Search Results (277)

This study reports the synthesis and evaluation of iron molybdate (Fe₂(MoO₄)₃) and iron tungstate (FeWO₄) as photocatalysts for the degradation of a real industrial effluent from aluminum anodizing processes under visible light irradiation. The oxides were synthesized via a co-precipitation method in an aqueous medium, followed by microwave-assisted hydrothermal treatment. Structural and morphological characterizations were performed using X-ray diffraction, field-emission scanning electron microscopy, Raman spectroscopy, ultraviolet–visible (UV–vis), and photoluminescence (PL) spectroscopies. The effluent was characterized by means of ionic chromatography, total organic carbon (TOC) analysis, physicochemical parameters (pH and conductivity), and UV–vis spectroscopy. Both materials exhibited well-crystallized structures with distinct morphologies: Fe₂(MoO₄)₃ presented well-defined exposed (001) and (110) surfaces, while FeWO₄ showed a highly porous, fluffy texture with irregularly shaped particles. In addition to morphology, both materials exhibited narrow bandgaps—2.11 eV for Fe₂(MoO₄)₃ and 2.03 eV for FeWO₄. PL analysis revealed deep defects in Fe₂(MoO₄)₃ and shallow defects in FeWO₄, which can influence the generation and lifetime of reactive oxygen species. These combined structural, electronic, and morphological features significantly affected their photocatalytic performance. TOC measurements revealed degradation efficiencies of 32.2% for Fe₂(MoO₄)₃ and 45.3% for FeWO₄ after 120 min of irradiation. The results highlight the critical role of morphology, optical properties, and defect structures in governing photocatalytic activity and reinforce the potential of these simple iron-based oxides for real wastewater treatment applications. Full article

This study investigated the degradation efficacy, kinetics, and mechanism of the ozone (O₃) process and two enhanced O₃ processes (O₃/peroxymonosulfate (O₃/PMS) and O₃/peroxymonosulfate/iron molybdates/biochar composite (O₃/PMS/FeMoBC)), especially the O₃/PMS/FeMoBC process, for the degradation of tetracycline (TC) in water. An FeMoBC sample was synthesized by the impregnation–pyrolysis method. The XRD results showed that the material loaded on BC was an iron molybdates composite, in which Fe₂Mo₃O₈ and FeMoO₄ accounted for 26.3% and 73.7% of the composite, respectively. The experiments showed that, for the O₃/PMS/FeMoBC process, the optimum conditions were obtained at pH 6.8 ± 0.1, an initial concentration of TC of 0.03 mM, an FeMoBC dosage set at 200 mg/L, a gaseous O₃ concentration set at 3.6 mg/L, and a PMS concentration set at 30 μM. Under these reaction conditions, the degradation rate of TC in 8 min and 14 min reached 94.3% and 98.6%, respectively, and the TC could be reduced below the detection limit (10 μg/L) after 20 min of reaction. After recycling for five times, the degradation rate of TC could still reach about 40%. The introduction of FeMoBC into the O₃/PMS system significantly improved the TC degradation efficacy and resistance to inorganic anion interference. Meanwhile, it enhanced the generation of hydroxyl radicals (^•OH) and sulfate radicals (SO₄^•−), thus improving the oxidizing efficiency of TC in water. Material characterization analysis showed that FeMoBC has a well-developed porous structure and abundant active sites, which is beneficial for the degradation of pollutants. The reaction mechanism of the O₃/PMS/FeMoBC system was speculated by the EPR technique and quenching experiments. The results showed that FeMoBC efficiently catalyzed the O₃/PMS process to generate a variety of reactive oxygen species, leading to the efficient degradation of TC. There are four active oxidants in O₃/PMS/FeMoBC system, namely ^•OH, SO₄^•−, ¹O₂, and •O₂⁻. The order of their contribution importance was ^•OH, ¹O₂, SO₄^•−, and •O₂⁻. This study provides an effective technological pathway for the removal of refractory organic matter in the aquatic environment. Full article

The probable solid phases controlling phosphorus (P) salts solubility in goat, swine, chicken, and dairy manures were investigated using chemical modeling software, Visual Minteq, coupled with serial dilution and EDTA extraction. In the serial dilution scheme, the manure (wet weight) to water ratios (MWR) used were 1:1, 1:2, 1:5, 1:10, 1:50, and 1:100. The EDTA concentrations used were 1, 5, and 10 mmol L⁻¹ at the 1:50 MWR. The total elemental concentrations in serially diluted samples were measured by ICP-OES, while in the EDTA extracts concentrations were measured by ICP-OES and P was also measured by the molybdate blue-P method. The percentage of total P dissolved from goat, swine, chicken, and dairy manure using serial dilution at 1:10 MWR was 4, 6, 7, and 34% of the total P; while at 1:100 MWR it was 44, 35, 36, and 65%, respectively. Chemical modeling suggested that between 1:1 to 1:10 MWR, Mg-phosphates, primarily struvite, was the probable solid phase controlling P salts solubility in all manures, except dairy. At the 1:50 and 1:100 MWR, the solid phases controlling P solubility shifted from Mg-phosphate to Ca-phosphate minerals in goat, swine, and chicken manures. The use of ICP or molybdate blue for chemical modeling showed the same solid phases in the EDTA extracts. From the EDTA extractions, it was determined that 5 mmol L⁻¹ EDTA lowered Ca and Mg activities that no mineral phases likely remained in goat, swine, and chicken manures. In conclusion, under the conditions of this study, P dissolution from salts present in manure is controlled by the cation concentration in solution. Full article

To enhance sensitivity in detecting phosphorus in water via laser-induced breakdown spectroscopy (LIBS), this study integrates liquid–solid conversion on graphite substrates with a PLS-SVR fusion algorithm. Optimized laser parameters (500 mJ, 13 pulses) improved plasma excitation and signal-to-noise ratios. The graphite substrate adsorbed phosphorus, converting liquid samples into a solid matrix to suppress matrix interference and intensify spectral lines (P I 213.6 nm and 214.9 nm), achieving detection limits of 0.09 mg/L and 0.23 mg/L, respectively. Calibration curves showed high accuracy (R² = 0.9936). In real-world testing, absolute errors were below 0.017 mg/L, with relative errors <12%, aligning closely with traditional ammonium molybdate spectrophotometry. The PLS-SVR algorithm boosted prediction accuracy through data enhancement and spectral feature extraction, reducing errors to 2.1% (0.625 mg/L) and 5.6% (2.5 mg/L). With rapid sample preparation (<10 min), this method offers an efficient, low-cost solution for in situ phosphorus monitoring, advancing LIBS from lab to field use and supporting precise eutrophication management. Full article

Promethazine hydrochloride (PMH) is a first-generation antipsychotic drug created from phenothiazine derivatives that is widely employed to treat psychiatric disorders in human healthcare systems. However, an overdose or long-term intake of PMH can lead to severe health issues in humans. Hence, establishing a sensitive, accurate, and efficient detection approach to detect PMH in human samples is imperative. In this study, we designed orthorhombic copper molybdate microspheres decorated on reduced graphene oxide (Cu₃Mo₂O₉/RGO) composite via the effective one-pot hydrothermal method. The structural and morphological features of the designed hybrid were studied using various spectroscopic methods. Subsequently, the electrochemical activity of the composite-modified screen-printed carbon electrode (Cu₃Mo₂O₉/RGO/SPCE) was assessed by employing voltammetric methods for PMH sensing. Owing to the uniform composition and structural benefits, the combination of Cu₃Mo₂O₉ and RGO has not only improved electrochemical properties but also enhanced the electron transport between PMH and Cu₃Mo₂O₉/RGO. As a result, the Cu₃Mo₂O₉/RGO/SPCE exhibited a broad linear range of 0.4–420.8 µM with a low limit of detection (LoD) of 0.015 µM, highlighting excellent electrocatalytic performance to PMH. It also demonstrated good cyclic stability, reproducibility, and selectivity in the presence of chlorpromazine and biological and metal compounds. Furthermore, the Cu₃Mo₂O₉/RGO/SPCE sensor displayed satisfactory recoveries for real-time monitoring of PMH in human urine and serum samples. This study delivers a promising electrochemical sensor for the efficient analysis of antipsychotic drug molecules. Full article

MoS₂, a key material for supercapacitors, batteries, photovoltaics, catalysis, and sensing applications, was synthesized using the hydrothermal method. Different precursors such as molybdenum sources (ammonium heptamolybdate tetrahydrate ((NH₄)₆Mo₇O₂₄·4H₂O) and sodium molybdate hydrate (Na₂MoO₄·2H₂O)) combined with L-cysteine, thiourea, and thioacetamide, as the sulfur source, were involved. The obtained samples were morphologically and structurally characterized by X-ray diffraction, Raman spectroscopy, N₂ adsorption/desorption measurements, and Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM–EDX). Electrochemical impedance spectroscopy was involved in MoS₂ characterization as electrode materials. The objective of this study was to ascertain the impact of precursor combinations on the morphological, structural, and electrochemical characteristics of MoS₂. A thorough examination of the empirical data revealed that the MoS₂ compounds, which were synthesized using thiourea as the sulfur source, exhibited a more pronounced flower-like morphology, increased crystallite size, and enhanced electrochemical properties with potential electrochemical applications. Full article

Molybdenum (Mo) is a critical industrial metal valued for its corrosion resistance and strength-enhancing properties. However, increasing demand necessitates more efficient and sustainable recovery methods. Bio-recovery of Mo by biosorption is a promising resolution, especially by the use of surface-engineered microbes that express metal binding proteins on its cell surface. This study investigates the potential of Saccharomyces cerevisiae strain ScBp6, which displays a molybdate-binding protein (ModE) on its cell surface, immobilized on porous materials. Our findings reveal that polyurethane sponges (PS) significantly outperform ceramic materials in yeast immobilization, entrapping 1.76 × 10⁷ cells per sponge compared to 1.70 × 10⁶ cells per ceramic cube. Furthermore, the yeast–PS complex demonstrated superior Mo adsorption, reaching 2.16 pg Mo per yeast cell under 10 ppm Mo conditions, comparable to free yeast cells (1.96 pg Mo per yeast cell). These results establish PS as an effective and scalable platform for Mo recovery, offering high biosorption efficiency, reusability, and potential for industrial wastewater treatment applications. Full article

The elimination of absorbance of excess dye by selective oxidation was first proposed for analytical methods using the formation of ion-association complexes (IAs). On this basis, a new sensitive and selective spectrophotometric method for the determination of phosphate in the form of the IA of 11-molybdovanadophosphate with diindodicarbocyanine (DIDC) was developed. Symmetric diindodicarbocyanine and diindotricarbocyanine dyes can be completely oxidized by sufficiently strong oxidizing agents such as permanganate, dichromate, cerium (IV), and vanadate. Of the three dyes investigated (DIDC, N,N’-dipropyldiindodicarbocyanine, and diindotricarbocyanine), the best results were obtained with DIDC. A mixture of molybdate, vanadate, and nitric acid was preferably used as an oxidizing agent. Selective decolorization of only free dye ions, as well as changes in the IA spectrum compared to the dye spectrum, were explained by the isolation of the dye due to the formation of poorly soluble IA nanoparticles and changes in the redox potential of the dye due to its aggregation. The following optimal conditions for phosphate determination were found: 0.3 M nitric acid, 0.43 mM sodium molybdate, 0.041 mM sodium vanadate, 0.015 mM DIDC, and 18 min for the reaction time. The molar absorptivity of the IA was 1.86 × 10⁵ mol⁻¹·L·cm⁻¹ at 600 nm, and the detection limit for phosphate was 0.013 µM. The developed method was applied to the determination of phosphate in natural water samples. Full article

The adoption of chrome-free anodizing and sealing systems for aluminum alloys, particularly AA2024, is gaining prominence due to environmental and health concerns associated with traditional Cr(VI)-based processes. This study evaluates the environmental and economic impacts of sulfuric acid anodizing (SAA) combined with sealing based on fluorozirconate, molybdate, and cerate. Comparative analyses were conducted against conventional Cr(VI) systems and SAA with Cr(III) sealing, focusing on corrosion resistance, energy consumption, washing steps and material flows. The entire anodizing process was examined, including pretreatment, anodization, and sealing. Electrochemical analyses and surface characterization through SEM/EDS, FIB, and XPS were conducted. The results demonstrate that the chromium-free system offers competitive corrosion resistance while significantly reducing environmental and economic costs. Furthermore, fluorozirconate, molybdate, and cerate-based post-treatments broaden its application spectrum in corrosion science and warrant further exploration. However, adopting new sealing technologies in aerospace requires extensive certification involving corrosion resistance, durability assessments, and stringent environmental simulations. Compliance with regulatory standards set by the FAA (Federal Aviation Administration) and EASA (European Union Aviation Safety Agency) necessitates thorough documentation, third-party validation, and testing to ensure safety and performance before industrial implementation. These challenges underscore the complexity of transitioning to more sustainable anodizing and sealing technologies in the aerospace industry. Full article

The catalytic esterification of levulinic acid (LA) to methyl levulinate (ML) was investigated using copper molybdate (Cu₃(MoO₄)₂(OH)₂) as a heterogeneous catalyst. The catalyst, synthesized via chemical precipitation, exhibited a monoclinic structure with self-assembled nanoplates forming spherical mesostructures. Structural characterization confirmed its high crystallinity, while textural analysis revealed a BET surface area of 70.55 m² g⁻¹ with pore sizes in the nanometric range (1–6 nm). The catalytic performance was systematically evaluated under varying reaction conditions, including temperature, catalyst dosage, reaction time, methanol-to-LA molar ratio, alcohol type, and catalyst reusability. Optimal conversion of 99.3% was achieved at 100 °C, a 1:20 methanol-to-LA molar ratio, 5% catalyst loading, and a reaction time of 4 h. Comparative analysis with other heterogeneous catalysts demonstrated superior efficiency and stability of Cu₃(MoO₄)₂(OH)₂, with minimal activity loss over four reuse cycles (final conversion of 77.1%). Mechanistic insights suggest that its high activity is attributed to Lewis and Brønsted acid sites, facilitating efficient esterification. This study underscores the potential of copper molybdate as a sustainable and recyclable catalyst for biofuel additive synthesis, advancing green chemistry strategies for biomass valorization. Full article

The removal of methylene blue (MB) cationic dye from aqueous solutions was investigated by applying magnesium molybdate (β-MgMoO₄) as a nanosorbent. The β-MgMoO₄ was synthesized through a simple, rapid, and efficient method. The MB dye removal process was optimized by evaluating various parameters such as temperature, contact time, nanosorbent dosage, pH, and initial cationic dye concentration. The optimal conditions for MB removal were found to be pH 3, with a 99% removal efficiency achieved in just 10 min of contact time, when using an MB cationic dye concentration of 160 ppm. Magnesium molybdate (β-MgMoO₄) showed a maximum adsorption capacity of 356 mg/g, according to Langmuir model-based calculations. The MB dye removal process occurred spontaneously while being favorable and endothermic. The kinetic investigation showed that the pseudo-second-order model accurately represented the reaction kinetics. The thermal regeneration test results indicated that the removal efficiency remained stable even after three consecutive rounds of reuse. A Fourier Transform Infrared (FTIR) spectroscopic analysis confirmed the adsorption and desorption of MB on β-MgMoO₄ and its regeneration. Overall, these results indicate that a β-MgMoO₄ nanosorbent is a favorable and robust adsorbent for the removal of MB cationic dye from wastewater at its maximum capacity. Full article

The use of dyes as sensitizing agents to increase semiconductor activity is a strategy already adopted in the field of heterogeneous photocatalysis, but the compounds applied are noble metal-based and sometimes difficult to synthesize, which make it more expensive. In this work, it was discovered that methylene blue can perform such an effect on an iron molybdate functionalized with peroxo groups on the surface. This material, called MoOxoFe, was tested together with its analogue MoFe (produced without H₂O₂ in the synthesis) in the degradation of methylene blue. The rapid degradation of the dye led to the hypothesis of sensitization, which was investigated and proven by additional photocatalytic tests with sensitized material, MoOxoFe-MB, and spectroscopies, such as EPR and XPS. Full article

In this study, PTA&PMA/NiMoO₄@NF was synthesized on nickel foam through wet chemical etching to promote the kinetics of the oxygen evolution reaction (OER) effectively. OER benefits from two cationic (Ni and Mo) defects and the optimized electronic configuration of PTA&PMA/NiMoO₄@NF. Thus, it only needs 200 mV to reach the current density of 10 mA cm⁻² in 1.0 mol/L of KOH. This value is nearly 100 mV lower than the value needed by pure NiMoO₄. After being used as an anode for water splitting in an alkaline solution, the as-obtained catalyst can operate at a current density of 10 mA cm⁻² for 24 h of good stability. The synthesis strategy adopted in this study can provide an effective, low-cost, simple, and convenient strategy for improving the OER electrocatalytic performance of other transition metal oxides. Full article

The effective removal of organic pollutants and bacteria are of great significance considering the hazards to the environment and human health. The two-dimensional AgBiO₃/Bi₂MoO₆ heterojunction with rich oxygen vacancies was successfully fabricated via a hydrothermal method and systematically characterized by various analytical techniques. The photocatalytic experimental results revealed that the addition of AgBiO₃ improved the photocatalytic performance of Bi₂MoO₆, and the AgBiO₃/Bi₂MoO₆-10 heterojunction possessed the best degradation effect toward RhB (72%) within 100 min, with 1.38 and 1.44 times higher activity than pure Bi₂MoO₆ and AgBiO₃, respectively. The bacteria were completely inactivated within 90 min by AgBiO₃/Bi₂MoO₆-10 heterojunction. The reason for the enhancement of photocatalytic activity was the synergistic effect between AgBiO₃ and Bi₂MoO₆. The constructed Z-scheme heterojunction with oxygen vacancies improved the separation efficiency of photo-induced electrons and holes and broadened the range of visible-light absorption. The trapping experiments and ESR indicated that superoxide radical and holes were the main reactive species. Full article

As a transition metal chalcogenide, molybdenum disulfide is an important two-dimensional material. Due to its structural anisotropy, its different morphological structures impact performance. Therefore, improving existing preparation methods enhances its applications. Single-layer molybdenum disulfide is a direct bandgap semiconductor with excellent mechanical properties and chemical stability. We chose ammonium molybdate as the molybdenum source and L-cysteine as the sulfur source. By changing the pH and the reaction time in the environment, the hydrothermal method is used to synthesize the precursor and molybdenum disulfide with different morphologies to control its morphology. Electrochemical test results showed that the specific capacity of molybdenum disulfide synthesized at a current density of 0.6 A reaches 187.79 F/g at a reaction time of 24 h and a pH of 0.6. Its microstructure is in the shape of a flower ball, with a single piece size of about 50 nm and a thickness of about 5 nm. Its specific surface area reaches 36.88 m²/g, which provides enough active sites. Full article