Co-precipitation Method Research Articles

Photoelectric activity evaluation of surface-loaded ferroferric oxide/titanium dioxide composite prepared from ilmenite

This work demonstrates a surface-loaded Fe3O4/TiO2 composite with the magnetic Fe3O4 deposited on the surface of anatase TiO2 nanocrystal which can be directly prepared from the ilmenite using the coprecipitation method. After the acidolysis treatment with the 95% dissolution rate, the ilmenite will be first transformed into H2TiO3 and FeCl2, and the photoactive anatase TiO2 nanocrystals are obtained from the calcined H2TiO3 at 500[Formula: see text]C. Then a surface-loaded Fe3O4/TiO2 composite TF is finally achieved by the coprecipitation method, which is carefully elaborated to balance the magnetism and photoactivity of Fe3O4/TiO2 composite by the optimal contents of Fe3O4 and TiO2. It is encouraging to note that Fe3O4/TiO2 composite TF shows a good comprehensive performance in serial photodegradation experiments of Rhodamine B. The degradation rate of Rhodamine B is more than 99% during 60 min under the irradiation of both xenon lamp and sunlight. During at least six cycles, the composite TF can show stable photocatalytic activity and good durability together with the recovery and recycling potentials by using an external magnet.

Formation of Chemically Complex Intergranular Glass Film: An Effective Strategy to Hinder Grain Coarsening

Thermally driven grain coarsening is a commonly encountered issue in nanocrystalline ceramics, particularly in high‐temperature environments. The intergranular glass film (IGF) constitutes a crucial component of most ceramics and plays a pivotal role in the process of grain coarsening. In this study, it is proposed to impede grain coarsening by constructing a chemically complex IGF comprising multiple dopants with distinct ionic radii. Ternary dopants encompassing Al3+, Y3+, and La3+ ions are simultaneously incorporated into a ZrO2–SiO2 nanocomposite. To fabricate the nanocomposite, an amorphous precursor powder with uniformly dispersed dopants is prepared using a chemical coprecipitation method, followed by rapid hot pressing to obtain a dense bulk sample. The distribution behavior of ternary dopants at IGFs between adjacent ZrO2 nanocrystallites (NCs) is carefully examined. It is revealed that the ternary dopants coexist at the IGFs. Moreover, Si4+ ions exhibit preferential enrichment at the IGFs. Remarkably, the presence of chemically complex IGFs significantly enhances the resistance to grain coarsening in ZrO2 NCs up to 1000 °C. In these findings, valuable insights are offered for designing and fabricating nanocomposites with exceptional resistance against grain coarsening.

Greenly Synthesized Conducting Polymer Nanotunnels with Metal-Hydroxide Nanobundles in Single Dais for Unmitigated Water Oxidation.

Electrochemical water splitting required efficient electrocatalysts to produce clean hydrogen fuel. Here, we adopted greenway coprecipitation (GC) method to synthesize conducting polymer (CP) nanotunnel network affixed with luminal-abluminal CoNi hydroxides (GC-CoNiCP), namely, GC-Co1Ni2CP, GC-Co1.5Ni1.5CP, and GC-Co2Ni1CP. The active catalyst, GC-Co2Ni1CP/GC, has low oxygen evolution reaction (OER) overpotential (307 mV) and a smaller Tafel slope (47 mV dec-1) than IrO2 (125 mV dec-1). The electrochemical active surface area (EASA) normalized linear sweep voltammetry (LSV) curve exhibited outstanding intrinsic activity of GC-Co2Ni1CP, which required 285 mV to attain 10 mA cm-2. At 1.54 V, the estimated turnover frequency (TOF) of GC-Co2Ni1CP/GC (0.017337 s-1) was found to be 3-fold higher than that of IrO2 (0.0014 s-1). Furthermore, the GC-Co2Ni1CP/NF consumed a very low overpotential (281 mV) with a small Tafel slope of 121 mV dec-1. The ultrastability of GC-Co2Ni1CP for industrial application was confirmed by durability at 10 and 100 mA cm-2 for the OER (GC/NF-8 h, 2.0%/100 h, 2.2%) and overall water splitting (100 h, 3.8%), which implies that GC-Co2Ni1CP had adequate kinetics to address the elevated rates of water oxidation. The effect of pH and addition of tetramethylammonium cation (TMA+) reveal that GC-Co2Ni1CP follows the lattice oxygen mechanism (LOM). The solar-powered water electrolysis at 1.55 V supports the efficacy of GC-Co2Ni1CP in the solar-to-hydrogen conversion. The environmental impact studies and solar-driven water electrolysis proved that GC-CoNiCP has excellent greenness and efficiency, respectively.

Calcium Sulfide Based Nanophosphors-A Review on Synthesis Techniques, Characterization and Applications.

Calcium sulfide (CaS) is a widely investigated alkaline earth sulfide nanophosphor with promising applications in optoelectronics and biomedical fields due to its excellent photoluminescence properties. The selection of the synthesis method is a crucial factor in determining the efficacy of nanophosphors for various applications. This review provides a comprehensive overview of the various synthesis techniques employed to develop CaS nanophosphors, including solvothermal, alkoxide, sol-gel, microwave, wet chemical co-precipitation, solid-state diffusion, and single-source precursor methods. The structural and optical properties of CaS nanophosphors are discussed in detail, highlighting the influence of different dopants on the emission color, which can be tuned from blue to red. The review also explores the potential applications of CaS nanophosphors in optoelectronics and biomedicine. This review serves as a valuable resource for researchers interested in developing CaS nanophosphors for various optoelectronic and biomedical applications, providing insights into the latest advancements and future prospects in this field.

Exploring Multi-Parameter Effects on Iron Oxide Nanoparticle Synthesis by SAXS Analysis

Iron oxide nanoparticles (IONs) are extensively used in biomedical applications due to their unique magnetic properties. This study optimized ION synthesis via the co-precipitation method, exploring the impact of the reactant concentrations (Fe(II) and Fe(III)), NaOH concentration, temperature (30 °C–80 °C), stirring speed (0–1000 rpm), and dosing rate (10–600 s) on particle size and growth. Using small-angle X-ray scattering (SAXS), we observed, for example, that higher temperatures (e.g., 67 °C compared with 53 °C) led to a 50% increase in particle size, while the stirring speed and NaOH concentration also influenced nucleation and aggregation. These results provide comprehensive insights into optimizing synthetic conditions for targeted applications in biomedical fields, such as drug delivery and magnetic resonance imaging (MRI), where precise control over nanoparticle size and properties is crucial.

The effect of synthesis techniques on the gas sensing properties of TiO2/SiC/CoFe2O4 nanocomposites as gas sensor

This study investigates the impact of two distinct methodologies on the structural, morphological, and gas sensing properties of TiO2/SiC/CoFe2O4 (TSC) nanocomposites determined using x-ray diffraction (XRD), scanning electron microscopy (SEM), LCR meter, and gas sensing unit respectively. The TiO2/SiC/CoFe2O4 nanocomposites were synthesized using chemical co-precipitation method (C-TSC) and the solid state method (G-TSC). The Scherrer formula was used to calculate the average grain size of C-TSC and G-TSC, which was estimated to be 8 ± 2 nm and 10 ± 2 nm, respectively. The formation of TSC nanocomposites was confirmed by XRD, SEM, and EDX analysis. The response (%) toward ethanol and NH3 gas was tested as a function of flow rate (ppm) and temperature from room temperature (28 °C) to 300 °C. The response (%) was observed to be increasing with increasing temperature and three intermediate temperatures were found. The response and recovery time were also measured with varying gas concentrations. The long-term stability of devices was tested up to 30 days and less variation in result was found, which confirms stability of sensor. The material synthesized using chemical co-precipitation method (C-TSC) shows better properties than G-TSC.

Efficient separation of cerium from rare earth elements and major impurities using low cost manganese ferrites from highly acidic solutions

Sorption of REEs using spinel-ferrite nanoparticles has received great attention in the last decades, because of combining the advantages of iron and manganese metal oxides. Nano-manganese ferrite (MnFe2O4) was successfully synthesized using the co-precipitation method and modified with the addition of zinc to produce (Mn0.8Zn0.2Fe2O4). The synthesized materials were characterized using FTIR, SEM with EDX-mapping, XRD, chemical stability, and surface area. Several process parameters were studied to optimize the efficiency of Ce(III) separation from La(III), Eu(III), Pb(II), and Fe(III) from highly acidic media. The parameters include contact time, solution pH, and metal ion concentration. The sorption process was well fitted to the pseudo-2nd order model, which confirms the chemical nature of the sorption process where equilibrium was achieved after 30 minutes. The pH study's findings demonstrate that Ce(III) was most effectively separated at a very high, acidic pH of 0.5. Both MnFe2O4 and Mn0.8Zn0.2Fe2O4 have high chemical stability in different media where the weight loss was less than 10 %. The correlation coefficient and residual errors analysis confirm that the non-linear extended sips isotherm model more accurately expresses the behavior of the sorption process than the non-linear Freundlich and Langmuir isotherm models. The modified material Mn0.8 Zn0.2Fe2O4 shows higher sorption capacities for all the studied metal ions than MnFe2O4. The maximum sorption capacities of Ce(III), La(III), Eu(III), Pb(II), and Fe(III) in the mixture were 59.2, 6.5, 6.3, 15.4, and 13.7 mg/g, respectively.

Multilayer-coating process for the synthesis of nickel-silicate composite with high Ni loading as high-rate performance lithium-ion anode material

BackgroundMetal silicates possess several important advantages as electrode materials for lithium-ion batteries (LIBs), including straightforward synthesis, low cost, and high thermal stability. A green synthesis routes that are capable of increasing metal loading and reducing the impact on the environment are required. MethodsA Ni-silicate with a multilayer structure and a Ni/Si molar ratio of 0.25 is first prepared using the co-precipitation method. The as-synthesized product is then repeatedly immersed in a Ni2+ solution to obtain Ni-silicate with the desired Ni contents (Ni/Si molar ratio: 0.50–2.00). Finally, the resulting Ni-silicate is reconstructed by hydrothermal treatment under various temperatures (70 °C, 100 °C, 150 °C) and durations (3 h and 24 h) to obtain Ni-phyllosilicate. The effects of the hydrothermal treatment temperature, hydrothermal time, and Ni/Si ratio on the structure, morphology, and surface area of the Ni-silicate composites are examined. Significant FindingsThe Ni-silicate with a Ni/Si ratio of 1.5 has a reversible capacity of 729 mAhg-1, which exceeds traditional graphite anodes (372 mAhg-1). Furthermore, the material exhibits a capacity retention of up to 80 % as the current density is increased from 0.025 Ag-1 to 0.5 Ag-1. Thus, the synthesized Ni-silicate composite is a promising candidate material for LIB anode.

Iron oxide nanoparticles synthesized by coprecipitation method: Impacts of zinc doping and surface functionalization by polyvinylpyrrolidone on the magnetic properties and heating efficiency

Iron oxide nanoparticles synthesized by coprecipitation method: Impacts of zinc doping and surface functionalization by polyvinylpyrrolidone on the magnetic properties and heating efficiency

Enhanced photocatalytic performance of (Mg, Cu) Dual-Doped ZnS nanosheets for Solar-Driven water treatment and embedded with PVA polymer membrane for reusability

Photocatalysis uses semiconductor materials to solar energy effectively purify to water by eliminating pollutants. Organic Dye degradation serves as a standard to assess the photocatalytic effects of the materials. In this study Mg, Cu dual-doped ZnS nanosheets were synthesized using the coprecipitation method. The impact of the concentration on the structural, morphology, optical, and degradation efficiency was investigated with XRD, XPS, TEM with EDAX, and UV spectroscopy. The pure ZnS and Zn0.98-xCu0.02MgxS (x = 0, 0.01, 0.02) (ZCM1, ZCM2, ZCM3, and ZCM4) nanosheets, exhibited cubic structure with high phase purity. The average crystalline size was calculated as 1.66, 1.60, 1.45, and 1.47 nm for the ZCM1, ZCM2, ZCM3, and ZCM4 nanosheets, respectively. TEM analysis revealed the presence of crumpled nanosheets. The bandgap of the ZCM1, ZCM2, ZCM3, and ZCM4 nanosheets were 3.99, 3.78, 4.03, and 4.09 eV respectively. This study investigated the photocatalytic activity of crystal violet dye when exposed to natural sunlight irradiation. Notably, ZCM3 nanosheets exhibited a high degradation rate of 99 % over 120 min under sunlight. Furthermore, the proposed dye degradation mechanism, effect of dosage, effect of dye variation, reusability, scavenging activity, and hemolytic activity were comprehensively discussed. The nanosheets embedded with the Polyvinyl alcohol (PVA) polymer membrane for reusability.

Hexagonal boron nitride fibers as ideal catalytic support to experimentally measure the distinct activity of Pt nanoparticles in CO2 hydrogenation

Catalytic studies aim to design new catalysts to eliminate unwanted by-products and obtain 100 % selectivity for the preferred target product without losing activity. For this purpose, understanding the role of each component building up the catalyst is essential. However, determining the intrinsic catalytic activity of pure metals, especially precious metals in the CO2 hydrogenation reaction under ambient conditions is complex. This is because the catalyst supports used thus far always influence the catalytic process either directly or indirectly due to interface formation that modifies the electronic and morphological structure of the metals. Even SiO2, regarded as inert shows some activity owing to the hydroxyl groups on its surface. In this work, we propose chemically inert and defect-free hexagonal boron-nitride fibers (BNF) synthesized via a co-precipitation method with wide band gap and robust covalent bonds as an uncommon reference catalyst support to evaluate the catalytic activity of size-controlled Pt nanoparticles (4.7 ± 0.6 nm) in the hydrogenation of CO2. The fibers alone show no catalytic activity; however, Pt/BNF exhibited low but notable activity of 377 nmol/g at 400 °C and the catalyst can achieve nearly 100 % CO selectivity. X-ray photoelectron spectroscopy, transmission electron microscopy, and diffuse reflectance infrared Fourier transform spectroscopy measurements were used to indicate that hexagonal boron-nitride affects neither the metal nanoparticles nor the reaction itself; the measured catalytic activity stems from the activity of Pt deposites without the effect of the support, as they were alone. CO vibration spectroscopy studies suggest that due to the lack of substrate-metal interaction, Pt nanoparticles adopt an ideal spherical structure, resulting in several low coordination sites capable of CO2 conversion. Thus, BNF is proposed in the present article to be used as a reference catalyst support material. It can be efficiently used in investigations involving the proposed metal and reaction or under varying conditions with different metal nanoparticles and reaction systems.

Efficient photocatalytic degradation of Rhodamine B dye by undoped and zinc doped zirconium dioxide NPs

Undoped and Zinc-doped Zirconium Dioxide (ZrO2) nanoparticles (NPs) were synthesized via the co-precipitation method, employing Zirconium (IV) Oxynitrate hydrate (ZrO2N2·xH2O), Zinc Sulfate (ZnSO4·7H2O), and ammonia solution as precursor materials at room temperature. A comprehensive characterization of the structural, morphological, optical, and catalytic properties of the prepared samples was conducted using various techniques. Powder X-ray diffraction (PXRD) analysis revealed that the synthesized NPs exhibited a tetragonal phase structure, with crystallite sizes decreasing as doping concentration increased. Scanning electron microscopy (SEM) images confirmed the spherical shape of the NPs. Energy-dispersive X-ray spectroscopy (EDX) verified the presence of Zr, O, and Zn elements with high purity. Raman spectroscopy corroborated the tetragonal structure of the synthesized ZrO2 NPs. Ultraviolet–visible (UV–Vis) spectroscopy studies determined the cutoff wavelengths, while Tauc plot enabled the calculation of band gap energies. Fourier transform infrared spectroscopy (FTIR) confirmed the functional groups present in the synthesized samples. Photoluminescence spectroscopy provided evidence of defects and charge carrier recombination processes. The catalytic efficacy of the synthesized ZrO2 NPs was demonstrated through the degradation of Rhodamine B dye under visible and UV light.

Crystal structure, magnetic property and cryogenic magnetocaloric effect of Gd4Al2O9 aluminate

Developing magnetic materials with excellent magnetocaloric effect (MCE) is a vital prerequisite for practical magnetic refrigeration (MR) applications. Herein, a single-phased polycrystalline Gd4Al2O9 compound was fabricated using the co-precipitation method, and its structure, magnetic property together with magnetocaloric performance were investigated. The Gd4Al2O9 compound was found to crystallize in the monoclinic structure space group P21/c with lattice parameters a = 7.4852 Å, b = 10.5561 Å, c = 11.1774 Å, β = 108.95° and V=835.3107 Å3, and the constituent elementals had valence states of Gd3+, Al3+ and O2−. Excellent comprehensive MCE performance was observed for the Gd4Al2O9 compound in low-temperature regions. The obtained values of maximal magnetic entropy change, temperature-averaged entropy change (3 K) and relative cooling power under the magnetic flux density change of 0–7 T are 26.31 J/kg·K, 25.09 J/kg·K and 317.05 J/kg. The Gd4Al2O9 compound shows impressive comprehensive MCE performances compared with some recently reported rare earth-based MR materials with prominent performances, meaning that it is a suitable candidate material for low-temperature MR applications.

Photocatalytic magnetic bimetallic ferrite synergistically activates ammonium persulfate for the efficient degradation of tetrachlorobisphenol A(TCBPA)

The presence of tetrachlorobisphenol A(TCBPA) in the environment is continually increasing, which has potential negative effects on human health. Therefore, it is important to develop new materials that can degrade these compounds using various modification techniques. Recently, the photocatalytic degradation of organic pollutants using peroxides has been widely used as the focus of several research studies. This study synthesized Zr-doped NiFe2O4 (Zr-NiFe2O4) metal complex materials using a co-precipitation method and applied them to catalyze the degradation of a typical halogenated bisphenol A pollutant using different phase-catalyzed peroxydisulfate (PS) compounds. The results showed that Zr-NiFe2O4 significantly enhances the nitrogen-active adaptive catalytic action between the reactive species and (NH4)2S2O8, exhibiting an excellent catalytic performance (99 %). The degradation rate could reach 90 % after 30 mins with the low concentration of TCBPA (20 mg•L–1). Furthermore, the degradation of TCBPA in the Zr-NiFe2O4/LED/(NH4)2S2O8 system occurred over a wide pH range of 3–11. The results of leaching metals were detected that the concentrations of the leached zirconium, nickel and iron ions declined to 0.018 mg•L−1. In addition, the tri-metal synergistic effect of Zr-NiFe2O4 not only significantly improved the TCBPA removal efficiency, but also enhanced the long-term stability of the composite material. Mechanistic studies revealed that ·OH and SO4·– were involved in the TCBPA degradation process with ·OH being the primary active species, and the possible degradation pathways were deduced using mass spectrometry. The on-line infrared test experiments showed the disappearance of the hydroxyl and double bond within approximately 120 seconds. Moreover, the magnetic properties of Zr-NiFe2O4 met the water recovery requirements, effectively reducing secondary pollution, and aligned with the practical needs for water treatment, providing data for the construction of efficient magnetic catalysts.

Green biogenic synthesis of magnetite nanoparticles from indigenous Banksia Ashbyi leaf for enhanced sonochemical dye degradation

Abstract Developing alternative green and sustainable technologies to prevent, reduce, and remove toxic dyes present in effluent generated by the textile industry is of global importance. In this study, magnetite (Fe3O4) nanoparticles (MNPs) were successfully synthesized using a co-precipitation method that used Indigenous Banksia Ashbyi (BA) leaf extract in varying amounts (BA-MNP 1 to BA-MNP 4), to modulate particle size and size distribution. The formation of the MNPs was confirmed by a range of characterization techniques that included UV–visible spectrophotometry, Fourier transform infrared (FTIR) spectroscopy, x-ray diffraction (XRD) spectroscopy, thermo-gravimetric analysis (TGA) and scanning (FIBSEM) and high-resolution transmission (HRTEM) electron microscopy. The presence of the Fe–O bond located at 551 cm−1 in the FTIR spectra and XRD analysis of the samples confirmed the formation of crystalline MNPs. FIBSEM and HRTEM images of the BA-MNP 4 sample confirmed the MNPs were spherical (18 ± 5 nm) and tended to agglomerate. Moreover, UV–visible spectrophotometry revealed a board absorption band and an optical band-gap energy of 2.65 eV. The catalytic activity of BA-MNP 4 samples towards the degradation of a commercially available navy-blue RIT dye (BRD) were investigated under three operational senarios: 1) ultrasonic irradiation (US) + BRD; 2) BA-MNP 4 + BRD, and 3) US + BRD + BA-MNP 4. The investigation found there was an additive effect when US (80 W) was used in conjunction with BA-MNP 4 s during the dye degradation process. With no US, the BA-MNP 4 sample only achieved a dye degradation of 52% in 25 min. However, over the same period of time with US, the BA-MNP 4 sample achieved a dye degradation of 89.92%. In addition, kinetic modelling found the combined US and BA-MNP 4 process followed a pseudo-first-order kinetic model.

Novel Carbon@BaMoZrFe12O19 photocatalytic peroxymonosulfate activation for ibuprofen removal

This study reports a successful synthesis of a novel Carbon@BaMoZrFe12O19 M-hexaferrite photocatalyst (NPs) using the coprecipitation method. Afterthat, the NPs were used as an activator for peroxymonosulfate (PMS) to remove ibuprofen (IBU) from water. NPs were subjected for a thorough characterization process utilizing various analytical techniques including XRD, FTIR, UV, PL TEM, SEM/EDS, and X-ray photoelectron spectroscopy (XPS). Significantly, the utilization of NPs for PMS activation demonstrated a notable improvement in the elimination of IBU under visible light. The research conducted a thorough investigation into the effects of various parameters, such as activating systems, initial pH, inorganic salts, IBU contents, and water matrix on the efficiency of IBU degradation. The significance of reactive oxygen species, such as sulfate and hydroxyl radicals, as well as singlet oxygen, in the removal of IBU, was clarified by chemical quenching tests. In addition, NPs exhibited competent magnetic separation and reprocessing capacities. The magnetic NPs revealed excellent constancy and recyclability, by sustaining degrading productivity after five consecutive cycles. Therefore, the present study offers a significant contributions to the understanding of photocatalytic degradation for organic pollutants through the utilization of magnetic photocatalysts.

Tetravalent metals modulated Zn-based layered double hydroxides and their mixed metal oxides for catalytic depolymerization of carbonyl-coordinating plastic waste

Plastic waste generation has become a global issue and presents a significant challenge concerning degradability in the environment. This poses a serious threat and adverse impact on the health of living creature and the environment ecosystem. The up-/re-cycling of plastic waste through catalytic depolymerization is becoming a sustainable way to reduce economic concerns about production and serious environmental impacts. Here, in the present study an effort has been made for the development of catalysts for efficient recycling of carbonyl group containing polymer waste [Polyethylene terephthalate (PET) and polycarbonate (PC)]. The sequential preparation of ZnMIV- and ZnAlMIV- LDHs (layered double hydroxides) (MIV= Zr and Ti) and their respective mixed metal oxide (MMOs) based catalytic materials, has been carried out by one-pot co-precipitation and calcination methods. The structural parameters were examined through the various characterisation techniques including XRD, FTIR, TEM, SEM, and EDS. The layered structure, high crystalline nature and hexagonal 2D-sheet/flakes like morphology with average particle size ranging from ~14 to 51nm [for LDHs] and ~6 to 21nm [for MMOs] were observed. Depolymerization of PET and PC using LDHs/MMOs catalyst in ethylene glycols (EG) produced bis(2-hydroxyethyl terephthalate) (BHET) and bisphenol A (BPA) monomers as main products, respectively. The catalyst quantity, concentration of solvent, recyclability of catalysts, reaction duration, and crystallization time have also been further investigated for better yield during catalytic glycolysis. The isolated monomers were further characterized by using melting point, mass spectroscopy, 1H-NMR, 13C-NMR and FTIR analysis. The order of catalytic activities of prepared samples as ZnTi-LDH˃ ZnAlTi-LDH ˃ ZnTi-MMO˃ ZnAlZr-LDH˃ ZnAlTi-MMO˃ ZnZr-LDH in PET depolymerization while in case of PC, the order as ZnTi-LDH˃ ZnAlTi-LDH ˃ ZnZr-LDH˃ ZnAlZr-LDH˃ ZnZr-MMO˃ ZnAlZr-MMO˃ ZnTi-MMO˃ ZnAlTi-MMO were observed. LDH samples showed higher catalytic conversion than their respective MMOs during PET and PC depolymerization into monomers BHET and BPA with % yield of ~76-83% and ~81-89%, respectively. ZnTi-LDH shows high catalytic efficacy in depolymerization of PET and PC with yield of (~82%) BHET monomer and (89%) BPA. This catalyst displayed good recyclability more than eight cycles during this catalytic glycolysis study.

Selective CO2 hydrogenation to methanol over a novel ternary In-Co-Zr catalyst

To address the challenges of global warming and energy shortages, the technology to convert CO2 into methanol is of great significance Indium-cobalt catalysts have attracted widespread attention due to their significant activity and excellent stability. Herein, In-Co and In-Co-Zr catalyst rich in In2O3 were prepared through a citric acid-assisted co-precipitation method. The results show that the In-Co-Zr catalyst can significantly enhance the activity for hydrogenating CO2 to methanol, achieving a CO2 conversion rate of 17.4 % and a methanol selectivity of 77.7 % under the conditions (5.0 MPa, 310 °C, GHSV = 10.28 l·gcat-1·h-1, H2/CO2 ratio of 4). At a GHSV of 48 l·gcat-1·h-1, the space–time yield of methanol was 0.79 gMeOH·gcat-1·h-1, and the catalyst exhibited stable catalytic activity over a continuous reaction period of 120 h. It was revealed that the incorporation of ZrO2 could significantly improve methanol selectivity of In-Co catalyst. Moreover, an increased oxygen vacancy and strong interaction of the In-Co-Zr catalysts are conducive to improving the CO2 adsorption strength and capacity. It is expected that this novel ternary In-Co-Zr catalyst could inspire new opportunities for designing and developing multi-component hybrid catalysts for highly active, stable and selective CO2 hydrogenation to methanol

Chitosan-coated manganese ferrite nanoparticles enhanced Rhodotorula toruloides carotenoid production.

The present study aims to analyze the interaction between Rhodotorula toruloides and magnetic nanoparticles and evaluate their effect on carotenoid production. The manganese ferrite nanoparticles were synthesized without chitosan (MnFe2O4) and chitosan coating (MnFe2O4-CS) by the co-precipitation method assisted by hydrothermal treatment. XRD (X-ray diffraction), Magnetometry, Dynamic Light Scattering (DLS) and FTIR (Fourier-Transform Infrared Spectroscopy), are used to characterize the magnetic nanoparticles. The crystallite size of MnFe2O4 was 16 nm for MnFe2O4 and 20 nm for MnFe2O4-CS. The magnetic saturation of MnFe2O4-CS was lower (39.6 ± 0.6 emu/g) than the same MnFe2O4 nanoparticles (42.7 ± 0.3 emu/g), which was attributed to the chitosan fraction presence. The MnFe2O4-CS FTIR spectra revealed the presence of the characteristic chitosan bands. DLS demonstrated that the average hydrodynamic diameters were 344 nm for MnFe2O4 and 167 nm for MnFe2O4-CS. A kinetic study of cell immobilization performed with their precipitation with a magnet demonstrated that interaction between magnetic nanoparticles and R. toruloides was characterized by an equilibrium time of 2h. The adsorption isotherm models (Langmuir and Freundlich) were fitted to the experimental values. The trypan blue assay was used for cell viability assessment. The carotenoid production increased to 256.2 ± 6.1 µg/g dry mass at 2.0 mg/mL MnFe2O4-CS. The use of MnFe2O4-CS to stimulate carotenoid yeast production and the magnetic separation of biomass are promising nanobiotechnological alternatives. Magnetic cell immobilization is a perspective technique for obtaining cell metabolites.

Preparation and Characterization of Materials for Low- to Intermediate-Temperature CO2 Adsorption

Global carbon dioxide emissions are rising and the use of fossil fuels in several sectors are the leading causes. As global population and economies continue to grow significantly, the most practical method of lowering such emissions is to capture CO2. Although other technologies are more developed, adsorption is very promising and has attracted much attention. To ensure this technology’s success, it is essential to have suitable CO2 adsorbent materials. In this work, several new hydrotalcites (HTs) with different initial concentrations of ion precursors were prepared for the first time by the co-precipitation method—it was possible to verify that the ion concentrations influence the characteristics of the materials. The prepared HTs were characterized by thermogravimetric analysis (TG), X-Ray diffraction (XRD), surface area measurements and temperature-programmed desorption of CO2 (TPD-CO2) to relate their CO2 capture capacity to their physicochemical properties; the CO2 adsorption equilibrium isotherms were determined at 35 and 300 °C for the prepared samples, as well as for some commercial materials: magnesium oxide, calcium oxide, aluminium oxide and Zeolite 13X. After determining which materials present the best CO2 adsorption capacity, these were submitted to adsorption-desorption cycles to study their stability. The main objective of the work was to prepare and study different CO2 adsorbents for processes that are carried out at low and intermediate temperatures. From the experimental results, it was possible to conclude that the Zeolite 13X showed the best capacity at 35 °C, 3.38 mmol·g−1 (@ pCO2 = 1 bar), and a prepared calcined HT (c-HT2) was the best at 300 °C, 0.97 mmol·g−1 (@ pCO2 = 1 bar). Moreover, it seems there is an optimum initial concentration of the ions’ solutions for the tested HTs, which depends on the final application—c-HT1 showed a better capacity at 35 °C and c-HT2 at 300 °C. From the adsorption-desorption cycles—performed at 35 and 300 °C with the best materials using a magnetic suspension microbalance at 1 bar of CO2 partial pressure —, a working cyclic capacity of 2.69 mmol∙g−1 was achieved by the Zeolite at 35 °C; in turn, c-HT2 showed a working cyclic capacity of 0.79 mmol∙g−1 at 300 °C.