Surface Pore Research Articles

Evaluation of characterization and adsorption kinetics of natural organic matter onto nitric acid modified activated carbon

Natural organic substances (NOM) found in drinking water are a major contributor to disinfectant by-product formation and are potentially toxic to humans. Traditional water treatment techniques may not always effectively treat NOMs. Therefore, an advanced treatment method such as adsorption can be inexpensive, simple and efficient. The selected adsorbent's and the NOMs properties both affect the removal effectiveness of the adsorption method. Activated carbon (AC), which is widely used in real-scale water treatment plants, has been modified and used in recent years In order to oxidize the porous carbon surface, raise its acidic qualities, eliminate mineral components, and enhance the surface's hydrophilic qualities. In this research, AC was modified with nitric acid (M-PAC) and NOM removal was investigated. In addition, it is discussed how the modification with nitric acid changes the adsorbent structure and chemistry. A morphology with smooth and irregular voids was observed as a result of nitric acid modification of the original AC by SEM analysis. The particle size increased from 387.65 nm to 502.07 nm for the M-PAC adsorbent. The FTIR spectrum indicates that structures connected to aromatic rings get formed in the M-PAC adsorbent as a result of the modification. The highest NOM removal for the original powdered activated carbon (PAC), 47%, was observed at 36 hours of contact time. On the other hand, M-PAC adsorbent achieved 40% NOM removal at contact times of 72 hours and above. It was concluded that the pseudo-second order kinetic model better represented NOM adsorption for both adsorbents.

In Ukrainian

The CMs were obtained in argon in three stages: 1) heating (4 grad/min) to the specified temperature t in the range of 350–825 °С; 2) isothermal exposure 1 h; 3) cooling, washing from alkali and drying. Samples are denoted as CM(t). The CM yield (Y, %) and CMs elemental composition are determined. Based on low-temperature (77 K) nitrogen adsorption-desorption isotherms, integral and differential dependences of the specific surface area SDFT (m2/g) and pore volume V (cm3/g) on the average pore diameter (D, nm) were calculated by 2D-NLDFT-НS method (SAIEUS program). They were used to define volumes of ultramicropores (Vumi), supermicropores (Vsmi) and micropores (Vmi). The total pore volume V was calculated from the nitrogen amount adsorbed at a relative pressure p/p0 ~ 1.0. The S values of ultramicropores (Sumi), supermicropores (Ssmi) and micropores (Smi) were similarly determined. The CM yield was established to decrease linearly (R2 = 0.979) from 70.2 to 45.3 % with an increase in temperature from 350 to 825 °С. The carbon content decreases to a minimum value at 500 °С (72.6 %), and then increases to a maximum value (87.5 %) at 825 °С; the oxygen content changes antibatically. Two temperature regions were identified: region I (≤ 500 °С) of increasing the oxygen content due to reactions in which KOH acts as a donor of O atoms; region II (≥ 500 °C) of dominating the thermal destruction of functional groups (carboxyl, lactone, ester) with the release of CO and CO2, and condensation increasing the size of polyarenes of the CM secondary framework and formsng single Сar-Саr bonds between them. The CM(350) sample was found to contain only mesopores (D ≥ 10 nm) and macropores. An activation temperature increase to 400 °C initiates the additional formation of small-diameter micropores and mesopores. In samples CM(400) - CM(825), the main portion of newly formed pores falls on pores with D ≤ 5 nm. With increasing temperature, the micropores volume increases almost linearly (R2 = 0.992). The Vumi and Vsmi volumes increase up to 600 °C. At higher temperatures the ultramicropores volume decreases due to transforming ultramicropores (D ≤ 0.7 nm) into supermicropores (D = 0.7–2.0 nm). Portion of the ultramicropores volume changes with a maximum (23.9 %) in the CM(600) sample. The SBET specific surface area linearly (R2 = 0.992) increases with temperature up to 1729 m2/g. The SDFT values are close to SBET, but noticeably lower (1514–1530 m2/g) for CM(785)-CM(825). The micropores specific surface area increases to 1415 m2/g, and ultramicropore surface Sumi changes extremely with a maximum (526 m2/g) for the CM(600) sample, which should be expected based on the temperature dependence of the Vumi parameter. The decrease in Sumi values after the maximum is compensated by an increase in the supermicropore surface. Such an effect - the redistribution of pores by size in the microporous range (D ≤ 2 nm) with an increase in the alkaline activation temperature is not described in the literature. The portion of the micropores surface is dominant (92.6–97.0 %) in samples prepared at t ≥ 450 °C. The portion of the ultramicropore surface is maximum (56.3 %) in CM(500). Pores are revealed that do not form at all at 450–750 °C. These are supermicropores (D = 0.96–2.00 nm) and mesopores of small diameters (D = 2.0–2.82 nm). This effect was assumed to be due to the properties of the CM supramolecular framework, which is formed from polyarene fragments of the initial and activated coals having polyarenes with diameters of the same order (1.68–2.54 nm).

Synthesis of Fe-Loaded Biochar Obtained from Rape Straw for Enhanced Degradation of Emerging Contaminant Antibiotic Metronidazole

In this study, magnetic (Fe)-loaded biochar was successfully prepared by a simple impregnation pyrolysis method. Meanwhile, its degradation capability and mechanism for typical antibiotic metronidazole (MNZ) were systematically investigated under different conditions. The characterization of the synthesized material showed that the specific surface area, pore diameter, and pore volume changed significantly. Also, functional groups and metal element Fe were introduced on the surface of the biochar, leading to its better capability to activate peroxymonosulfate (PMS). The degradation experiments showed that the removal of MNZ in the Fe-BC/PMS system can reach up to 95.3% in 60 min under optimal conditions. Free-radical capture experiments showed that there were several active species of •OH, SO4•−, •O2−, and 1O2 present in the catalyst to synergistically degrade MNZ, among which SO4•− played a major role; it was also found that the material can be easily recycled and was still effective after several uses. Further, the main degradation pathways of MNZ include nitrohydroxylation, hydroxyethyl functional group deletion, carboxylation of the amino functional group of •OH, demethylation, oxidation, and carboxylation. It is obvious that the synthesized magnetic-loaded biochar, Fe-BC, generated from waste rape straw crops, shows high catalytic performance in pollutant degradation, providing an insight into the recycling potential of waste biomass in the catalytic field for pollutant removal.

Efficient degradation of norfloxacin via MnCo-LDH/sepiolite activating peroxymonosulfate: Performance, mechanism and degradation pathway

In this study, MnCo layered double hydroxide/sepiolite (MnCo-LDH/sepiolite) as PMS catalyst were synthesized using a simple water bath method. The results indicated that the composite exhibited the highest norfloxacin (NF) removal efficiency (90.14 % in 40 min), and its reaction rate constant (0.2049 min-1) was 2.0 times higher than that of pure MnCo-LDH. Compared with MnCo-LDH, MnCo-LDH/sepiolite catalyst had a larger specific surface area and pore volume which can provide more abundant active sites thereby improving the NF degradation performance. In addition, EPR and quenching experiments results revealed that SO4•- and 1O2 were the main active substances. Moreover, the successive redox of Mn and Co species contributed to the main driving force to effectively activate PMS. Furthermore, the possible catalytic mechanisms and NF degradation pathways were systematically analyzed. Overall, this study provides a new strategy for developing an economical, efficient and environmentally friendly PMS catalyst for wastewater treatment.

Synthesis of CBO (Co3O4-Bi2O3) Heterogeneous Photocatalyst for Degradation of Fipronil and Acetochlor Pesticides in Aqueous Medium

The excessive use of pesticides has led to the harmful contamination of water reservoirs. Visible-light-driven photocatalysis is one of the suitable methods for the removal of pesticides from water. Herein, the development of CBO (Co3O4-Bi2O3) as a heterogeneous catalyst for the visible light-assisted degradation of Fipronil and Acetochlor pesticides is reported. After synthesis via coprecipitation using cobalt (II) nitrate hexahydrate (Co(NO3)2·6H2O), bismuth (III) nitrate pentahydrate (Bi(NO3)3·5H2O) and sodium hydroxide (NaOH) as precursor materials, the prepared CBO was characterized using advanced techniques including XRD, EDS, TEM, SEM, FTIR, and surface area and pore size analysis. Then, it was employed as a photocatalyst for the degradation of Fipronil and Acetochlor pesticides under visible light irradiation. The complete removal of Fipronil and Acetochlor pesticides was observed over CBO photocatalyst using 50 mL (100 mg/L) of each pesticide separately within 120 min of reaction. The reaction kinetics was investigated using a non-linear method of analysis using the Solver add-in. The prepared CBO exhibited a 2.8-fold and 2-fold catalytic performance in the photodegradation of selected pesticides than Co3O4 and Bi2O3 did, respectively.

The surface morphologies and internal pores evolution of a CuSn10 alloy fabricated by laser powder bed fusion

The fabrication of high quality copper alloys using laser powder bed fusion (LPBF) technology remains challenging due to their low laser absorption and high thermal conductivity. LPBF often involves intrinsic defects, such as rough surface and internal pores, which largely deteriorate the performance of as-built copper alloy components. Here we studied the effect of scanning speed on the evolution of surface morphologies and internal pores of LPBF-fabricated CuSn10 alloy. The melt flow behaviors were studied by both experiments and in situ observations where combined a high-speed camera with an infrared thermal imager. With increasing the scanning speed, the morphology of melt track evolves from a continuous track to a discontinuous one, whereas the internal defects change from a great number of spherical pores to many irregular pores. A higher scanning speed decreases the peak temperature of the melt pool and causes less overlaps between neighboring melt tracks, thus deteriorating wetting behaviors. It is expected that the obtained results are beneficial for guiding the additive manufacturing of copper alloy parts with high metallurgical quality and thus promoting their industrial applications.

Hydrogen storage in M(BDC)(TED)0.5 metal-organic framework: physical insights and capacities.

Finding renewable energy sources to replace fossil energy has been an essential demand in recent years. Hydrogen gas has been becoming a research hotspot for its clean and free-carbon energy. However, hydrogen storage technology is challenging for mobile and automotive applications. Metal-organic frameworks (MOFs) have emerged as one of the most advanced materials for hydrogen storage due to their exceptionally high surface area, ultra-large and tuneable pore size. Recently, computer simulations allowed the designing of new MOF structures with significant hydrogen storage capacity. However, no studies are available to elucidate the hydrogen storage in M(BDC)(TED)0.5, where M = metal, BDC = 1,4-benzene dicarboxylate, and TED = triethylenediamine. In this report, we used van der Waals-dispersion corrected density functional theory and grand canonical Monte Carlo methods to explore the electronic structure properties, adsorption energies, and gravimetric and volumetric hydrogen loadings in M(BDC)(TED)0.5 (M = Mg, V, Co, Ni, and Cu). Our results showed that the most favourable adsorption site of H2 in M(BDC)(TED)0.5 is the metal cluster-TED intersection region, in which Ni offers the strongest binding strength with the adsorption energy of -16.9 kJ mol-1. Besides, the H2@M(BDC)(TED)0.5 interaction is physisorption, which mainly stems from the contribution of the d orbitals of the metal atoms for M = Ni, V, Cu, and Co and the p orbitals of the O, C, N atoms for M = Mg interacting with the σ* state of the adsorbed hydrogen molecule. Noticeably, the alkaline-earth metal Mg strongly enhanced the specific surface area and pore size of the M(BDC)(TED)0.5 MOF, leading to an enormous increase in hydrogen storage with the highest absolute (excess) gravimetric and volumetric uptakes of 1.05 (0.36) wt% and 7.47 (2.59) g L-1 at 298 K and 7.42 (5.80) wt% and 52.77 (41.26) g L-1 at 77 K, respectively. The results are comparable to the other MOFs found in the literature.

CuxO nanoparticles loaded LTA zeolite as non-enzymatic and noble-metal-free sensing platform for accurate and fast glucose detection

For glucose sensors, improved sensitivity, accuracy, stability and convenience have always been desired. A novel sensing platform combining CuxO (x = 1, 2) nanoparticles and LTA-structured zeolite well fulfills these requirements and achieves breakthrough sensing concentration (6.0 × 10−15 M). In hydrothermal conditions, highly dispersed CuxO nanoparticles are formed and restrined in the nano-opening windows of the zeolite surface pores, ultimately yielding CuxO LTA. These in situ-synthesized CuxO NPs have high catalytic activity, while the zeolite provides a stable and rigid framework. This sensor has good selectivity and sensitivity (1.45 μA μM−1 cm−2) for the determination of glucose under physiological conditions (pH = 7.4) using the DPV method with a limit of detection (LOD) as low as 6.0 × 10−15 M. The amperometry method exhibited a fast response time of only 0.1 s under strong alkaline conditions (1.0 M NaOH) and achieved a sensitivity of 6.94 μA μM−1 cm−2 and LOD of 2.0 × 10−9 M. This advanced hybrid sensor system not only provides a wide range of application environments, but also has important implications for the development of low-cost, stable, fast, and efficient non-enzymatic glucose sensors for noble metals. The theoretical support of density-functional theory (DFT) affirms the interaction between zeolite fine structure and glucose molecules.

In Situ Growth of Amorphous MnO2 on Graphite Felt via Mild Etching Engineering as a Powerful Catalyst for Advanced Vanadium Redox Flow Batteries.

Owing to the advantages of low cost, high safety, and a desirable cycling lifetime, vanadium redox flow batteries (VRFBs) have attracted great attention in the large-scale energy storage field. However, graphite felts (GFs), widely used as electrode materials, usually possess an inferior catalytic activity for the redox reaction of vanadium ions, largely limiting the energy efficiency and rate performance of VRFBs. Here, an in situ growth of amorphous MnO2 on graphite felt (AMO@GF) was designed for application in VRFBs via mild and rapid etching engineering (5 min). After the etching process, the graphite felt fibers showed a porous and defective surface, contributing to abundant active sites toward the redox reaction. In addition, formed amorphous MnO2 can also serve as a powerful catalyst to facilitate the redox couples of VO2+/VO2+ based on density functional theoretical (DFT) calculations. As a result, the VRFB using AMO@GF displayed an elevated energy efficiency and superior stability after 2400 cycles at 200 mA cm-2, and the maximum current density can reach 300 mA cm-2. Such a high-efficiency and convenient design strategy for the electrode material will drive the further development and industrial application of VRFBs and other flow battery systems.

Poly-l-Lactic Acid Scaffolds Additivated with Rosmarinic Acid: A Multi-Analytical Approach to Assess The Morphology, Thermal Behavior, and Hydrophilicity.

This study aims to demonstrate the possibility of incorporating a natural antioxidant biomolecule into polymeric porous scaffolds. To this end, Poly-l-Lactic Acid (PLLA) scaffolds were produced using the Thermally Induced Phase Separation (TIPS) technique and additivated with different amounts of rosmarinic acid (RA). The scaffolds, with a diameter of 4 mm and a thickness of 2 mm, were characterized with a multi-analytical approach. Specifically, Scanning Electron Microscopy analyses demonstrated the presence of an interconnected porous network, characterized by a layer of RA at the level of the pore's surfaces. Moreover, the presence of RA biomolecules increased the hydrophilic nature of the sample, as evidenced by the decrease in the contact angle with water from 128° to 76°. The structure of PLLA and PLLA containing RA molecules has been investigated through DSC and XRD analyses, and the obtained results suggest that the crystallinity decreases when increasing the RA content. This approach is cost-effective, and it can be customized with different biomolecules, offering the possibility of producing porous polymeric structures containing antioxidant molecules. These scaffolds meet the requirements of tissue engineering and could offer a potential solution to reduce inflammation associated with scaffold implantation, thus improving tissue regeneration.

Polystyrene composite system: an alternative for wastewater treatment

ABSTRACT Rapid population growth intensifies water scarcity, highlighting the importance of treatment technologies such as reverse osmosis and membrane filtration to ensure safe drinking water and preserve resources. The use of polystyrene as a filter for polluted water is valuable due to its porous surface, efficiently retaining impurities. The system, a tubular reactor with a mixed polystyrene bed, underwent evaluations with varying particle sizes, flow rates and times, operating in dead-end mode and series system without recirculation with theoretical residence times between 180 and 360 min. The study, divided into two phases, optimized the system in the first phase, characterizing the filter bed and carrying out maintenance for 360 min at 0.5 L/min. Phase two evaluated the performance of the reactor in treating wastewater with flow rates of 0.5 and 1 L/min for 180 min. Under the best conditions of Phase I, 55% of Escherichia coli and turbidity were deactivated, not meeting potability standards. In Phase II, there was efficiency in the removal of several parameters, such as chemical oxygen demand (78.26%), total phosphorus (75%), nitrate (73.42%), ammonia (73.13%), nitrite (69.33%), potassium (70.83%), and sodium (68.75%). In addition, 98.32% of E. coli was deactivated, meeting CONAMA Class 2 and 3 irrigation standards.

Surface characteristics and adsorption properties of polypropylene microplastics by ultraviolet irradiation and natural aging

The vast application and deep integration of plastic commodity with our human lives raise a great concern about the ubiquitous microplastics (MPs) in nature, yet the environmental behavior of MPs remain unclear. As a main type and candidate of MPs, pristine polypropylene MPs (PP-MP-Pris), as well as the influence of ultraviolet (UV) irradiation on the degree of aging and surface characteristics, were characterized quantitatively by Fourier infrared spectroscopy, scanning electron microscopy, contact angle meter, automatic specific surface area and pore analyzer and laser particle analyzer, with natural aged PP-MPs (PP-MP-Age) as comparison. The carbonyl index (CI) of UV aged PP-MPs (PP-MP-U) was increased with extension of exposure time, while biofilm with abundant functional groups and the maximum CI value were the characteristics of PP-MP-Age. Moreover, the adsorption capacity of PP-MP-U for crystal violet (CV) was increased and reached the maximum after 30 days, while that of PP-MP-Age was weakened, probably due to the enhanced hydrophilicity and the shedding of calcium carbonate (CaCO3) during the natural aging process, which was demonstrated by hydrochloric acid treatment, indicating the vital involvement of CaCO3. Moreover, the better fitting to PSO kinetics and Freundlich isotherm models indicated that the multilayered and non-homogeneous surface adsorption was acted as the rate-controlling step. Furthermore, the positive values of ΔGθ, ΔHθ and ΔSθ indicated that the adsorption was a non-spontaneous, endothermic process with increased degree of the freedom on the interface of PP-MPs and CV solution. The presence of divalent salts inhibited CV adsorption, demonstrating that electrostatic attraction played a major role in CV capture. The hydrophobic interaction, micropore filling, hydrogen bonding, and π - π conjugation were possible involved. This study is of great significance for better understanding the complex pollution of MPs and its potential environmental risks in the future.

Selective Use of Modern Cementless Total Knee Arthroplasty is Not Associated with Increased Risk of Revision in Patients Aged 65 or Greater: An Analysis from the American Joint Replacement Registry.

Modern highly porous surfaces have increased confidence and use of cementless total knee arthroplasty (TKA) in the United States. As cementless TKA use increases, there remains a paucity of literature regarding associated risk of revision in patients aged ≥65 years. We analyzed the American Joint Replacement Registry (AJRR) data from January 2012 to March 2020 identifying patients aged ≥65 years undergoing primary TKA with linked cases to supplemental centers for Medicare and Medicaid data. Patients with hybrid fixation, reverse hybrid fixation, missing component data, highly constrained implants, and stem extension/augmentation were excluded. We identified 442,745 cemented TKAs and 19,841 modern cementless TKAs with a minimum of 2-year follow-up. Cumulative incident function (CIF) curves and cause-specific Cox models evaluated the risk of all-cause revision and revision for mechanical loosening, adjusting for body mass index (BMI), sex, age, cruciate retaining (CR) versus posterior stabilized (PS) femoral design, patellar resurfacing, and Charlson's comorbidity index (CCI). Patients with cementless compared with cemented TKA were younger (mean age: 71.9 vs. 73.2 years, p < 0.001), more likely to be male sex (48.8 vs. 39.0%, p < 0.001), more likely to have a CR femoral design (81.1 vs. 45.7%, p < 0.001), less likely to have patellar resurfacing (92.7 vs. 95.0%, p < 0.001), and had a lower CCI (mean: 2.9 vs. 3.1, p < 0.001). Adjusted hazard ratios (HRs) showed no difference in associated risk for all-cause revision (HR: 1.07; 95% confidence interval [CI]: 0.92-1.24; p = 0.382) or revision for mechanical loosening (HR: 1.38; 95% CI: 0.9-2.12; p = 0.14) for cementless versus cemented TKA. Our results suggest that current selective use of cementless fixation for TKA in patients aged ≥65 years in the United States is not associated with an increased risk of revision. While encouraging, further study is necessary to establish indications for use in this age group prior to broader adoption in this patient population. LEVEL OF EVIDENCE: Therapeutic Level III.

Applicability assessment of a plasma melting technology for a fly ash recycling system in the Republic of Korea

ABSTRACT The Ministry of Environment of Korea has proposed a ban on landfill disposal of municipal solid waste (MSW) from 2026. Thus, it is inferred that the amount of incineration ash will increase drastically. Against this backdrop, this study assessed the applicability of a plasma melting process to fly ash. Fly ash was collected from 14 incineration facilities to analyze its basic properties and perform melting experiments. Furthermore, scanning electron microscope (SEM) analysis and economic feasibility assessment were conducted. The molten fly ash slag exhibited a pH value of 9.9, and the ignition loss of fly ash was found to range from 14.5 to 25.7 wt.%. None of seven toxic elements (arsenic (As), cadmium (Cd), cyanide (CN), mercury (Hg), hexavalent chromium (Cr(VI)), copper, and lead (Pb)) was detected from the molten slag. In addition, 99.3 wt.% of chloride ion (Cl−), 97.9 wt.% of fluoride ion (F−), and 98.1 wt.% of sulphate ion (SO4 2−) were removed. The contents in the molten slag were found to be 0.19, 7.8, 27.8, 33.1, and 38 mg/kg for Cd, Pb, zinc, nickel, and F, respectively, and none of CN, Hg, and As was detected, thereby meeting the criteria for soil pollution. All of the environmental standards were met, and SEM analysis confirmed stable quality with high density and no surface pore. In the economic feasibility assessment, a profit of approximately 152.4 $/ton was also estimated compared to landfill disposal.

Physico-mechanical, structural, and mineralogical analysis of composite concrete incorporating hydraulic lime and pozzolan

This study investigates alternatives to Portland cement (PC) through the utilization of pozzolanic materials like natural hydraulic lime and pozzolan in mortar and concrete production, offering both environmental and economic advantages. Natural hydraulic lime is particularly esteemed for its relevance in restoring architectural relics and preserving cultural heritage, while the incorporation of pozzolan and fine and coarse aggregates adds value to local resources. The study employs a range of comprehensive characterization techniques, including physico-chemical, mineralogical, and mechanical analyses such as X-ray fluorescence, particle size assessment, bulk density evaluation, shrinkage testing, water absorption analysis, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and Proctor Normal and compressive strength tests, among others. Five different formulations, varying from 20 % to 40 % hydraulic lime content and a fixed 25.00 % pozzolan content, underwent testing across five curing periods (7, 14, 28, and 90 days). The results underscore the significant influence of curing time and hydraulic lime proportion on the physical, mineralogical, and mechanical characteristics of lime concrete. Scanning electron microscopy reveals a well-structured matrix in samples from various formulations, credited to effective void filling by lime and pozzolan. Furthermore, the identification of C-S-H phases through X-ray diffraction analysis enhances the concrete matrix, leading to a notable increase in compressive strength of up to 22.00 MPa. Water absorption rises with curing time due to the air curing process, fostering the formation of minor surface pores. This research assesses the environmental impact of hydraulic lime concrete across its lifecycle, underscoring the potential of pozzolans and natural hydraulic lime to produce locally-sourced, economical, and environmentally friendly construction materials, thereby contributing to global efforts in reducing carbon emissions.

Structure and positive charge regulation in nanofiltration membrane by novel nanomaterial g-C3N5 for efficient Li+/Mg2+ separation

The positively charged nanofiltration (NF) membrane prepared via interfacial polymerization (IP) of polyethyleneimine (PEI) and trimesoyl chloride (TMC) has drawn considerable attention for lithium-magnesium separation, particularly crucial for lithium recovery from salt lakes with high Mg2+/Li+ mass ratios. However, NF membranes prepared solely from amine monomers have not achieved efficient Li+ and Mg2+ separation. In this study, PEI-g-C3N5/TMC composite NF membranes were successfully fabricated by mixing amino-rich graphitic carbon nitride (g-C3N5) with PEI, followed by the IP reaction of the mixed solution with TMC. Molecular dynamics (MD) simulation results showed that g-C3N5 had an attractive effect on PEI, which led to a decrease in the diffusion rate of PEI, thereby resulting in a thinner separation layer. Density functional theory (DFT) revealed that g-C3N5 competed with PEI, leading to a reduction in the crosslinking within the polyamide (PA) layer and subsequently causing an increase in the surface pore size of the membrane. Besides, the hydrophilicity and positive charge of the modified membrane were both improved. MD simulations, transition state theory, and DLVO principles indicated that the modification of the PA layer by g-C3N5 enhanced the repulsion of Mg2+ and the transport of Li+ during the NF process. This breakthrough effectively overcame the trade-off effect between membrane separation and permeability, especially at a g-C3N5 content of 0.06 wt%, where the lithium-magnesium selectivity coefficient (SLi, Mg = 18.18) and pure water flux (Flux = 58.59 L m−2 h−1) reached the optimum values. Meanwhile, the PEI-g-C3N5/TMC membrane demonstrated stable separation performance during prolonged filtration and in solutions with varying Mg2+/Li+ mass ratios. This study not only provides an effective strategy for the design of NF membranes but also expands the application prospects of nanomaterials in the field of membrane separation.

Ethylene Polymerization over Metal-Organic Framework-Supported Zirconocene Complexes.

Metallocene immobilization onto a solid support helps to overcome the drawbacks of homogeneous metallocene complexes in the catalytic olefin polymerization. In this study, valuable insights have been obtained into the effects of pore size, linker composition, and surface groups of metal-organic frameworks (MOFs) on their role as support materials for metallocene-based ethylene polymerization catalysis. Three distinct Zn-based metal-organic frameworks (MOFs), namely, MOF-5, IRMOF-3, and ZIF-8, with different linkers have been activated with methylaluminoxane (MAO) and zirconocene complexes, followed by materials characterization and testing for ethylene polymerization. Characterization has been performed by multiple analytical tools, including X-ray diffraction (XRD), scanning electron microscopy (SEM), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and CO Fourier transform infrared (FT-IR) spectroscopy. It was found that the interactions between MOFs, MAO, and the zirconocene complex not only lead to both catalyst activation and deactivation but also result in the creation of multiple active sites. By alteration of the MOF support, it is possible to obtain polyethylene with different properties. Notably, ultrahigh molecular weight polyethylene (UHMWPE, M W = 5.34 × 106) was obtained using IRMOF-3 as support. This study reveals the potential of MOF materials as tunable porous supports for metallocene catalysts active in ethylene polymerization.

Effect of the Number of Methyl Groups in DMOF on N2O Adsorption and N2O/N2 Separation.

Nitrous oxide (N2O), as the third largest greenhouse gas in the world, also has great applications in industry, so the purification of N2O from N2 in industrial tail gas is a crucial process for achieving environmental protection and giving full play to its economic value. Based on the polarity difference of N2O and N2, N2O adsorption was researched on DMOF series materials with different polarities and methyl numbers of the ligand. N2O adsorption at 0.1 bar is enhanced, attributed to an increase of the methyl group densities at the benzenedicarboxylate linker. Grand canonical Monte Carlo simulations demonstrate the key role of methyl groups within the pore surface in the preferential N2O affinity. Methyl groups preferentially bind to N2O and thus enhanced low (partial) pressure N2O adsorption and N2O/N2 separation. The result shows that DMOF-TM has the highest N2O adsorption capacity (19.6 cm3/g) and N2O/N2 selectivity (23.2) at 0.1 bar. Breakthrough experiments show that, with an increase of the methyl number, the coadsorption time and retention time also increase, and DMOF-TM has the best N2O/N2 separation performance.

Confinement Effects on Proton Transfer in TiO2 Nanopores from Machine Learning Potential Molecular Dynamics Simulations.

Improved understanding of proton transfer in nanopores is critical for a wide range of emerging applications, yet experimentally probing mechanisms and energetics of this process remains a significant challenge. To help reveal details of this process, we developed and applied a machine learning potential derived from first-principles calculations to examine water reactivity and proton transfer in TiO2 slit-pores. We find that confinement of water within pores smaller than 0.5 nm imposes strong and complex effects on water reactivity and proton transfer. Although the proton transfer mechanism is similar to that at a TiO2 interface with bulk water, confinement reduces the activation energy of this process, leading to more frequent proton transfer events. This enhanced proton transfer stems from the contraction of oxygen-oxygen distances dictated by the interplay between confinement and hydrophilic interactions. Our simulations also highlight the importance of the surface topology, where faster proton transport is found in the direction where a unique arrangement of surface oxygens enables the formation of an ordered water chain. In a broader context, our study demonstrates that proton transfer in hydrophilic nanopores can be enhanced by controlling pore size, surface chemistry, and topology.

An insight into the characteristics of some oxidized low-grade coals of Indian origin

ABSTRACT The conversion of coal to a hydrophilic state presents a significant challenge for process engineers, especially when treating oxidized coals in flotation-based beneficiation plants. Flotation of oxidized coal often requires a substantial consumption of oily collectors, resulting in unacceptably low yields. To address this, several pre-processing methods have emerged for coal deoxidation, including mild grinding, surface activation, and ultrasonic or microwave treatment. However, their effective application depends on a thorough understanding of the degree of oxidation in the coals. Therefore, it is crucial to gain insights into the nature of oxidized coal before initiating the deoxidation process. This present study provides various characterization techniques such as XRD, SEM-EDS, FTIR Spectroscopy, Raman Spectroscopy, TGA, and Zeta Potential Analysis employed on oxidized low-grade coals. The study revealed that the proximate analysis of low-grade coals KC, DC, RC, and PC contains varying ash percentages of 32.65%, 44.47%, 25.44%, and 37.53%, respectively, with SiO2 and Al2O3 comprising over 80% of the total ash. XRD characterizations identified quartz and kaolinite as major mineral phases in all samples, while SEM-EDS confirmed rough coal surfaces with peeling, off-white aggregations, and surface pores. HGI value ranging from 80 to 91 was attributed to partial decomposition and surface cracking due to oxidation. FTIR spectra revealed pronounced oxidation behavior, with strong −OH peaks in the 3600–3700 cm−1 range. Zeta potential analysis affirmed the oxidized nature of the coals with a pH below 3.1 and an extremely negative zeta potential beyond 3.1. The findings mentioned above showcase the distinct characteristics of oxidized low-grade coals, which serve as crucial indicators for exploring coal beneficiation, especially through the flotation process.