Particle Pore Size Research Articles

A novel magnetic porous organic cage adsorbent for high-efficient removal of endocrine disrupting chemicals from environmental water

Endocrine disrupting chemicals (EDCs) are pervasive emerging pollutants found in environmental water, stemming from their widespread use in personal consumer products. This study presents a novel magnetic Porous organic cage (POC) material, Fe3O4-COOH@CC3R-OH, which has been proven to be highly effective in eco-friendly eliminating EDCs. Featuring a tetrahedral morphology with core–shell structure, the new magnetic adsorbent boasts a substantial Brunauer-Emmett-Teller surface area of 94.02 m2/g and a particle pore size of 1.14 nm. Rigorous optimization of adsorption conditions for eight specific EDCs was conducted, complemented by insightful molecular docking simulations shedding light on the adsorption mechanisms. Furthermore, the developed Fe3O4-COOH@CC3R-OH magnetic solid phase extraction-assisted high performance liquid chromatography-tandem mass spectrometry (MSPE-HPLC-MS/MS) method exhibits good sensitivity and precision in the quantitative detection of EDCs in environmental water samples. This integrated approach provides a robust platform for both efficient removal and accurate detection of EDCs, advancing water quality control and safeguarding human health.

Superior removal performance for methylene blue onto Spartina alterniflora biochar via solvothermal method: Equilibrium, kinetics and mechanism analyses

In this study, an activated biochar derived from Spartina alterniflora (SRHH) was innovatively synthesized to efficiently remove dye contaminants from aqueous solution. A series of characterizations exhibited that solvothermal process effectively increased the mesopores and functional group structure (OH, NHR, CO, CO and RNCO) of the nanomaterial, which could also acquire amorphous carbon-doped biochar with less energy consumption. Moreover, the results showed that the as-prepared sample in a solvothermal kettle at 180 °C displayed superior dye adsorption and degradation performance, and the removal efficiency entirely could reach up to 93% within 4 h at neutral condition. The adsorption process was both consistent well with the pseudo-second-order and intraparticle diffusion models, indicating that diffusion resistance within the particle pore size and chemical action might be predominantly controlled factor. Therefore, the prepared catalyst has enormous potential in the removal of organic pollution as a low-cost and economical in-situ remediation material.

Study of Ce, Ca, Fe, and Mn-Doped LaCoO3 Perovskite Oxide for the Four-Way Purification of PM, NOx, CO, and HC from Diesel Engine Exhaust.

Perovskite-type catalysts were widely used in the field of automobile exhaust purification due to their inherent physicochemical properties and excellent doping characteristics. A series of La1−xMxCo1−yNyO3 (M = Ce, Ca; N = Fe, Mn) perovskite-type catalyst samples were prepared by sol-gel method for the four-way purification of PM, NOx, CO, and HC emitted by diesel exhaust. The activity of catalyst samples was tested by simulation experiments and hydrogen temperature-programmed reduction (H2-TPR). Catalyst samples were characterized by means of XRD, FT-IR, SEM, BET, and XPS analysis. The results demonstrated that the perovskite-type catalyst samples with a particle pore size of 3–5 μm can be prepared by sol-gel method. When A-site of LaCoO3 perovskite-type oxide was doped by cerium ions, the catalyst samples produced small distortion. The doping of cerium ions to A-site was more conducive to the four-way purification of diesel exhaust than calcium ions. La0.8Ce0.2CoO3 perovskite-type samples showed the best purification efficiency, and the purification efficiencies of PM, NOx, CO, and HC were 90%, 85%, 94%, and 100%, respectively. When the B-site of La0.8Ce0.2CoO3 perovskite was doped with iron ions, the purification efficiency of catalyst samples for PM and NOx can be further enhanced. When the B-site of La0.8Ce0.2CoO3 perovskite was doped with manganese ions, the purification efficiency of the catalyst samples for PM can be further enhanced. It can be seen from the simulation experiments that La0.8Ce0.2Co0.7Fe0.3O3 perovskite was the best doping amount, and the purification efficiencies of PM, NOx, CO, and HC were 95%, 92%, 94%, and 100%, respectively.

Nanotechnology: Recent Progress in Agriculture and Effects on Physiology of Plants

The naturally occurring and synthesised nanoparticles (NPs) display significant effects on the physiology of plants. This paper emphasised the current application of synthetic NPs in agriculture, several advantages and physiological responses during the growth of plants. Nano pore size of particles provides higher surface areas hence enhances the water holding capacity of the soil, efficacy delivery of fertilisers and pesticides (pest and diseases infestation) on crops. The application of NPs via soil or mist involves uptake by plant via roots or foliar cell wall and translocation to other organs through vascular system and plasmodesmata within the cells. The physicochemical properties of NPs have advantages including enabling the increase of soil water retention in mitigating the drought and/or salinity stresses in plants. Nanoparticles enhance the germination of seed and maintain plant growth by promoting the production of enzymes in scavenging oxygen radicals, phytohormone balancing, nutrient metabolisms and expression of amino acid biosynthetic genes and photosystem. Given the diverse physiological and molecular effects of NPs, precautionary steps prior to their application either as fertiliser or carrier should be considered to avoid toxicity and destructive effects on plants, animals, water body and the environment.

Investigation of the silica pore size effect on the performance of polysulfone (PSf) mixed matrix membranes (MMMs) for gas separation

Abstract MCM-41 and SBA-15 mesoporous silica materials with different pore sizes (3.08 nm for small pore size MCM-41 (P 1), 5.89 nm for medium pore size SBA-15 (P 2), and 7.81 nm for large pore size SBA-15 (P 3)) were synthesized by the hydrothermal method and then functionalized with 3-aminopropyltrietoxysilane by postsynthesis treatments. Next, polysulfone-mesoporous silica mixed matrix membranes (MMMs) were prepared by the solution casting method. The obtained materials and MMMs were characterized by various techniques including X-ray diffraction, scanning electron microscopy, and N2 adsorption-desorption, and Brunauer-Emmett-Teller method to examine the crystallinity, morphology, and particle size, pore volume, specific surface area, and pore size distribution, respectively. Finally, the gas permeation rates of prepared MMMs were measured in 8 bar and 25 °C and the effect of pore size of modified and unmodified mesoporous silica on the gas separation performance of these MMMs were investigated. The experimental results indicate that the carbon dioxide (CO2) and methane (CH4) permeability and CO2/CH4 selectivity were increased with an enhancement in the particle pore size.

Importance of Particle Pore Size in Determining Retention and Selectivity in Reversed Phase Liquid Chromatography

Column selection often centers on the identification of a stationary phase that increases resolution for a certain class of compounds. While gains in resolution are most affected by selectivity of the stationary phase or modifications of the mobile phase, enhancements can still be made with an intentional selection of the packing material's microstructure. Unrestricted mass transfer into the particle's porous structure minimizes band broadening associated with hindered access to stationary phase. Increased efficiency, especially when operating above the optimal flow rates, can be gained if the pore size is significantly larger than the solvated analyte. Less studied are the effects of reduced access to pores due to physical hindrance and its impact on retention. This article explores the relationship between pore size and reversed phase retention, and specifically looks at a series of particle architectures with reversed phase and size exclusion modes to study retention associated with access to stationary phase surface area.

Synthesis and Use of Valsartan Metal Complexes as Media for Carbon Dioxide Storage.

To address global warming through carbon dioxide storage, three valsartan metal complexes were synthesized in excellent yields (87–92%) through a reaction of the appropriate metal chloride (tin chloride, nickel chloride hexahydrate, or magnesium chloride hexahydrate) and excess valsartan (two mole equivalents) in boiling methanol for 3 h. The structures of the metal complexes were established based on the data obtained from ultraviolet-visible, Fourier transform infrared, and proton nuclear magnetic resonance spectra, as well as from elemental analysis, energy-dispersive X-ray spectra, and magnetic susceptibility. The agglomeration and shape of the particles were determined using field emission scanning electron microscopy analysis. The surface area (16.63–22.75 m2/g) of the metal complexes was measured using the Brunauer-Emmett-Teller method, whereas the Barrett-Joyner-Halenda method was used to determine the particle pore size (0.011–0.108 cm3/g), total average pore volume (6.50–12.46 nm), and pore diameter (6.50–12.47 nm), for the metal complexes. The carbon dioxide uptake of the synthesized complexes, at 323 K and 4 MPa (40 bar), ranged from 24.11 to 34.51 cm2/g, and the nickel complex was found to be the most effective sorbent for carbon dioxide storage.

Mesoporous Silica Colloids: Wetting, Surface Diffusion, and Cationic Surfactant Adsorption

We have investigated the wetting and surface diffusion of mesoporous colloidal silica particles at the water surface and the adsorption of cationic cetyltrimethylammonium (CTA+) surfactant on these particles. Porous silica colloids diffuse at the surface of water and in the volume, interacting with cationic surfactants that can adsorb inside the pores of the particles. We observed that surfactant adsorption on mesoporous silica depends dramatically not only on the particle pore size but also on specific counterion effects. We measured striking differences both on a macroscopic property of the interface, i.e., surface tension, and also at a single particle level by evaluating the translational diffusion of partially wetted particles at the fluid interface. We varied the pore size from 2 to 7 nm and explored the effects of ions possessing different hydration number and kosmotropic/chaotropic character. At concentrations lower than the critical micellar concentration, we evidence that cationic surfactants adsorb on silica as surface micelles and surfactant adsorption inside the pores occurs only if the pore diameter is larger than the size of surface micelles. With a view to understand the surprising different adsorption behavior of CTA+OH– and CTA+Br– on porous silica particles, we investigated the effect of counterions on the surfactant adsorption on porous silica colloids by tuning the pH and the counterion properties.

A particle-resolved CFD model coupling reaction-diffusion inside fixed-bed reactor

Fixed bed reactor is widely used in the petrochemical industry. The most rigorous description of it is particle-resolved simulation. In this study, a particle-resolved CFD model coupling reaction-diffusion was developed. The gas and porous particle phase were solved separately and the data of heat and mass is exchanged across the phase interface. Detailed flow and reaction process for synthesis of vinyl acetate were investigated by this model. The results showed that the local flow was not uniform under different flow patterns, which leads to the non-uniform distributions of temperature and concentration. In addition, the intra-particle pore diffusion influenced the reactor performance. The increase of particle pore size can obviously promote average reaction rate and decrease product concentration inside particles. The proposed modeling provided deep insight for local flow and reaction-diffusion process and can be extended to entire fixed bed reactor.

AgPO microcrystals with complex polyhedral morphologies diversity obtained by microwave-hydrothermal synthesis for MB degradation under sunlight

Abstract This research addresses the synthesis of silver phosphate microcrystals with complex polyhedral morphologies as rhombic dodecahedral, trapezoidal, tetrahedral and cuadri-hexahedral polyhedrons as well as structures of shape corners and edges. These structures are obtained simultaneously by means of few modifications to the hydrothermal method using microwave and basic medium for the chemical synthesis. The photo-degradation activity of silver phosphate microcrystals was measured using methylene blue (MB) under sunlight while stirring. The degradation time of the MB was reported at 4 min using 0.1 gr of microparticles suspended on 50 mL of MB at 5 × 10 5 mol/L concentration. These Ag3PO4 polyhedric microcrystals were characterized by different techniques: energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (DRX), atomic force microscopy (AFM), scanning electron microscopy (SEM) and Nitrogen adsorption at 77 K. Reaction order and rate law were determined as well. A particle pore size distribution with order diameter of 4.862 nm and pore families between 5 and 20 nm linked to interstitial mesopores were well identified. Furthermore, these type of materials synthesis is environmental friendly due to its basic nature.

Gas permeation modeling of mixed matrix membranes: Adsorption isotherms and permeability models

In order to calculate the permeability of gases in mixed matrix membranes (MMMs) filled with porous particles, the first step is to calculate the permeability of filler particles. Because particle pore sizes of the considered sodium zeolite Y (NaY) in this study is greater than the molecular sizes of the tested gases (CO2 and N2), it is assumed that diffusion of the gases in the zeolite particles is from Knudsen type. Moreover, the gas sorption data (isotherms) were measured experimentally and then fitted with Langmuir and Freundlich model equations to calculate the related constants. Finally, the experimental CO2 and N2 permeabilities of cellulose acetate (CA)/NaY MMMs were compared with the corresponding data predicted by the well‐known permeability models in this field. It was concluded that the Bruggeman model has better predictions among the other models, especially for the higher particle loadings. POLYM. COMPOS., 39:4560–4568, 2018. © 2017 Society of Plastics Engineers

Enhancing gas permeability in mixed matrix membranes through tuning the nanoparticle properties

Mixed matrix membranes containing a variety of nanoparticles were fabricated by the solvent casting method using a commercial aromatic polyimide as the base polymer. All gas permeabilities increased with increasing particle loading with no reduction in the selectivity, reflecting adequate polymer/particle compatibility. Importantly, under such conditions the permeability enhancement depended only upon the pore volume within the particle, regardless of the particle chemistry or the morphology of the membrane structure. Remarkably, despite a range of membrane chemistries and filler loadings, this permeability enhancement could be readily described with a simple free volume relationship. The results suggest that nanoparticle porosity should be the focus of research into mixed matrix membrane structures. These results are likely to apply in all diffusivity dominated systems where the particle pore size is significantly larger than the penetrant size, as is the case with glassy polymers and many inorganic additives at low pressures.

Manufacturing of agarose-based chromatographic adsorbents – Effect of ionic strength and cooling conditions on particle structure and mechanical strength

The effect of ionic strength of agarose solution and quenching temperature of the emulsion on the structure and mechanical strength of agarose-based chromatographic adsorbents was investigated. Solutions of agarose containing different amounts of NaCl were emulsified at elevated temperature in mineral oil using a high-shear mixer. The hot emulsion was quenched at different temperatures leading to the gelation of agarose and formation of soft particles. Analysis of Atomic Force Microscopy (AFM) images of particle surfaces shows that pore size of particles increases with ionic strength and/or high quenching temperature. Additionally it has been found that the compressive strength of particles measured by micromanipulation also increases with ionic strength of the emulsion and/or high quenching temperature but these two parameters have no significant effect on the resulting particle size and particle size distribution. Results from both characterization methods were compared with Sepharose 4B, a commercial agarose-based adsorbent. This is the first report examining the effect of ionic strength and cooling conditions on the microstructure of micron-sized agarose beads for bioseparation.

Porous Fe3O4 nanoparticles: Synthesis and application in catalyzing epoxidation of styrene

A facile route was employed to synthesize porous magnetite via reaction of FeCl3·6H2O with N2H4·H2O in ethylene glycol without any structure-directing agent. The resultant Fe3O4 particles were characterized by transmission electron microscopy, N2 adsorption, X-ray photoelectron spectroscopy, and thermal gravimetric analysis. It was demonstrated that the particle size varied in the range of 40–220nm, and the pore size of particles was centered around 2nm. The gases produced in the formation process of the particles played key role in the formation of the porous structure. The obtained porous magnetite was used as support to immobilize Au nanoparticles with size less than 2nm with the assistance of l-cysteine. The as-prepared Fe3O4 particles can effectively catalyze epoxidation of styrene, and the immobilization of Au nanoparticles on the Fe3O4 support significantly improved the activity of the catalyst.

Determination of dye concentration in water using mesoporous particle coated QCR sensor

A quartz crystal resonator sensor coated with mesoporous carbon cryogel particles is developed to utilize for the determination of dye concentration in water. The sensor module is designed for a flow measurement system to make an in-line application available. The preparation details of the carbon cryogel particles and the coated sensor are explained, and the detection performance of the developed module is examined with reactive dyes, Black 5 and Red E and phenol. The experimental results indicate that the measurement sensitivity of phenol is the highest, that of Black 5 is the next and that of Red E is the lowest. The sensitivity difference is explained with the pore size of particles and the molecular size of measured substances, and the possible utilization of the proposed measurement system for the determination of dye concentration in water is discussed.

Silica particles encapsulated poly(styrene-divinylbenzene) monolithic stationary phases for μ-high performance liquid chromatography

In the paper we demonstrate a new approach for the preparation and application of continuous silica bed columns that involve encapsulation (entrapment) of functionalized silica microparticles, which can be used as packing material in micro high performance liquid chromatography (μ-HPLC) and capillary electrochromatography (CEC). Like traditional packed columns, these capillaries possess characterized silica particles that offer high phase ratio and narrow pore size distribution leading to high retention and separation efficiency, respectively. More importantly, immobilization of the microparticles stabilizes the separation bed and eliminates the need for retaining frits. The developed capillary columns were fabricated in exactly the same way as a packed capillary column (slurry packing) but with an additional entrapment step. This immobilization of the packed bed was achieved by in situ polymerization of styrene and divinylbenzene in presence of decanol as a porogen and azobisisobutyronitrile as thermal initiator. Silica particles with different particle sizes and pore sizes ranging from 60 to 4000 Å were studied. In addition different modified silica was used, including C-18 reversed phase, anion exchange and chiral stationary phases. Efficient separation of polyphenolic compounds, peptides, proteins and even DNA mutation were achieved using the developed technique depending on the properties of the silica particles used (particles pore size). For example, using 3 μm ProntoSIL C-18 particles with 300 Å pore size, separation efficiencies in the range of 120,000–200,000 plates/m were obtained for protein separation, in a 6 cm × 200 μm i.d. capillary column. Using encapsulated silica C-18 with 1000 Å pore size, separation of DNA homo and hetero duplexes were achieved under denaturing HPLC conditions for mutation detection. In addition, nucleotides were separated using anion exchange material encapsulated with poly(styrene-divinylbenzene) (PS/DVB), which indicated that the chromatographic properties of the silica packing material were still active after polymerization. The prepared capillary columns were found to be stable and could easily be operated continuously up to a pressure of 350 bar without column damage and capillary can be cut to any desired length.

High speed gradient elution reversed-phase liquid chromatography

A major disadvantage of gradient elution in terms of speed results from the need to adequately re-equilibrate the column. This work distinguishes two states of re-equilibration: (1) run-to-run repeatability and (2) full equilibration. We find that excellent repeatability (+/-0.002 min in retention time) is achieved with at most 2 column volumes of re-equilibration whereas full equilibration can require considerably more than 20 column volumes. We have investigated the effects of adding ancillary solvents (e.g. n-propanol, n-butanol) to the eluent and changing the particle pore size, initial eluent composition and type, column temperature and flow rate on the speed of full equilibration. Full equilibration seems to be more thermodynamically limited than kinetically controlled. Also, we show that the main limitation to reducing the full equilibration time is related to instrument design issues; a novel approach to overcome these instrumental issues is described.

Protonic Conduction and Impedance Analysis in CsHSO4 / SiO2 Composite Systems

Proton conductivity measurement and ac impedance analysis of composites were carried out using two different methods to prepare sample powders: mechanical mixing and evaporation to dryness. At temperatures below the superprotonic phase transition temperature of ca. 140°C, the conductivity of the composite prepared by the evaporation to dryness method was larger by 4 orders of magnitude than that of pure and larger by 2 orders of magnitude than that of the composite prepared by mechanical mixing. The pore size of particles (2-16 nm) influenced the conductivity, with the conductivity becoming higher as the pore size became larger. In the impedance spectra, two semicircles appeared in the composite system and were deconstructed to study proton conduction processes. Impedance analysis suggests that the formation of an interface between and and the high dispersion of particles result in the enhancement of conductivity. X-ray diffraction and differential thermal analysis indicate that structural disorder in the interface would induce a significant enhancement of conductivity even at temperatures below the phase transition temperature. © 2004 The Electrochemical Society. All rights reserved.

Protein unfolding during reversed-phase chromatography: I. Effect of surface properties and duration of adsorption.

Residue-level features of bovine pancreatic trypsin inhibitor (BPTI) unfolding on reversed-phase chromatography (RPC) surfaces were investigated using hydrogen-deuterium exchange labeling and NMR. A set of silica-based RPC surfaces was used to examine the influence of alkyl chain length and media pore size on adsorbed BPTI conformation. In all cases there was substantial unfolding in the adsorbed state; however, residual protection from exchange was consistently observed. Particle pore size did not influence conformation substantially for C4-alkyl modified silica; however, 120 A pore C18 media produced more hydrogen exchange than any other surface examined. In this case, the radius of curvature inside the pore approaches the size of the BPTI molecule. Generally, the pattern of hydrogen exchange protection was uniform; however, the beta-sheet region was selectively protected on the large-pore C18 media. The beta-sheet region forms a hydrophobic core that forms early when BPTI folds in solution. This suggests that partially unfolded states possessing a native-like structure play an important role in adsorption and elution in RPC. Finally, increased contact time with the surface before elution fostered unfolding and altered chromatographic behavior considerably.

Peak capacity in packed capillary column solvating gas chromatography

In this paper, a general peak capacity expression was evaluated using columns containing various packing materials under solvating gas chromatography (SGC) conditions. Differing from column efficiency, peak capacity can describe both separation capability and speed when introducing the dead time into the peak capacity expression. Various factors that influence peak capacity in SGC are described, including particle pore size, chemical surface modification, particle size, column length, temperature, and pressure.