•Effective thermal conversion of coal slag through multiple reactions scheme.•Process was governed by variations in melt viscosity and by the composition gradient.•Successful SiO2 dissolution was ...achieved over low activation energy catalytic pathway.•At T = Tiso, conversion process is freed from dependence on temperature and pressure.•Enthalpy-entropy compensation effect was identified, with “tunnel effect” phenomenon.
This study provides insight into benefits of thermo-chemical conversion of coal slag as recovery process into value-added products. This research involves kinetic analysis of process conducted through non-isothermal thermal analysis measurements, with additional raw material characterization. Kinetic results showed that decomposition proceeds through two consecutive reactions steps (first one, including anorthite P1̅ → I1̅ phase transition, and then production of incongruent melting product (ternary system: CaO·Al2O3·2SiO2 (CAS2), where viscosity of slag changes), and second one including dehydration and formation of meta-muscovite, and subsequently, thermal disruption of muscovite de-hydroxylated phase, which proceeds with breaking of octahedral Al–O bonds), and one single-step reaction (attributed to CO-reduction of hematite to magnetite). Thermodynamic results showed an existence of physically meaningful isokinetic temperature (Tiso), which corresponds to active vibrational frequency of surroundings of SiO2 reaction site, manifested through Si‒O bond weakening by catalytic reaction of freed hydroxide ion (OH−). It was concluded that at temperature T = Tiso, the course of process loses its dependence on temperature and pressure, regulating changes between thermodynamic parameters, through enthalpy-entropy compensation (EEC) effect.
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Molybdenum disulfide (MoS2) is considered promising noble metal-free catalysts for the hydrogen evolution reaction (HER). Whereas the bulk MoS2 does not exhibit significant activity, the catalytic ...properties of various nanostructures are noticeable. Therefore we synthesized flower-like molybdenum disulfide with the simple, one-step hydrothermal method. To enhance the catalytic activity of the material, low-energy ion irradiation is employed. As-prepared MoS2 is irradiated with hydrogen and carbon ions of various energies (20–40 keV) and fluences (1014-1017 ion/cm2). Our results show that irradiation has beneficial influence on MoS2 catalytic activity toward hydrogen evolution reaction. By producing morphological changes and defects in the structure, ion irradiation also impacts the conductivity of the material, which shows predominant effect on hydrogen evolution. The increase of current density at an overpotential of 300 mV with hydrogen ion irradiation is even 6 times higher than for as-synthesized catalyst.
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•Ion irradiation of MoS2 is an efficient method of improving its catalytic performance.•The changes in the catalyst behavior is dependable on the incident ion properties.•The dominant effect of irradiation is reduction in MoS2 charge transfer resistivity.•In irradiated materials, the current density increased up to six times.
•Successful thermally induced conversion of seashells into value-added products.•Isentropic oxidation which requires a large amount of heat causing entropy penalty.•According to XRD patterns CaCO3 is ...completely transformed into CaO at yet 850 °C.•Recommended high temperature to shifts reaction equilibrium towards decarbonation.•Agglomeration of CaO grains was favored by temperature-enhanced lattice diffusion.
Thermo-oxidative degradation of mollusk shells to CaO through intermediate phase of CaCO3 has been investigated using various analytical techniques. Powders of shells species (Dosinia exoleta and Ostrea edulis), with particle size fractions of 0.045 – 0.125 mm, 0.125–0.2 mm, and 0.2–1 mm, were subjected to degradation at the various heating rates (5, 10, 15 and 20 °C min−1). Degradation pathway of this carbonate-rich waste material has not yet been analyzed in detail at particulate level. Understanding transformation process in air should lead to control over yield and morphology of final product. Thermogravimetric analysis (TGA) and X-ray diffraction (XRD) techniques were used to benchmark transformation steps at different heating rates and final decarbonation temperatures, while scanning electron microscope (SEM) was used to analyze the effect of temperature on evolution of morphological changes for particles of different fractions. It was found that sintering in the presence of carbon dioxide (CO2) could be triggered by agglomeration of CaO crystals, enhanced by CO2 adsorption that increases surface energy.
Organophosphorus pesticide dimethoate was adsorbed onto gold nanospheres and nanorods in aqueous solution using batch technique. Adsorption of dimethoate onto gold nanoparticles was confirmed by ...UV-Vis spectrophotometry, TEM, AFM, and FTIR analysis. The adsorption of nanospheres resulted in aggregation which was not the case with nanorods. Nanoparticles adsorption features were characterized using Langmuir and Freundlich isotherm models. The Langmuir adsorption isotherm was found to have the best fit to the experimental data for both types of nanoparticles. Adsorption capacity detected for nanospheres is 456 mg/g and for nanorods is 57.1 mg/g. Also, nanoparticles were successfully used for dimethoate removal from spiked drinking water while nanospheres were shown to be more efficient than nanorods.
BACKGROUNDAlthough luteolin has been confirmed as potent anticancer agent, its potential application as therapeutic is limited by its water solubility. To overcome this shortcoming nanoparticle ...technology approach was applied. Owing to their proven low toxicity and the possibility to be easily functionalized gold nanoparticles (AuNP) were the nanosystem of choice used in this study. Novel luteolin capped gold nanoparticles (AuNPL) were synthesized and their anticancer effect towards human cervical adenocarcinoma HeLa cells was investigated in vitro.METHODSAuNPL were synthesized by reducing chloroauric acid by trisodium citrate with subsequent addition of luteoline during synthesis and their physicochemical characterization was done. AuNPL cytotoxicity against HeLa, human malignant melanoma A375, and normal human keratinocytes HaCaT cells was tested by MTT cell survival assay, and their IC50 values were determined. The capability of AuNPL to induce cell cycle arrest and apoptosis in HeLa cells were demonstrated by flow cytometry. The antioxidant activity of AuNPL was assessed by DPPH· and ABTS·+ scavenging assays. Cytoprotective properties of AuNPL towards HaCaT cells were examined by measuring the physiological and H2O2 induced intracellular reactive oxygen species (ROS) levels using flow cytometry. Also, genotoxicity of AuNPL in HaCaT cells was investigated by the single cell alkaline comet assay.RESULTSSpherical AuNPL, stable in aqueous solution up to six months at 4 °C were obtained in the synthesis. The selectivity in the cytotoxic action of AuNPL on HeLa and A375 cancer cells compared with their cytotoxicity on normal keratinocytes HaCaT was observed. AuNPL exerted their cytotoxic activity against HeLa cells through accumulation of the cells in the subG1 phase of the cell cycle, inducing the apoptotic cell death mediated by the activation of caspase-3 - 8, and - 9. AuNPL antioxidative potential was confirmed by DPPH· and ABTS·+ scavenging assays. IC50 concentration of AuNPL exerted cytoprotective effect against HaCaT cells by the significant reduction of the physiological intracellular ROS level. Additionally, AuNPL were shown as more cytoprotective towards HaCaT cells then luteolin due to the more successful elimination of H2O2 induced intracellular ROS. Moreover, nontoxic concentrations of AuNPL did not cause considerable DNA damage of HaCaT cells, indicating low genotoxicity of the nanoparticles.CONCLUSIONSynthesized AuNPL showed selective cytotoxic activity against HeLa cells, while being nontoxic and cytoprotective against HaCaT cells. The observed findings encourage further investigation of AuNPL as a promising novel anticancer agent.
Presented research aimed to develop an alternative approach for the estimation of biosorption capability of sunflower husk. The acid-pretreated sunflower biomass was characterized by scanning ...electron microscopy combined with energy dispersive X-Ray spectroscopy (SEM-EDX) analysis and Fourier transform infrared (FTIR) spectroscopy. Biosorption efficiency has been evaluated using inductively coupled plasma optical emission spectroscopy (ICP-OES) and laser-induced breakdown spectroscopy (LIBS). The adsorption capacity of the adsorbent was determined as the function of the pH of the solution, the initial concentration of heavy metal solutions, and contact time. The optimal conditions were achieved after 15 min of contact at pH 6, while the percentage of the removal was from 80.0?98.7 %, depending on the element. The results obtained from the kinetic and isotherm studies show that maximum adsorption of ions was quickly reached and followed the pseudo-second-order kinetic model. Real samples were tested and obtained Ni values by LIBS method were 3100?200 and 1240?100 mg kg-1, while estimated values by the ICP-OES were 2995?20 and 1130?10 mg kg-1, respectively. The obtained results prove that LIBS method can be used as a ?green alternative? for the evaluation of biosorption efficiency.
Hydrogen desorption properties of MgH2 ball milled with two different TiO2 polymorphs, rutile and anatase, were studied. Structural characterization has been done by X-ray diffraction (XRD) analysis, ...particle size analysis (PSD) and scanning electron microscopy (SEM). The mechanism of desorption and the apparent activation energy for desorption were investigated by applying isoconversional kinetic analysis of DTA spectra, while desorbed species were followed by TPD coupled with mass spectroscopy. It has been demonstrate that the addition of rutile TiO2 significantly decrease the apparent activation energy for desorption (Edesa), while addition of anatase titania has negligible influence on Edesa. Such behaviour could be explained in terms of the same crystal structure of rutile TiO2 and MgH2. Further, the mechanism of desorption changes from Avrami–Erofeev n = 3 for pure MgH2 to Avrami–Erofeev n = 4 for composite materials.
•Effect of different TiO2 phases on H desorption from MgH2–TiO2 composite is studied.•Addition of rutile notably reduce the apparent activation energy for desorption.•Such behaviour is due to the same crystal structure of rutile TiO2 and MgH2.
The polyanion cathodes for Li-ion batteries, namely LiFePO
4
, Li
2
FeP
2
O
7
and Li
2
FeSiO
4
, were synthesized by very short high-temperature treatment (approximately several minutes) and ...subsequent quenching. Methylcellulose—a polymer with thermally driven water solubility—was used as the medium in which the precursor solutions were dispersed prior to high temperature treatment. The methylcellulose pyrolytically decomposes to carbon, thus producing the polyanion material/carbon composites of LiFePO
4
/C, Li
2
FeP
2
O
7
/C and Li
2
FeSiO
4
/C. The obtained powders have reduced crystallinity and significant microstructural characteristics: low crystallite size and notable microstrain. They exhibit stable electrochemical performances in both aqueous and organic electrolyte. The broadening of existing peaks in cyclic voltammetry and/or the emergence of new broad peaks was attributed to the presence of the amorphous phase in the samples. In galvanostatic charge–discharge tests, the materials provided high capacities at low current densities, while the highest rate performance was demonstrated by olivine-phosphate when compared to the other two materials.
Graphical abstract
Ion beam irradiation is a versatile tool for structural modification and engineering of new materials. In this study, 12‐tungstophosphoric acid (WPA) films of different thickness were spin‐coated on ...platinized silicon substrate and irradiated with low energy hydrogen ions (10 keV) and swift heavy ions (Bi, Xe, and V) with energies up to 710 MeV. The different energy/fluence combinations allowed controllable structural changes that were investigated in detail using Raman and Infrared spectroscopy. For 120‐nm‐thick WPA samples, the irradiation led to the decrease of intensity of the skeletal and W‐Oc‐W bands of Keggin anion in order: Bi < V < Xe (for their applied energy/fluence combination). Also, symmetry change of Keggin anion similar to the one observed in the case of Keggin anions interacting with the supports was observed. For the selected ion beam irradiation parameters, xenon ion beam induced transformation of WPA to polytungstate. For 20‐μm‐thick WPA samples, the irradiation with hydrogen ion beam induced changes of skeletal vibrations and increased individualistic behavior of Keggin anions. As the fluence increased, the amount of the Keggin anions partially transformed to bronze also increased. Irradiation with vanadium also caused transformation to bronze‐like structure but with higher ratio of terminal W=Od bonds. The overall results show clear correlation between degree of structural modification of WPA and the calculated displacement per atom value. These results open possibilities for engineering new catalytically active structures of polyoxometalates with the help of ion beams.
In this study, 12‐tungstophosphoric acid (WPA) films (120 nm and 20 μm) were irradiated with hydrogen (10 keV) and swift heavy ions (Bi, Xe, and V, up to 710 MeV). The different energy/fluence combinations allowed controllable changes, from breaking of symmetry to bronze‐like structures, that were investigated in detail using Raman and Infrared spectroscopy. Structural changes of ion beam irradiated WPA might be beneficial for application in catalysis where the engineered structures can produce additional active sites for different reactions.
In recent years polyoxometalates (POMs) have attracted significant research interest due to versatile properties. These properties are determined by the size, structure and elemental composition of ...POMs and hence play an important role in their application. In the present study, the ion beam irradiation (10 keV C+ ions, 5 × 1014–2.5 × 1015 ions/cm2) has been utilized for modification of physicochemical properties of 120 nm-thick layer of 12-tungstophosphoric acid (WPA). Scanning electron microscopy analysis of irradiated films showed change of morphology i.e. an increase of WPA grain size with irradiation and coalescence of grains at the highest fluence. This was accompanied by structural changes. Attenuated total reflectance Fourier transform infrared analysis revealed that vibration bands of Keggin anion became less pronounced as fluence increased, while Raman spectra appeared as strongly modified. The effect of irradiation with 1.25 × 1015 ions/cm2 on the structure of WPA was similar to the effect of thermal treatment at 600 °C. Irradiation of WPA led to decrease of the band gap (from 4.07 to 3.92 eV), which was correlated to transformation Keggin anions into a network of WO6 octahedra and PO4 tetrahedra. This is in line with increased number of W=Od bonds observed by UV–Visible diffuse reflectance spectroscopy. Beside transformation to bronzes a reduction of WPA was observed by X-ray Photoelectron Spectroscopy (shift to lower binding energy) and Raman methods, whereas the Raman spectra of irradiated samples were similar to heteropoly blue. The electrochemical properties of irradiated WPA were also assessed. Cyclic voltammetry measurements showed that at up to 1.25 × 1015 ions/cm2 lithiation capacity of WPA increases and activity for hydrogen evolution reaction (HER) improves. The highest fluence caused interconnection of WO6 octahedra, closing of lithiation pathways and decrease in the number of active sites for HER. Our results provide a novel insight into the effects of ion beam irradiation on WPA and demonstrate high potential for tuning of physicochemical properties of POMs that are relevant in wide range of applications.
•Ion beam irradiation was used for structural modification of 12-tungstophosphoric acid (WPA).•By controlling the fluence the WPA structure can be tuned from mildly modified WPA to bronze-like character.•Induced changes are similar to the ones induced by high temperature treatment (T > 600 °C).•At optimal fluence the increased lithiation capacity and activity for HER was observed.•The work illustrates potential of ion beam irradiation for structural modification of polyoxometalates.
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