Irregular Porous Structure Research Articles

Facile preparation of recyclable and flexible BiOBr@TiO2/PU-SF composite porous membrane for efficient photocatalytic degradation of mineral flotation wastewater

Various semiconductor nanopowders can photodegrade wastewater efficiently, but their practical application is grievously limited due to poor recycling performance, insufficient sunlight utilization and potential secondary pollution. Membrane materials have been widely used for water treatment, including oil-water separation, desalination and sewage purification. In this paper, a novel BiOBr@TiO2/PU-SF composite porous membrane was prepared via a facile blending-phase separation-impregnation-precipitation method, and this was the first time that the novel membrane material was used as a photocatalyst for mineral flotation wastewater disposal. The PU-SF composite membrane with irregular porous structure acted as a loading substrate, which not only provided abundant space to immobilize BiOBr and TiO2 nanoparticles but also offered more photocatalytically active sites. The as-prepared BiOBr@TiO2/PU-SF composites were well characterized and exhibited higher photocatalytic activity as compared to BiOBr/PU-SF and TiO2/PU-SF. Combining the result of the characterization and free radical capture experiments with correlative theoretical calculations, we confirmed that the significant enhanced photocatalytic performance of BiOBr@TiO2/PU-SF membranes was attributed to the Z-scheme heterojunction formed between BiOBr and TiO2. In addition, the novel composite membrane material is flexible, it can be sheared, folded, and stretched arbitrarily. More importantly, the BiOBr@TiO2/PU-SF membrane can be readily taken out from the photocatalytic reaction system by tweezers, and the catalytic activity was essentially unchanged after being reused for 3 times. This novel recyclable flexible photocatalytic membrane will have promising prospect in field of actual mineral flotation wastewater treatment.

Recent Advances in Graphene Oxide‐Based Membranes for Heavy Metal Ions Separation

AbstractGraphene oxide (GO)‐based membranes have been widely investigated for separation of dyes, salt ions, heavy metal ions, and biomolecules due to their high mechanical strength, single‐layered structure, large surface area, and high affinity. However, due to irregular pore structure, nanochannels, interlayer distance, easy functionalization, swelling effect, and chemical stability under aqueous environment limited their separation efficiency. In this review, different fabrication methods of GO membranes are summarized. The role of functionalization and cross‐linking on membrane's structural properties, separation performance, and practical applications are discussed. Further, the GO‐based membranes (GOMs) for separation and removal of heavy metal ions are discussed in detail. The factors which influence the separation performance are also highlighted. Finally, recommendations and future directions are suggested.

The Hollow Porous Sphere Cell Carrier for the Dynamic Three-Dimensional Cell Culture.

Large-scale mammalian cell culture is essential in cell therapy, vaccine production, and the manufacturing of therapeutic protein drugs. Due to the adherent growth characteristic of most mammalian cell types, the combination of cell carrier and bioreactor is a common choice in large-scale mammalian cell culture. Current cell carriers developed by polymer crosslinking, lithography, or emulsion drops are unable to obtain a structure with uniformed porous structure and porous interior design, which results in an inhomogeneous culture condition for cells and therefore cannot ensure an optimal dynamic culture condition for cell proliferation, matrix production, and cell differentiation. In addition, the fluidic shear stress (a standard mechanical stimulation in bioreactor culture) and inner-carrier velocity (to ensure nutrient transport and waste exchange), which influence cell viability and growth, are not well-controlled/analyzed due to an irregular porous structure with these traditionally synthesized cell carriers. To solve these problems, we designed four types of hollow porous spheres (HPS, 1.0 cm diameter) with different porous structures. To investigate the impacts of porous structure on surface shear stress and inner velocity, computational fluid dynamics (CFD) simulations were conducted to analyze the liquid flow behavior in HPSs, based on which an optimal structure with minimal surface shear stress and best inner velocity was obtained and fabricated using fused deposition modeling three-dimensional (3D) printing technology. Inspired by the industrial large-scale culture system, a novel 3D dynamic culture system was then established using HPSs to seed the cells, which were then placed in a mini bioreactor on a tube roller. CFD analysis showed that under 0.1 m/s water flow, the shear stress at most surface areas from four HPSs was lower than 20 dynes/cm2, which suggests that the HPSs should provide protection against physical stress to the cells living on the scaffold surface. A dynamic cell seeding was developed and refined using the 3D culture system, which increased the 32% seeding efficiency of MC3T3 cells compared to the traditional static cell seeding method. The cell proliferation analysis demonstrated that HPSs could speed up cell growth in dynamic cell culture. The HPS with a honeycomb-like structure showed the highest inner pore velocity (CFD analysis) and achieved the fastest cell proliferation and the highest cell viability. Overall, our study, for the first time, developed a 3D printed HPS cell culture device with a uniformed porous structure, which can effectively facilitate cell adhesion and proliferation in the dynamic cultural environment, thereby could be considered an ideal carrier candidate.

Pyrolysis Characteristics and Effect on Pore Structure of Jimsar Oil Shale Based on TG-FTIR-MS Analysis

The study of the pyrolysis characteristics of oil shale, an important strategic resource, is of great significance for oil shale refining and in situ underground mining. In this study, using the oil shale from Jimsar region of Xinjiang, in combination with thermogravimetric analyzer (TG), Fourier transform infrared spectroscopy (FTIR), and mass spectrometry (MS) techniques, the pyrolysis characteristics and mechanism of the oil shale are analyzed according to the experimental results and explored the effect of its pyrolysis on the development of the pore. The results, the pyrolysis with three stages, show the following: (1) The first stage is 23-390°C. The precipitation of adsorbed water within the oil shale and the dehydration of gypsum are mainly at 100°C or so, appearing some microcapillary pores and other temperature sections change little. (2) The second stage is 390-527°C. The organic matter pyrolysis of Jimsar oil shale accounts for 71.1% of the total weight loss of oil shale. This stage has the greatest impact on the evolution of pore structure, and there are two weight loss peaks at 458°C and 506°C, respectively, in the thermogravimetric curve. Combined with FTIR-MS, the main products of its pyrolysis gas are H2, H2O, CO2, CH4, and CnHm and will change the original pore surface of oil shale, create new pore volume, and produce complex and irregular pore structure. (3) In third stage (527-800°C), the formation of H2, CO2, and hydrocarbon gases suggests that this stage includes not only the decomposition of major inorganic components like carbonate and clay but also the degradation process of some organic matter. At this stage, the CO2 generated in the precipitation process will lead to a large number of pores in oil shale. Crack grids will appear, due to the melting and recrystallization of some clay minerals. Once the interaction between the two is particularly intense, the mineral skeleton may rupture and collapse. The pyrolysis characteristics above provide a basis for the analysis of the pore structure evolution of oil shale and are of implications and practical application value to the exploitation of shale oil.

The Physicochemical Properties and Antioxidant Activity of Spirulina (Artrhospira platensis) Chlorophylls Microencapsulated in Different Ratios of Gum Arabic and Whey Protein Isolate.

Spirulina (Artrhospira platensis) is rich in chlorophylls (CH) and is used as a potential natural additive in the food industry. In this study, the CH content was extracted from spirulina powder after ultrasound treatment. Microcapsules were then prepared at different ratios of gum Arabic (GA) and whey protein isolate (WPI) through freeze-drying to improve the chemical stability of CH. As a result, a* and C* values of the microcapsules prepared from GA:WPI ratios (3:7) were −8.94 ± 0.05 and 15.44 ± 0.08, respectively. The GA fraction increased from 1 to 9, and encapsulation efficiency (EE) of microcapsules also increased by 9.62%. Moreover, the absorption peaks of CH at 2927 and 1626 cm−1 in microcapsules emerged as a redshift detected by FT-IR. From SEM images, the morphology of microcapsules changed from broken glassy to irregular porous flake-like structures when the GA ratio increased. In addition, the coated microcapsules (GA:WPI = 3:7) showed the highest DPPH free radical scavenging activity (SADPPH) (56.38 ± 0.19) due to low moisture content and better chemical stability through thermogravimetric analysis (TGA). Conclusively, GA and WPI coacervates as the wall material may improve the stability of CH extracted from spirulina.

Adsorption Characteristics and Charge Transfer Kinetics of Fluoride in Water by Different Adsorbents

Water containing high concentrations of fluoride is widely distributed and seriously harmful, largely because long-term exposure to fluoride exceeding the recommended level will lead to fluorosis of teeth and bones. Therefore, it is imperative to develop cost-effective and environmentally friendly adsorbents to remove fluoride from polluted water sources. In this study, diatomite (DA), calcium bentonite (CB), bamboo charcoal (BC), and rice husk biochar (RHB) were tested as adsorbents to adsorb fluoride (F‐) from water, and this process was characterized by scanning electron microscopy (FEI-SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The effects of pH, dosage, and the initial mass concentration of each treatment solution upon adsorption of F‐ were determined. Kinetic and thermodynamic models were applied to reveal the mechanism of defluoridation, and an orthogonal experiment was designed to obtain the optimal combination of conditions. The results show that the surfaces of CB, BC, and RHB have an irregular pore structure and rough surface, whereas DA has a rich pore structure, clear pores, large specific surface area, and high silica content. With regard to the adsorption process for F‐, DA has an adsorption complex electron interaction; that of CB, BC, and RHB occur mainly via ion exchange with positive and negative charges; and CB on F‐ relies on chemical electron bonding adsorption. The maximum adsorption capacity of DA can reach 32.20 mg/g. When the mass concentration of fluoride is 100 mg/L, the pH value is 6.0 and the dosage is 4.0 g/L; the adsorption rate of F‐ by DA can reach 91.8%. Therefore, we conclude that DA soil could be used as an efficient, inexpensive, and environmentally friendly adsorbent for fluoride removal, perhaps providing an empirical basis for improving the treatment of fluorine-containing water in the future.

Internal flow field analysis of heterogeneous porous scaffold for bone tissue engineering

The internal pore structure of the porous scaffold for bone tissue engineering and the pressure and velocity distributions of its flow field affect the attachment, proliferation and differentiation of osteoblasts. The permeability of the porous scaffold determines its ability to transport cellular nutrients and metabolites. Therefore, studying the fluid flow characteristics of the porous scaffold plays a vital role in its biological applications. Heterogeneous porous scaffolds (HPS) with irregular internal pore structure have more bionic characteristics of natural structure than uniform porous scaffolds with regular internal pore structure. In order to comprehensively grasp the biological properties of HPS, this article designed HPS with different porosities based on the Voronoi generation method and random theory, and then used computational fluid dynamics (CFD)software to conduct fluid flow simulations. The velocity and pressure distribution rules of the internal flow field of HPS with different porosities were obtained by CFD simulation analysis, and the relationship between the porosity and the distribution rules was studied. Furthermore, the permeabilities of HPS with different porosities were calculated based on Darcy's law, and the influence rule of porosity on the permeability was obtained.

Design of multi-auxetic microstructures for sound absorbing applications

Auxetics are known to improve sound absorption performance due to their irregular porous structure. However, it is still difficult to control the porous microstructure to absorb a specific frequency range, although mechanical rigidity and improved sound absorption performance were achieved by manufacturing polyurethane foam for auxetics. Hence, we report, for a first time, a multi-auxetic porous microstructure fabricated via a triaxial thermal compression method applied simultaneously with two or more different compression ratios. The upper and lower parts of the multi-auxetic foam have two or more different positive or negative Poisson’s ratio, respectively. Consequently, the manufactured multi-auxetic foam has a single negative Poisson’s ratio property with enhanced sound absorption performance in the low-frequency range by twisting and forming a long sound wave path. Moreover, it was confirmed that the multi-auxetic sound absorber has an adjustable sound absorbing performance in a specific frequency range according to the difference in variety of pore sizes for each upper or lower part as well as the direction of incidence of the sound waves. This work suggests that the multi-auxetic porous microstructure can be mass-produced by a simple and fast manufacturing method, and it can be provided at a low price by manipulating the cellular structure of the conventional material.

The reduced phosphomolybdate as dual-functional electrocatalyst and electrochemical sensor for detecting hydrogen peroxide and dopamine

Two reduced phosphomolybdate hybids, (Hbtb)2 (btb)[CuMo12O24 (OH)6(H2PO4)6(HPO4)2]·7H2O (1) and [{Ni(tpp)}2{Ni(H2O)0·5Na2 (H2O)1.5}2{NiMo12O24(OH)6(PO4)6(H2PO4)2}]·2H2O (2), (btb ​= ​1,4-bis (1,2,4-triazol-1-yl)butane; tpp ​= ​2,4,6-tri-(2,2,3-pyridyl)-1-pyridine) were synthesized and characterized. Compound 1 is a 12-linked 3D supermolecule web with a 336∙448∙57 topology. In compound 2, an unusual ligand bpp was synthesized in situ from simple ligands ptz and dpp. Each {Ni(bpp)} modified single-arm {Ni(P4Mo6)2} dimer were joined to two hexanuclear junction unit {Na4Ni2(H2O)4} to yield an extended 1-D chain, which were extended into stacked 3-D networks with irregular apertures via unique multinuclear hybrid rings and rich π-π interaction. Compound 2 possesses more prominent electrocatalytic activity than 1, thus 2-AB-GCE was studied as a sensor. The modified electrode shows the lower detection line (0.007 ​mM and 0.032 ​μM) for both H2O2 and DA in the wider linear range, as well as merit selectivity, stability, and reproducibility. The outstanding sensing properties are correlated with the enhance redox activity, ion/electron transfer ability and structural stability due to the irregular pore structure formed by the introduction of {Ni(tpp)} complexes and π-π interactions. The accurate detection of two substrates in the human serum and urine testifies the practical detection ability of 2-AB-GCE in biological samples.

Facile synthesized NaGdF4 :Yb,Er peanut-shaped, highly biocompatible, colloidal upconversion nanospheres.

A facile method was used for the synthesis of peanut-shaped very emissive NaGdF4 :Yb, Er upconversion nanospheres (UCNSs) at lower temperatures with uniform size distribution. Crystallographic structure, phase purity, morphology, thermal robustness, biocompatibility, colloidal stability, surface chemistry, optical properties, and luminesce properties were explored by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), zeta potential, thermogravimetric/differential thermal analysis (TGA/DTA), Fourier-transform infrared (FTIR), ultraviolet (UV)-visible and photoluminescence spectroscopic tools. XRD pattern verified the construction of a single-phase, highly-crystalline NaGdF4 phase with a hexagonal structure. Peanut-shaped morphology of the sample was obtained from SEM micrographs which were validated from high-resolution TEM images, to have an equatorial diameter of 170 to 200 nm and a length of 220 to 230 nm, with irregular size, monodispersed, porous structure, and rough surface of the particles. The positive zeta potential value exhibited good biocompatibility along with high colloidal stability as observed from the absorption spectrum. The prepared UCNSs revealed high dispersibility, irregular size peanut-shaped morphology, rough surface, good colloidal stability, and excellent biocompatibility in aqueous media. A hexagonal phase NaGdF4 doped with ytterbium (Yb) and erbium (Er) UCNSs revealed the characteristics of highly dominant emissions located at 520-525, 538-550, and 659-668 nm corresponding to the 2 H11/2 → 4 I15/2 , 4 S3/2 → 4 I15/2 , and 4 F9/2 → 4 I15/2 transition of Er3+ ions, respectively, as a result of energy transfer from sensitizer Yb3+ ion to emitter Er3+ ion.

Self‐assembly of triblock copolymers in the slits of neutral plates to form porous membranes and the pore size distribution: dissipative particle dynamics simulation

AbstractThe self‐assembly morphology of triblock copolymers confined between the slits of neutral plates is investigated with the dissipative particle dynamics simulation method. A porous membrane structure with uniform pore size distribution is obtained. The pore size distribution shows linear laws affected by the concentration of the polymer solution, the hydrophilic and hydrophobic properties of the block as well as the polymer topology and slit thickness. When the concentration is in the range 0.4 to 0.7, the linear triblock copolymer forms continuous circular pores through self‐assembly, and block components present a laterally layered texture. The ring triblock copolymer has no end groups and exhibits a unique self‐assembly behavior. The cyclic triblock copolymer self‐assembled in the slit is able to form an interpenetrating porous continuous structure, and the polymer film has a longitudinal layered structure. The star triblock copolymer has a more unique structure and can self‐assemble into worm micelles with irregular pore structure and continuous interpenetration. In addition, the microphase separation structure of the triblock copolymer melt between the slits is studied. Generally, linear triblock copolymers generate longitudinal stripes, ring triblock copolymers form horizontal stripes and star triblock copolymers form a ‘lattice’ structure. © 2022 Society of Industrial Chemistry.

Physical similarity and parametric sensitivity analysis of the capacitive deionization process

ABSTRACT Capacitive deionization is an electrochemical ion removal technique that has broad application prospects for the efficient desalination of brackish water. The current research mainly focuses on the improvement of the electrode material performance and device structure for capacitive deionization. However, the capacitive deionization process is subject to the coupling effect of multiple physical parameters inside the porous electrode, the dominant order and optimization of multiple physical parameters in the capacitive deionization process are needed to be further investigated. In this study, the ion transport in porous electrode of the capacitive deionization is investigated via numerical simulation and physical similarity analysis. Fourteen dimensional physical parameters involved in ion transport are unified into eight dimensionless parameters based on the nondimensionalization of Navier–Stokes and Poisson–Nernst–Planck equations, and the dimensionless parameters are summarized into four categories, including ion adsorption capability, ion transport characteristics, ion motion driving force, and ion adsorption equilibrium time. Analysis based on the numerical models with an irregular porous electrode structure shows that the dimensionless parameters can explain a series of similar physical phenomena in the capacitive deionization processes. Moreover, a parametric sensibility analysis is performed to reveal that the concentration and velocity of inlet solution are dominant factors for optimizing the salt adsorption capacity per unit area and the average salt removal rate. In addition, the inlet solution concentration and electrode potential are critical factors for improving the removal efficiency. The physical similarity and parametric sensitivity analysis in this study provide theoretical guidance for performance improvement in the practical application of capacitive deionization.

A Simple and Effective Modeling Method for 3D Porous Irregular Structures

Porous structures are kinds of structures with excellent physical properties and mechanical characteristics through components and internal structure. However, the irregular internal morphology of porous structures poses new challenges to product modeling techniques. Traditional computer-aided design (CAD) modeling methods can only represent the external geometric and topological information of models, lacking the description of the internal structure and conformation, which limits the development of new porous products. In this paper, a new simple and effective modeling method for 3D irregular porous structures is proposed, which improves the controllability of pore shape and porosity, thus overcoming the limitations of existing methods in 3D and concave structures. The key idea is to solve isothermal for modeling the porosity of porous units. Experimental results show that the method can easily obtain smooth and approximate porous structures from arbitrary irregular 3D surfaces.

Electrochemically Initiated Synthesis of Polyacrylamide Microgels and Core-shell Particles.

Herein, we developed a simple procedure for synthesizing micrometer-sized microgel particles as a suspension in an aqueous solution and thin films deposited as shells on different inorganic cores. A sufficiently high constant potential was applied to the working electrode to commence the initiator decomposition that resulted in gelation. Under hydrodynamic conditions, this initiation allowed preparing different morphology microgels at room temperature. Importantly, neither heating nor UV-light illumination was needed to initiate the polymerization. Moreover, thin films of the cross-linked gel were anchored on different core substrates, including silica and magnetic nanoparticles. Scanning electron microscopy and transmission electron microscopy imaging confirmed the microgel particles’ and films’ irregular shape and porous structure. Energy-dispersive X-ray spectroscopy indicated that the core coating with the microgel film was successful. Dynamic light scattering measured the micrometer size of gel particles with different combinations of acrylic monomers. Thermogravimetric analysis and the first-derivative thermogravimetric analysis revealed that the microgels’ thermal stability of different compositions was different. Fourier-transform infrared and 13C NMR spectroscopy showed successful copolymerization of the main, functional, and cross-linking monomers.

Mechanical and permeability properties of porous scaffolds developed by a Voronoi tessellation for bone tissue engineering.

Irregular porous structures for guided bone regeneration applications have gained increasing attention as they are similar to human bone and more suitable for bone tissue growth. However, pore irregularity as a critical characteristic has been poorly explored. This study proposed a method for parametrically designing porous scaffolds based on a Voronoi tessellation which were manufactured by selective laser sintering (SLS) using the polyamide 12 (PA12) material. The deformation mechanism and energy absorption properties of the prepared Voronoi scaffolds were investigated by quasi-static compression experiments. The results demonstrated that the Voronoi scaffold underwent bending deformation subsequent to transverse expansion under compression, and the Voronoi scaffold simultaneously had been indicated to be effective in improving the carrying capacity and energy absorption performance. Subsequently, computational fluid dynamics (CFD) and cell proliferation tests were introduced to comprehensively assess the influence of the scaffolds on cell growth. CFD analysis showed that the permeability of the surveyed scaffolds is between 3.65 × 10-8 and 12.05 × 10-8 m2 similar to that of natural cancellous bone. The cell test expressed that the scaffold exhibits good cell activity, which can be used to promote cell adhesion and migration with superior potential for development and application.

Multiscale Research on Pore Structure Characteristics and Permeability Prediction of Sandstone

The random existence of many irregular pore structures in geotechnical materials has a decisive influence on its permeability and other macroscopic properties. The analysis and characterization of the micropore structure of the material and its permeability are of great significance for geotechnical engineering. In this study, digital images with different magnifications were used to examine the pore structure and permeability of sandstone samples. The image processing method is used to obtain binary images, and then, the pore size distribution method is used to calculate the pore size distribution. Therefore, based on the Hagen-Poiseuille formula, we get the prediction value of material’s permeability and compare it with the value obtained from mercury intrusion porosimetry (MIP). It is found that different microscopic images with different magnification and various statistical methods of pore size have a specific influence on the characterization of pore structure and permeability prediction. The porosity of different magnifications is not the same, and the results obtained at higher magnifications are more consistent with the results obtained with MIP. With the increase of magnification, we can observe more pores in large sizes. The effect of CPSD (continuous pore size distribution) in pore size statistics is better than that of DPSD (discrete pore size distribution). In permeability prediction, the prediction result of higher magnification images are closer to the instrument test value, and the value of DPSD is more significant than that of CPSD. In future research, an appropriate method should be selected to obtain a reasonable prediction of the permeability of the target material.

Numerical Simulation of Combustion and Characteristics of Fly Ash and Slag in a “V-type” Waste Incinerator

This study is focused on a “V-type” waste incinerator for municipal solid waste (MSW) combustion. Computational fluid dynamics (CFD) methods are used to study the MSW combustion process. The characteristics of fly ash and slag are analyzed by using a laser particle analyzer, scanning electron microscope, X-ray fluorescence, and X-ray diffraction. The results show that the error between the CFD simulation data and measured data is less than 10%, and the changing trend of the combustion process is well-modeled. The fly ash mainly has an irregular spherical or ellipsoid structure, whereas the slag mainly has an irregular porous structure. The main constituents of the ash and slag are CaO and SiO2, along with heavy metal elements such as Cu, Pb, and Cr.

Microencapsulation of roasted coffee oil Pickering emulsions using spray‐ and freeze‐drying: physical, structural and in vitro bioaccessibility studies

SummaryMicrocapsules produced from well‐defined emulsion templates are an interesting alternative for lipid encapsulation. This work aimed to produce microcapsules by the freeze‐drying (FD) and spray‐drying (SD) of Pickering emulsions of roasted coffee oil (RCO) stabilised with chitosan nanoparticles produced by self‐aggregation or by crosslinking with tripolyphosphate. The dried microcapsules were characterised in terms of particle size, oil retention and structure; furthermore, the in vitro bioaccessibility of polyphenols from microencapsulated RCO was investigated. The use of chitosan nanoparticles to stabilise the emulsions increased oil retention in the microcapsules giving values between 83.04% and 95.36%. SD produced spherical microcapsules with small particle sizes (˜11 μm), whereas FD microcapsules showed an irregular shape and porous structure. Although FD had the lowest impact on the bioactive compounds, SD promoted better protection for phenolic compounds and antioxidant activity during in vitro digestion.

Magnesium-Palm Kernel Shell Biochar Composite for Effective Methylene Blue Removal: Optimization via Response Surface Methodology

This study investigates the properties and potential application of Mg-PKS biochar composite for methylene blue solution (MB) adsorption. The Mg-PKS biochar composite was developed from palm kernel shell biochar via steam activation followed by MgSO4 treatment and carbonization. The effect of process parameters such as solution pH (4-10), contact time (30-90 min) and adsorbent dosage (0.1-0.5 g) were investigated via central composite design, response surface methodology. Results revealed that the Mg-PKS biochar composite has irregular shapes pore structure from SEM analysis, a surface area of 674 m2g-1 and average pore diameters of 7.2195 μm based on BET analysis. RSM results showed that the optimum adsorption of MB onto Mg-biochar composite was at pH 10, 30 min contact time and 0.5 g/100 mL dosage with a removal efficiency of 98.50%. In conclusion, Mg treatment is a potential alternative to other expensive chemical treatment methods for biochar upgrading to the adsorbent.

A neighborhood median weighted fuzzy c-means method for soil pore identification

Complex soil pore geometry and heterogeneity determines the ability of a soil to retain moisture and conduction. These soil properties are widely recognized as key factors of essential ecological functions and services. However, until recently, the existing pore identification methods have the problems of low identification accuracy and operating efficiency, which has restricted the development of soil science. The objective of this study was to propose a neighborhood median weighted fuzzy c-means method based on grayscale-gradient feature (NMFCM-G) to identify soil pore structure automatically and accurately. By combining three-dimensional (3D) printing technology with X-ray computed tomography technology, a 3D simulation model with known aperture (10-cm inner diameter) was adopted to evaluate the pore identification error rate of the NMFCM-G method quantitatively. Compared to the methods commonly applied in previous studies, the NMFCM-G method had the smallest average area relative error (2.98%), which was only 1/6 of that of the Image J method with the largest area relative error (18.46%). The NMFCM-G method also had the smallest average perimeter (5.46%), about 3/5 of that of the Image-Pro Plus method with the largest perimeter relative error (8.35%). Meanwhile, the NMFCM-G method was successfully tested on undisturbed cylindrical soil samples, providing encouraging results in terms of identifying irregular pore structure from the complex hierarchical organization of soil. The results show that the NMFCM-G method had the smallest distribution entropy (0.81), the smallest inter-class correlation (0.164 0), and the largest distribution coefficient (0.11), which proves that the NMFCM-G method performed the best in identifying different soil pore structures. Overall, the NMFCM-G method provides new insights into identifying pore structures and thus could provide an automatic and high-efficiency technique for studying the effects of tillage and freeze-thaw cycles on pore structure and soil quality in the future.