gas-phase batch photoreactor under UV–Vis irradiation. The investigated photocatalysts were prepared by treating P25-copper(II) nitrate suspensions (with various Cu²⁺ concentrations), alkalized with ammonia water, in a microwave-assisted solvothermal reactor. The titania-based photocatalysts were characterized by SEM, EDS, ICP-OES, XRD and UV-Vis/DR methods. Textural properties were measured by the low-temperature nitrogen adsorption/desorption studies at 77 K. P25 photocatalysts modified with copper(II) nitrate used in the process of carbon dioxide reduction allowed for a higher efficiency both for the photocatalytic reduction of CO₂ to CH₄ and for the photocatalytic water decomposition to hydrogen as compared to a reference. Similarly, modified samples showed significantly higher selectivity towards methane in the CO₂ conversion process than the unmodified sample (a change from 30% for a reference sample to 82% for the P25-R-Cu-0.1 sample after the 6 h process). It was found that smaller loadings of Cu are more beneficial for increasing the photocatalytic activity of a sample. Full article

To be able to study the permeability coefficient and radon reduction effect of three materials before and after the solidification of uranium tailings. Firstly, uranium tailings, blast furnace slag, lime, fly ash and cement were selected as raw materials for the experiment. Three solidified materials were mixed with 7.5%, 10% and 12.5% of equal proportions of cement. The curing samples of nine kinds of solidified bodies were prepared after curing. Subsequently, the permeability coefficient was determined through the utilization of X-ray diffraction (XRD) and scanning electron microscopy (SEM). And cumulative radon concentrations in uranium tailings and samples were measured by RAD7. Thus, the radon exhalation rate of the original sample and the sample were determined. The experimental results show that the permeability coefficient of nine samples decreased with the quadratic function with the increase in the amount of curing agent. Microscopic scanning results show that there is a positive correlation among the radon exhalation rate, permeability coefficient and cementation degree. The best material for solidifying uranium tailings and radon insulation was blast furnace slag, followed by fly ash. Full article

Contamination by heavy metals (HMs) such as Pb, Cd, Cr, and Hg poses significant risks to the environment and human health owing to their toxicity and persistence. Geopolymers (GPs) have emerged as promising materials for immobilizing HMs and reducing their mobility through physical encapsulation and chemical stabilization. This study explored the novel use of isotactic polypropylene functionalized in the molten state with maleinized hyperbranched polyol polyester (PP-g-MHBP) as an additive in coal fly ash (CFA)-based GPs to enhance HM immobilization. Various characterization techniques were employed, including compressive strength tests, XRD, ATR-FTIR, SEM-EDX, XPS analyses, and TCLP leaching tests, to assess immobilization effectiveness. These results indicate that although the addition of PP-g-MHBP does not actively contribute to the chemical interactions with HM ions, it acts as an inert filler within the GP matrix. CFA/PP-g-MHBP-based GPs demonstrated significant potential for Cd²⁺ immobilization up to 3 wt% under acidic conditions, although the retention of Pb²⁺, CrO₄²⁻, and Hg²⁺ varied according to the specific chemistry of each metal, weight percentage of the added metal, matrix structure, and regulatory standards. Notably, high immobilization percentages were achieved for CrO₄²⁻ and Hg²⁺, although the leaching concentrations exceeded US EPA limits. These findings highlight the potential of CFA/PP-g-MHBP-based GPs for environmental applications, emphasizing the importance of optimizing formulations to enhance HM immobilization under varying conditions. Full article