Search Results (76)

The development of dye-sensitized solar cells (DSSCs) has gained prominence as an economical alternative for photovoltaic energy conversion. This work investigates the synthesis of niobium pentoxide (Nb₂O₅) by the Pechini method, followed by calcination at different temperatures (500 °C, 600 °C and 700 °C) to evaluate its structural, morphological, and electrochemical properties as a photoanode material in DSSCs. SEM and XRD analyses revealed that calcination at 600 °C produced a material with optimized particle size (642.17 ± 37 nm) and adequate crystalline structure, favoring dye adsorption and electronic transport. Electrochemical characterization, including open-circuit potential and impedance spectroscopy, indicated that the sample at 600 °C presented superior photovoltaic performance, achieving a power conversion efficiency of 1.39% and electron lifetime equal to 0.159 s. These findings suggest that Nb₂O₅, under controlled calcination conditions, may act as a promising alternative to TiO₂ substitution in DSSC applications. Full article

Crystal violet dye poses significant environmental and human health risks due to its toxicity, persistence, and bioaccumulative nature. It contributes to potential carcinogenicity, cytotoxicity, and systemic toxicity upon human exposure. To address this issue, a novel SrCO₃/MgO/CaO/CaCO₃ nanocomposite was synthesized using the Pechini sol-gel method, producing AE500 and AE700 at 500 and 700 °C, respectively, for the efficient removal of crystal violet dye from aqueous media. X-ray diffraction (XRD) analysis confirmed the formation of crystalline phases, with average crystallite sizes of 64.53 nm for AE500 and 75.34 nm for AE700. Energy-dispersive X-ray spectroscopy (EDX) revealed elemental compositions with variations in carbon, oxygen, magnesium, calcium, and strontium percentages influenced by synthesis temperature. Field-emission scanning electron microscopy (FE-SEM) showed morphological differences, where AE500 had irregular polyhedral structures, while AE700 exhibited more compact spherical formations, with average grain sizes of 99.98 and 132.23 nm, respectively. High-resolution transmission electron microscopy (HR-TEM) confirmed the structural integrity and nano-scale morphology, showing aggregated irregularly shaped particles in AE500, while AE700 displayed well-defined polyhedral and nearly spherical nanoparticles. The calculated average particle diameters were 21.67 nm for AE500 and 41.19 nm for AE700, demonstrating an increase in particle size with temperature. Adsorption studies demonstrated maximum capacities of 230.41 mg/g for AE500 and 189.39 mg/g for AE700. The adsorption process was exothermic, spontaneous, and physical, following the pseudo-first-order kinetic model and Langmuir isotherm, indicating monolayer adsorption onto a homogenous surface. Full article

Excessive levels of Zn(II) ions in aquatic environments pose significant risks to both ecosystems and human health. In aquatic systems, Zn(II) ions disrupt metabolic functions in organisms, leading to toxicity and bioaccumulation. For humans, prolonged exposure can result in gastrointestinal distress, immune system dysfunction, and neurological complications, necessitating effective removal strategies. This study reports the synthesis and characterization of CoFe-MgO-C-M600 (CoFe₂O₄@MgO@(Mg_0.23Co_0.77)(Mg_0.35Co_1.65)O₄@C) and CoFe-MgO-C-M800 (CoFe₂O₄@MgO@C) nanocomposites for the efficient removal of Zn(II) ions from aqueous media. The nanocomposites were synthesized using the Pechini sol-gel method and characterized through X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscopy (HR-TEM). XRD analysis confirmed the crystalline structure of both nanocomposites, with CoFe-MgO-C-M600 exhibiting a smaller average crystallite size (38.67 nm) than CoFe-MgO-C-M800 (75.48 nm). EDX results verified the elemental composition of the nanocomposites, ensuring the successful incorporation of key elements. FE-SEM analysis revealed significant morphological differences, with CoFe-MgO-C-M600 displaying smaller and more uniform grains compared to CoFe-MgO-C-M800. The results show that CoFe-MgO-C-M600 possesses a highly porous and interconnected structure, enhancing its surface area and adsorption potential. In contrast, CoFe-MgO-C-M800 demonstrates larger and more compact grains, which may affect its adsorption performance. HR-TEM further confirmed these findings, demonstrating that CoFe-MgO-C-M600 had a smaller average particle diameter (35.45 nm) than CoFe-MgO-C-M800 (321.14 nm). Adsorption studies indicated that CoFe-MgO-C-M600 and CoFe-MgO-C-M800 achieved maximum adsorption capacities of 276.24 and 200.00 mg/g, respectively. The adsorption process was determined to be exothermic, spontaneous, and physical in nature, following the pseudo-second-order kinetic model and the Langmuir isotherm. Full article

Cd(II) ions pose significant environmental and health threats due to their extreme toxicity, persistence, and bioaccumulation in ecosystems. They are associated with severe health disorders such as bone damage, kidney failure, and carcinogenic effects and disrupt aquatic life by impairing enzymatic and reproductive processes. In this research, novel Fe_0.65Mg_0.35Cr₂O₄@C nanocomposites, synthesized using the Pechini sol–gel method at 600 °C (F600) and 800 °C (F800), were investigated for their efficacy in removing Cd(II) ions from aqueous media. FE-SEM analysis showed that F600 had agglomerated spherical nanoparticles with an average grain size of 45.71 nm and a relatively porous structure, while F800 displayed denser and more compact spherical nanoparticles with an average grain size of 73.65 nm. HR-TEM images confirmed these findings, showing that F600 nanoparticles were loosely arranged with an average particle diameter of 14.72 nm, whereas F800 exhibited larger, more aggregated particles with an average diameter of 59.22 nm, reflecting enhanced particle coalescence at higher temperatures. EDX analysis confirmed the elemental composition of both samples, with F600 containing higher carbon content (7.0%) compared to F800 (3.4%), attributed to the more complete combustion of organic precursors during F800’s synthesis. This difference in composition, along with the structural variations, influenced their adsorption performance. F600 demonstrated superior adsorption with a maximum capacity of 295.86 mg/g compared to F800’s 185.19 mg/g. Thermodynamic and kinetic analyses confirmed that the adsorption was exothermic, spontaneous, and governed by a physical mechanism following the pseudo-second-order model and Langmuir isotherm. The superior performance of F600 is attributed to its higher surface area, porosity, and smaller particle size, which enhance the availability of active adsorption sites. Full article

A single (Ba_0.85Ca_0.15)(Zr_0.10Ti_0.90)O₃ phase material with a tetragonal structure is processed and synthesized with a modified Pechini method using ethylenediaminetetraacetic acid and glycerol as chelating and esterifying agents, respectively. The complete chemical transformation to the desired phase is achieved at 900 °C, which is 300 °C lower than conventional synthesis methods. Its consolidation, reaching up to 91% relative density, is carried out at 1400 °C. It is clearly demonstrated that the use of ethylenediaminetetraacetic acid and glycerol reagents is particularly beneficial for inducing a homogeneous grain size distribution (10 μm), which leads to very promising electromechanical properties (d₃₃ = 451 pC/N; d₃₁ = 160 pC/N; kp = 0.40; $\epsilon {\prime }_{33}^T$ = 4790 and Q_m = 358) of the densified system. Full article

Kaolin is a common mineral resource that is used commercially. However, when processed, it generates a large amount of waste, usually rich in kaolinite, mica and quartz, which gives rise to the need to manage and reuse these mineral residues, in agreement with the SDG 12/UN (ensuring sustainable consumption and production) requirements. Therefore, this work aims to explore how to add value to this residue via its use as a photocatalytic support for TiO₂, while also meeting the SDG 6 (clean water and sanitization) requirements. After determination of its chemical and mineralogical composition, the residue underwent mineralogical separation, by mechanical stirring and sieving of its aqueous suspension. After separation, TiO₂ was deposited on the quartz fraction of the residue by the modified-Pechini method, using different quartz proportions and at different calcination temperatures. For the deposition of TiO₂ on the mica fraction, the conventional hydrothermal synthesis was used, with 20% of the mica. Each material was tested in a photohydroxilation of terephthalic acid under UV-C irradiation to evaluate the formation of hydroxyl radicals. The results of the photocatalytic tests demonstrated that quartz and mica are inert to photocatalysis but provide an interesting support for TiO₂. The highest photocatalytic efficiency was obtained for the material synthesized at 600 °C with 20% of the quartz. Full article

This article presents the synthesis, electrophysical, and catalytic properties of a La_0.9MnO₃–LaFeO₃ nanocomposite material. The nanocomposite was synthesized via the sol–gel (Pechini) method. X-ray diffraction (XRD) analysis revealed a polycrystalline, biphasic perovskite structure combining both hexagonal and cubic symmetry. The microstructure and elemental composition, examined using field emission scanning electron microscopy (FESEM), indicated an average particle size of approximately 186.9 nm. The composite exhibits semiconducting behavior within the temperature ranges of 293–323 K and 343–393 K. Developing electrocatalysts free of precious metals for the hydrogen evolution reaction (HER) is increasingly important to facilitate the production of hydrogen from renewable sources. In this study, the conductive La_0.9MnO₃–LaFeO₃ composite was deposited on graphite and, for the first time, evaluated as an electrocatalyst for HER in acidic media. The resulting composite films were tested using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in a glassy carbon electrode (GCE) setup, providing insights into their potential as effective, cost-efficient electrocatalysts. Full article

The aim of this work was to verify the possibility of forming Ni-Fe and Co-Fe alloys via topotactic ion exchange exsolution in Fe-infiltrated (La,Sr,Ce)_0.9(Ni,Ti)O_3-δ or (La,Sr,Ce)_0.9(Co,Ti)O_3-δ ceramics. For this purpose, samples were synthesized using the Pechini method and then infiltrated with an iron nitrate solution. The reduction process in dry H₂ forced the topotactic ion exchange exsolution, leading to the formation of additional round-shape structures on the surfaces of grains. EDS scans and XRD analysis confirmed the formation of bimetallic alloys, which suggests that these materials have great potential for further use as anode materials for Solid Oxide Fuel Cells (SOFCs). Full article

In this study, magnetic copper ferrite (CuFe₂O₄) nanoparticles were synthesized via the Pechini sol-gel method and evaluated for the removal of Cd(II) ions from aqueous solutions. PF600 and PF800 refer to the samples that were synthesized at 600 °C and 800 °C, respectively. Comprehensive characterization using FTIR, XRD, FE-SEM, HR-TEM, and EDX confirmed the successful formation of CuFe₂O₄ spinel structures, with crystallite sizes of 22.64 nm (PF600) and 30.13 nm (PF800). FE-SEM analysis revealed particle diameters of 154.98 nm (PF600) and 230.05 nm (PF800), exhibiting spherical and irregular shapes. HR-TEM analysis further confirmed the presence of aggregated nanoparticles with average diameters of 52.26 nm (PF600) and 98.32 nm (PF800). The PF600 and PF800 nanoparticles exhibited exceptional adsorption capacities of 377.36 mg/g and 322.58 mg/g, respectively, significantly outperforming many materials reported in the literature. Adsorption followed the Langmuir isotherm model and pseudo-second-order kinetics, indicating monolayer adsorption and strong physisorption. The process was spontaneous, exothermic, and predominantly physical. Reusability tests demonstrated high adsorption efficiency across multiple cycles when desorbed with a 0.5 M ethylenediaminetetraacetic acid (EDTA) solution, emphasizing the practical applicability of these nanoparticles. The inherent magnetic properties of CuFe₂O₄ facilitated easy separation from the aqueous medium using a magnet, enabling efficient and cost-effective recovery of the adsorbent. These findings highlight the potential of CuFe₂O₄ nanoparticles, particularly PF600, for the effective and sustainable removal of Cd(II) ions from water. Full article

Methylene blue dye in water sources can pose health risks to humans, potentially causing methemoglobinemia, a condition that impairs the blood’s ability to carry oxygen. Hence, the current study investigates the synthesis of novel magnesium borate/magnesium oxide (Mg₃B₂O₆/MgO) nanostructures and their efficiency in removing methylene blue dye from aqueous media. The nanostructures were synthesized using the Pechini sol–gel method, which involves a reaction between magnesium nitrate hexahydrate and boric acid, with citric acid acting as a chelating agent and ethylene glycol as a crosslinker. This method helps in achieving a homogeneous mixture, which, upon calcination at 600 and 800 °C, yields Mg₃B₂O₆/MgO novel nanostructures referred to as MB600 and MB800, respectively. The characterization of these nanostructures involved techniques like X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, N₂ gas analyzer, and field-emission scanning electron microscope (FE-SEM). These analyses confirmed the formation of orthorhombic Mg₃B₂O₆ and cubic MgO phases with distinct features, influenced by the calcination temperature. The mean crystal size of the MB600 and MB800 samples was 64.57 and 79.20 nm, respectively. In addition, the BET surface area of the MB600 and MB800 samples was 74.63 and 64.82 m²/g, respectively. The results indicated that the MB600 sample, with its higher surface area, generally demonstrated better methylene blue dye removal performance (505.05 mg/g) than the MB800 sample (483.09 mg/g). The adsorption process followed the pseudo-second-order model, indicating dependency on available adsorption sites. Also, the adsorption process matched well with the Langmuir isotherm, confirming a homogeneous adsorbent surface. The thermodynamic parameters revealed that the adsorption process was physical, exothermic, and spontaneous. The MB600 and MB800 nanostructures could be effectively regenerated using 6 M HCl and reused across multiple cycles. These findings underscore the potential of these nanostructures as cost-effective and sustainable adsorbents for methylene blue dye removal. Full article

Compared with conventional methane reforming technologies, chemical looping reforming (CLR) has the advantages of self-elimination of coke, a suitable syngas ratio for certain down-stream processes, and a pure H₂ or CO stream. In the reduction step of CLR, methane combustion has to be inhibited, which could be achieved by designing appropriate oxygen carriers and/or optimizing the operating conditions. To gain a further understanding of the combustion reaction, methane oxidation by perovskite (SrFeO_3-δ) at 900 °C and 1 atm in a pulse mode was investigated in this work. The oxygen non-stoichiometry of SrFeO_3-δ prepared by a Pechini-type polymerizable complex method is 0.14 at ambient conditions, and it increases to 0.25 and subsequently to 0.5 when heating from 100 to 900 °C in argon that contains 2 ppmv of molecular oxygen. The activation energies of the first and second transitions are 294 and 177 kJ/mol, respectively. The presence of 0.99 vol.% hydrogen in argon significantly reduces the amount CO₂ produced. At a pulse interval of 10 min, the amount of CO₂ produced in the absence of hydrogen is one order of magnitude greater than that in the presence of hydrogen. In the former case, the amount of CO₂ produced dramatically decreases first and then gradually approaches a constant, and the oxygen species involved in methane combustion can be partially replenished by extending the pulse interval, e.g., 82.5% of this type of oxygen species is replenished when the pulse interval is extended to 60 min. The restored species predominantly originate from those that reside in the surface layer or even in the bulk. Full article

Lead contamination in water poses significant health risks, making its removal imperative. In this study, magnetic strontium ferrite (SrFe₁₂O₁₉) nanoparticles were facilely synthesized by the Pechini sol–gel method and subsequently functionalized with a novel chitosan–Schiff base ligand to obtain a novel inorganic/organic nanocomposite for removing Pb(II) ions from aqueous solutions. The chitosan–Schiff base ligand was synthesized through the reaction of chitosan with 2,4,5-trihydroxybenzaldehyde. The presence of two X-ray diffraction (XRD) peaks at 2Ɵ = 10.5° and 2Ɵ = 20.5°, alongside the characteristic SrFe₁₂O₁₉ peaks, confirmed the functionalization of the nanoparticles with the ligand. Additionally, a significant decrease in the saturation magnetization value from 40.29 emu/g in pure SrFe₁₂O₁₉ nanoparticles to 17.32 emu/g in the nanocomposite further verified the functionalization. The presence of carbon (C) and nitrogen (N) atoms in the energy-dispersive X-ray (EDX) pattern of the nanocomposite, in addition to iron (Fe), strontium (Sr), and oxygen (O), also confirmed the functionalization. The nanocomposite’s maximum adsorption capacity for Pb(II) ions was 390.63 mg/g. Moreover, the adsorption process is endothermic, spontaneous, and chemical, occurring via complexation with -C=N and -OH groups, and it fits well with the Langmuir equilibrium isotherm and the pseudo-second-order kinetic equation. Full article

Congo red dye is classified as a toxic chemical and can be harmful if ingested, inhaled, or in contact with the skin or eyes. It can cause irritation, allergic reactions, and skin sensitization in some individuals. Thus, in this paper, CaFe₂O₄ nanoparticles were produced by a simple Pechini sol-gel approach and used as an adsorbent material for the efficient disposal of Congo red dye from aqueous solutions. The maximum adsorption capacity of the CaFe₂O₄ towards Congo red dye is 318.47 mg/g. Furthermore, the synthesized CaFe₂O₄ nanoparticles exhibit an average crystal size of 24.34 nm. Scanning electron microscopy (SEM) examination showed that the CaFe₂O₄ nanoparticles are basically ball-like particles with a mean grain size of 540.54 nm. Moreover, transmission electron microscopy (TEM) examination showed that the CaFe₂O₄ sample revealed aggregated spherical particles with a mean diameter of 27.48 nm. The Energy-dispersive X-ray spectroscopy (EDS) pattern reveals that the produced CaFe₂O₄ nanoparticles are composed of Ca, Fe, and O elements, with an atomic ratio of 1:2:4 of these elements, respectively. The disposal of Congo red dye by the synthesized CaFe₂O₄ nanoparticles is chemical, spontaneous, exothermic, perfectly aligned with the pseudo-second-order kinetic model, and exhibited excellent conformity with the Langmuir equilibrium isotherm. Full article

Safranine T dye causes health problems such as skin and respiratory irritations. Hence, the safranine T dye was efficiently removed from aqueous media employing a simply synthesized manganese ferrite (MnFe₂O₄) nanoadsorbent. The synthesis of manganese ferrite nanoparticles was carried out by the pechini sol–gel approach using tartaric acid to serve as a chelating agent in addition to 1,2-propanediol to serve as a crosslinker. The TEM analysis showed that the shape of MnFe₂O₄ nanoparticles is semi-spherical, with an average particle size of 19.32 nm that coincides well with that measured from the XRD (18.89 nm). Further, the several factors that influenced the removal process of safranine T dye were examined, such as time, dye concentration, pH, and temperature. The ideal experimental conditions that achieved the highest safranine T dye removal percentage are pH 8, 80 min, and 298 K. The maximum adsorption capacity of MnFe₂O₄ nanoparticles towards safranine T dye equals 334.45 mg/g. The removal process of safranine T dye by manganese ferrite nanoparticles was chemical, exothermic, and well defined through the Langmuir equilibrium sorption isotherm in addition to the pseudo-second-order model. The synthesized manganese ferrite nanoparticles have the ability to be reused many times without losing their efficiency. Full article

Indigo carmine dye falls into the category of toxic chemicals, potentially leading to irritation and allergic reactions in certain individuals. Thus, this study employed the Pechini sol–gel strategy to easily produce CoFe₂O₄ nanoparticles, which serve as an effective adsorbent for the disposal of indigo carmine dye from aqueous solutions. The maximum adsorption capacity of CoFe₂O₄ for indigo carmine dye was determined to be 421.94 mg/g. The synthesized CoFe₂O₄ nanoparticles exhibited an average crystallite size of 18.75 nm. SEM analysis revealed that these nanoparticles were nearly spherical, with an average grain size of 198.32 nm. Additionally, TEM analysis indicated a fully agglomerated spherical morphology for the CoFe₂O₄ sample, with an average diameter of 15.37 nm. The EDS spectrum confirmed that the synthesized CoFe₂O₄ nanoparticles consisted of Co, Fe, and O elements, with respective weight percentages of 17.82%, 49.46%, and 32.72%. The removal of indigo carmine dye by the synthesized CoFe₂O₄ is spontaneous, chemical, exothermic, closely fitting the pseudo-second-order kinetic model, and demonstrating a strong concordance with the Langmuir equilibrium isotherm. Full article