Search Results (44)

This study investigates the dynamic operation of a pilot-scale precipitation reactor designed to produce oxygenated phosphocalcium apatites with controlled composition and low crystallinity, closely mimicking the mineral phase of bone. Our approach is based on integrating kinetic monitoring and dynamic reactor control to direct the formation of apatites with tailored structural and chemical properties. Three synthesis routes were explored using CaCO₃, Ca(NO₃)₂, and CaCl₂ as calcium precursors, under optimized Ca/P molar ratios. The evolution of ionic concentrations (Ca²⁺, PO₄³⁻), peroxide and molecular oxygen incorporation, and carbonate content was monitored over a reaction time range of 2 min to 4 h. Characterization by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and chemical analysis revealed a time-dependent transformation of amorphous phases into poorly crystalline apatites with specific textures. After 60 min, the Ca/P atomic ratio stabilized at approximately 1.575, and the resulting apatites exhibited structural features comparable to those of human bone. This study highlights the influence of reactor operation time on precipitation kinetics and the properties of bioactive apatites in a scalable system. The results offer promising prospects for the large-scale production of bone-mimetic materials. However, the lack of biological validation remains a limitation. Future studies will assess the cytocompatibility and bioactivity of these materials to confirm their potential for biomedical applications. Full article

A novel amorphous Fe-doped manganese carbonate (a-FeMn-1) was synthesized via a facile co-precipitation method and evaluated as an efficient heterogeneous catalyst for the activation of peroxymonosulfate (PMS) in the degradation of Orange II. Among various Fe/Mn molar ratios, the 1:1 composition (a-FeMn-1) showed optimal catalytic activity, achieving 98% removal efficiency within 60 min under near-neutral pH conditions. Characterization results indicated that Fe doping effectively induced an amorphous structure and increased surface area and oxygen defects, promoting PMS activation. The system displayed broad pH applicability and resistance to Cl⁻ and natural organic matter, while degradation was inhibited by HCO₃⁻ and PO₄³⁻. EPR and quenching experiments confirmed that surface-bound sulfate radicals (SO₄^•−), hydroxyl radicals (^•OH), and singlet oxygen (¹O₂) were the primary reactive species. XPS analysis further revealed the redox cycling of Fe and Mn and the involvement of defect oxygen in the PMS activation process. The catalyst also demonstrated excellent reusability over five cycles without significant loss in efficiency. This work provides insights into the rational design of amorphous bimetallic materials for sulfate radical-based advanced oxidation processes. Full article

Iron and iron-nickel alloy electrodeposits synthesized from sulfate-based electroplating baths were applied to a mild carbon steel substrate. Coated specimens were immersed in an oxygen-saturated, weak ammonium hydroxide solution (pH 9.5–10.0), and their corrosion performance was evaluated using electrochemical techniques. Galvanic and general corrosion behaviors were analyzed to assess the sacrificial protection provided by Fe and Fe-Ni coatings relative to uncoated steel. The influence of anode-to-cathode (A/C) surface area ratios (1:1, 10:1, and 100:1) on the occurrence of plating-induced surface cracks was also examined. Surface morphology and elemental composition of the deposits were characterized. Results of the study indicated that increasing the Ni²⁺/Fe²⁺ molar ratio of the electroplating bath from 0 to 0.167 led to (1) reduced surface porosity and cracking, (2) decreased galvanic corrosion rates between the electrodeposit and substrate, and (3) a progressive increase in the temperature dependence of the general corrosion rate between 20 °C and 60 °C. The development of Fe and Fe-Ni alloy electrodeposits as protective coatings is of particular interest in water-tube power boiler applications, where production of corrosion products must be controlled. Further research is needed to develop coatings that perform predictably under elevated pressures and temperatures typical of operating boiler environments. Full article

The present study reported, for the first time, the fabrication and characterization of electrospun nanofibers based on arabinoxylans (AXs) alone. The Fourier transform infrared spectrum of ferulated water-extractable AXs recovered from wheat endosperm confirmed the molecule identity. The carbon and oxygen signals in X-ray photoelectron spectrometry (XPS) were recorded for this molecule. The AXs had weight-average molar mass, intrinsic viscosity, radius of gyration, and hydrodynamic radius values of 769 kDa, 4.51 dL/g, 55 nm, and 31 nm, respectively. The calculated AX characteristic ratio and persistence length were 10.7 and 3.2 nm, respectively, while the Mark–Houwink–Sakurada α and K constants were 0.31 and 9.4, respectively. These macromolecular characteristics indicate a molecular random coil structure in the polysaccharide. Using aqueous acetic acid 50% (v/v) as a solvent favored the Taylor cone establishment and the fabrication of electrospun nanofibers. The morphology of nanofibers was revealed by scanning electron microscopy images. Atomic force microscopy analysis of AX nanofibers exposed the material deposition in layers; these nanofibers had an average diameter of 177 nm. These nanofibers could be used as advanced biomaterials for biomedical applications such as wound dressing. Full article

The steel manufacturing industry is a major source of global air pollution, with sintering processes contributing over 70% of emissions, primarily carbon monoxide (CO), a significant uncontrolled pollutant. This study explores Mn-Cu bimetallic catalysts as a cost-effective and environmentally friendly alternative to noble metal-based systems, addressing the urgent need for efficient CO oxidation catalysts. Mn-Cu catalysts with different Mn/Cu molar ratios were synthesized via hydrothermal methods and systematically characterized using XRD, XPS, BET, H₂-TPR, etc., to assess their physicochemical properties and catalytic performance. The Mn₄Cu₁ catalyst demonstrated the highest CO oxidation activity, achieving complete conversion at 175 °C. This performance is attributed to its optimal Mn/Cu molar ratio, high specific surface area, abundant oxygen vacancies, and superior redox properties. The catalyst’s enhanced performance is further supported by its low reduction temperature and high Mn³⁺ and Cu⁺ content, which promote efficient electron transfer and oxygen activation. These findings highlight the crucial role of Mn/Cu molar ratios in optimizing catalytic performance and offer valuable insights for designing high-efficiency, low-cost catalysts to reduce CO emissions in industrial applications. Full article

To explore the application of industrial lignin, a waste biomass resource, in the field of metallurgy, the kinetic behavior of iron ore powder reduction by Shenmu bituminous coal, Lu’an anthracite, and industrial lignin under different carbon–oxygen molar ratios (n_c:n_o = 0.5, 0.7, 1.0, 1.2, and 1.5) was studied using a thermogravimetric analyzer and reduction furnace. The results show that the reduction process of iron ore powder with three reducing agents conforms to the D1 model, that is, the kinetic equation is $G\left(\alpha \right)={\alpha }^2$. Under the same carbon–oxygen molar ratio, the activation energy of the iron ore powder reduced by industrial lignin is lower than that of pulverized coal. The activation energy increases first, then decreases and then increases with the increase in the carbon–oxygen molar ratio. When the molar ratio of carbon to oxygen is 1.2, the reaction activation energy is the lowest. At this time, the reaction activation energy of industrial lignin reduction iron ore powder is 14.21 kJ·mol⁻¹, that of Shenmu bituminous coal is 16.81 kJ·mol⁻¹, and that of Lu’an anthracite is 37.13 kJ·mol⁻¹. Full article

Although the hopcalite catalyst, primarily composed of manganese oxide and copper oxide, has been extensively studied for carbon monoxide (CO) elimination, there remains significant potential to optimize its structure and activity. Herein, Cu-doped Mn₃O₂@MnO₂ catalysts featuring highly exposed interfacial regions were prepared. The correlation between interfacial exposure and catalytic activity indicates that the interfacial region serves as the active site for CO catalytic oxidation. The characteristic adsorption of CO by Cu species significantly enhances the catalytic activity of the catalyst. And XPS and ICP-OES analyses reveal that Cu ions coexist in both the interlayer and lattice of δ-MnO₂. Furthermore, XPS analysis was employed to quantify the average oxidation state (AOS) of Mn and the molar ratios of oxygen species, demonstrating that both surface-adsorbed oxygen and surface lattice oxygen act as reactive oxygen species in the catalytic reaction, playing a crucial role in CO oxidation. Notably, the surface reactive oxygen species influence the adsorption of CO onto Cu species, and the replenishment of these reactive species is identified as the rate-limiting step in the CO catalytic oxidation process. Full article

Electrocatalytic water splitting is a promising approach for obtaining clean hydrogen energy. In this work, novel molybdate@carbon paper composite electrocatalysts (CoxFe10-xMoO@CP), displaying outstanding electrocatalytic capabilities, were deriving from anchoring cobalt/iron molybdate materials onto the surface of carbon paper fibers. By adjusting the cobalt-to-iron ratio, the composite (Co5Fe5MoO@CP), with the optimal molar proportion (Co/Fe = 5/5), exhibited a distinctive nanoflower morphology (50–100 nm), which provided a significant number of active sites for electrocatalytic reactions, and showed the strongest electrocatalytic potency for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Specifically, the overpotentials for HER and OER were 123.6 and 245 mV at 10 mA·cm⁻², with a Tafel slope of 78.3 and 92.2 mV·dec⁻¹, respectively. The hydrogen and oxygen evolution reactions remained favorable and stable over 35 days and 2 weeks of cyclic voltammetry cycles. In a two-electrode system, efficient overall water splitting was achieved at a cell voltage of 1.60 V. Under high alkaline concentration and temperature conditions, the Co5Fe5MoO@CP composite still maintained excellent HER and OER catalytic activity and stability, indicating its satisfactory potential for industrial applications. Density functional theory (DFT) analysis revealed that the promoted hydrogen evolution capability derived from the synergistic catalytic effect of iron and cobalt atoms within the molecule, while cobalt atoms functioned as the catalytic core for the oxygen evolution process. This work provides a novel strategy towards high-efficiency electrocatalysts to significantly accelerate the overall water splitting. Full article

The chemical-looping reforming (CLR) of methane for hydrogen production employs a solid oxygen carrier (OC) and combines endothermic and exothermic stages, allowing for potential autothermal operation. This study conducted a thermodynamic analysis using Gibbs free energy minimization and energy balances to assess the behavior of WO₃, MnWO₄, and NiWO₄ as OCs in the CLR process. The effects of CH₄:OC ratios and reactor temperatures on equilibrium composition and the energy performance were examined. The results demonstrated that elevated reduction temperatures promote OC conversion and the formation of more reduced solid products. Molar ratios above stoichiometric prevent carbon formation, whereas stoichiometric ratios result in higher H₂ yield, achieving 98% at 1000 °C. However, these conditions do not support autothermal operation, which requires CH₄:OC molar ratios above stoichiometric. Additionally, lower oxidation temperatures are preferred regardless of the OC, due to the lower heat needed to preheat the air, which has a greater effect on the net heat. For the reduction temperature, its effect depends on the type of OC analyzed. The maximum H₂ yield obtained under autothermal operation was 88% for the three OCs, at 875 °C for MnWO₄ and 775 °C for both WO₃ and NiWO₄. Full article

The study conducted isothermal tests for biochar-based N-absorption reaction in Chemical Looping Ammonia Generation to investigate the factors affecting biochar conversion, the kinetic model, and the reaction mechanism. The results show that the N₂ gas flows had little effect on biochar conversion. Raising the reaction temperature and the molar ratio of α-Al₂O₃ to C enhanced the conversion of biochar. When the N₂ flow rate was set to 200 mL/min, the reaction temperature to 1600 °C, and the α-Al₂O₃/C molar ratio to 3:3, the biochar conversion reached its peak at 95.45%. After evaluating several kinetic models, the D₁ diffusion model was found to provide the closest match to the biochar conversion. The activation energy decreased from 241.91 kJ/mol at a 1:3 α-Al₂O₃/C molar ratio to 146.77 kJ/mol at a 3:3 ratio with an increasing α-Al₂O₃/C molar ratio. The biochar’s high specific surface area and abundant pore structure facilitated a rapid reaction between carbon and oxygen on the carbon surface. Additionally, the diffusion of oxygen produced during the decomposition of α-Al₂O₃ became the limiting factor in the N-absorption reaction. Full article

Challenges in the treatment and removal of recalcitrant emerging organic pollutants in wastewater prompt the development of advanced oxidative processes (AOPs). Hydroxyl radicals are non-specific and capable of reacting with a diverse range of pollutants of emerging concern. In this study, hydroxychloroquine (HCQ) was removed from aqueous solutions with removal efficiencies between 80 and 90%. The presence of H₂O₂, humic acid, and other inorganic ions negatively influenced the degradation efficiency. However, the presence of S₂O₈²⁻ was found to increase the removal efficiency, which was attributed to the formation of SO₄^•− in addition to •OH radicals. Additionally, Fenton-assisted electron beam treatment showed an improved removal of 2.88 × 10⁻⁴ M of HCQ with an average improvement of ≈10% at doses between 0.5 to 2.0 kGy in addition to the total organic carbon and chemical oxygen demand reduction. The H₂O₂ concentration and molar ratio of H₂O₂: Fe²⁺ influenced the removal capacity of the Fenton-assisted electron beam process. A degradation mechanism for HCQ has been proposed based on the reactions of •OH radicals and e_aq⁻. Full article

A series of bimetallic Ni_xCu_y catalysts with different metal molar ratios, supported on nitric acid modified rice husk-based porous carbon (RHPC), were prepared using a simple impregnation method for the liquid-phase hydrogenation of furfural (FFA) to tetrahydrofurfuryl alcohol (THFA). The Ni₂Cu₁/RHPC catalyst, with an average metal particle size of 9.3 nm, exhibits excellent catalytic performance for the selective hydrogenation of FFA to THFA. The 100% conversion of FFA and the 99% selectivity to THFA were obtained under mild reaction conditions (50 °C, 1 MPa, 1 h), using water as a green reaction solvent. The synergistic effect of NiCu alloy ensures the high catalytic activity. The acid sites and oxygen-containing functional groups on the surface of the modified RHPC can enhance the selectivity of THFA. The Ni₂Cu₁/RHPC catalyst offers good cyclability and regenerability. The current work proposes a simple method for preparing an NiCu bimetallic catalyst. The catalyst exhibits excellent performance in the catalytic hydrogenation of furfural to tetrahydrofurfuryl alcohol, which broadens the application of non-noble metal bimetallic nanocatalysts in the catalytic hydrogenation of furfural. Full article

The electrocatalytic oxygen evolution reaction (OER) is an arduous step in water splitting due to its slow reaction rate and large overpotential. Herein, we synthesized glycerate-anion-intercalated nickel–iron glycerates (NiFeGs) using a one-step solvothermal reaction. We designed various NiFeGs by tuning the molar ratio between Ni and Fe to obtain Ni₄Fe₁G, Ni₃Fe₁G, Ni₃Fe₂G, and Ni₁Fe₁G, which we tested for their OER performance. We initially analyzed the catalytic performance of powder samples immobilized on glassy carbon electrodes using a binder. Ni₃Fe₂G outperformed the other NiFeG compositions, including NiFe layered double hydroxide (LDH). It exhibited an overpotential of 320 mV at a current density of 10 mA cm^–2 in an electrolytic solution of pH 14. We then synthesized carbon paper (CP)-modified Ni₃Fe₂G as a self-supported electrode (Ni₃Fe₂G/CP), and it exhibited a high current density (100 mA cm⁻²) at a low overpotential of 300 mV. The redox peak analysis for the NiFeGs revealed that the initial step of the OER is the formation of γ-NiOOH, which was further confirmed by a post-Raman analysis. We extensively analyzed the catalyst’s stability and lifetime, the nature of the active sites, and the role of the Fe content to enhance the OER performance. This work may provide the motivation to study metal-alkoxide-based efficient OER electrocatalysts that can be used for alkaline water electrolyzer applications. Full article

In this research, a new catalyst for activating persulfate was developed by loading iron and nickel ions onto powdered activated carbon (PAC) for treating methyl orange, and the preparation process was optimized and characterized. The efficacy of the treatment was evaluated using the Chemical Oxygen Demand (COD) removal rate, which reflects the impact of various process parameters, including catalyst dosage, sodium persulfate dosage, and reaction pH. Finally, the recovery and reuse performance of the catalyst were studied. The optimal conditions for preparing the activated sodium persulfate catalyst were determined to be as follows: a molar ratio of Fe³⁺ and Fe²⁺ to Ni of 4:1, a mass ratio of Fe₃O₄ to PAC of 1:4, a calcination temperature of 700 °C, and a calcination time of 4 h. This preparation led to an increase in surface porosity and the formation of a hollow structure within the catalyst. The active material on the surface was identified as nickel ferrite, comprising the elements C, O, Fe, and Ni. The magnetic property is beneficial to recycling. With the increase in catalyst and sodium persulfate dosage, the COD removal efficiency of the oxidation system increased first, and then, decreased. The catalyst showed good catalytic performance when the pH value was in the range of 3~11. Furthermore, Gas Chromatography–Mass Spectrometry (GC-MS) analysis indicated the complete oxidation of methyl orange dye molecules in the system. This result highlights the important role of the newly developed catalyst in activating persulfate. Full article

This work presents a biological remediation process for molybdenum-bearing wastewater which may lead to the fabrication of biogenic Mo chalcogenide particles with (photo)catalytic properties. The process is based on dissimilatory sulphate reduction, utilising sulphate-reducing bacteria (SRB), and reductive precipitation of molybdate which is the predominant species of molybdenum in oxygenated water/wastewater. The SRB culture was established in a biofilm reactor which was fed with synthetic solutions containing sulphate (17.7 mM), molybdate molybdenum (2 mM), divalent iron (1.7 mM) and ethanol as the carbon/electron donor. The performance of the bioreactor was monitored in terms of pH, sulphate and molybdenum (Mo(VI) and total) content. The presence of thiomolybdate species was studied by scanning UV-Vis absorbance of samples from the reactor outflow while the reactor precipitates were studied via electron microscopy coupled with energy dispersive spectrometry, X-ray diffractometry and laser light scattering. A molar molybdate/sulphate ratio of 1:12.5 proved effective for molybdate reduction and recovery by 76% in 96 h, whereas sulphate was reduced by 57%. Molybdenum was immobilised in the sulphidic precipitates of the bioreactor, presumably via two principal mechanisms: (i) microbially mediated reduction and precipitation, and (ii) thiomolybdate formation and sorption/incorporation into iron sulphides. Full article