Specific Surface Area Measurements Research Articles

Polymer Gel Substrate: Synthesis and Application in the Intensive Light Artificial Culture of Agricultural Plants.

This work is devoted to the description of the synthesis of hydrogels in the process of cryotropic gel formation based on copolymerization of synthesized potassium 3-sulfopropyl methacrylate and 2-hydroxyethyl methacrylate (SPMA-co-HEMA) and assessing the potential possibility of their use as substrates for growing plants in intensive light culture in a greenhouse. Gel substrates based on the SPMA-co-HEMA were created in two compositions, differing from each other in the presence of macro- and microelements, and their effects were studied on the plants' physiological state (content of chlorophylls a and b, activity of catalase and peroxidase enzymes, intensity of lipid peroxidation, elemental compositions) at the vegetative period of their development and on the plants' growth, productivity and quality of plant production at the final stages of development. Experiments were carried out under controlled microclimate conditions. Modern and standard generally accepted methods of gels were employed (ATR-FTIR and 13C NMR spectral studies, scanning electron microscopy, measurement of specific surface area and pore volume), as well as the methods of the physiological and chemical analysis of plants. The study demonstrated the swelling ability of the created gel substrates. Hydrogels' structure, their specific surface area, porosity, and pore volume were investigated. Using the example of representatives of leaf, fruit and root vegetable crops, the high biological activity of gel substrates was revealed throughout the vegetation period. Species specificity in the reaction of plants to the presence of gel substrates in the root-inhabited environment was revealed. Lettuce, tomato and cucumber plants were more responsive to the effect of the gel substrate, and radish plants were less responsive. At the same time, more pronounced positive changes in plant growth, quality and productivity were observed in cucumber and lettuce in the variant of gel substrates with macro- and microelements and in tomato plants in both variants of gel substrates. Further research into the mechanisms of the influence of gel substrates on plants, as well as the synthesis of new gel substrates with more pronounced properties to sorb and retain moisture is promising.

Graphene thermally modified with polyvinyl alcohol applied as conductive water-based paints based on polyurethane

This paper presents the fabrication of thermally reduced graphene modified with polyvinyl alcohol (PVA), which can be used as a conductive water-based paint based on polyurethane (PU). Graphite oxide (GO) was oxidised from graphite by the Hummer method, and then graphene was formed by the thermal-reducing GO method. The graphene was modified by dispersing it into a PVA solution with various concentrations and mass ratios to optimise the modification process. The graphene modified with PVA could be easily dispersed in water. Water-borne PU film-forming polymer was prepared by polymerisation reaction between isophorone diisocyanate with poly(tetramethylene glycol) and dimethylolpropionic acid. The carboxylate functional groups on the surface of the polymer particles make the polymer particles dispersed well and stable in water, so this polymerisation process does not use any surfactants. The characterisation methods included field emission scanning electron microscope with energy-dispersive X-ray spectroscopy (FESEM-EDX), specific surface area measurement, Raman microspectroscopy, resistance measurement... The graphene-based conductive paint has good adhesion, conductivity of the dry paint film was from 0.1-4 mS/cm with graphene content in the dry paint film was about 5-10 wt%.

Synthesis of zeolite and aluminum-modified zeolite from lake sediment for simultaneous immobilization of cationic and anionic pollutants in lakes

Aiming at the development of ecologically safe and environmentally friendly materials to immobilize both anionic and cationic pollutants in eutrophic lakes, we have attempted to synthesize zeolites and aluminum-modified zeolites (AMZs) from four lake sediments by a fusion-assisted hydrothermal method. Characterization by X-ray fluorescence spectrometry, X-ray diffraction analysis, Fourier-transform infrared spectrometry, scanning electron microscopy, and specific surface area measurements confirmed that zeolites including Na–X, Na–P1, and hydroxysodalite were successfully synthesized, and the AMZs composed of zeolite and amorphous hydrous aluminum oxide were formed. The cation-exchange capacity (representing the ability to adsorb cationic pollutants) and the phosphate adsorptive capacity (representing the ability to adsorb anionic pollutants) of zeolites (204.3–305.7 cmol/kg and 9.3–16.3 mgP/g, respectively) and AMZs (105.7–309.2 cmol/kg and 26.8–38.9 mgP/g, respectively) were much higher than those of the original lake sediments (3.7–6.4 cmol/kg and 0.5–1.7 mgP/g, respectively). Incubation of sediment in lake water under anoxic conditions, which are commonly encountered at the beds of eutrophic lakes, triggered substantial release of phosphorus, iron, manganese, and ammonium, but amendment with AMZ significantly reduced the concentrations of these pollutants in the overlying water. Our findings demonstrated that zeolite and AMZ synthesized from lake sediments may be applied as suitable materials for the remediation of eutrophic lakes.

Magnetite nanoparticles obtained by solution combustion synthesis

This research presents a comprehensive investigation into the synthesis and characterization of magnetite nanoparticles through solution combustion reactions ignited by conventional means. In addition to the structural and compositional findings, this study's main investigation results include the specific surface area measurements conducted using the BET method. The analysis revealed specifi c surface area values for the synthesized magnetite nanoparticles at varying propellant-to-oxidant ratios, demonstrating a substantial decrease in specific surface area as the ratio increased. Specifically, specific surface areas of 72.203 m2/g for the 1:1 ratio, 22.240 m2/g for the 1:1.5 ratio, and 9.204 m2/g for the 1:2 ratio were determined. Furthermore, calculations based on the BET results and assuming spherical magnetite nanoparticles provided average particle sizes of 16±1 nm for the 1:1 ratio, 51±2 nm for the 1:1.5 ratio, and 125±4 nm for the 1:2 ratio. These findings highlight the impact of synthesis parameters on the nanoparticles' surface area and size, shedding light on their potential applications in various fields, including nanomedicine and magnetic diagnostics. Overall, this research contributes valuable insights into the synthesis, characterization, and tunable properties of magnetite nanoparticles, offering potential avenues for their utilization across diverse industries.

INFLUENCE OF TEMPERATURE ON THE PROPERTIES OF FREE LOADED INORGANIC OXIDE NANO POWDERS

A comparative study was carried out on the possibility of controlling the average sizes of nano-sized powders of silicon dioxide and aluminum oxide obtained by electron beam evaporation, pyrogenic, liquid chemical and plasma chemical methods, by keeping them in the temperature range of 800 – 1300 ?C in an air atmosphere. The average size of the resulting particles was estimated from specific surface area measurements using the Brunauer–Emmett–Taylor (BET) adsorption method at liquid nitrogen temperature. Crystallographic parameters in the treated powders were assessed using X-ray diffraction analysis. It has been shown that by appropriate choice of temperatures and initial powder, it is possible to achieve an average particle size in the resulting powder close to a given one and a phase composition.

Effect of the Calcination Duration on the Electrochemical Properties of Na2Ti3O7 as Anode Material for Na-Ion Batteries

The growing interest in Na-ion batteries as a “beyond lithium” technologies for energy storage drives the research for high-performance and environment-friendly materials. Na2Ti3O7 (NTO) as an eco-friendly, low-cost anode material shows a very low working potential of 0.3 V vs. Na+/Na but suffers from poor cycling stability, which properties can be significantly influenced by materials synthesis and treatment. Thus, in this work, the influence of the calcination time on the electrochemical performance and the reaction mechanism during cycling were investigated. NTO heat-treated for 48 h at 800 °C (NTO-48h) demonstrated enhanced cycling performance in comparison to NTO heat-treated for only 8 h (NTO-8h). The pristine material was thoroughly characterized by X-ray diffraction, laser granulometry, X-ray photoelectron spectroscopy, and specific surface area measurements. The reaction mechanisms induced by sodiation/desodiation and cycling were investigated by operando XRD. Electrochemical impedance spectroscopy was used to evidence the evolution of the solid electrolyte interface layer (SEI) and modification of charge transfer resistances as well as the influence of cycling on capacity decay. The evolution of the crystallographic structure of NTO-48h revealed a more ordered structure and lower surface contamination compared to NTO-8h. Moreover, the residual Na4Ti3O7 phase detected after the sodium extraction step in NTO-8h seems correlated to the lower electrochemical performance of NTO-8h compared to NTO-48h.

Synthetic Opals or Versatile Nanotools-A One-Step Synthesis of Uniform Spherical Silica Particles.

Synthetic opals, a composition of homogeneous silica spheres in the mesoscale size range, have attracted the attention of scientists due to their favorable chemical and physical properties. Their chemical inertness and stability, biocompatibility, homogeneity, elevated specific surface area, and ease of functionalization of their surfaces make them a versatile nanotool. In the present study, the Stöber process was used to investigate the effect of parameters, such as reagent concentration and synthesis temperature, on the resulting silica particle size and structure. The optimal conditions for successfully obtaining homogeneous particles in the mesoscale range with high reproducibility were investigated. Several synthesis procedures and their dependence on the reaction temperature were presented to allow the selection of the assumed diameter of silica spheres. The numerous samples obtained were examined for size, homogeneity, structure, and specific surface area. On the basis of specific surface area measurements and nuclear magnetic resonance studies, the internal hierarchical structure of the spherical silica was confirmed as consisting of a solid core and layers of secondary spheres covered by a solid shell. Structural studies (X-ray Spectroscopy, X-ray Absorption Near-Edge Structure, and nuclear magnetic resonance), together with infrared vibrational spectroscopy, showed no dependence of the structure of the obtained mesospheres on the concentration of reagents and the size of the obtained particles.

Comparative study of Na0.67Ni0.25Co0.17Mn0.58O2 P-Type cathode materials for sodium-ion batteries: Combustion synthesis and combined analysis of structural, electrical, and dielectric properties

In this study, we present a promising sodium-ion cathode material, Na0.67Ni0.25Co0.17Mn0.58O2, which was synthesized by combustion method, and subsequent heat treatment at various calcination temperatures (700 °C, 800 °C, and 900 °C). The samples underwent analysis using various techniques, including Thermogravimetric Analysis (TGA), Differential Thermal Analysis (DTA), Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) combined with Energy Dispersive X-ray Analysis (EDS), Specific Surface Area Measurements (BET), and Impedance Spectroscopy Measurements (EIS). The XRD pattern of the sample prepared at 700 °C reveals that the lower annealing temperature induces the formation of a new phase, P3. Indeed, the phase transition from the rhombohedral P3-phase to hexagonal P2-phase at 900 °C via mixed phases (P3/P2) yielded at 800 °C. Furthermore, Rietveld refinement using the hexagonal unit cell leads the calculation of the network parameters and the structural stacking, showing that the P2-phase exhibits a more pronounced two-dimensional character compared to the P3-phase. FT-IR spectra reveal that the lattice structures of the samples consist of NaO6 and MeO6 (Me = Ni, Co, Mn) octahedra. SEM-EDS analysis shows a homogeneous surface morphology in good agreement with the theoretical and experimental proportions of the elements constituting the three P-type phases. Subsequently, we extensively investigated the effect of our P-type materials on the electrical and dielectric properties of the cathodes using EIS measurements. Our findings suggest that the low-cost and eco-friendly P2–Na0.67Ni0.25Co0.17Mn0.58O2 phase shows promise as a cathode material for sodium-ion batteries and represents a competitive alternative to the P3/P2- and P3–Na0.67Ni0.25Co0.17Mn0.58O2 phases.

Ultrasonic-assisted of TiO2-MWCNT nanocomposite with advanced photocatalytic efficiency for elimination of dye pollutions

Nanocomposites of titanium dioxide (TiO2) and multi-wall carbon nanotubes (MWCNTs) were successfully synthesized (TiO2-MWCNTs) from MWCNTs and titanium tetrachloride (TiCl4) as starting precursors using ultrasonic-assisted technique. The impact of the different weight percentages of MWCNTs (1, 3, 5, and 7 wt%) on TiO2 optical, structural, and morphological properties were investigated. Subsequently, the photocatalytic activity was assessed by organic dyes degradation such as methylene Blue (MB) and rhodamine B (RhB) under ultraviolet (UV) light exposure. The characterization of synthesized materials demonstrated the anatase phase formation in both pure TiO2 and the TiO2-MWCNTs nanocomposite, according to X-ray diffraction analysis. The morphology analysis of TiO2-MWCNTs nanocomposites using FESEM and TEM confirmed the uniform dispersion of MWCNTs with an exterior diameter of 12–16 nm within the TiO2 matrix. The BET measurement of the sample's specific surface areas identified that the MWCNTs addition resulted in the increase of surface area from 76.34 to 194.35 m2 g−1 for pure TiO2 and TiO2/7 wt% MWCNTs, respectively. Furthermore, TiO2/7 wt% MWCNTs nanocomposite had lower optical bandgap energy and higher photocatalytic performance as compared to the pure TiO2. The photodegradation efficiency of TiO2/7 wt% MWCNTs nanocomposite increased from 63.63 % to 92.36 % for MB and 71.56 % to 94.13 % for RhB compared to pure TiO2, after 60 min UV light exposure.

Optimization of Grinding Parameters for the Mechanochemical Activation of Kaolin with the Addition of Trass

At present, to achieve further reductions in CO2 emissions in the cement industry, it is essential to improve the efficiency of grinding processes and reduce the energy demand. This study examined the effects of various grinding parameters (addition of trass, ball to powder mass ratio (BPR), material of grinding bodies and jars, rotational speed, and mill type) to minimize the energy consumption of the mechanochemical activation of kaolinite. X-ray diffraction, Fourier transform infrared spectroscopy, inductively coupled plasma optical emission spectroscopy, scanning electron microscopy, and specific surface area measurements were used to examine the influence of grinding parameters. It was found that the addition of as little as 25% (mass percent) trass reduced the specific energy demand for the complete amorphization of kaolinite by 56%. The application of steel grinding bodies (instead of ZrO2 ones) had a slight influence on the amorphization kinetics of kaolinite, but it could mechanochemically activate 30% more samples at the same BPR and specific energy demand. The use of the four-pot milling instead of the one-pot could considerably decrease the specific energy demand of the complete and incomplete (α = 0.9) amorphization of kaolinite. Overall, a 94% reduction was achieved in specific energy demand with steel grinding material, 14:1 BPR, four-pot milling, and the incomplete amorphization of kaolinite.

Valorisation of Chlorella sp. biomass in 5-HMF through a two-step conversion in the presence of Nb2O5 and NbOPO4 and optimisation through reactive extraction

The valorisation of recalcitrant Chlorella sp. microalgal biomass by the extraction of the sugar content and its conversion into 5-hydroxymethyl furfural (5-HMF) has been carried out in two-steps. In the first step, a pre-treatment of the biomass was optimized to obtain, by sonication and hydrothermal treatments also in the presence of acetic acid and SiO2 pellets, the maximum release of carbohydrate and their hydrolysis to monosaccharides. The second step, carried out under hydrothermal conditions, was devoted to the heterogeneous catalytic isomerisation/dehydration of the monosaccharides (essentially glucose and fructose) released from algae in the first reaction step to yield 5-HMF in presence of two commercial samples of niobium-based catalysts that were characterized with several techniques like specific surface area and superficial acidity measurements, SEM, HRTEM, EDX, FTIR and Raman. Other important features of the two catalysts are largely present in the literature due to the fact that they are commercial materials. The isomerisation/dehydration reactions of the monosaccharides proceed through a tandem pathway involving the Lewis and Brønsted acid sites provided by the surface of the acidic solids giving rise to the isomerization of glucose to fructose, followed by dehydration of fructose to 5-HMF. The optimisation of the reaction conditions was carried out in the presence of Nb2O5 by using a Design of Experiment (DoE) approach. The optimised parameters were identified as temperature 210 °C and 4.45 h of reaction time, providing a yield to 5-HMF of about 18% on the total sugars contained in the algae. A further optimisation has been achieved in the presence of NbOPO4 instead of Nb2O5, which still led to 21% yield to 5-HMF on the total sugars. Moreover, using an H2O/MIBK system, a reactive extraction was performed, obtaining the very good value of yield to 5-HMF of 29% on total sugars. In this way, a multi-approach process optimisation was performed, in line with the principles of process intensification, with the aim of improving the energy-efficiency of the entire process.

Study of the Mechanism of Dearsenification of Arsenopyrite Enhanced by Mechanically Modified Pyrite and Bacteria

This study investigated the impact of mechanically modified pyrite on the dearsenification of arsenopyrite through bacterial oxidation. Pyrite was mechanically modified using a planetary high-energy ball mill, and the resulting changes in the crystal structure were characterized using particle size analysis, specific surface area measurements, scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). Pearson correlation analysis was employed to examine the relationship between the crystal structure of modified pyrite and the bacterial oxidation of arsenopyrite. The study also investigated the mechanism of arsenic removal using pyrite with varying degrees of mechanical modification during arsenopyrite bio-oxidation. The key findings are as follows: (1) The maximum extent of arsenopyrite dearsenification by bacteria was achieved at a pyrite modification degree of 400 r·min−1 and reached 96.01%, which was 14.49% higher than that for unmodified pyrite and 24.13% higher than that in the absence of pyrite. At this degree, the modified pyrite exhibited a median diameter of 1.33 μm (minimum) and a specific surface area of 3123 m2·kg−1 (maximum). (2) Pearson correlation analysis revealed a significant negative correlation between the extent of arsenopyrite dearsenification and the particle size and grain size of pyrite, and a significant positive correlation with the specific surface area and the amorphous degree of pyrite. A smaller particle size and grain size, larger specific surface area, and a higher amorphous degree were associated with a higher extent of dearsenification. (3) The mechanism of enhanced arsenopyrite dearsenification using mechanically modified pyrite was attributed to autocatalytic dissolution. The galvanic effect directly enhanced dearsenification, while the mechanical modification facilitated the direct oxidation of pyrite by bacteria, releasing a significant amount of Fe3+ and indirectly enhancing the dearsenification of arsenopyrite.

Material jetting of carbon nano onions for printed electronics

As an additive manufacturing process, material jetting techniques allow to selectively deposit droplets of materials in liquid or powder form through a small-diameter aperture, such as a nozzle of a print head. For the fabrication of printed electronics, a variety of inks and dispersions of functional materials can be deposited by drop-on-demand printing on rigid and flexible substrates. In this work, zero-dimensional multi-layer shell-structured fullerene material, also known as carbon nano-onion (CNO) or onion-like carbon, is printed on polyethylene terephthalate substrates using drop-on-demand inkjet printing. CNOs are produced using a low-cost flame synthesis technique and characterized by electron microscopy, Raman, x-ray photoelectron spectroscopy, and specific surface area and pore size measurements. The produced CNO material has an average diameter of ∼33 nm, pore diameter in the range ∼2–40 nm and a specific surface area of 160 m2.g−1. The CNO dispersions in ethanol have a reduced viscosity (∼1.2 mPa.s) and are compatible with commercial piezoelectric inkjet heads. The jetting parameters are optimized to avoid satellite drops and to obtain a reduced drop volume (52 pL), resulting in optimal resolution (220 μm) and line continuity. A multi-step process is implemented without inter-layer curing and a fine control over the CNO layer thickness is achieved (∼180 nm thick layer after 10 printing passes). The printed CNO structures show an electrical resistivity of ∼600 Ω.m, a high negative temperature coefficient of resistance (−4.35 × 10−2 °C−1) and a marked dependency on relative humidity (−1.29 × 10−2 RH% −1). The high sensitivity to temperature and humidity, combined to the large specific area of the CNOs, make this material and the corresponding ink a viable prospect for inkjet-printed technologies, such as environmental and gas sensors.

Dynamic stability of mineral-associated organic matter: enhanced stability and turnover through organic fertilization in a temperate agricultural topsoil

Soil organic matter (SOM) plays a vital role for soil quality, sustainable food production and climate change mitigation. It is common knowledge that SOM consists of different pools with varying qualities, quantities, and turnover times. However, it is still poorly understood how mineral and organic fertilization affects the formation and stabilization of mineral-associated organic matter (MAOM) and how long it can remain there. Here, we report on the long-term effects of different farming systems on the stability and turnover of the fine silt and clay-sized MAOM fraction (<6.3 μm) of a Haplic Luvisol (0–20 cm) in the DOK long-term trial (Switzerland). We compared three farming systems with contrasting fertilization (CONMIN = pure mineral, CONFYM = mineral + organic, BIODYN = pure organic) with an unfertilized control (NOFERT) between 1982 and 2017. We performed specific surface area (SSA) measurements on fractionated MAOM samples (<6.3 μm) from 1982 to 2017, before and after removal of OM, measured the 14C activity of all samples during the entire period and estimated the mean residence time (MRT) with a model taking into account ‘bomb 14C’ and radioactive decay. We found constant MAOM-C contents under organic fertilization. Results of SSA analysis indicate best conditions for MAOM-C stabilization under organic fertilization and different sorption mechanisms in MAOM between farming systems with and without organic fertilization. The modelled MRTs were significantly higher in NOFERT (238 ± 40 yrs) and CONMIN (195 ± 27 yrs), compared to CONFYM (138 ± 18 yrs) and BIODYN (140 ± 19 yrs), implying a high C turnover (i.e. more active MAOM) at high C contents under organic fertilization. Our findings show that MAOM is not the dead OM but corroborates the concept of ‘dynamic stability’. Continuous OM inputs from organic fertilizers and their rapid and constant turnover are needed to stabilize the “stable” MAOM-C fraction.

Superparamagnetic Spinel-Ferrite Nano-Adsorbents Adapted for Hg2+, Dy3+, Tb3+ Removal/Recycling: Synthesis, Characterization, and Assessment of Toxicity.

In the present work, superparamagnetic adsorbents based on 3-aminopropyltrimethoxy silane (APTMS)-coated maghemite (γFe2O3@SiO2-NH2) and cobalt ferrite (CoFe2O4@SiO2-NH2) nanoparticles were prepared and characterized using transmission-electron microscopy (TEM/HRTEM/EDXS), Fourier-transform infrared spectroscopy (FTIR), specific surface-area measurements (BET), zeta potential (ζ) measurements, thermogravimetric analysis (TGA), and magnetometry (VSM). The adsorption of Dy3+, Tb3+, and Hg2+ ions onto adsorbent surfaces in model salt solutions was tested. The adsorption was evaluated in terms of adsorption efficiency (%), adsorption capacity (mg/g), and desorption efficiency (%) based on the results of inductively coupled plasma optical emission spectrometry (ICP-OES). Both adsorbents, γFe2O3@SiO2-NH2 and CoFe2O4@SiO2-NH2, showed high adsorption efficiency toward Dy3+, Tb3+, and Hg2+ ions, ranging from 83% to 98%, while the adsorption capacity reached the following values of Dy3+, Tb3+, and Hg2+, in descending order: Tb (4.7 mg/g) > Dy (4.0 mg/g) > Hg (2.1 mg/g) for γFe2O3@SiO2-NH2; and Tb (6.2 mg/g) > Dy (4.7 mg/g) > Hg (1.2 mg/g) for CoFe2O4@SiO2-NH2. The results of the desorption with 100% of the desorbed Dy3+, Tb3+, and Hg2+ ions in an acidic medium indicated the reusability of both adsorbents. A cytotoxicity assessment of the adsorbents on human-skeletal-muscle derived cells (SKMDCs), human fibroblasts, murine macrophage cells (RAW264.7), and human-umbilical-vein endothelial cells (HUVECs) was conducted. The survival, mortality, and hatching percentages of zebrafish embryos were monitored. All the nanoparticles showed no toxicity in the zebrafish embryos until 96 hpf, even at a high concentration of 500 mg/L.

Lignin degradation by Coprinus comatus in corn stalk

Coprinus comatus is a kind of fungus, which reveal the degradation of lignocellulose. In the present study, the strain was optimum cultivated and lignin degradation in corn stalk was investigated. The changes of corn stalk were characterized by scanning electron microscopy (SEM), specific surface area measurement (BET), X-ray diffraction (XRD), Fourier infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS). The results showed that the strain got its degradation of lignin up to 38.66 %. The strain eroded structure of corn stalk and formed pores, which accelerated the degradation of lignin. Treated by Coprinus comatus increased the specific surface area and reduced the crystallinity of corn stalk. Meanwhile, small molecular substances found in the treated corn stalk matrix. These demonstrated the effectives of Coprinus comatus for corn stalk degradation. The potentials of Coprinus comatus in this field need further investigation.

Oxygen defects and S-scheme heterojunctions synergistically promote the photocatalytic hydrogen evolution activity and stability of WO2.72/Zn0.5Cd0.5S-DETA nanocomposites

The study analyzed the impact of oxygen defects and S-scheme heterojunction on the performance and stability of WO2.72/Zn0.5Cd0.5S-DETA (WO/ZCS) nanocomposites photocatalysts for hydrogen evolution. Results showed that ZCS alone under visible light had good photocatalytic hydrogen evolution activity (1.762 mmol g−1h−1) and stability (79.5 % activity retention rate after seven cycles, 21 h). The WO3/ZCS nanocomposites with S-scheme heterojunction had better hydrogen evolution activity (2.287 mmol g−1h−1), but poor stability (41.6 % activity retention rate). The WO/ZCS nanocomposites with S-scheme heterojunction and oxygen defects showed excellent photocatalytic hydrogen evolution activity (3.94 mmol g−1h−1) and stability (89.7 % activity retention rate). The specific surface area measurement and ultraviolet–visible spectroscopy diffuse reflectance spectroscopy indicate that oxygen defects lead to larger specific surface area and improved light absorption, respectively. The charge density difference confirms the existence of the S-scheme heterojunction and the amount of charge transfer, which accelerates the separation of photogenerated electron-hole pairs and enhances the utilization efficiency of light and charge. This study offers a new approach using the synergistic impact of oxygen defects and S-scheme heterojunction to enhance the photocatalytic hydrogen evolution activity and stability.

Magnetite interaction with arsenic during sorptive removal from groundwater: a mechanistic study

A magnetic mixed iron oxide, magnetite (Fe3O4), was synthesized in the laboratory and characterized before its use as sorbent for arsenic removal. The characterization techniques used were X-ray diffraction (XRD), specific surface area, zeta potential and particle size measurements. The sorbent was applied for arsenic removal, without any pre or post treatment, from groundwater. The efficiency of sorption can only be improved by understanding the sorbent–sorbate interaction. For onsite monitoring of the sorbent-sorbate interaction, an electrochemical investigation using cyclic voltammetry (CV) measurement was developed. The study confirmed that the sorption of As(III) on Fe3O4 is dynamic (reversible) whereas that of As(V) is static (irreversible) in nature. Detailed investigation after the sorption was carried out utilizing X-ray photoelectron spectroscopy (XPS) measurement. The complexation of As(III)-Fe3O4 and As(V)-Fe3O4 without any redox transformation was evident from the XPS data. By careful examination of the results, a mechanism of arsenic removal by Fe3O4 was proposed.

Synthetic silico-metallic particles-SSMMP-Ni and SSMMP-Ni-IL: CO2 capture and utilization

Synthetic silico-metallic mineral particles (SSMMP) containing different amounts of Ni (SSMMP-Ni) and SSMMP-Ni functionalized with different IL (SSMMP-Ni-IL) were obtained and successfully used as solid adsorbents for CO2 sorption, CO2/N2 separation and highly recyclable heterogeneous catalysts active in the synthesis of different cyclic carbonates using CO2 as a starting reagent. Samples were characterized by infrared spectroscopy (FTIR), RAMAN spectroscopy, X-ray diffraction (XRD), thermal analysis (TGA), specific surface area measurements (BET) and scanning electron microscopy (SEM). Samples containing IL demonstrated high CO2 capture capacity (1.18–1.91 mmol CO2/g adsorbent − 1 bar CO2), CO2 selectivity (7.5–14.7) and stability. As catalysts, SSMMP-Ni 50% achieved a yield of 93.3% in propylene carbonate production (20 bar, 100 °C and 7 h) and constant yield up to 10 cycles. These materials are easy to synthesize, with low energy demand, high stability and versatile to be used as adsorbent in CO2 capture and catalyst for CO2 transformation.

Nitrogen, nickel and graphene oxide doped carbon xerogel as an active electrode of an electrochemical capacitor

N-, Ni-, and graphene oxide (GO)-doped carbon xerogel were synthesized from melamine-resorcinol-formaldehyde gels by drying followed by pyrolysis at 950 °C. The mass of nickel and GO in carbon xerogel, formed after carbonization was 5 and 1%, respectively. The obtained product was characterized by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The characteristics were completed by measurements of BET specific surface area as well as pore distribution. For graphene oxide and nickel doped carbon xerogel, a decrease in the BET surface area of about 2% compared to unmodified carbon xerogel was observed with a simultaneous increase of cumulative pore volume and average pore diameter of about 50 and 32%, respectively. Electrochemical properties of doped carbon xerogel were evaluated in 6 M KOH by cyclic voltammetry (CV) and galvanostatic modes. It was revealed, that the highest specific capacitance of 222 Fg−1 was reached for N-Ni-GO-doped carbon xerogel during the process of galvanostatic charge-discharge (GCD). Moreover, this sample also exhibited 100% stability during GCD and about 98% stability during 3000 cycling tests.Graphical abstractCharacterization of morphology, structure and electrochemical properties of xerogels where:MRF-CX - melamine-resorcinol-formaldehyde xerogel,MRF-GO-Ni-CX - melamine-resorcinol-formaldehyde-graphene oxide-nickel xerogel