Pechini Sol Gel Research Articles

New NASICON-type phosphates, KNbM(PO4)3 (M = Ti, V), exhibiting a reversible alkali metal intercalation

The NASICON framework is an attractive object for designing polyanion electrode materials for metal-ion batteries. Two new NASICON-structured (S.G. R-3c) niobium phosphates KNbTi(PO4)3 (a = 8.4307(1) Å, c = 23.3955(4) Å, V = 1440.11(5) Å3) and KNbV(PO4)3 (a = 8.4892(1) Å, c = 23.3042(4) Å, V = 1454.45(3) Å3) were synthesized by the Pechini sol–gel method. Rietveld refinement revealed the potassium atoms occupy only the A(1) 6-fold antiprismatic site in both structures. Nb K-edge XANES measurements confirmed the presence of Nb5+ in KNbV(PO4)3 and the mixed-valent Nb5+/4+ in KNbTi(PO4)3 phosphates. Electrochemical measurements showed that both compounds deliver the initial discharge capacity of 110–120 mAh g−1 at a C/10 rate in the Na-half cell. KNbV(PO4)3 also maintains a reversible K+ intercalation at about 1.5 V vs. K+/K with a significant hysteresis (∼0.35 V at a C/10 rate) indicating a sluggish K+ diffusion. The mobility of alkali metal ions within the framework of new phosphates is discussed in terms of bond valence site energy calculations.

Facile synthesis of novel nanocomposite composed of Co3O4, MgO, and Mg3B2O6 for malachite green dye decontamination from aqueous media

Malachite green is a hazardous chemical that poses serious threats to aquatic ecosystems due to its toxicity and persistence in the environment. Additionally, it is harmful to human health, recognized as a carcinogenic and mutagenic agent that can cause long-term adverse effects. Hence, in this study, malachite green dye was efficiently removed from aqueous media using Co3O4/MgO/Mg3B2O6 novel nanocomposites, known as CBM600 and CBM800. The CBM600 and CBM800 nanocomposites were facilely fabricated through the Pechini sol-gel procedure at 600 and 800 °C, respectively. Besides, X-ray diffraction analysis showed their crystalline structures, including Co3O4 and MgO in cubic systems, and Mg3B2O6 in an orthorhombic system. For the CBM600 and CBM800 nanocomposites, the average crystal sizes are 40.76 nm and 57.43 nm, with BET surface areas of 74.25 m2/g and 57.59 m2/g, respectively. The highest uptake capacities for malachite green dye by the CBM600 and CBM800 nanocomposites are 492.61 mg/g and 440.53 mg/g, respectively. The pseudo-second-order model and Langmuir isotherm were the best fits for the adsorption data. Also, the uptake of malachite green dye by the CBM600 and CBM800 nanocomposites is spontaneous, physical, and exothermic. The nanocomposites were regenerated using 6 M HCl and repeatedly used to remove malachite green dye with very small loss in efficiency, demonstrating their robust reusability.

Optical investigation of Dy3+/ Eu3+ co-activated K2NaAlF6 fluorophosphor for color tunable lighting system: Structural analysis and warm light generation

Nowadays, research is mostly focused on developing luminous materials. Specifically, compounds based on inorganic phosphorus have found widespread use in a variety of applications, like radiation dosimetry, field emission displays (FEDs), cathode ray tubes (CRTs), lamp industries, and white light emitting diodes (WLEDs). In order to achieve white light emission, we successfully synthesized single-host K2NaAlF6 co-doped with Dy3+/Eu3+ in this study utilizing the pechini sol-gel approach. Under UV light, the synthesized samples' luminescence characteristics were examined. XRD analysis verified K2NaAlF6's phase purity. The phosphor materials have a tendency to aggregate, as seen by SEM pictures. The K2NaAlF6:Dy3+ doped phosphors showed good excitation at 349 nm in photoluminescence (PL) experiments, with strong emission bands at 489 nm (blue) and 576 nm (yellow). Strong orange emissions were seen for K2NaAlF6: Eu3+ doped phosphors at 595 nm and 614 nm, which correspond to the 5D0→7F1 and 5D0→7F2 transitions in Eu3+ ions. When these rare earths were co-doped, intense red, yellow, and blue emissions were produced. The Commission Internationale de l'Eclairage (CIE) coordinates were used to calculate the colour characteristics of the luminous produced samples. Consequently, these results imply that Dy3+/Eu3+ co-doped K2NaAlF6 phosphors, when stimulated by UV LEDs, could be appropriate for creating reddish-orange and warm white lighting systems.

Modification of nickel ferrite nanoparticles by sodium docusate surfactant for superior crystal violet dye removal from aqueous solutions

In this study, nickel ferrite (NiFe2O4) nanoparticles were synthesized using the Pechini sol-gel method and modified with sodium docusate surfactant. The modified nanoparticles showed an enhanced adsorption capacity of 384.62 mg/g for crystal violet dye, compared to 237.53 mg/g for unmodified NiFe2O4. Characterization was performed using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and scanning electron microscopy (SEM) techniques. The adsorption process was spontaneous, exothermic, and followed the Langmuir isotherm and pseudo-second-order kinetic model. Optimal conditions for maximum dye removal were achieved at pH 10, 50 min, and 298 K. Additionally, the synthesized adsorbents demonstrated excellent regeneration and reusability over five adsorption-desorption cycles with minimal efficiency loss.

Efficient removal of basic yellow 28 dye from water using facilely synthesized ZnO and Mg3B2O6 nanostructures

Basic yellow 28 dye, used extensively in the textile and leather industries, poses significant environmental and health risks, including allergic reactions, skin irritation, and respiratory problems. This study reports the Pechini sol-gel synthesis of novel ZnO/Mg3B2O6 nanostructures for the decontamination of basic yellow 28 dye from aqueous solutions. The nanostructures were synthesized by calcining at 650 and 850 °C for 5 h, producing ZM650 and ZM850, respectively. The average crystallite sizes were 39.28 nm for ZM650 and 51.03 nm for ZM850. BET surface areas were 70.71 m2/g for ZM650 and 48.13 m2/g for ZM850. FE-SEM and HR-TEM analyses revealed distinct morphological structures, with ZM650 exhibiting a dense aggregation of rod-like particles and ZM850 showing larger clusters. The maximum adsorption capacities were 381.68 mg/g for ZM650 and 303.03 mg/g for ZM850. The optimum adsorption was observed at a pH of 10, a contact time of 70 min, and a temperature of 298 K. Regeneration using a 6 M HCl solution demonstrated efficient reusability over five cycles. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm, indicating monolayer adsorption. Also, the adsorption process was found to be physical and exothermic.

Fe2O3-Co3O4 nanocomposite gas sensor for ethanol sensing studies

This study focused on pristine Fe2O3, pristine Co3O4, and Fe2O3-Co3O4 composite using the Pechini sol-gel method for ethanol gas sensing applications. Advanced characterization techniques were used to analyze the phase, morphology, and composition of the synthesized materials. Gas sensors were then fabricated and used for ethanol gas sensing at different temperatures. The results indicated that Fe2O3-Co3O4 composite gas sensor crystallized at 600 °C, had higher response compared to both pristine Fe2O3 and pristine Co3O4 gas sensors. The composite sensor manifested a high response of 26.2–100 ppm ethanol at 250 °C, while maximum responses of pristine Co3O4 gas sensor was only 4.4 at 200 °C and that of pristine Fe2O3 sensor was 11.4 at 300 °C. The boosted sensing performance of the composite sensor was related to the formation of p-n heterojunctions between Co3O4 and Fe2O3 in composite sensor, the formation of dangling bonds at interfaces, and high intrinsic ethanol sensing properties of Fe2O3.

Study of thermal behavior and crystallization kinetics of glass microspheres in the Y3Al5O12-Al2O3 system

Five types of glass microspheres with alumina and 40–80 mol.% Y3Al5O12 were prepared using solgel Pechini and flame synthesis techniques. Glass thermal behavior was analyzed using DSC/TG, XRD and SEM, and the JMAK model was applied to study crystallization kinetics and determine prevailing mechanisms. All samples, except the one with 80 mol.% YAG, had two exothermic effects in their DSC curves. The first appeared between 937 and 950 °C, while the second was observed between 958 and 1102 °C. XRD analysis of crystallized microspheres confirmed the presence of YAG and various forms of alumina phases in the samples with lower YAG/higher Al2O3 content (40 and 50 mol.%). The sample with the highest YAG content showed the strongest tendency to crystallize in the kinetics study. The value of apparent activation energy (Eapp) of this sample was 987.3 ± 13.0 kJ mol−1. For the remaining samples, the values of Eapp were higher and ranged from 1215.1 ± 10.6 to 1847.5 ± 9.3 kJ mol−1, indicating the lowest ability of these compositions to crystallization. The growth of three-dimensional (3-D) YAG crystals was predominant in glasses with the highest (80 mol.%) YAG content. One-dimensional (1-D) growth of γ-Al2O3 crystals and 3-D growth of YAG crystals was predominant in glasses with the lowest (40 mol.%) YAG content.

Simplified synthesis and identification of novel nanostructures consisting of cobalt borate and cobalt oxide for crystal violet dye removal from aquatic environments

Crystal violet dye poses significant health risks to humans, including carcinogenic and mutagenic effects, as well as environmental hazards due to its persistence and toxicity in aquatic ecosystems. This study focuses on the efficient removal of crystal violet dye from aqueous media using novel Co3O4/Co3(BO3)2 nanostructures synthesized via the Pechini sol–gel approach. The nanostructures, which were abbreviated to EN600 and EN800, were fabricated at calcination temperatures of 600 and 800 °C, respectively. X-ray diffraction (XRD) analysis revealed that the synthesized samples have a cubic Co3O4 phase and an orthorhombic Co3(BO3)2 phase, with mean crystal sizes of 43.82 nm and 52.93 nm for EN600 and EN800 samples, respectively. The Brunauer–Emmett–Teller (BET) surface areas of EN600 and EN800 samples were 65.80 and 43.76 m2/g, respectively, indicating a significant surface area available for adsorption. Optimal removal of crystal violet dye was achieved at a temperature of 298 K, a contact time of 70 min, and a pH of 10. The maximum adsorption capacities were found to be 284.09 mg/g for EN600 and 256.41 mg/g for EN800, which are notably higher compared to many conventional adsorbents. The adsorption process followed the pseudo-second-order kinetic model and fitted well with the Langmuir isotherm. The adsorption was exothermic, spontaneous, and physical in nature. Moreover, the adsorbents exhibited excellent reusability, retaining high efficiency after multiple regeneration cycles using 6 mol/L hydrochloric acid. These findings highlight the potential of these Co3O4/Co3(BO3)2 nanostructures as effective and sustainable materials for water purification applications.

Enhanced Removal of Cd(II) Ions from Aqueous Media via Adsorption on Facilely Synthesized Copper Ferrite Nanoparticles.

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.

Efficient Removal of Methylene Blue Dye from Aqueous Media Using Facilely Synthesized Magnesium Borate/Magnesium Oxide Nanostructures.

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.

Photodegradation, kinetics and non-linear error functions of methylene blue dye using SrZrO3 perovskite photocatalyst

The degradation of methylene blue dye-contaminated wastewater via photocatalysis is an efficient approach towards environmental remediation. The SrZrO3 perovskite photocatalyst was synthesized using the modified Pechini sol-gel method, and characterized using XRD, FESEM, FTIR, and UV–visible spectrophotometer. Crystallite size obtained by the Scherrer and Williamson-Hall methods were 45.56 and 44.50 nm, respectively. The sample exhibited an orthorhombic crystal structure. The optical bandgap was estimated to be 5.31 eV. Kinetic study for the degradation of methylene blue dye using SrZrO3 in the presence of H2O2 showed complete decontamination of the methylene blue dye in the time interval of 90–120 min under visible light irradiation. The degradation efficiency was above 80.1 % under illumination and less than 40.1 % in dark. Kinetic studies were performed by varying the dose of photocatalyst and initial concentration of methylene blue. It was observed that higher dose of the photocatalyst and lower concentration of the contaminant produced higher rate of degradation. The solution pH 3 and catalysts dosage of 200 mg yielded the highest rate of degradation. The experimental data fitted best into the Psuedosecond order kinetic model with the highest R2 value, indicating a strong linear relationship. The experimental data was subjected into nonlinear error functions, where the Psuedo-second order kinetic model demonstrated lower values of error functions. The results suggest that the prepared SrZrO3 photocatalyst coupled H2O2 is a promising photocatalyst for the decontamination of methylene blue dye under visible light irradiation.

In-situ synthesis of samarium activated MgO–LaAlO3 nanocomposite for enhanced and prolonged phosphorescence

A series of MgO–La1-xAlO3:xSm (x = 0–5 mol.%) nanocomposite phosphors have been synthesized in-situ using Pechini sol-gel method. The rhombohedral and face-centered crystal structures of LaAlO3 and MgO, respectively, were corroborated utilizing X-Ray Diffractograms and their Rietveld refinement. The optical band gaps of these nanocomposites have been observed in the range of 5.20–5.63 eV. Upon excitation by n-UV 405 nm radiation, the emission characteristics of these phosphors spanning 450–750 nm have been thoroughly investigated. The most notable emission occurred at 599 nm in the orange region, confirmed by CIE-1931 chromaticity coordinates. The MgO–La1-xAlO3:xSm (x = 2 mol.%) is found to be the optimum concentration exhibiting maximum luminescence with a high color purity of 90 %. Insights from Riesfeld's theory pointed towards d-q multipolar interactions as the underlying mechanism behind concentration quenching observed beyond this optimum concentration. Bi-exponential decay behavior was observed via Time-Resolved Photoluminescence (TRPL) technique, with an Internal Quantum Efficiency of 63 % calculated utilizing Auzel's formalism. The study extensively explored the impact of MgO addition on the crystallite size, band-gap, luminescence, and life-time properties, attributing the enhanced and prolonged luminescence behavior to the MgO–La1-xAlO3:xSm (x = 2 mol.%) nanocomposite. Assessment of additional parameters such as CCT (Correlated Color Temperature) and energy transfer efficiencies further reinforced the suitability of these orange emissive phosphors for potential applications in photonics and forensics, underlining their promising prospects in various technological domains.

Effect of rare earth substitution on magnetic properties of strontium hexaferrite prepared by Pechini method

This study presents a comprehensive investigation into the impact of substituting rare earth elements on the magnetic properties of strontium hexaferrite. The samples, synthesized by the sol-gel Pechini method, followed the formula Sr1-xRexFe12O19 with Re = Gd, Sm, Nd, Pr, and La, for 0.025 ≤ x ≤ 0.100. The findings revealed that Re substitution promotes a considerable increment of the coercive field. However, the magnetic yield dropped with increasing the Re content. Therefore, the higher coercivity field, largest magnetization and maximum energy product (BHmax) were reached for samples with x = 0.025. This tendency was consistent across all rare earth-substituted samples although the hexaferrite substituted with samarium and praseodymium showed the strongest hard-magnetic properties. This behavior has been attributed to a reduction of the interaction field due to the emergence of a monodomain structure, and to the limited solubility of rare earth elements within the structure of strontium hexaferrite.

Functionalization of Strontium Ferrite Nanoparticles with Novel Chitosan–Schiff Base Ligand for Efficient Removal of Pb(II) Ions from Aqueous Media

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.

Temperature sensing by means of a near-infrared luminescent Ca8NaBi(PO4)6F2:Nd3+ fluorapatite phosphor

Microrods of calcium sodium bismuth fluorapatite doped with neodymium, denoted as Ca8NaBi1-xNdx(PO4)6F2 (with x ranging from 0 to 0.5), were synthetized using a modified Pechini sol–gel method. The crystalline structure of these phosphors was refined using the Rietveld method and exhibited hexagonal symmetry with space group P63/m—C26h, where the lattice parameters were a = 9.3855(5) Å and c = 6.8998(6) Å for x = 0.2. The particles morphology was analyzed through SEM, revealing an average length of approximately 1.5 µm. When excited at 808 nm, the Ca8NaBi(PO4)6F2:0.2Nd3+ microrods emitted strongly at 872, 957 and 1055 nm, falling within the near-infrared region. These emissions correspond to the 4F3/2 → 4I9/2 (P2), 4F5/2 → 4I11/2(P3), 4F3/2 → 4I11/2(P1) transitions of Nd3+ ions, respectively, and are situated within the first and second biological windows. The luminescence lifetime of the 4F3/2 state of Nd3+ was measured to be 294.4 µs for the sample with the lowest Nd3+ concentration of x = 0.05. In addition, the luminescence intensity ratios P2/P1 and P3/P1 were found to be temperature dependent, potentially making it suitable for luminescent ratiometric thermal sensing. These findings suggest that the synthesized Ca8NaBi(PO4)6F2:Nd3+ microrod thermometers exhibit favorable characteristics in terms of relative sensitivity, temperature uncertainty, and repeatability within the temperature range of 303–403 K.

Sol-gel Pechini preparation of CuEr2TiO6 nanoparticles as highly efficient photocatalyst for visible light degradation of acid red 88

This study reports preparation of CuEr2TiO6 nanoparticles using Pechini sol-gel method. The characterization of nanoparticles was carried out using FESEM, EDX, XRD, PL, DRS, Raman, and FTIR. DRS analysis shows that the prepared nanoparticles can serve as an effective visible light photocatalyst. Photocatalytic activity of the prepared nanoparticles was investigated toward degradation of aqueous solution of acid red 88 (AR88) under visible light irradiation. The highest photoactivity (91.2 %) was achieved after 150 min illumination using 40 mg of the photocatalyst. Effect of some contributing factors was studied on degradation rate of AR 88, including amount of photocatalyst and H2O2 concentration. Also, in order to examine stability of the prepared nanoparticles for long-time applications, the recyclability experiments were conducted at 7 successive reaction cycles which confirm the great stability of the prepared nanoparticles. Also, radical scavenging experiments reveal that the dominant species in photocatalytic reactions are hydroxyl radicals.

Cu-doped LaFe1-xCuxO3 perovskites nano-crystallites for enhanced VOCs detection

Highly sensitive, and versatile metal oxide semiconductors, including perovskites, are used in gas sensors for environmental, and safety applications. This study described the substitution of Cu for Fe in LaFe1-xCuxO3 nanostructured perovskites, denoted as Cx’s, using Pechini sol-gel method at 600 °C, to detect the volatile organic compounds (VOCs). Characterization techniques, including TGA/DTA, XRD, BET, FE-SEM/EDS, Raman, PL, XPS, UV-DRS, FTIR, TPD-O2 and ethanol chemisorption showed significant enhancements in physicochemical, and gas sensing properties of LaFeO3 perovskites, upon copper doping in its structure. The responses to ethanol improved, the average crystallite and nanoparticle sizes decreased, and the electrical conductivity increased as the perovskite copper content increased to x = 0.6. The crystallite size of 20.5 nm for LaFeO3 decreased to 12.7 nm for LaFe0.4Cu0.6O3. The SC0.6 thick film gas sensor showed high potential in the VOCs detection, with best responses of 17 for ethanol, 18 for acetone, and 16 for acetaldehyde when exposed to each of 300 ppm at 300 °C. At these conditions, the response and recovery times of highly stable SC0.6 sensor for ethanol gas were 4 and 11 min, respectively.

CO2 capture and methanation using Ru/Na2O/Al2O3 dual-function materials: Effect of support synthesis method and Ru load

Ru/Na2O/Al2O3 dual-function materials were prepared by varying the support synthesis method and Ru load. Different sol-gel-type and precipitation/ hydrothermal preparation methods were employed in order to synthesize materials with variable nanostructure, surface chemistry and textural properties, thereby effectively tuning the material activity for the methanation of pre-adsorbed CO2. The materials were thoroughly characterized and evaluated during the integrated CO2 capture and methanation process. It was found that the Pechini sol-gel synthesis method led to the structure with the highest porosity, basic site population and high dispersion of methanation and adsorption active Ru0 and Al-O--Na+ sites. The corresponding material displayed the highest CH4 yield (0.47 mmol/g) and fastest CH4 production kinetics, while stable performance was achieved under successive adsorption-hydrogenation cycles and under the co-presence of O2 and H2O during CO2 adsorption. Lastly, the increase in Ru load (0.25 wt% - 4 wt% range) could incrementally improve the CH4 production kinetics during hydrogenation.

Synthesis of nano-crystalline K2NiF4-type phases La1+xSr1-xCoO4 (x = 0.0, 0.2, and 0.5): Effect of mixed valence state of Co on structural, magnetic and photocatalytic properties

A lot of work has already been reported on bulk K2NiF4-type layered perovskite oxides but hardly is known about their nano-crystalline state as they are generally prepared at high temperatures. In this connection, we have synthesized nanocrystalline La1+xSr1-xCoO4 layered perovskites oxides via sol-gel Pechini method. Efforts were also done to synthesize phases with x > 0.5 but remained unsuccessful. The Rietveld refinement investigation has confirmed the successful formation of single-phase compounds that crystallize in the I4/mmm space group with tetragonal symmetry. The X-ray photoelectron spectroscopy (XPS) analysis revealed that Co in La1+xSr1-xCoO4 has mixed valence states of +2 and + 3. Dominant anti-ferromagnetic (AFM) super-exchange Co2+―O―Co2+ and Co3+―O―Co3+ interactions were observed in all the synthesized nanophases and the existence of weak ferromagnetic (FM) interactions due to the generation of double-exchange Co2+―O―Co3+ interaction because of mixed valent state of Co. The increase in Néel temperature (TN) values with La doping has been attributed by the increased prevalence of anti-ferromagnetic (AFM) super-exchange Co2+―O―Co2+ and Co3+―O―Co3+ interactions. The band gap energy values (Eg) for all the prepared nano samples vary from 1.57 to 1.64 eV, rendering them highly competent catalysts for degradation of dyes. Additionally, the photocatalytic performance of the prepared nano photocatalysts was evaluated using cationic (MB & RhB) and anionic (MO) dye contaminants as well as their ternary mixture. LaSrCoO4 photocatalyst has been found to efficiently and swiftly degrade all three dye pollutants separately as well as in mixtures, with outstanding recyclability and durability. It has been observed that the x = 0.0 photocatalyst showed best degradation efficacy for RhB dye, i.e., ∼99 % in 100 min, compared to ∼91 % and ∼84 % for the x = 0.2 and 0.5 photocatalysts in the same time interval, respectively. These results suggest that LaSrCoO4 nano powder can be considered a promising photocatalyst in the dyes degradation.

Calcium Ferrite Nanoparticles: A Simple Synthesis Approach for the Effective Disposal of Congo Red Dye from Aqueous Environments

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.