Additional Calcination Research Articles

Short process for Li2CO3 synthesis and spent LiCoO2 remediation via Glycine-LiOH slurry electrolysis

Effectively recycling spent lithium-ion batteries (S-LIBs) has considerable economic and environmental benefits. In this study, a novel approach for simultaneously synthesizing Li2CO3 and remediating LiCoO2 from S-LIBs via slurry electrolysis is proposed, employing glycine-LiOH as the electrolyte. The operating conditions were optimized to a solid-to-liquid ratio of 20 g/L, slurry electrolysis time of 8 h, current density of 50 mA/cm2, reaction temperature of 80 °C, and glycine concentration of 1.0 mol/L. Li2CO3 was directly synthesized in the anode region, with a purity of up to 99.52 %. Additionally, LiCoO2 was partially remediated in the cathode, increasing Li-Co molar ratio from 0.659 to 0.93. The obtained Li2CO3 and the electrolysis residue LiCoO2 then underwent additional calcination, yielding a layered LiCoO2. At a Li-Co molar ratio of 1.1, the initial specific capacity of the calcined LiCoO2 material was 129.9 mAh/g, exhibiting a capacity retention rate of 50.48 % over 100 cycles. Therefore, a novel, cost-effective, and energy-saving strategy for recycling S-LIBs is proposed.

Enhanced photocatalytic degradation of rhodamine B dye and antibacterial activity of diatomite-supported TiO2/ZnS hybrid catalyst via additional calcination

Enhanced photocatalytic degradation of rhodamine B dye and antibacterial activity of diatomite-supported TiO2/ZnS hybrid catalyst via additional calcination

A PEDOT-Pt-TiO2 hybrid material synthesized by the casting method for photocatalytic hydrogen generation

This study describes the synthesis and characterisation of a hybrid material consisting of titanium dioxide nanotube arrays (TiO2 NTs) modified by platinum nanoparticles (Pt-TiO2 NTs) via radiolysis and a conductive poly(3,4-ethylenedioxythiophene) (PEDOT) layer, for the first time. The NTs were fabricated by a two-step anodic oxidation process and exhibited different morphologies using electrolyte solutions with different water contents (2–10 vol%). The polymer layer of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) was coated on the Pt-TiO2 scaffold using the casting method. The PEDOT:PSS-PT-TiO2 NTs exhibited stability in the photocatalytic process after additional calcination which was carried out to remove the PSS part; the nanotubes with lengths of ∼3 μm exhibited the highest photocatalytic activity (∼4.5 × 10−3 μmol cm−2 of H2). Additionally, the samples obtained from electrolyte solutions containing 5 and 10 vol% water exhibited nanostructures with the highest catalytic activity.

Palladium-Containing Catalysts Based on Functionalized CNFs for the Dehydrogenation of Methylcyclohexane

The activity of palladium-containing catalysts based on functionalized carbon nanofibers prepared by an incipient wetness impregnation method in the dehydrogenation reaction of methylcyclohexane was investigated. Methylcyclohexane is considered as one of the most promising liquid hydrogen carriers. The dependence of the catalytic characteristics of the samples on the functionalization conditions of carbon nanofibers has been studied. By temperature-programmed desorption, it was shown that an increase in the treatment time of carbon nanofibers in concentrated nitric acid from 1 to 3 h increases the number of hydroxyl groups on their surface, and treatment for 6 h contributes to a rise in the concentration of carboxyl groups and their derivatives (esters and anhydrides). Additional calcination of the functionalized nanofibers in an inert atmosphere at 530°C yielded a sample containing predominantly hydroxyl groups. The presence of hydroxyl groups on the surface of the carbon material has a positive effect on the performance of the catalysts, while the presence of carboxyl groups leads to a decrease in the yield of toluene. It is assumed that the observed differences in catalyst activity are due to differences in dispersion and localization of palladium particles.

Structural and Optical Properties of Bismuth-doped Cerium Oxide Prepared at a Low Temperature

Cerium oxide (CeO2) is a functional material with excellent physicochemical properties. Its properties can be modified by doping with different elements, including bismuth, which can be done through various synthesis methods. The precipitation method combined with ultrasonic radiation was used to synthesize bismuth-doped cerium oxide (CeO2:Bi) at a low temperature of 200oC. In this study, we investigate the alteration of structural and optical properties of as-prepared CeO2:Bi by subjecting it to additional calcination at a high temperature of 500oC. The structural and optical properties of CeO2:Bi were characterized using thermal gravimetric analysis, X-ray diffraction, Scanning Electron Microscope-Energy Dispersive X-Ray, Fourier Transform Infrared spectroscopy, and UV-Visible spectroscopy. The additional calcination produced a less significant weight-loss percentage than the as-prepared CeO2:Bi observed from the gravimetric curve. The Fourier transform infrared spectrum revealed the loss of a small number of hydroxyl molecules trapped on the CeO2:Bi surface when additional calcination was subjected. Based on the X-ray diffraction spectra, additional calcination results in the smallest crystallite size and compressive strain without the changed cubic crystal structure of CeO2:Bi. The successful doping of Bi in CeO2 was confirmed by the composition analysis from Energy Dispersive X-Ray measurement. Scanning electron microscope image showed spherical and agglomerated particles of calcined CeO2:Bi. The optical properties of both CeO2:Bi possessed similar trend absorption spectra and almost the same band gap energy. The results indicated that the calcination of as-prepared CeO2:Bi at a temperature of 500oC did not affect its structural and optical properties significantly. Thus, combining ultrasonic radiation with precipitation is an advantageous method to synthesize at a low temperature of stable CeO2:Bi crystalline.

Preparation of Mo–Cu composite powder with high homogeneity by solution combustion synthesis

In order to reduce the sintering temperature of the Mo–Cu composites, solution combustion synthesis was used to fabricate ultrafine Mo–Cu composite powders, in which Mo and Cu mixed uniformly. Firstly, solution combustion synthesis was conducted to prepared molybdenum and copper oxides composite powders. However, the residual carbon in the as-synthesized precursors requires additional calcination in nitrogen atmosphere during the reduction process to obtain pure Mo–Cu composite powders. Then the Mo–Cu composites were fabricated by liquid phase sintering at low temperatures of 1050–1180 °C using the Mo–Cu composite powders. The Mo–20Cu and Mo–30Cu composites can reach a relative density of >95% after sintering at a low temperature of 1100 °C, which may be attributed to both the small particle size of Mo and the high uniformity of Mo and Cu distribution.

Ecotoxicological characteristics and properties of zinc-modified biochar produced by different methods

Despite the dynamic progress of BC engineering, there is a lack of knowledge on the toxicity and environmental impact of modified BC. The aim of this study was the ecotoxicological evaluation of BC modified with zinc (Zn) using different methods: impregnation of feedstock with Zn before pyrolysis (PR), impregnation with Zn after pyrolysis (PS) and impregnation with Zn after pyrolysis with an additional calcination step (PST). The ecotoxicological assessment was based on tests with invertebrates (Folsomia candida, Daphnia magna) and bacteria (Aliivibrio fischeri). The post-treated and calcined composites had a higher content of total (Ctot) PAHs (144–276 μg kg−1) than pre-treated BC-Zn (68–157 μg kg−1). All BC-Zn treatments stimulated the reproduction of F. candida at the lowest BC dose (0.5%) by 4–24%. Increasing the biochar dose to 1% and 3% retained the stimulating effect of the pre-modified biochars (from 19 to 41%). Pre-modified BC-Zn reduced the luminescence of A. fischeri from 40% to 80%. Post-treated BCs reduced bacterial luminescence by 99%, but the calcination step limited the toxic effects to the level observed for the control. Post-treated BCs had a toxic effect on D. magna, with EC50 values ranging from 433 to 783 mg L−1. The ecotoxicity of composites depends on modification methods, BC dose and pyrolysis temperature. The application of limiting conditions for HM leaching (i.e., pre-modification, calcination) increased the safety of using Zn-biochar composites.

Sustainable approach for reclamation of graphite from spent lithium-ion batteries

A scalable and facile regeneration route is utilized to recover the graphite from a spent lithium-ion battery (LIB). Eco-friendly organic acid is employed as a leaching-curing reagent for the present work. All the unwanted content of elements e.g. Ni, Co, Li, Cu and Al has been completely terminated from the graphite after the purification step without any additional calcination process. The optical, structural and electrochemical properties of as-reclaimed graphite have been studied by several analytical methods. Regenerated graphite is restored to its layered crystal structure along with expansion in the interlayer distance, and the same is confirmed from scanning electron microscopy and X-ray diffraction analysis respectively. Notably, high purity graphite is achieved and tested in its electrochemical storage property in supercapacitor (SC) applications. As an outcome, recreated graphite exhibits a maximum areal capacitance of 285 mF cm−2 at 5 mV s−1. The fabricated symmetric SC demonstrates the superior energy storage performance in terms of durability and higher capacitance (131 mF cm−2) with better capacity retention over several cycles. It is worth mentioning that this curing process is a facile route, consumes lower energy and eco-friendly methodology and thereby may have futuristic extent for the bench scale reclamation of graphite from spent LIBs.

Spinel ferrite nanomaterials - MgFe2O4 - Synthesis by appropriate microwave solution combustion (Msc) method of visible light–responsive photocatalyst for Rb21 dye degradation

Ferrite’s spinel has acquired appeal for its use in biomedical, pharmaceuticals, electrical devices, photocatalyst, and other fields. Spinel may also be manufactured using the Microwave Solution Combustion (MSC) process, which is a viable alternative to sol–gel, co-precipitation, hydrothermal, and Hammer's methods since it is rapid, energy-efficient, and requires lesser equipment. The MSC technique provides insight into the impact of its many factors. Microwave irradiation is utilized in this method to retain precursors in an excited state and make them highly reactive. This technique is usually carried out using a Raga's scientific microwave reactor with a frequency of 2.45 GHz, T = 100°C. Metal nitrates (precursers) and Urea are the most often utilized preparation for nanomaterials. Because of its high-temperature range or propellant combustion requirements, urea is the most used fuel. To accomplish a quicker and better yield product, many factors such as fuel to oxidizer ratio, irradiation period, microwave power, temperature and pressure may be tuned. This procedure does not require any additional calcination; however, it does necessitate numerous washing steps to purify the final result. The 4000–400 cm−1 peaks were examined in the composition characterization of spinel ferrites using FTIR findings. The focus of the research was to find a MgFe2O4 spinel with a Magnesium A-site in Ferrite particles. This study is to explore catalyst behaviour in sessions of structural, compositional, crystallinity, and magnetic stability with neodymium magnets used for the separation of RB21 dye from synthetic wastewater. To check the reusability at 20 mg catalyst dosage at 20 mg/L dye concentration which gives 4 runs efficiency 90% − 66% observed.

The Synergetic Effect of Support‐oxygen Groups and Pt Particle Size in the Oxidation of α‐D‐glucose: A Proximity Effect in Adsorption

AbstractThe influence of the support‐oxygen groups and Pt particle size on the catalytic performance of Pt/AC for the aerobic oxidation of α‐D‐glucose to gluconic acid (glycolate) was studied. Surface‐oxygen groups were introduced by treating the activated carbon support with diluted HNO3 without significantly affecting the support porosity. The platinum particle size could be decreased on both the treated and untreated support by adding an additional calcination step to the synthesis. The presence of oxygen‐containing groups is shown to be highly beneficial (∼4 fold increase in the turnover frequency) only for the smallest Pt particle size (1.8–2.5 nm, determined by TEM). For the catalyst with the larger Pt size (3.4–3.6 nm), the presence of additional oxygen‐contacting groups does not significantly enhance the activity. Since the size of the smaller Pt particles is close to the product/substrate molecular diameter (glucose/gluconic acid, ∼0.9 nm) the observed effect can be attributed to the effective repulsion by the negatively charged oxygen groups in close proximity to the glycolate reaction product. The increase in activity originates from the resulting enhanced desorption of glycolate by alleviating the product inhibition presence due to the strong interaction of glycolate with Pt.

Fabrication and microstructure evolution of monolithic bridged polysilsesquioxane-derived SiC ceramic aerogels

SiC aerogels are representative high-temperature ceramic aerogels that have demonstrated extensive potential utility in the thermal insulation field under extreme conditions. Although the efficient fabrication of monolithic and highly crystalline SiC aerogels is crucial, it remains highly challenging. Herein, a one-step pyrolysis strategy of a bridged polysilsesquioxane (BPSi) aerogel precursor is reported. The preceramic BP aerogel was prepared via a sol-gel method followed by vacuum drying, and the subsequent pyrolysis process conveniently converted the BPSi aerogel precursor into a SiC aerogel. This circumvents the need for harsh synthetic conditions, high-cost noble metal catalysts, special drying, and additional calcination processes. Furthermore, a competitive mechanism between the “gas-escape” caused by the volatilization of low molecular compounds and carbothermal reduction reaction, and the “volume-shrinkage” resulting from high-temperature sintering was proposed to explain the evolution of phase composition and pore hierarchy of BPSi-derived ceramic aerogels.

Single-step acid-catalyzed synthesis of luminescent colloidal organosilica nanobeads

We present a single-step, room-temperature synthesis of fluorescent organosilica nanobeads (FOS NBs). The FOS NBs were synthesized under aqueous conditions using (3-aminopropyl)triethoxysilane (APTES) as the silicon source in the presence of l-ascorbic acid (L-AA). In the APTES/L-AA/water ternary phase, the hydrolysis and condensation reaction of APTES occurred under acidic conditions to form spherical FOS NBs with an average diameter of 426.8 nm. FOS NBs exhibit excellent colloidal stability in aqueous media. The formation of FOS NBs was complete within a 10 min reaction time, which indicates potential for large-scale mass-production synthesis of luminescent colloidal NBs. The FOS NBs exhibited blue photoluminescence (PL) under UV excitation in the absence of an additional high temperature calcination process or with the incorporation of any fluorophores. This phenomenon is attributed to the presence of carbon-containing defects, which act as luminescent centers formed by the reaction between amino groups in the APTES and l-ascorbic acid reductant. Finally, the results of a cytotoxicity test and cellular uptake experiments revealed that the FOS NBs showed potential as optical contrast agents for bioimaging.Graphical

Recovering phosphorus from aqueous solutions using water hyacinth (Eichhornia crassipes) toward sustainability through its transformation to apatite

This work provides circular leveraging strategies for using water hyacinth (Eichhornia crassipes) (WH) in the removal and recovery of phosphorus (P) from aqueous solutions. This study also assesses the transformation of the adsorbed phosphorus into a high value-added product (apatite) and its potential as a soil amendment. The materials evaluated were recovered from WH calcination at temperatures ranging between 350 °C and 700 °C, which evidenced great amounts of Ca(OH)2, MgO, Al2O3, and Ca5(PO4)3OH. The material that evidenced highest P removal capabilities was CWH-650, which was produced from calcination at 650 °C; hence, it was used during the P adsorption process. The results showed that chemisorption is the limiting step in the adsorption process, with a maximum adsorption capacity determined by its adaptation to the Langmuir model at 21.21 mg P/g. Likewise, the study determined that the exchange of ligands followed by precipitation in the apatite formation process were the dominant mechanisms during the adsorption process. An additional calcination step conducted on the CWH-650 adsorbent previously used in the removal of P denoted an increase in the amount of apatite (up to 41.0%), as demonstrated through Fourier-transform infrared spectroscopy and X-ray diffraction analysis. Subsequently, this study concluded that the Ca- and P-enriched phases exhibited a higher solubility of P in 2% formic acid than in deionized water, which fostered the release of up to 60 mg P/g, indicating its potential use as a phosphate fertilizer and an acid-soil amendment.

Highly active ZIF-8 derived CuO@ZnO p-n heterojunction nanostructures for fast visible-light-driven photooxidation of antibiotic waste in water

Nanostructured photocatalysts represent an eco-friendly material for photooxidation of toxins beneath light radiation. However, the surface structure and large bandgap energies are the main issues for realizing these photocatalysts under visible-light operation. Herein, we obtain high surface area ZnO by the calcination of solution-prepared zeolitic imidazolate framework (ZIF-8). Also, the ZIF-8 is loaded with Cu precursor to obtain 1.0 − 4.0 wt.% CuO@ZnO p-n heterojunctions by an additional calcination process. The CuO loaded on derived ZnO fashioned a mesoporous texture with an extreme surface area of 1485 m2 g‒1. The introduction of CuO to ZnO exposed a broader light absorption and bandgap reduction to 2.63 eV from 3.43 eV for ZnO and a significant increase of the surface area to 1665 m2 g‒1 for the 3.0 wt.% CuO-loaded ZnO. The fabricated CuO@ZnO employed for tetracycline's (TC) photooxidation, as an antibiotic target in water systems. The optimal 3.0 wt.% CuO@ZnO performed a complete TC photooxidation within 45 min with an oxidation rate of 113.5 × 10−3 min−1 at a dose of 1.5 gL−1. This heterojunction exhibited exceptional recyclability for five cycles. The high activity is regarded to the extreme surface area and the migrated photoinduced charges within the CuO@ZnO.

Regulation of electro-optical activities of nanostructured SnO2:Al powders by using a micro drop fluidized reactor

Nanostructured SnO2:Al powders were prepared and their electro-optical activities were regulated by using a micro drop fluidized reactor (MDFR), which were conducted continuously in a simple one-step process without additional calcination, annealing, and drying steps. The crystallite size and BET surface area (up to a 2.6 times) increased but bandgap energy of SnO2:Al powders decreased, respectively, by providing the unique pyro-hydraulic reaction conditions during the formation of powders. The micro shear force and strain generated due to the fluidization of micro drops could enhance the doping effects and surface activities of SnO2:Al powders. The analyzes of room-temperature photoluminescence (PL) spectra, UV–vis photospectroscope and X-ray photoelectron spectra (XPS) exhibited that the surface activities of SnO2:Al powders were enhanced considerably by regulating the excitation and separation of electrons and holes and increasing the oxygen vacancies at the surface of SnO2:Al powders by means of UMB control. The optimum amount of dopant of Al3+ ions (CAl) and flow rate of micro bubbles (UMB) for effective surface activities were 2.0at% and 1.0 L/min, respectively. The scheme of photocatalytic mechanism of SnO2:Al powders to degrade the methylene blue (MB) was discussed by means of surface charge transfer and morphology of the powders.

Enhancing the electrochemical activity of an IrOx–Ta2O5/Ti anode via radiofrequency-driven rapid plasma annealing

Electrochemical oxidation has attracted much attention in the wastewater treatment field due to its strong oxidation performance and control easiness. In the present study, the electrochemical activity of an IrOx–Ta2O5/Ti anode was enhanced via radiofrequency (RF)-driven rapid plasma annealing (RPA) process; a 2.0 MHz plasma jet was applied to the surface of the precursor-brushed IrOx–Ta2O5/Ti anode, changing the surface morphology and electrochemical characteristics of its coating. The final surface morphology, resulting from the subsequent calcination, exhibited a spongy-like microstructure and much smaller cracks compared with the coatings treated with the conventional thermal decomposition (CTD) process. Moreover, the RPA-treated samples showed lower overpotential (j = 10 mA/cm2) of 261 mV (vs. RHE) and higher voltammetric charges (330.26 mC/cm2). Compared with the CTD-treated one, the electrochemical activity of the RPA-treated samples was greatly improved with a comparable stability after additional calcination at 480 °C. This enhancement in the electrochemical performance indicates that an RF plasma jet, as an RPA tool, has a great potential for improving the catalytic activity of IrOx–Ta2O5/Ti anodes.

Selective Catalytic Oxidation of Benzyl Alcohol by MoO2 Nanoparticles

Selective oxidation of benzyl alcohol to benzaldehyde was carried out with MoO2 nanoparticles (MoO2 NPs). MoO2 NPs were synthesized by two different approaches and characterized by several techniques. The synthesis was done by a hydrothermal procedure using ethylenediamine and either Fe2O3 or hydroquinone. In the latter case, an additional calcination step under N2 was performed to eliminate passivating agents at the surface of the nanoparticles. The synthesized nanocatalysts showed similar catalytic properties, being efficient catalysts in the oxidation of benzyl alcohol. High substrate conversion and product selectivity were achieved under all tested conditions. Studies were conducted using two different oxidants: tert-butyl hydroperoxide and hydrogen peroxide, in our continuous effort to obtain more efficient catalysts for more sustainable catalytic processes. When H2O2 was used as the oxidant, 94% yield was achieved with 100% selectivity for benzaldehyde, which was a very promising result to undergo other studies with this system. Moreover, to elucidate some aspects of the reaction mechanism, a study was conducted, and it was possible to conclude that the reaction undergoes, to some extent, through a radical mechanism with both oxidants.

Effect of defect states in the optical and magnetic properties of nanocrystalline NiO synthesised in a single step by an aerosol process

Nanocrystalline nickel oxide (NiO) was successfully synthesised as a phase-pure product from an inorganic precursor through a “single-pot”, gas-phase synthesis method, nebulised spray pyrolysis (NSP). Functional properties such as magnetic behaviour, luminescence and band gap were studied and compared with the properties of NiO powder synthesised by a conventional reverse co-precipitation process (RCP) which also needed an additional calcination step. Although NiO crystallised in the cubic (rocksalt) form, Rietveld analysis of X-ray diffraction data revealed the synthesised nanopowders to be in a distorted cubic (rocksalt) or monoclinic form. This distortion resulted from the antiferromagnetic exchange interaction energy and increased magnetic surface anisotropy, as seen from the bond lengths determined from Fourier transform infra-red (FTIR) studies. Raman spectroscopy also confirmed the distortion in the structure indicated by the presence of a first order phonon peak. The band gap decreased in case of both the powders and was attributed to the shallow donor or acceptor levels created due to the presence of defect states as determined from photoluminescence studies. The NSP powders also exhibited a dependence on the excitation wavelength during emission luminescence. A mixed antiferromagnetic and ferromagnetic behaviour was observed in the NSP powders and the susceptibility of each was deconvoluted through low and high field magnetometry studies. Further, the nanopowders from both the processes showed “core-shell” magnetism, with paramagnetic behaviour in the shell and antiferromagnetism in the core. The thicknesses of the core and shell were also determined.

Organic frameworks induce synthesis and growth mechanism of well-ordered dumbbell-shaped ZnO particles

Coordination bonds of ligands and metal ions are generally considered for improving agglomeration during the synthesis of metal oxides. However, the strong interactions always limit the performance due to the requirement of additional energy and calcination. A new strategy of synthesizing ZnO particles is proposed through a hydrothermal inducing redox method by using 2-methyl imidazole and Zn(NO3)2. In situ direct redox between this organic ligand and NO3− in a hydrothermal condition is confirmed radical change instead of the simple coordination between organic ligands with Zn2+ in traditional method. The directly acquired ZnO particles possessing uniform dumbbell-like morphology have no obvious agglomeration. The yield reaches >95%. In particular, the synthesis mechanism and morphology evolution during the ZnO aggregates growth were carefully explored and proposed. Density functional theory (DFT) and surface energy calculations demonstrated the effects of activity variation of reactive groups and preferred growth surface of ZnO crystals. This work gives new insights into new synthesis strategy of ZnO particles via hydrothermal condition.

Characteristics and Sinterability of Ceria Stabilized Zirconia Nanoparticles Prepared by Chemical Methods

Microwave assisted and molten salts synthesis were extended for preparation of ceria (10 mol%; 15 mol%) stabilized zirconia and their parameters and sinterability were compared with that of particles prepared by the sol-gel combustion method. As-prepared powders by using microwave assisted and sol-gel combustion synthesis contained single tetragonal ZrO2 phase but powders prepared by molten salts combustion method contained two ceria-stabilized tetragonal phases with different content of ceria. The crystallite size of the as-prepared zirconia phases was in the range of 3.2 – 9.4 nm and the average particles size is in the range of 7.6 – 24.6 nm depending on the synthesis method. Additional calcination of the powders up to 1000 °C led to increase of crystallite size in the range of 19 – 25 nm and decrease of specific surface area in the range of 18 – 21 m2/g and partial formation of monoclinic phase of ZrO2. Bulk materials with fine-grained microstructure (0.8 – 1.6 µm) and density in the range of 95.2 – 97.2 % were obtained by spark plasma sintering at 1280 – 1310 °C during 3 min. Nanoparticles prepared by microwave assisted synthesis showed better sinterability and higher density.DOI: http://dx.doi.org/10.5755/j01.ms.24.3.18288