Bimodal Pore Size Distribution Research Articles

Stress-dependent water retention behaviour of two intact aeolian soils with multi-modal pore size distributions

The water retention curve (WRC) of unsaturated soils plays a significant role in evaluating rainfall-induced geohazards in geological and geotechnical engineering, such as ground subsidence and slope failure. Stress can affect WRC because loading/unloading alters not only density but also pore size distribution (PSD). Previous studies of stress-dependent WRC focused on soils with mono- and bi-modal PSDs only. In this study, the WRCs of intact paleosol and intact loess with quadri- and tri-modal PSDs were measured using suction- and stress-controlled pressure plate tests. The full-range PSDs of tested specimens were determined by combining X-ray computed tomography (CT) and mercury intrusion porosimetry (MIP). Experimental results show that the multi-modal PSDs and hence WRCs of both soils are strongly affected by stress in a similar approach. For instance, the relationship between degree of hysteresis and suction showed a double-humped pattern, in which the Peak-I and Peak-II were identified at the relatively low (0.1–20 kPa) and high (20–400 kPa) suctions, respectively. The application of stress resulted in a decrease of hysteresis in the Peak-I (about 30%) but an increase in the Peak-II (about 31%). The increase of hysteresis in the Peak-II differs from the behaviour of soils with mono- and bi-modal PSDs, mainly because the reduction of mega- and macro-pore diameters upon loading increases pore non-uniformity in the range corresponding to the Peak-II.

Evolution of pore structure in nanoparticle deposits from unimodal to bimodal pore size distributions: Focus on structural features of dendritic structures

Nanoparticle deposits can exhibit various structures, including compact and dendritic structures, depending on the deposition conditions. While previous studies have characterized deposit structures using factors such as porosity and spatial autocorrelation index, the pore size distribution (PSD), which is an essential structural property, has only been explored in compact structures. In this study, we investigate the PSDs of the entire nanoparticle deposits, ranging from compact to dendritic structures. Deposits are formed using an off-lattice Monte Carlo simulation, and deposition conditions are represented by two dimensionless numbers (KnD, χF). The diffusive Knudsen number (KnD) ranges from 10−1.5 to 101.5, while the dimensionless translational energy of a particle (χF) ranges from 10−3 to 101.5. We use the Delaunay triangulation algorithm for fast PSD calculation, and validate the calculation method using theoretical values of ideal structures and experimental literature data. Our results show that bimodal PSDs appear under thermally-dominated conditions with high values of KnD, while unimodal PSDs with a constant mode radius (∼2.5 rp) are observed under highly advective conditions with high values of χF. We present the geometric mean radii and mode radii of pores as color-filled contours to show their variation trends with KnD and χF. Additionally, we propose a simple model that predicts dendrite width by combining the overall porosity and mode radii of pores. Our model's predictions reasonably match the dendrite width data obtained using a density-based clustering algorithm.

Modeling bimodal capillary bundle two-phase flow in the shale matrix for predicting water saturation distribution

In gas field development, the distribution of water saturation is one of the most effective estimated two-phase flow law methods for the shale matrix. Water saturation has been widely studied; however, few studies exist to show that water saturation distribution is related to pore diameter distribution of shale matrix. Furthermore, based on experimental observations, imbibition and gas-driven water flow nuclear magnetic resonance experiments also show the phenomenon. Therefore, the objective of this work is to build a bimodal capillary bundle two-phase flow model to investigate the relation of water saturation with pore diameter distribution of shale matrix. Firstly, this work combines the bimodal pore size distribution with the truncated Gaussian distribution theory to present the shale matrix pore. Moreover, we develope a shale core imbibition model and a gas-driven water flow model to predict the distribution of the water saturation distribution during the two-phase flow, by using the gas-water two-phase seepage theory. Shale imbibition and gas-driven water flow experiments are carried out on shale samples from the underground Longmaxi Formation. The relative error of distribution curve of water saturation predicted by model and experiments has been calculated. At the initial stage of imbibition the shale matrix core is not completely dried model values do not match the measured values, but, the relative error is stable at 1–2% at the late stage of imbibition. The average relative error is 2.13% in gas-driven water flow process. As a result, the shale imbibition model and the displacement model can accurately characterize the two-phase (gas-water) flow process, providing a theoretical support to study the two-phase flow in the shale matrix.

Numerical Design of Microporous Carbon Binder Domains Phase in Composite Cathodes for Lithium-Ion Batteries.

Lithium-ion battery (LIB) performance can be significantly affected by the nature of the complex electrode microstructure. The carbon binder domain (CBD) present in almost all LIB electrodes is used to enhance mechanical stability and facilitate electronic conduction, and understanding the CBD phase microstructure and how it affects the complex coupled transport processes is crucial to LIB performance optimization. In this work, the influence of microporosity in the CBD phase has been studied in detail for the first time, enabling insight into the relationships between the CBD microstructure and the battery performance. To investigate the effect of the CBD pore size distributions, a random field method is used to generate in silico a multiple-phase electrode structure, including bimodal pore size distributions seen in practice and microporous CBD with a tunable pore size and variable transport properties. The distribution of macropores and the microporous CBD phase substantially affected simulated battery performance, where battery specific capacity improved as the microporosity of the CBD phase increased.

Laboratory Study on Entire Range Suction Measurement and Microstructure Change of Granite Residual Soil

The shear strength of unsaturated granite residual soil (GRS) will decline rapidly when moisture content increases, because of loss of matric suction in the soil. This can lead to slope instability and embankment collapse during rainfall. Determining the matric suction of GRS accurately at different conditions can improve the accuracy of stability analysis. Generally, matric suction can be characterized as the soil–water characteristic curve (SWCC), and it is closely related to soil microstructure. In this study, the entire range of matric suction was measured using a combination of pressure plate method, filter paper method, and vapor equilibrium method. Microstructure change was investigated based on mercury intrusion porosimeter tests, in which the pore size distribution (PSD) curves of GRS samples with different initial densities and moisture content were measured. The PSDs of samples before and after wetting were also measured and compared to investigate the influence of water intrusion. Test results indicate that the combination of measurement methods can cover the entire matric suction range. The microstructure of GRS with different initial conditions presents a clear bimodal PSD. At the same density, the increase in initial moisture content can increase intra-aggregate pores and decrease inter-aggregate pores. When initial density increases, only the volume of inter-aggregate pores decreases. Wetting can decrease inter-aggregate pores and increase intra-aggregate pores. Finally, the Li model is applied in SWCC fitting for tested samples, the result of which performs well with a high correlation coefficient (R2 > 0.95) and is recommended for GRS analysis.

Microstructure evolution of a compacted lateritic silt upon drying–wetting and loading

Lateritic soil usually contains a large amount of iron and aluminium, which promotes the formation of large-size aggregations and further affects soil fabric. It has been demonstrated that the microstructure of soil influences the hydraulic and mechanical behaviour significantly. As a commonly used filling material with special mineral composition, the microstructure change of lateritic soil under common environment actions, such as wetting and loading, is thus of great importance. In this study, the microstructure properties of a lateritic silt under drying–wetting and one-dimensional compression were investigated using mercury intrusion porosimetry and scanning electron microscopy. Test results show that large-sized aggregates are formed in the compacted lateritic silt with 10% of hematite. These aggregates induce a bi-modal pore size distribution (PSD) which includes both micropore and macropore peaks. The different macropore distributions under various dry densities lead to scattered soil–water characteristic curves in a suction range less than 20 MPa. Changes in volume and pore structure mainly occur in the suction path within the “transition zone” where the dominant capillarity affects only the macropore. Drying causes an increase in macropores due to the decreased volume of aggregates, while has limited effect on micropores, whereas wetting weakens the bonding between aggregates, and induces a reduction in macropores. The compacted lateritic silt shows obvious collapse upon soaking, in which the collapse grows up to a peak and then turns to decrease with increasing stress level. Both loading and soaking lead to the collapse of macropores, whereas soaking tends to affect a broader range of pore sizes. It is inferred that, the strong particle cementation produced by hematite leads to a strong micropore structure, which is almost unaffected by the suction change under both confined and unconfined conditions. The PSD change due to the variation in suction is different from that observed on other compacted fine-grained soils, which verifies the effects of special mineral composition (iron and aluminium) on microstructure and further the hydro-mechanical behaviour of lateritic soil.

Scale transition: Pore network study of how pore structure affects the macroscopic parameters of the continuum model for drying

The scale transition from discrete pore network model (PNM) simulations to one-equation continuum model (CM) of drying has been investigated in previous studies for uniformly structured porous media. This investigation is extended in the present work to porous media with widely different pore size distributions, as well as to those with spatially correlated networks of small and large pores. The key questions examined here are how and to what extent pore-structural features can be reflected in the local macroscopic parameters of the one-equation CM derived by traditional homogenization. For this purpose, three-dimensional model capillary structures with monomodal and bimodal pore size distributions are generated and drying simulations are conducted at the limit of viscous-capillary dominated regime. By leveraging volume-averaged data obtained from PNM simulations the one-equation CM is parameterized and thus its local parameters are expressed in dependence on the pore structure. The simulation results show that for the monomodal and bimodal pore structures the profiles of the moisture transport coefficients are complex and non-unique over the entire drying process. Moreover, the deviation of the water vapor partial pressure from the saturation vapor pressure in the presence of liquid water – which is referred to as non-local equilibrium effect – is less pronounced for the bimodal pore structure compared to the monomodal pore structures. Finally, comparisons are performed between the volume-averaged data obtained at different stages of drying by the discrete simulations with monomodal and bimodal pore structures and results of the continuum model of drying.

Wafer-Scale Fabrication of Hierarchically Porous Silicon and Silica by Active Nanoparticle-Assisted Chemical Etching and Pseudomorphic Thermal Oxidation.

Many biological materials exhibit a multiscale porosity with small, mostly nanoscale pores as well as large, macroscopic capillaries to simultaneously achieve optimized mass transport capabilities and lightweight structures with large inner surfaces. Realizing such a hierarchical porosity in artificial materials necessitates often sophisticated and expensive top-down processing that limits scalability. Here, an approach that combines self-organized porosity based on metal-assisted chemical etching (MACE) with photolithographically induced macroporosity for the synthesis of single-crystalline silicon with a bimodal pore-size distribution is presented, i.e., hexagonally arranged cylindrical macropores with 1 µm diameter separated by walls that are traversed by pores 60 nm across. The MACE process is mainly guided by a metal-catalyzed reduction-oxidation reaction, where silver nanoparticles (AgNPs) serve as the catalyst. In this process, the AgNPs act as self-propelled particles that are constantly removing silicon along their trajectories. High-resolution X-ray imaging and electron tomography reveal a resulting large open porosity and inner surface for potential applications in high-performance energy storage, harvesting and conversion or for on-chip sensorics and actuorics. Finally, the hierarchically porous silicon membranes can be transformed structure-conserving by thermal oxidation into hierarchically porous amorphous silica, a material that could be of particular interest for opto-fluidic and (bio-)photonic applications due to its multiscale artificialvascularization.

Mechanical and Hydration Characteristics of Stabilized Gold Mine Tailings Using a Sustainable Industrial Waste-Based Binder.

Sustainable resource utilization of tailings is a long-term challenge. Therefore, a novel waste-based binder is proposed in this study to stabilize/solidify gold mine tailings (GMTs). This binder is composed of fly ash (FA), ground blast furnace slag (GBFS), and metakaolin (MK) activated with mixed calcium carbide residue (CCR) as well as pure reagent grade chemical, sodium hydroxide (SH, NaOH), and plaster gypsum (PG, CaSO4·2H2O). The mechanical properties and hydration of stabilized tailings with curing period were investigated. Tests included triaxial compression test and nitrogen adsorption to evaluate the strength of the stabilized tailings and microstructure. The results show that the addition of the waste-based binder yields significant improvement in shear strength. Strain softening occurred for all cured samples, and a local shear band can be observed in all failed stabilized samples. Based on the relationship between strength and curing period, it can be speculated that the hydration reaction of the sample ends after around 40 days of curing. A bimodal pore-size distribution was observed in all solidified/stabilized samples. FTIR and 27Al MAS-NMR were used to analyze hydration products. The strength improvement of stabilized tailings was mainly attributed to the formation of ettringite and C-S-H gels after various polymerization reactions. These new hydrates bind tailings particles and fill the pores to form a more stable structure, which supplied superior mechanical properties. This paper can provide a theoretical basis for exploring the application of the industrial waste-based binder to modify the mechanical properties of gold tailings.

Characterization of quenched MD simulated porous carbon electrodes for supercapacitors

Energy storage devices are playing a significant role in reducing the harmful effects of global warming. Automobile manufacturers are already shifting towards electric vehicles (EVs) in order to curb vehicular pollution. One of the significant drawbacks of the current EV batteries lies in their power density which limits their application. Supercapacitors are a category of energy storage devices that keep excellent specific power capacity and can be used in a hybrid setup with Li-ion batteries in order to make EVs with longer life and rapid acceleration. Electrode porosity in supercapacitors performs a major role in defining their energy and power density. This work explores the quenched molecular dynamics (QMD) simulations followed by thorough characterization for understanding the bimodal pore size distribution (combination of micro- & mesopores) of a porous electrode structure for maintaining a high energy and power density. We performed simulations at various quench rates on porous carbon structures ranging from 600 K/ps to 5 K/ps. Once the porous structures obtained room temperature (300 K), we characterized it for its pore sizes that allow ions to move in and out of the pores during charging and discharging, respectively. The interconnected channeling method has been developed to identify the channel throats and their lengths for different cases of quench rates. Direct output of this study will help experimentalists in fabricating tunable porosity in order to achieve high energy density while maintaining a relatively good power density of supercapacitors.

Investigation on microstructure evolution of clayey soils: A review focusing on wetting/drying process

Variability in moisture content is a common condition in natural soils. It influences soil properties significantly. A comprehensive understanding of the evolution of soil microstructure in wetting/drying process is of great significance for interpretation of soil macro hydro-mechanical behavior. In this review paper, methods that are commonly used to study soil microstructure are summarized. Among them are scanning electron microscope (SEM), environmental SEM (ESEM), mercury intrusion porosimetry (MIP) and computed tomography (CT) technology. Moreover, progress in research on the soil microstructure evolution during drying, wetting and wetting/drying cycles is summarized based on reviews of a large body of research papers published in the past several decades. Soils compacted on the wet side of optimum water content generally have a matrix-type structure with a monomodal pore size distribution (PSD), whereas soils compacted on the dry side of optimum water content display an aggregate structure that exhibits bimodal PSD. During drying, decrease in soil volume is mainly caused by the shrinkage of inter-aggregate pores. During wetting, both the intra- and inter-aggregate pores increase gradually in number and sizes. Changes in the characteristics of the soil pore structure significantly depend on stress state as the soil is subjected to wetting. During wetting/drying cycles, soil structural change is not completely reversible, and the generated cumulative swelling/shrinkage deformation mainly derives from macro-pores. Furthermore, based on this analysis and identified research needs, some important areas of research focus are proposed for future work. These areas include innovative methods of sample preparation, new observation techniques, fast quantitative analysis of soil structure, integration of microstructural parameters into macro-mechanical models, and soil microstructure evolution characteristics under multi-field coupled conditions.

Coupled hydro-mechanical behaviour of a Kaolin Clay in the context of the geothermal use of geotechnical structures

An experimental study regarding the hydro-mechanical behaviour of a Malaysian Kaolin is presented. Strain rate-controlled oedometer tests have been conducted on compacted samples. The influence of initial water content on the pore-size distribution (PSD) of compacted samples was investigated by Mercury Intrusion Porosimetry (MIP) tests. The drying path of the soil-water characteristic curve was experimentally determined for initially compacted samples and slurry samples. The preconsolidation stress was found to increase with increase in initial dry density and with decrease in initial water content. The compression curves merge into a single line, as soon as they have reached full saturation during loading. Samples at the dry side of Proctor water content showed a bi-modal PSD, whereas a mono-modal PSD was found for Proctor water content and at the wet side. The different initial compaction states of the samples were getting reflected in the drying SWCC until a suction of about 2 MPa, beyond which the drying paths were found to be identical.

Sulfur-doped CMK-5 with expanded lattice for high-performance lithium ion batteries

Heteroatom-doped porous carbon materials are very attractive for lithium ion batteries (LIBs) owing to their high specific surface areas, open pore structures, and abundant active sites. However, heteroatom-doped porous carbon with very high surface area and large pore volume are highly desirable but still remain a big challenge. Herein, we reported a sulfur-doped mesoporous carbon (CMK-5-S) with nanotubes array structure, ultrahigh specific surface area (1390 m2/g), large pore volume (1.8 cm3/g), bimodal pore size distribution (2.9 and 4.6 nm), and high sulfur content (2.5 at%). The CMK-5-S used as an anode material for LIBs displays high specific capacity, excellent rate capability and highly cycling stability. The initial reversible specific capacity at 0.1 A/g is as high as 1580 mAh/g and simultaneously up to 701 mAh/g at 1 A/g even after 500 cycles. Further analysis reveals that the excellent electrochemical storage performances is attributed to its unique structures as well as the expanded lattice by sulfur-doping.

On the optimal cathode catalyst layer for polymer electrolyte fuel cells: Bimodal pore size distributions with functionalized microstructures

A high advancement has been achieved in the design of proton exchange membrane fuel cells (PEMFCs) since the development of thin-film catalyst layers (CLs). However, the progress has slowed down in the last decade due to the difficulty in reducing Pt loading, especially at the cathode side, while preserving high stack performance. This situation poses a barrier to the widespread commercialization of fuel cell vehicles, where high performance and durability are needed at a reduced cost. Exploring the technology limits is necessary to adopt successful strategies that can allow the development of improved PEMFCs for the automotive industry. In this work, a numerical model of an optimized cathode CL is presented, which combines a multiscale formulation of mass and charge transport at the nanoscale(∼10nm)and at the layer scale(∼1μm). The effect of exterior oxygen and ohmic transport resistances are incorporated through mixed boundary conditions. The optimized CL features a vertically aligned geometry of equally spaced ionomer pillars, which are covered by a thin nanoporous electron-conductive shell. The interior surface of cylindrical nanopores is catalyzed with a Pt skin (atomic thickness), so that triple phase points are provided by liquid water. The results show the need to develop thin CLs with bimodal pore size distributions and functionalized microstructures to maximize the utilization of water-filled nanopores in which oxygen transport is facilitated compared with ionomer thin films. Proton transport across the CL must be assisted by low-tortuosity ionomer regions, which provide highways for proton transport. Large secondary pores are beneficial to facilitate oxygen distribution and water removal. Ultimate targets set by the U.S. Department of Energy and other governments can be achieved by an optimization of the CL microstructure with a high electrochemical surface area, a reduction of the oxygen transport resistance from the channel to the CL, and an increase of the catalyst activity (or maintaining a similar activity with Pt alloys). Carbon-free supports (e.g., polymer or metal) are preferred to avoid corrosion and enlarge durability.

Boosting the performance of Zn-air cells by spinel catalysts with bimodal pore structure and gill filament configuration

Spinel oxides with specific morphology are importantly multifunctional materials for various applications. Here we report various morphological spinel oxides with one and two-modal pore size structures. The surface microstructure, phase composition, specific surface areas and electrocatalytic OER/ORR activities are examined. The results reveal that the bicomponent (NiCo2O4 and Co3O4) spinel exhibits a bimodal pore size distribution, high specific surface area, good OER activity (an overpotential of 313 mV at 10 mA cm−2Geo) and low Tafel slope of 73.1 mV dec−1. The Co3O4 component presents a perforated sheet morphology similar to an ancient window configuration with regular hole patterns, which benefits for mass transfer and O2 bubble detachment. By comparison, the single-component NiCo2O4 spinel having the morphology of more open self-assembled nanoneedle spheres or nanorod clusters, similar to the configuration of fish gill filaments, shows better ORR activities. The morphology, similar to the fish gills, can readily capture dissolved oxygen molecules from the film electrolyte at the three-phase interface and improve ORR performance. In addition, calcination temperatures also significantly affect pore structure, surface areas, and electrocatalytic activities. Finally, small Lab size Zn-air cells are assembled using thin flexible air electrodes with the self-assembled nanoneedle NiCo2O4 catalysts. Electrochemical charging-discharging performance and cycling durability are evaluated.

The impact of bimodal pore size distribution and wettability on relative permeability and capillary pressure in a microporous limestone with uncertainty quantification

Pore-scale X-ray imaging combined with a steady-state flow experiment was used to study the displacement processes during waterflooding in an altered-wettability carbonate, Ketton limestone, with more than two orders of magnitude difference in pore size between macropores and microporosity. We simultaneously characterized macroscopic and local multiphase flow parameters, including relative permeability, capillary pressure, wettability, and fluid occupancy in pores and throats. An accurate method was applied for porosity and fluid saturation measurements using greyscale based differential imaging without image segmentation. The relative permeability values were corrected by considering the measured saturation profile along the sample length to account for the so-called capillary end effect. The behaviour of relative permeability and capillary pressure was compared to other measurements in the literature to demonstrate the combined effects of wettability and pore structure. Typical oil-wet behaviour in resolvable macropores was measured from contact angle, fluid occupancy and curvature. The capillary pressure was negative while the oil relative permeability dropped quickly as oil was drained to low saturation and flowed through connected oil layers. Brine initially largely flowed through water-wet microporosity, and then filled the centre of large oil-wet pore bodies. Thus, the brine relative permeability remained exceptionally low until brine formed a connected flow path in the macropores leading to a substantial increase in relative permeability. Overall, this work demonstrates that not only wettability but also pore size distribution and microporosity have significant impact on displacement processes.

Construction of novel super microporous silica adsorbents using pluronic triblock copolymer as template towards desulfurization from fuel

As an efficient fuel purification technique, adsorption desulphurization has attracted wide attention. Silicon oxide has been verified as a promising candidate for adsorption desulfurization reagent due to the advantages of stable structure, inexpensiveness and accessibility. However, its adsorption desulfurization performance is always weakened by the limited pore channel size leading to pore diffusion resistance over the traditional microporous silicon oxide, and it suffers from the poor shape selectivity of mesoporous silicon oxide as well. In this work, we successfully prepared a novel super microporous silica material (SMS) with a unique bimodal micro-mesoporous pore size distribution mainly around 1.2 nm, 1.6 nm and 1.8 ∼ 3.5 nm, using a pluronic triblock copolymer with approximately an average molecular weight of 3858 as template by hydrothermal synthesis. The SMS possessed the characteristics of Ia3d cubic phase and super microporous as well as mesoporous silica structure, according to the X-ray diffraction characterization as well as nitrogen adsorption isotherms. The SMS could effectively reduce the diffusion resistance and exhibit improved shape selectivity compared to microporous or mesoporous silicon oxide, respectively, by virtue of its bimodal micro-mesoporous pore size distribution. Under an optimized crystallization temperature of 100 °C for 24 h, the as-synthesized SMS displayed a notable desulfurization performance with a breakthrough capacity of 0.122 mmol S/g benzothiophene, which was significantly superior to that of traditional mesoporous silica KIT-6 (0.04 mmol S/g). Furthermore, the desulfurization performance of SMS adsorbent was not significantly reduced after three cycles of regeneration. The SMS exhibited high desulfurization capacity, easy regeneration and satisfactory regeneration performance, and it could be applied in adsorptive desulfurization technology.

Bottom-up design of porous electrodes by combining a genetic algorithm and a pore network model

The microstructure of porous electrodes determines multiple performance-defining properties, such as the available reactive surface area, mass transfer rates, and hydraulic resistance. Thus, optimizing the electrode architecture is a powerful approach to enhance the performance and cost-competitiveness of electrochemical technologies. To expand our current arsenal of electrode materials, we need to build predictive frameworks that can screen a large geometrical design space while being physically representative. Here, we present a novel approach for the optimization of porous electrode microstructures from the bottom-up that couples a genetic algorithm with a previously validated electrochemical pore network model. In this first demonstration, we focus on optimizing redox flow battery electrodes. The genetic algorithm manipulates the pore and throat size distributions of an artificially generated microstructure with fixed pore positions by selecting the best-performing networks, based on the hydraulic and electrochemical performance computed by the model. For the studied VO2+/VO2+ electrolyte, we find an increase in the fitness of 75 % compared to the initial configuration by minimizing the pumping power and maximizing the electrochemical power of the system. The algorithm generates structures with improved fluid distribution through the formation of a bimodal pore size distribution containing preferential longitudinal flow pathways, resulting in a decrease of 73 % for the required pumping power. Furthermore, the optimization yielded an 47 % increase in surface area resulting in an electrochemical performance improvement of 42 %. Our results show the potential of using genetic algorithms combined with pore network models to optimize porous electrode microstructures for a wide range of electrolyte composition and operation conditions.

Paracetamol and Ibuprofen Removal from Aqueous Phase Using a Ceramic-Derived Activated Carbon.

Emerging pollutants, including pharmaceuticals and personal care products, have been detected in surface and groundwaters. The adsorption of paracetamol and ibuprofen, two widespread drugs, has been studied in aqueous medium, using a ceramic-derived carbon (CeDC) and a commercial activated carbon (CoAC). CeDC yielded a BET surface area of 895 m2 g−1, a bimodal pore size distribution (13.2 and 35 nm) and a total pore volume of 1.99 cm3 g−1. CoAC had an approximate surface area of 1000 m2 g−1, a homogeneous pore size distribution and a total pore volume of 0.42 cm3 g−1. Kinetic and equilibrium tests were carried out in batch systems to study the materials’ sorption performances. The intraparticle diffusion model best fitted the experimental kinetic data. The maximum ibuprofen sorption capacities were 120 mg g−1 and 133 mg g−1 for CoAC and CeDC, respectively, whereas no major differences on the maximum paracetamol sorption capacities (qm) were observed among the sorbents (150–159 mg g−1). Therefore, CeDC, synthesized easily from a ceramic composite, improved time and sorption capacity of paracetamol and ibuprofen compared to the commercial activated carbon, indicating the potential of the developed carbon as an emerging pollutant sorbent material.

Incorporation of magnesium phosphate into magnesium oxide on Mg[sbnd]Ag alloy through plasma electrolytic oxidation

The application of MgAg alloy for the fabrication of orthopedic implant requires its enhanced corrosion resistance, desired biocompatibility and bactericidal capability without cytotoxicity. Herein, to achieve those purposes, a novel plasma electrolytic oxidation (PEO) treatment was proposed. The PEO coating with a bimodal pore size distribution could form on MgAg alloy surface to enhance its corrosion resistance. Further, the incorporation of magnesium phosphate in the PEO coating may also benefit its biocompatibility. Finally, Ag within the alloy could be gradually oxidized to form incorporated Ag+ and nano-sized Ag2O particles in the coating, which potentially optimize the ionic release kinetics of Ag for a desired antibacterial capability without cytotoxicity. Hence, the present work offers a novel PEO method to improve the corrosion resistance and biological response of MgAg alloy, which enlightens the application of antibacterial Mg alloy in the field of biomedical devices.