A continuous-flow exposure method to determine degradation of polyphenylene sulfide non-woven bag-filter media by NO2 gas at high temperature

The degradation behavior of polyphenylene sulfide (PPS) fabric filter media by NO₂ gas at high temperatures was investigated in detail with a continuous-flow type exposure method, as specified in ISO16891:2016. An increase in the exposure time to NO₂ gas lessened the tensile strength and elongation of the PPS filter media in both machine and transverse directions. These reductions were observed in the transverse direction (TD) more markedly than in the machine direction (MD). Exposure to NO₂ gas enhanced the oxidation of sulfur, and introduced new oxygen-containing functional groups (e.g., SO and OSO) into the PPS molecular structure, which reduced the atomic ratio of carbon in the PPS filter media with increasing exposure time. These chemical degradations severely damaged the PPS fiber through cracking, splitting, and formation of protrusions on the surface.Furthermore, assuming that the chemical reaction between PPS and NO₂ gas is diffusion-controlled by NO₂, a model to estimate the change in the conversion of PPS and the NO₂ concentration in the exhaust gas was proposed, based on an unreacted core model. It could successfully reproduce the experimental data. A model to evaluate the change in the tensile strength of the filter media was also proposed, which could express experimental data only in the MD.     

Incorporating polyimide cathode materials into porous polyaniline xerogel to optimize the zinc-storage behavior

Polyimide is a kind of promising organic-based electrode material for zinc ion batteries (ZIBs), with the merits of resource sustainability, environmental friendliness and structural diversity. At present, however, the study on polyimide-based electrode for ZIBs is fairly few, and the limited conductivity and capacity are also needed to be overcome. Here, a polyimide cathode material denoted as PUI is synthesized by using perylene-3,4,9,10-tetracarboxylic dianhydride and urea, and the zinc-storage performance is comprehensively optimized by taking advantage of a 3-D porous polyaniline (PANI) xerogel carrier, for instance, the specific capacity of PUI/PANI composite is 72 % higher than that of PUI, and the rate performance and cycling stability are both improved as well. The analysis of electrochemical kinetics reveals that the 3-D porous PANI can facilitate fast electron/ion transportation and high capacitive contribution during discharging and charging. Moreover, the mechanism analysis demonstrates the synergistically enhanced zinc-storage capacity of CO (in PUI) and N (in PANI) in PUI/PANI. This work promotes the application potential of polyimide-based cathode materials, and also highlights the valuable role of porous conducting polymer (e.g., PANI) in constructing high-performance cathode materials for ZIBs.     

Magnetically separable Zn1-xCuxFe2O4 (0 ≤ x ≤ 0.5) nanocatalysts for the transesterification of waste cooking oil

Copper doped zinc ferrite Zn_1-xCu_xFe₂O₄ (0 ≤ x ≤ 0.5) spinels were synthesized via sonication assisted microwave method. The prepared nanoparticles were characterized by XRD, FTIR, HR-SEM, EDX, DRS and VSM analysis. Average crystallite size were in range 5.84 nm to 8.55 nm. FTIR results reveal, bands at 420 cm⁻¹ (Zn²⁺O²⁻) and 547 cm⁻¹ (Fe³⁺O²⁻) confirming tetrahedral and octahedral positions of the spinel structure formation. All the samples showed ferromagnetic behavior at room temperature. The Zn_0.5Cu_0.5Fe₂O₄ sample showed high saturation magnetization (M_s = 74.09 emu/g) and high magnetic moment (3.0 μ_B). The prepared magnetic nano spinels were subsequently employed to evaluate the catalytic activity for biodiesel production. The transesterification process followed pseudo first order rate kinetic model. An excellent catalytic activity for biodiesel production was acheived (98.9%) and the catalyst was recoverable quickly using an external magnet.     

Facile synthesis of SiBCN powders by a carbonitriding route

SiBCN ceramic powders were facilely synthesized from the compacts of silicon, B₄C and cornstarch by a carbonitriding route. Effects of silicon content in raw materials on phase composition, chemical bond, microstructure and oxidation resistance of as-received products after heated at 1550 °C were investigated. The featured chemical bonds such as CN and BCN in as-received products were detected by X-ray photoelectron spectroscopy (XPS). The microstructure of BN(C) distributed around nano-sized α/β -SiC/SiCN grains was revealed by transmission electron microscopy (TEM). The synthesized products with the Si/B/C ratio of 1:1:1 presented better oxidation resistance than SiC because of the strengthened chemical bonds and BN(C) formation.     

Using ToF-SIMS to study metal ions transfer between chalcopyrite and galena during grinding

Grinding has an important effect on the chemical composition of the mineral surface. In this study, the interaction of galena and chalcopyrite during grinding was studied by time-of-flight secondary ion mass spectrometry (ToF-SIMS), principal component analysis (PCA), and inductively coupled plasma optical emission spectrometry (ICP-OES). Results showed that during mixed grinding, the surface compositions of chalcopyrite and galena became more similar, and the dissolution of chalcopyrite and galena was promoted. Grinding not only results in the adsorption of lead ions released from galena to the chalcopyrite surface, but also results in the adsorption of copper and iron ions released from chalcopyrite to the galena surface. The Cu, Fe, and Pb atoms on the surface of chalcopyrite and galena may be bonded in the form of PbOCu, PbOFe, and PbSCu. This study can provide a surface chemical basis for controlling the grinding process of copper-lead sulfide ore.     

Effects of NO2 gas concentration on the degradation of polyphenylene sulfide non-woven bag filter at high temperature

The influence of NO₂ concentration and exposure time on the degradation of polyphenylene sulfide (PPS) fabric filter at high temperature was investigated in detail. PPS fiber damage in the filter became more severe with increasing NO₂ concentration and exposure time. The elastic modulus of the PPS filter increased rapidly during the initial stage of exposure, and then increased more slowly to reach an almost constant value, nearly independent of NO₂ concentration. The tensile strength also decreased significantly during the initial stage, gradually attaining a constant value with increasing exposure time. Higher NO₂ concentrations resulted in rapid reducing of the tensile strength. Short exposure time to lower NO₂ concentrations caused the oxidation of S atoms in PPS to SO and OSO, whereas oxidation of benzene rings in PPS were induced only with longer exposure times and higher NO₂ concentrations. The model proposed in our previous paper accurately expresses the change in PPS conversion and reaction rate for every NO₂ concentration. An improved model that successfully estimated the degradation of tensile strength in both the machine direction and transverse direction, regardless of NO₂ concentration, was also proposed.     

MIL-88A grown in-situ on graphitic carbon nitride (g-C3N4) as a novel sorbent: Synthesis,characterization, and high-performance of tetracycline removal and mechanism

The extensive and accumulative use of tetracycline (TC) in the environment has become a serious problem. In this study, MIL-88A/g-C₃N₄ micro-nano particles were successfully prepared through a simple, low-cost, one-step hydrothermal method for TC adsorption in water. At a pH of 7.0, the maximum adsorption capacity (154.51 mg·g⁻¹) of MIL-88A/g-C₃N₄ is reached at room temperature. Owing to its porous structure and large pore size (>2.06 nm) of MIL-88A/g-C₃N₄, TC can be adsorbed on both external and internal surfaces. Kinetic and thermodynamic studies have shown that the pseudo-second-order kinetic and the Langmuir-Freundlich model can be used to describe the adsorption process, which is a spontaneous endothermic process. The mechanism study reveals that the TC adsorption process by MIL-88A/g-C₃N₄ is mainly through electrostatic interaction and the ion exchange of COOH and NH₂ groups on MIL-88A/g-C₃N₄ to TC. After simple pickling and water washing, MIL-88A/g-C₃N₄ can still reach 83.1% of the original adsorption capacity after five cycles, which proves that MIL-88A/g-C₃N₄ can be a promising adsorbent.     

Mechanism of arsenate coprecipitation at the solid/liquid interface of ferrihydrite: A perspective review

Arsenate (As(V)) is a toxic element in acid mine drainage and has to be removed during the neutralization process. Coprecipitation with ferrihydrite is the main mechanism for As(V) removal from acid mine drainage. To improve treatment efficiency, a quantitative understanding of the coprecipitation mechanism is required. Coprecipitation can incorporate more As(V) into ferrihydrite than adsorption. The results of XRD (X-ray Diffraction) and XANES (X-ray Adsorption Near Edge Structure) analysis confirmed that the formation of poorly crystalline ferric arsenate increased when the initial As/Fe molar ratio increased in the coprecipitation with ferrihydrite. EXAFS (Extended X-ray Adsorption Fine Structure) analysis at the iron K-edge showed that the proportion of octahedral structures in ferrihydrite increased when the initial As/Fe molar ratio increased. Moreover, EXAFS analysis at the arsenic K-edge, assuming three kinds of surface complexes for the AsFe bond, revealed that the coordination number for AsFe with an atomic distance of 2.85 × 10⁻¹⁰ m increased and that for As-Fe with an atomic distance of 3.24 × 10⁻¹⁰ m decreased as the initial As/Fe molar ratio increased. Thus, for more efficient wastewater treatment, active control of coprecipitation phenomena according to mechanistic details is essential.     

Biomineralization,antibacterial activity and mechanical properties of biowaste derived diopside nanopowders

This work reports on the preparation and characterization of mesoporous nano diopside (CaMgSi₂O₆) using a simple and cost-effective sol-gel combustion route. Stoichiometric oxidant/fuel ratio was adopted for the combustion reaction. Eggshell was used as a calcium source, glycine (fuel) as reductant, magnesium nitrate and nitric acid as oxidant were used in the preparation. The thermal behavior of the precursor was studied by thermo-gravimetric analysis (TGA) and heating microscopy. The temperature required for the transformation of the precursor into pure diopside was optimized at 1100 °C. Rietveld refinement method was utilized to confirm the phase purity of diopside. The resultant powder contains 36 nm particle with a specific surface area of 51 m²/g. The appearance of Ca, Mg, Si, and O peaks in EDX pattern confirmed the existence of essential elements. The rapid consumption of calcium and phosphorus ions from the simulated body fluid during dissolution indicated their involvement in apatite deposition on the surface of the nano diopside. FT-IR spectra showed that the SiO and SiOSi groups were replaced by phosphate bands due to hydroxyapatite deposition. The mechanical stability of the diopside after bioactivity studies was found to be superior to the cancellous bone. The release of alkaline earth ions (Ca²⁺ and Mg²⁺) from the diopside sample into the bacterial culture medium increases the pH (7.4), which inhibits the bacterial growth. The surface properties, concentration, and type of bacteria are the other factors responsible for the antibacterial activity of the nano diopside.     

Novel application of g-C3N4/NaNbO3 composite for photocatalytic selective oxidation of biomass-derived HMF to FFCA under visible light irradiation

The g-C₃N₄/NaNbO₃ photocatalyst was synthesized by simply calcining the mixture of NaNbO₃ and melamine. The synthesized composite exhibits high photocatalytic performance in the selective oxidation of 5-Hydroxymethylfurfural (HMF) to 5-formyl-2-furancarboxylic acid (FFCA) when using water as solvent. The structure and composition of g-C₃N₄/NaNbO₃ photocatalysts were characterized by TG, XRD, SEM, UV–Vis, FT-IR, and XPS methods, and the optical and electrochemical properties were investigated by EIS, PC, and PL techniques. O₂⁻ was inferred to be the primary active species in this process based on the active species trapping experiment. Heterostructure formation of g-C₃N₄/NaNbO₃ composites efficiently promoted the separation of photo-generated electron-hole pairs and accelerated the electron transfer rate, thus reduced the formation of OH, and sequentially improved the selectivity of FFCA. The highest HMF conversion of 35.8% with FFCA selectivity of 87.4% was achieved on C/N-59.6 photocatalyst under the irradiation of visible light. The possible mechanism and reaction route were also proposed.     

Atomic-level insights into the modification mechanism of Fe (III) ion on smithsonite (1 0 1) surface from DFT calculation

Fe(III) ion can strongly inhibit the sulphidation amine flotation of smithsonite. However, its modification mechanism on smithsonite surface is still obscure. In this work, a systematic study of the modification of Fe(III) ion on smithsonite (1 0 1) surface was performed using DFT calculation. The optimal number of H₂O ligands for Fe(III) ion hydrates in aqueous conditions was probed, and [Fe(OH)₂(H₂O)₄]⁺ and [Fe(OH)₄]^? were identified as the major modification species, then their adsorption and bonding mechanisms were further revealed by analyzing the frontier orbitals, density of state, Mulliken population, and electron density. The calculated adsorption structures were consistent with the former experiment, and we found the O site that bonded to the C atom on smithsonite surface was the most favorable position for [Fe(OH)₂(H₂O)₄]⁺ and [Fe(OH)₄]^? adsorptions. Besides, their adsorption mechanisms on smithsonite surface were principally due to the combined effect of FeO bond and hydrogen bonding. Simultaneously, hydrogen bonding greatly enhanced the stability of the adsorption structures. Moreover, the dominant orbital contribution for the bonding of FeO was primarily due to the orbital hybridization between Fe 3d and O 2p orbitals. This work can help in deeper understanding of the depression of Fe(III) ion on the sulphidation amine flotation of smithsonite.     

Sluggish,chemical bias and percolation phenomena in atomic transport by vacancy and interstitial diffusion in NiFe alloys

In this article, we report the results of extended atomistic modeling of intrinsic mobility of point defects and associated atomic transport in NiFe model binary alloys. We consider the effects of composition and temperature and present evidence of the sluggish and chemically biased diffusion, and percolation effects occurring in atomic transport via the vacancy and interstitial migration mechanisms. The results are analyzed and discussed in the light of previous studies and some experimental observations. It is demonstrated that the sluggish diffusion, the chemically biased diffusion, and the percolation are interlinked phenomena that are defined by the chemical complexity of particular alloys. Methods for predicting these phenomena in multicomponent alloys are discussed.We report a fundamental understanding of sluggish diffusion, chemically-biased diffusion, as well as percolation phenomena, in NiFe random alloys for vacancy and interstitial atom migration mechanisms.     

Efficient removal of Cr(VI) from aqueous solution by natural pyrite/rhodochrosite derived materials: Performance,kinetic and mechanism

In this work, pyrite/rhodochrosite (Py_xRh_y) composite synthesized from natural pyrite and rhodochrosite to remediate Cr(VI) containing wastewater was systematically investigated and evaluated. Results show that pyrite/rhodochrosite (1:1) showed the best Cr(VI) removal performance. XRD showed that emergence of MnS and pyrrhotite contributed to a significant increasing Cr(VI) reduction rate. The estimated maximum adsorption capacity was 95.58 mg/g at pH value of 6, temperature of 303.15 k, which was larger than other iron and manganese-based materials. Additionally, thermodynamic study illuminated that Cr(VI) removal by Py₁Rh₁ was a spontaneous and endothermic process. Taffel curve and EIS result presented higher corrosion current and lower electrical resistance for Py₁Rh₁, respectively, which was more favorable for the electron transfer. The surface cyclic regeneration of Fe(II) and Mn(II) provided long-term electron transfer to the Cr(VI) reduction. Our results demonstrated the great potentials of natural pyrite and rhodochrosite synthetic materials in the remediation of Cr(VI) polluted water.     

Luminescence and scintillation properties of BaF2Ce transparent ceramic

Cerium doped Barium Fluoride (BaF₂Ce) transparent ceramic was fabricated and its luminescence and scintillation properties were studied. The photoluminescence shows the emission peaks at 310 nm and 323 nm and is related to the 5d-4f transitions in Ce³⁺ ion. Photo peak at 511 keV and 1274 keV were obtained with BaF₂Ce transparent ceramic for Na-22 radioisotopes. Energy resolution of 13.5% at 662 keV is calculated for the BaF₂Ce transparent ceramic. Light yield of 5100 photons/MeV was recorded for BaF₂Ce(0.2%) ceramic and is comparable to its single crystal counterpart. Scintillation decay time measurements shows fast component of 58 ns and a relatively slow component of 434 ns under 662 keV gamma excitation. The slower component in BaF₂Ce(0.2%) ceramic is about 200 ns faster than the STE emission in BaF₂ host and is associated with the dipole-dipole energy transfer from the host matrix to Ce³⁺ luminescence center.     

Construction of hierarchical FeIn2S4/BiOBr S-scheme heterojunction with enhanced visible-light photocatalytic performance for antibiotics degradation

Constructing heterojunction provides a promising tactic to improve the photocatalytic efficiency of catalysts. In this paper, hierarchical FeIn₂S₄/BiOBr heterostructure photocatalysts were prepared by facile two step methods and applied to effectively remove ciprofloxacin (CIP) and tetracycline (TC) under visible light. Compared to single catalyst, FeIn₂S₄/BiOBr hybrids display significantly improved photocatalytic activity. Among the series, 6 wt% FeIn₂S₄/BiOBr shows the optimal photocatalytic performance, where the degradation efficiencies of TC and CIP are 3.15 and 2.88 times greater than pure BiOBr, respectively. Such an improvement could arise from the S-scheme heterojunctions and unique hierarchical structures, which brings stronger light absorption, higher photoexcited charge separation efficiency and superior redox ability. Furthermore, 6 wt% FeIn₂S₄/BiOBr composite exhibits excellent stability and reusability. Radical capture experiments and EPR analyses uncover that O₂^–, h⁺ and OH are primarily reactive substances during photocatalytic removal of TC. The products of TC were detected by LC-MS analyses and possible decomposition paths are proposed. Eventually, a possible photodegradation mechanism over FeIn₂S₄/BiOBr S-scheme heterojunction is proposed. These findings supply new perspective for the simple synthesis of S-scheme photocatalysts with promising applications in environment remediation.     

Recyclable and highly efficient photocatalytic fabric of Fe(III)@BiVO4/cotton via thiol-ene click reaction with visible-light response in water

In this article, we designed a photocatalytic cotton fabric of Fe(III)@BiVO₄/cotton via thiol-ene click reaction and achieved an enhanced photocatalytic performance and excellent recyclability under visible-light irradiation. The Fe(III)@BiVO₄ and cotton fabric were modified with KH570 (including CC groups) and KH580 (including SH groups), respectively. Then, the Fe(III)@BiVO₄/KH570 and KH580/cotton reacted and connected via thiol-ene click reaction, which can effectively solve its recyclability in practical application and realize ideal all-in-one structure. The as-prepared Fe(III)@BiVO₄/cotton not only exhibited an excellent photocatalytic performance in reducing Cr(VI) to Cr(III), but also showed a remarkable performance in degradation of C.I. reactive blue 19 (RB-19) under visible-light. Meanwhile, various analysis technique were used to confirm the successful connection between Fe(III)@BiVO₄ and cotton fabric via thiol-ene click reaction. Moreover, the photocatalytic mechanism was also discussed comprehensively in view of trapping experiments and ESR analysis.     

Evaluating the adsorption mechanism of a novel thiocarbamate on chalcopyrite and pyrite particles

The selective adsorption of surfactants on minerals can strengthen the differences of physical and chemical properties of mineral surfaces, thereby improving the separation efficiency of the refractory minerals. Herein, a novel surfactant S-carboxyethyl-N-benzoyl thiocarbamate (CEBTB) was prepared and utilized as a collector to selective separation of chalcopyrite from pyrite. The adsorption performances and mechanism of CEBTB on chalcopyrite and pyrite surface were studied. It showed that the functional groups (CO, CS and –COOH) of CEBTB could selectively anchor on the chalcopyrite surface and increase its surface hydrophobicity, whereas the adsorption of CEBTB on pyrite surface was weak with the surface hydrophobicity improved insignificantly. Flotation experimental indicated that CEBTB exhibited superior flotation selectivity for chalcopyrite against pyrite than the common collector of SIBX. Batch adsorption experimental results demonstrated that the adsorption of CEBTB onto chalcopyrite surface was performed by a monolayer chemisorption, as well as the adsorption process was endothermic and spontaneous.     

Vanadium carbide with periodic anionic vacancies for effective electrocatalytic nitrogen reduction

Although electrocatalytic nitrogen reduction reaction (NRR) has been considered as an emerging pathway to produce ammonia (NH₃) under ambient conditions owing to its low energy consumption, it still lacks efficient the electrocatalysts to dissociate inert NN bonds. Here, we develop an efficient approach to produce vanadium carbide with abundant periodic carbon vacancies (12.5 at. %) and mesoporous structure as electrocatalysts for NRR via a carbothermic reaction. The typical synthesis protocol involves the use of zinc vanadate decorated vanadium pentoxide nanosheets to homogeneously guide the nucleation and growth of metal organic frameworks (MOFs) on their surface, thus facilitating the in-situ formation of unique vanadium carbide during the subsequent carbothermic reaction. Owing to the optimized substrate-adsorbate binding strength, the intrinsic periodic carbon vacancies of the resultant vanadium carbide could act as coordinatively unsaturated sites to adsorb and activate nitrogen through π-back-donation process, thus promoting the reduction of N₂ to NH₃. As a consequence, a high yield rate and high Faradaic efficiency with good stabilities are achieved for producing NH₃ under ambient conditions.     

Novel porous perovskite composite CeO2@LaMnO3/3DOM SiO2 as an effective catalyst for activation of PMS toward oxidation of urotropine

Perovskites with stable crystal structure and excellent catalytic performance have attracted extensive attention in peroxomonosulfate (PMS) activation, however, severe agglomeration has always been the main obstacle limiting the catalytic activity of them, so novel perovskite catalysts are urgently needed. In this study, three-dimensional ordered macroporous silica (3DOM SiO₂) was prepared by colloidal crystal template method, then CeO₂@LaMnO₃/3DOM SiO₂ was prepared by sol-gel method combined with impregnation method and used to activate PMS for urotropine (URO) degradation. CeO₂@LaMnO₃/3DOM SiO₂ activated PMS system exhibited high URO removal efficiency and quick kinetic, as 99.98 % URO was degraded even within 30 min. The catalyst has a wide pH range and still has high catalytic activity in the presence of organic matter and inorganic ions. The three components in CeO₂@LaMnO₃/3DOM SiO₂ showed a synergetic effect. CeO₂ and LaMnO₃ were uniformly loaded on 3DOM SiO₂, which effectively avoided agglomeration. The specific surface area of CeO₂@LaMnO₃/3DOM SiO₂ was 11.88 times that of LaMnO₃ prepared by sol-gel method. There are two redox cycles of Ce³⁺/Ce⁴⁺ and Mn²⁺/Mn³⁺/Mn⁴⁺ in CeO₂ and LaMnO₃, respectively, which synergistically realize the activation of PMS. Both quenching experiments and electron paramagnetic resonance (EPR) analysis revealed that that SO₄^?, OH and ¹O₂ jointly achieved the degradation of URO. In summary, CeO₂@LaMnO₃/3DOM SiO₂ would be a promising candidate for practical wastewater treatment.     

Synthesis and photocatalytic activity of BiOCl/diatomite composite photocatalysts: Natural porous diatomite as photocatalyst support and dominant facets regulator

BiOCl/diatomite composite with enhanced photocatalytic property for the degradation of liquid Tetracycline hydrochloride (TC) and gaseous formaldehyde (HCHO) were successfully prepared by a facile hydrothermal method at different pH value. The structure and morphology characterizations of BiOCl/diatomite composite exhibit that diatomite not only acts as a natural porous support of photocatalyst but also acts as dominant facets regulator at pH = 3 when the doping amount is change, owing to the surface electrical property of the diatomite and interaction between diatomite and BiOCl. This interaction is certified by XPS and FT-IR which indicate that Bi in layer structure of [Bi₂O₂]²⁺ group interacts with the O in SiOSi bond when the formation of BiOCl with the participation of diatomite. The BET characterization confirms that the increasing amount of diatomite enables the composite with more reaction points for light harvest and molecule adsorption than pure BiOCl. Furthermore, TC and formaldehyde are targeted as degradation objects to test the photocatalytic property of BiOCl/diatomite composite. The optimum photocatalytic property are BiOCl(3–1.2) and BiOCl(12–0.6) at TC degradation and BiOCl(3–0.3) and BiOCl(12–0.6) at formaldehyde elimination, which is much better than that of pure diatomite or BiOCl. The difference of optimum photocatalysts in liquid and gaseous phase systems can be attributed to the photoelectric performances of BiOCl/diatomite composite, which were characterized by DRS, PL, transient photocurrents and the electrochemical impedance spectroscopy technique.