In this study, zinc oxide nanoparticles (ZnO NPs) were biosynthesized with the use of an extract derived from seaweed (Sargassum sp.) and used as a sorbent for the removal of Cr(III) ions from wastewater. The biosorption properties of the seaweed itself as well as of the post-extraction residue were investigated for comparison. ZnO NPs were characterized with UV−vis, ICP-OES, FTIR, XRD, and SEM techniques. The sorption capacity of the (bio)sorbents was investigated as a function of contact time at different pH values and initial concentrations of metal ions. Sorption kinetics and isotherms were studied in order to comprehend the sorption nature and mechanism. The sorption kinetic data were well-fitted with the pseudo-second-order model, and the highest sorption capacity was calculated for ZnO NPs (137 mg/g), whereas those calculated for Sargassum sp. (82.0 mg/g) and the post-extraction residue (81.3 mg/g) were comparable (at pH 5 and 300 mg of Cr(III) ions/L). The adsorption isotherms... [more]

Whilst Cu(In,Ga)Se2 (CIGSe) is an extremely promising material for solar cell fabrication, the widening of the band gap beyond the standard 1.1 eV is highly desirable for semitransparent applications. By replacing Cu with Ag and increasing the Ga content, we fabricate ACIGSe absorbers with band gaps ranging from 1.27−1.55 eV. An Ag/(Ag + Cu) ratio from 0.36−1.00 is chosen, as well as a Ga/(Ga + In) ratio from 0.25−0.59. The larger Ag and Ga contents lead to the expected band gap widening, which is, together with high sub-gap transparency, essential for semitransparent applications. The crystalline properties are confirmed by Raman spectroscopy and X-ray diffraction, which both reveal peak shifts according to the composition variations: a higher Ag content results in lower Raman shifts as well as in lower angles of X-ray diffraction for the main peaks due to the larger mass of Ag compared to Cu and the larger lattice constant of Ag-rich compounds. Increased open circuit voltages and dec... [more]

Highly efficient visible-light-driven heterogeneous photocatalyst Ag3PO4/g-C3N4 with different weight ratios from Ag3PO4 to g-C3N4 were synthesized by a facile in situ hydrothermal method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), photoluminescence spectra (PL), UV−vis diffuse reflectance spectra (UV-Vis), and electrochemical impedance spectra (EIS). Under visible light irradiation, Ag3PO4/g-C3N4 showed very excellent photocatalytic activity for sulfapyridine (SP) which is one of the widely used sulfonamide antibiotics. When the ratio from Ag3PO4 to g-C3N4 was 1:2, the degradation rate of SP at 120 min was found to be 94.1%, which was superior to that of pure Ag3PO4 and pure g-C3N4. Based on the experimental results, the possible enhanced photocatalytic mechanism of Ag3PO4/g-C3N4 was proposed.

Unconstrained metal powders of Cu, Cr, Ni and Al were applied to submerged arc welding (SAW) to clarify the chemical behaviour of copper in this modified SAW process. Aluminium metal is avoided in SAW because it is easily oxidised. Excessive aluminium oxides in the form of slag or inclusions in the weld metal will lead to poor weld metal materials properties. Aluminium is an effective deoxidiser and can be used to prevent Cr and Ni loss to the slag by preventing oxidation of these metals. The results show that carbon steel was alloyed to 5.3% Cr, 5.3% Ni, 3.6% Al and 5.2% Cu at 80% Cr yield, 81% Ni yield, 54% Al yield and 79% Cu yield. BSE (backscattered electron) images of the three-dimensional (3D) post-weld slag sample show 3D structures within the slag dome. The 3D structures contain features of vapour formation and recondensation. In addition, nano-strands appear in the 3D structures and confirm the vaporisation and recondensation of fluorides. The chemical behaviour of copper met... [more]

The aim of this Special Issue “Innovative Materials and Processes for Removal of Biopersistent Pollutants” (https://www [...]

The current study focused on the heterogenous catalytic hydrothermal liquefaction (HTL) of Brachychiton populneus biomass seed, using Ni as hydrogenation catalyst and Fe as active hydrogen producer. The activity of Ni metal and of Ni/Al2O3 in the HTL of seed (BS) and of a mixture of seed and shell (BM) was studied. To establish the best operating process conditions, the influence of variation of temperature and reaction time on the product yields was also examined. The highest bio-crude yields of 57.18% and 48.23% for BS and BM, respectively, were obtained at 330 °C and 10 min of reaction time, in the presence of Ni/Al2O3 as catalyst and Fe as hydrogen donor. Elemental analysis results showed that at these operative conditions, an increase of the higher heating value (HHV) from 25.14 MJ/kg to 38.04 MJ/kg and from 17.71 MJ/kg to 31.72 MJ/kg was obtained for BS and BM biomass, respectively, when the combination of Fe and Ni/Al2O3 was used. Gas chromatography−mass spectrometry (GC-MS) and... [more]

For the successful discovery and development of tight sand gas reserves, it is necessary to locate sand with certain features. These features must largely include a significant accumulation of hydrocarbons, rock physics models, and mechanical properties. However, the effective representation of such reservoir properties using applicable parameters is challenging due to the complicated heterogeneous structural characteristics of hydrocarbon sand. Rock physics modeling of sandstone reservoirs from the Lower Goru Basin gas fields represents the link between reservoir parameters and seismic properties. Rock physics diagnostic models have been utilized to describe the reservoir sands of two wells inside this Middle Indus Basin, including contact cement, constant cement, and friable sand. The results showed that sorting the grain and coating cement on the grain’s surface both affected the cementation process. According to the models, the cementation levels in the reservoir sands of the two w... [more]

When designing crash absorber particles for application as a filling material in the double-hull of ships, the main goal is to achieve an optimal mechanical performance, in combination with a low-density particle structure, while fulfilling several additional requirements regarding, for example, non-toxic and hydrophobic behavior. In this study, a fluidized bed was used to coat Poraver® glass particles with Candelilla wax and silicone to attain these specifications. A uniform coating was achieved with wax, but the process turned out to be far more challenging when using silicone. To evaluate the suitability of coated particles as a granular filling material, and to compare their performances with that of untreated Poraver® particles, several mechanical tests, as well as structural investigations, were conducted. While no notable improvement in mechanical behavior was observed on the single-particle level, bulk tests showed promising results regarding compressibility and abrasion resist... [more]

Green synthesized silver nanoparticles (AgNPs) have been used against antibiotic-resistant bacteria and chemo-resistant cancer cells. We synthesized AgNPs from Acacia nilotica pods, evaluating their antibacterial activity against eight bacterial strains and anticancer efficiency against two colon cancer cell lines, SW620 and SW480. Expression levels of eight genes (β-catenin, APC, TP53, Beclin1, DKK3, Axin, Cyclin D1, and C-myc) were checked by a reverse transcription-polymerase chain reaction in cancer cells before and after treatment with A. nilotica extract and A. nilotica-AgNPs. Prepared nanoparticles were characterized through ultraviolet-visible (UV-vis), Zetasizer, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FTIR) was used to identify the functional group in extracts. At first, AgNPs were confirmed by a sharp peak of surface plasmon resonance at 375 nm. The Z-average size was 105.4 nm with a polydispers... [more]

SSCN is a new type of self-sensitive photocatalyst. It consists of oxygenated carbon nitride-containing microspheres inside and polymerized triazine dye (TBO) formed on its surface by in situ polymerization. The presence of TBO endows SSCN with a wide range of optical responses. However, the TBO would self-degrade under light, making SSCN extremely unstable in photocatalytic reactions and limiting the practical application of SSCN. The introduction of phosphorus into the structure of SSCN significantly improved the electron−hole separation efficiency and reduced the self-degradation of surface TBO. Phosphorus-doped self-sensitive carbon nitride microspheres (P-SSCN) are easily synthesized by a one-pot solvothermal method—the phosphorus source was added to the precursor solution of SSCN. This resulting material was used for the photodegradation of tetracycline hydrochloride (TC-HCl) for the first time, giving improved visible light sensitivity and high stability in the photocatalytic pr... [more]

TG-FTIR and PY-GC/MS were used to analyze the pyrolysis behaviors of pine wood, urea-formaldehyde resin (UF resin) and their blended pellets. The pyrolysis process was divided into three stages: water evaporation, devolatilization and pyrolysis residue decomposition. During the pyrolysis process of the blended pellets, with the increase of the addition ratio of UF resin, the peak value of the weight loss decreased in the decomposition stage of the pyrolysis residue, while the temperature shifted to the low-temperature region. This was mainly due to the structural stability of pyrolytic carbon produced by UF resin, which hindered the thermal decomposition of lignin-produced residues in pine. FTIR showed that CO2 was the main product of pyrolysis. For UF resin, nitrogen compounds accounted for a large proportion. With the addition of UF resin, the nitrogen in the blended pellets increased significantly. Since the synergistic effect promoted the further decomposition of the organic oxygen... [more]

Since the 1950s, major breakthroughs have been made in the field of carbonate oil and gas exploration, and large reservoirs have been found in carbonate strata in many countries; however, the validity of highly evolved carbonate source rocks has been controversial. Because of the loss of organic carbon during acid-solution processing in conventional total organic carbon (TOC) determination, we decided to use a new method of reducing acid-solution losses in order to more effectively quantify acid-soluble organic matter in carbonate rock samples. Different levels of acid-soluble organic matter were present in different types of samples, and there was no positive correlation between the content of acid-soluble organic matter and conventionally measured TOC values. However, the thermal evolutionary maturity of samples with high acid-soluble organic matter content is relatively low, and the high hydrocarbon generation conversion rate of acid-soluble organic matter and conventional TOC in ca... [more]

Various experiments, including routine petrophysical measurements, thin section and scanning electronic microscope (SEM), high-pressure mercury intrusion (HPMI), and nuclear magnetic resonance (NMR), were performed to characterize the microscopic pore structure of tight sandstone in the Huagang Formation (E3h), Xihu Sag, East China Sea Basin, China. Specifically, NMR was used to investigate the dynamic variation of fractal dimensions during centrifugation, and the comparison of HPMI and NMR were used to clarify the difference of fractal dimensions. The results showed that there were four types of pores observed in thin section and SEM images: primary intergranular pores, intergranular dissolution pores, intragranular dissolution pores, and micropores within clay aggregates. The geometric shape and pore size of different pore types showed huge differences, indicating the formation of complex and diverse pore structures in the E3h formation. The flow capability of the reservoir was domin... [more]

Large gas reserves have been found in the Permian platform margin of the Kaijiang-Liangping area of the Sichuan Basin in SW China. They are assumed to be a widely developed reef−shoal reservoir. However, the tight matrix reservoir cannot support high gas production using conventional development technology at deep subsurface. In this contribution, we analyze the fractured reservoirs along the strike-slip fault zones using the compiled data of cores, well logging, and production data, and provide a seismic description. It was shown that the fractures and their dissolution developed along the strike-slip fault zones. The porosity and permeability of the fractured reservoir could increase by more than one and 1−2 orders of magnitude, respectively. The seismic anisotropic energy found in the steerable pyramid process suggests that fractured reservoirs have a strong heterogeneity, with a localized fault damage zone. This fracturing has both positive and negative effects, showing varied rese... [more]

The effects of cold surface temperature, wet air state (temperature and humidity) and original drop size on frost dendrites growth of two neighboring separate frozen water drops of same size under natural convection conditions were investigated by quantitative measurement. It was determined that for different cold plate surface temperature conditions, i.e., the ordinary-low temperature and the cryogenic temperature range, the frost formation mechanism is different. Under the conditions that the air temperature is not too high and absolute humidity is not too excessive, the influence of frozen water drop size on the longest dendrite of frost crystals becomes more and more obvious with the decrease in cold plate temperature. The changes in air temperature and relative humidity both change air absolute humidity, so they have similar effects on the growth of dendrites. However, the effect of wet air state on the growth of frost dendrites is not monotonous, which needs to be considered comp... [more]

Commercial cerium−zirconium oxide supports (Ce0.5Zr0.5O2, Ce0.75Zr0.25O2, and Ce0.4Zr0.5Y0.05La0.05O2) were used to prepare Ru/CeZrOx catalysts. According to the XRD and IR spectroscopy data, the supports consist of ceria-based substitutional solid solutions. The specific surface areas of supports and catalysts are similar and range from 71−89 m2/g. As shown by TEM and XRD methods, the size of support particles equals 6−11 nm. According to the TEM data, the size of ruthenium particles does not exceed 1.3 nm. The catalyst activity in the ammonia decomposition process was studied. The Ru/Ce0.75Zr0.25O2 catalyst at temperature 500 °C and GHSV 120,000 h−1 demonstrated the highest hydrogen productivity of 53.3 mmol H2/(gcat·min) and compares well with the best results reported in the literature. The kinetics of ammonia decomposition reaction were calculated using the Temkin−Pyzhov exponential expression. The developed mathematical model well described the experimental data. The studied cata... [more]

During well drilling in offshore conditions beyond the North of the Arctic Circle, there are often problems associated with deviations in the rheological parameters of the drilling mud as the temperature changes. Mud temperature in the upper part of the well in most cases is in the range up to 20 °C, whereas in the productive formation it is up to 80 °C and more. For such conditions, it is necessary to estimate the influence of temperature on the rheological parameters of drilling fluids, which is done in this paper. Compositions of water-based and hydrocarbon-based muds that may be used in the conditions of the offshore hydrocarbon fields were considered. The paper presents the authors’ formula for a drilling mud that possesses more stable rheological parameters in the temperature conditions of the offshore oil field and is more environmentally friendly. The physical properties of the newly designed drilling mud were measured with laboratory equipment. Rheological investigations were... [more]

A semi-empirical method is proposed for determining the rate of gas production in a flow-through gas generator (GG) with the allocation of a part of the gas flow produced by gasification of a low-melting solid material (LSM) in the total gas flow rate through the GG. The method is verified by test fires with polypropylene sample gasification by hot air under conditions of incoming supersonic flow with Mach number 2.43, 2.94, and 3.81 and stagnation temperature 600−700 K. The mean flow rates of gasification products obtained in test fires were 0.08 kg/s at Mach 2.43, 0.10 kg/s at Mach 2.94, and 0.05−0.02 kg/s at Mach 3.81. For obtaining 1 kg of gasification products in the test fires there was a need of 1.61 to 2.86 kg of gasifying agent.

Exhaust emissions from vehicles are the subject of numerous studies and legal acts. In the European Union, exhaust emissions are regulated by “Euro” emission standards, which limit emissions of gaseous pollutants such as CO, CO2, HC, and NOx, as well as the particulate matter (PM) and particle number (PN). Solid particles consist of a number of micro-contaminants, inter alia polycyclic aromatic hydrocarbons (PAHs) and their nitrated and oxygenated derivatives. Despite their highly mutagenic and carcinogenic character, these micro-contaminants are not regulated in Euro emissions standards. This paper presents both a general discussion of the phenomenon of particulate formation in and emission from direct injection gasoline engines, as well as a wide range of results on the subject. The subject of the micro-contaminants in solid particles from modern gasoline vehicles is explored. The samples of solid particles were collected from 11 groups of vehicles according to the WLTP test methodol... [more]

In view of the main problems of the condensing heat discharge modes of the existing underground air-conditioning system, the technical scheme of using phase change heat storage modules to improve the heat storage capacity of the reservoir is proposed. By establishing a 3D flow and transient heat transfer model of the phase change reservoir, the effects of thermal property parameters, package size and arrangement of the phase change heat storage modules on the heat storage performance of the phase change reservoir were quantitatively analyzed based on three indexes: heat storage capacity per volume Δq, guaranteed efficiency coefficient η and slope of temperature rise per unit load ε. The results show that when the phase change temperature is 29 °C (23 °C increased to 33 °C) and the latent heat value is 250 kJ/kg (100 kJ/kg increased to 250 kJ/kg), Δq (110.92 MJ/m3, 112.83 MJ/m3) and η (1.22, 1.24) under both conditions are at their most, respectively, indicating that the phase change te... [more]

Fractional-slot PMSM motors allow for obtaining high values of power density factors, but at the same time, they are characterized by high values of rotor losses—in the rotor core and permanent magnets. The main causes of rotor losses in this type of motor are subharmonics and a high content of higher harmonics in the distribution of the magnetomotive force MMF. The use of a solid rotor core simplifies the construction and technology of the rotor but eddy current losses in the core account for a significant percentage of the total rotor losses. It is well known that a laminated core reduces eddy currents, while for motors with an outer rotor, it complicates the construction and increases weight. Thus, the question arises about the necessity to use a laminated core in a high power density motor and the real benefits of this. The article presents a comparison of the motors with a solid rotor core and a laminated rotor core, considering the value of rotor losses, power density factor, eff... [more]

Polyacrylamide (PAM)/polyethyleneimine (PEI) gels doped with graphene oxide (GO) were prepared. Their structure and properties were systematically studied by X-ray diffraction (XRD), Fourier transition infrared spectrum (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and rheological experiments. The results showed that the graphene oxide (GO) nanosheets were significantly involved in the cross-linking reaction between the main agent (PAM) and the cross-linker (PEI), serving as multi-functional cross-linker and effective reinforcing nanofillers. Increasing the main agent and cross-linker content, the strength of gels was enhanced effectively. The GO could effectively adjust the strength and the gelation time to exhibit characteristics of weak gel, thanks to the improved three-dimensional honeycombed structure with controllable pore size. The DSC confirmed that the PAM/PEI/GO gel exhibited excellent thermal stability and did not d... [more]

A Mg65Ni20Cu5Y10 metallic glass was produced by melt spinning and was mixed with a 5 wt.% multiwall carbon nanotube additive in a high-energy ball mill. Subsequently, the composite mixture was exposed to high-pressure torsion deformation with different torsion numbers. Complimentary XRD and DSC experiments confirmed the exceptional structural and thermal stability of the amorphous phase against severe plastic deformation. Combined high-resolution transmission electron microscopy observations and fast Fourier transform analysis revealed deformation-induced Mg2Ni nanocrystals, together with the structural and morphological stability of the nanotubes. The electrochemical hydrogen discharge capacity of the severely deformed pure metallic glass was substantially lower than that of samples with the nanotube additive for several cycles. It was also established that the most deformed sample containing nanotubes exhibited a drastic breakdown in the electrochemical capacity after eight cycles.

With the continuous development and utilization of clean energy, the thermal utilization of solar energy is an important research direction. In view of the problems of the low utilization rate of solar heat in alpine regions of solar energy, an air-type vacuum-tube solar collector (AVSC) with air as the heat-exchange medium was designed. The vacuum tube of the solar heat collector adopted a double-pass spiral direct-current structure, and the vacuum tube had a built-in heat-storage rod. In order to test the heat collection performance of the designed air evacuated-tube solar collector, a heat collection performance test of the collector was conducted. The results showed that the average heat collection efficiency of the vacuum tube solar collector without phase-change heat-storage rods was 38%. The evacuated-tube solar collector using water as the heat transfer medium had an average heat collection efficiency of 58%. The average equivalent heat collection efficiency of the AVSC with a... [more]

Due to a high operating voltage and theoretical capacity, P2-type layered Mn-based metal oxides are considered to be promising cathodes in sodium-ion batteries, but their poor structural stability in the process of Na+ insertion/deinsertion severely hinders their practical application. Here, an interesting K+ pre-intercalation is used to expand the interlayer distance and enhance the electrochemical reversibility of KsFexAlyMnzO2. With a suitable K+ content, the optimized electrode shows a high specific capacity of 135 mAh g−1 at 0.1 C, a good rate capability of 80 mAh g−1 at 5 C and an excellent cycling performance of 76.4% capacity retention after 200 cycles at a high rate of 5 C. This work proves the feasibility of a K+ pre-intercalation strategy in a P2-type layered cathode.