Average Specific Surface Area Research Articles

Material mapping strategy to identify the density-dependent properties of dry natural snow

The mechanical properties of natural snow play a crucial role in understanding glaciers, avalanches, polar regions, and snow-related constructions. Research has concentrated on how the mechanical properties of snow vary, primarily with its density; the integration of cutting-edge techniques like micro-tomography with traditional loading methods can enhance our comprehension of these properties in natural snow. This study employs μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document}CT imaging and uniaxial compression tests, along with the Digital Volume Correlation (DVC) to investigate the density-dependent material properties of natural snow. The data from two snow samples, one initially non-compressed (test 1) and the other initially compressed (test 2), were fed into Burger’s viscoelastic model to estimate the material properties. μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mu$$\\end{document}CT imaging with 801 projections captures the three-dimensional structure of the snow initially and after each loading step at -18∘\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${^\\circ }$$\\end{document}C, using a constant deformation rate (0.2 mm/min). The relative density of the snow, ranging from 0.175 to 0.39 (equivalent to 160–360 kg/m3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^3$$\\end{document}), is determined at each load step through binary image segmentation. Modulus and viscosity terms, estimated from Burger’s model, exhibit a density-dependent increase. Maxwell and Kelvin–Voigt moduli range from 0.5 to 14 MPa and 0.1 to 0.8 MPa, respectively. Viscosity values for the Maxwell and Kelvin–Voigt models vary from 0.2 to 2.9 GPa-s and 0.2 to 2.3 GPa-s within the considered density range, showing an exponent between 3 and 4 when represented as power functions. Initial grain characteristics for tests 1 and 2, obtained through image segmentation, reveal an average Specific Surface Area (SSA) of around 55 1/mm and 40 1/mm, respectively. The full-field strain distribution in the specimen at each load step is calculated using the DVC, highlighting strong strain localization indicative of non-homogeneous behavior in natural snow. These findings not only contribute to our understanding of natural snow mechanics but also hold implications for applications in fields such as glacier dynamics and avalanche prediction.

Adsorption of heavy metals from aqueous solutions by magnetic barium hydroxyapatite nanoparticles

ABSTRACT Magnetic barium hydroxyapatite (Fe3O4@BaHAP) nanoparticles were synthesised and used as a sorbent for the removal of several heavy metal ions from aqueous solutions. The sorbent characterisation was performed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), vibrating-sample magnetometer (VSM) and Fourier transform infrared spectroscopy (FTIR) techniques. A homemade device, named continuous collection of magnetic sorbent (CCMS), was designed for efficient removal of heavy metal ions from aqueous solutions and simultaneous collection of the sorbent by a permanent magnet at the end of the process. Results of BET analysis show that average pore diameter, average pore width, pore volume and specific surface area of the Fe3O4@BaHAP NPs were 10.9 nm, 11.6 nm, 0.16 cm3/g and 55.7 m2/g, respectively. Influential parameters on the removal efficiency were investigated and optimised using a central composite design method. The optimised values for solution pH, sorbent amount, stirring and circulating times were 6.2, 150 mg, 13 and 25 min, respectively. Magnetic BaHAP nanoparticles were shown to have higher removal efficiency than BaHAP or Fe3O4 alone. Under optimised conditions, adsorption capacities for Pb2+, Cr3+, Cd2+ and Cu2+ were 99.0, 66.5, 91.2 and 92.1 mg/g, respectively. The results demonstrated that the synthesised magnetic BaHAP nanoparticles can effectively remove several metal ions from contaminated water sources.

Demonstrating resonant ultrasound spectroscopy as a viable technique to characterize thermally conditioned high explosive materials

We present results of resonant ultrasound spectroscopy (RUS) measurements applied to granular high explosive materials at different bulk pressing densities and degree of thermal conditioning. The material chosen in this study is a ubiquitously used explosive material known as pentaerythritol tetranitrate (PETN), which is used commercially in civil and defense applications both as a binderized plastic bonded explosive material and an unbinderized neat material. However, changes in granular PETN bulk elastic properties due to thermal conditioning, which could have implications for better understanding environmental aging-related effects, have not been well studied even though it is believed that elasticity may play an important role in explosive material initiation mechanisms. Furthermore, monitoring elastic property changes in granular explosive pressings has not yet been demonstrated using RUS, which is an appealing non-destructive characterization tool that requires only dry point contact with the explosive material. To this end, we report the first study using RUS to quantify the elastic properties of binderized and neat PETN pressings as well as to quantify changes in elastic properties as a function of both thermal conditioning and bulk pressing density. Elastic stiffness coefficients, sometimes more commonly referred to as elastic constants, calculated from the RUS measurements on the different PETN-based materials show a significant increase for the post-conditioned samples compared to the pre-conditioned samples. This trend of increasing elastic properties with thermal conditioning was consistent for different density pressings, different thermal exposure conditions, and even different neat PETN pressings of differing average crystal sizes and/or specific surface areas.

Hydrodynamics of a bubble passing through a Kelvin cell in microchannel with shear-thinning fluid

Open cell solid foams (OCSF) show great potential for process intensification in heterogeneously catalyzed reactions due to their favorable properties regarding heat-mass transfer, pressure drop and specific surface area (SSA). As one of the most ideal OCSF structure, Kelvin cell (KC) exhibits a fundamental importance in fully understanding the complex flow and transport properties of these reactions, but the research involving gas-liquid two-phase flow is still missing. In this work, the hydrodynamics of a bubble through a representative elementary volume with KC model in minichannel with sodium carboxymethyl cellulose aqueous solution are investigated by coupled level-set and volume-of-fluid method. The regime of bubble penetration into KC is elucidated. The specific surface area and permeability of bubble are studied by systematically analyzing the influences of solution concentration, liquid velocity, KC's porosity and contact angle, as well as fluid type. Four penetration regimes of approaching stage, engraving stage, extruding stage, and deviating stage are identified, and a typical curve of SSA of bubble in terms of flow time is acquired accurately. It is found that the drastic changes in SSA and permeability are closely related to the engraving and extruding stages. The average SSA in two involved stages increases with solution concentration, decreases with KC's porosity. The maximum permeability corresponding to the transition point between two stages, decreases with solution concentration, increases slightly with KC's porosity. However, liquid flow velocity and KC's contact angle have no significant effect on both the average SSA and the maximum permeability. Compared with water, a small SSA tends to be obtained and the permeability climbs slowly but reaches a high peak in CMC solution.

Influence mechanism of dispersion and agglomeration characteristics of micron/nano carbon dust on its combustion kinetics and explosion process

Due to the widespread use of lithium-ion batteries, evaluations of the flammability and explosive characteristics of carbon dust materials as anodes require attention. Carbon dust often reaches the micron/nano scale, and dust particle state and explosion risk generated in different industrial scenarios are different, which is in urgent need of research. Nanoscale dust has relatively static coagulation properties and shows characteristics of dispersion and reagglomeration under a certain airflow. The particle size characteristics affect its thermodynamic characteristics and various consequence parameters of dust explosion. The oxidation and combustion characteristics are mainly affected by dust particle size distribution characteristics. The apparent activation energy is mainly affected by the proportion of small and medium-sized particles and pre-exponential index factor is mainly affected by the dust overall average particle size and specific surface area. The explosion consequence parameters are affected by the thermodynamic parameters, by the disturbance state, particle distribution degree of dust cloud and other factors, which affect the heat radiation and heat transfer process to some extent resulting in different explosion consequence parameters. Due to the agglomeration characteristics of nano-level dust, the minimum ignition energy and minimum ignition temperature of nano-level dust are generally smaller than that of micron level dust.

In situ synthesis and regulation of spherical Ti6Al4V powder by calciothermic self-propagating metallurgy

In this paper, spherical Ti6Al4V alloy powder was successfully prepared by calciothermic self-propagating rapid reaction method, in which TiO2, V2O5, Al and Ca were used as raw materials. The reduction reaction can be completed in minutes with no need for any external energy and additives in the reaction process. By investigating the influence of the additives, the amount of reductant Ca added, the reaction pressure and the particle size of Ca, on the composition as well as the morphology of the product, the optimal alloy powder with an low oxygen content of 0.21 wt% was obtained, whose average particle size and specific surface area were 15.28 μm and 0.284 m2/g respectively. Moreover, this research implied the adiabatic temperature of the system and the liquid Ca are the main factors that pose influence to the powder morphology during sintering-reduction-spheroidization-solidification process. Compared with the traditional Ti6Al4V alloy powder preparation process, this process stands out with characteristics of high purity, short production cycle and environmental friendliness, which show high commercialization potential for industrial preparation of Ti6Al4V and similar alloy powders.

Removal performance and mechanism of tetracycline hydrochloride in aqueous by geopolymers from tourmaline tailings

Tetracycline hydrochloride (TCH) is one of the widespread pollutants in wastewater, which easily causes severe threat to human health and ecological environment. Geopolymers (GPs) have demonstrated potential applications as adsorbents for effluent treatment. Herein, a research on the removal performance and mechanism of TCH by geopolymers from tourmaline tailings (TMT) was introduced. The TMT exhibited the typical characteristics of the amorphous state of geopolymer gel to varying degrees under a series of alkali activator modulus, and the sample with a modulus of 1.2 had the highest average pore diameter and specific surface area, which were 5.83 nm and 150.17 m2·g−1, respectively. The kinetic data were well fitted by pseudo-second-order kinetic model for the adsorption process of TCH on TMT-GP1.2, and the maximum theoretical adsorption capacity, obtained from the Langmuir model, was 105.4 mg·g−1 at 318 K and pH= 5. Thermodynamics indicated that the adsorption process of TCH on TMT-GP1.2 was not only endothermic, but also feasible and spontaneous. The adsorption of TCH by TMT-GP1.2 involved the combined effect of physical and chemical adsorption, including pore filling, electrostatic attraction, hydrogen bonding and ion exchange interactions. Notably, TMT-GP1.2 might show the superposition of excellent functions from the geopolymers and schorl, especially in ion exchange and electrostatic attraction, thus enhancing the removal efficiency of TCH. The adsorption capacity of the TMT-GP1.2 for TCH reached 46.64 mg·g−1 after 5 cycles. Based on the price-effectiveness, effective removal capacity and acceptable reusability, the tourmaline tailings geopolymers were expected to be potential environmentally friendly TCH adsorbents.

Synthesis of phosphoric acid-based mesoporous geopolymers from tourmaline tailings for effective adsorption of tetracycline hydrochloride in aqueous environment

As a porous material, geopolymers (GPs) have attracted more attention for wastewater purification. Herein, a low-cost and environmentally friendly phosphoric acid-based tourmaline tailings geopolymers (PTMT-GP) were fabricated, and used as adsorbents for removal of tetracycline hydrochloride (TCH) in solution. The morphological and structural evolution of TMT after phosphoric acid attack was confirmed by XRD, SEM and FT-IR. The optimal PTMT-GP0.7 had the largest average pore and specific surface area, which were 3.89 nm and 115.66 m2 g−1, respectively. The observed adsorption process of TCH on PTMT-GP0.7 could be perfectly explained by pseudo-second-order kinetic model, and the maximum theoretical adsorption capacity, obtained from the Langmuir model, was 82.56 mg g−1 at 318 K and pH = 3. Thermodynamics indicated that the adsorption process of TCH on PTMT-GP0.7 was not only endothermic, but also feasible and spontaneous. The removal of TCH in aqueous by PTMT-GP0.7 suggested the combined effect of physical and chemical adsorption, including pore filling, electrostatic, H-bonding and ion exchange interaction. After 5 reuse cycles, PTMT-GP0.7 maintained 86.56% of the first saturated adsorption capacity for TCH, and the adsorption capacity of PTMT-GP0.7 calcined at 400 °C for 2 h decreased by 4.56%. This work will provide a valuable reference for evaluating the adsorption performance of phosphate-based geopolymer materials synthesized from tailings, which are expected to be a low-cost, green and stability adsorbent to remove TCH from wastewater.

Hydrous Pyrolysis of Source Rocks with Different Maturity in Dongying Sag, Bohai Bay Basin, China: Implications for Shale Oil Exploration and Development

Shale oil yield, movability, and reservoir brittleness are three factors that must be focused on for shale oil exploration and development. The yield and composition of hydrocarbons and mineral composition have changed significantly during diagenesis, affecting the yield and movability of shale oil and the brittleness of the rock. In this study, the source rocks at different depths in the Dongying Sag were subjected to hydrous pyrolysis, and the yield and composition of pyrolyzed hydrocarbons and mineral composition were systematically analyzed. The brittleness index (BEI), weighted average specific surface area (SSAWA), and polarity index (PI) have been established to quantitatively characterize the brittleness and adsorption capacity of rock as well as the mobility of shale oil. The results suggest that diagenetic evolution controls rocks’ brittleness and adsorption capacity by changing their mineral composition. In the low-temperature stage, the mineral transformation is not obvious, and the BEI and SSAWA fluctuate in a small range. In the high-temperature stage, the rapid smectite illitization leads to an increase in the brittleness and a decrease in the adsorption capacity. In addition, the nonpolar components such as saturates and aromatics in the pyrolyzed hydrocarbons gradually increased with the increasing temperature, enhancing the mobility of the shale oil. Based on the three evaluation indexes of BEI, PI, and SSAWA, and combined with the changes in hydrocarbon yields during hydrous pyrolysis, we comparatively analyzed the differences in the mobility and yields of original soluble organic matter as well as pyrolyzed hydrocarbons of the source rocks at different depths. Based on the above results, it can be concluded that the shale in the depth range of 3300–3795 m is a favorable area for shale oil exploration and development in the study area. This work suggests that predicting the sweet spot for shale oil exploration and development requires more attention to the impact of diagenetic evolution on the composition of minerals and hydrocarbons.

Analysis of the Pore Structure and Fractal Characteristics of Coal and Gas Outburst Coal Seams Based on Matrix Compression Correction

The comparative analysis of coal samples under different gas occurrence conditions systematically reveals the pore structure characteristics of coal and gas outburst coal seams. The functional relationship between R0,max and Kc was clarified using mathematical statistical methods, and the pore structure and fractal characteristics of coal and gas outburst coal seams were analyzed on the basis of modified mercury pressure data and fractal analysis. The results show that the functional relationship between R0,max and Kc is consistent with y = 1.59x−0.48, and when the mercury inlet pressure is 10~120 MPa, the coal sample is the most affected by the matrix compression effect. The average pore volume and average specific surface area of the outburst coal samples were 41.71% and 23.09%, which is greater than those of the non-outburst coal samples, respectively, and the specific surface area and pore volume provided by the outburst mining micropores were 46.24% and 81.67%, respectively. The fractal dimension, D, of the coal seam increased with the increase in metamorphism, and compared with low gas mines, the fractal dimension of coal samples in the coal and gas outburst mines was higher, the influence of the matrix compression effect was more obvious, and the heterogeneity was stronger.

Thermochemical energy storage in CaCl2-NH3 pair evaluated by rapid multiple adsorption-desorption cycles controlled with wasted iron induction heating

Energy storing systems can provide leverage to the current supply demand intermittency issue thus increasing energy efficiency. Among many available technologies, thermochemical energy storage is highly promising. In this work, we investigate, experimentally, for the first time, inductive heating as an approach to direct coupling of power systems with thermal energy technologies. This system also allows for versatile measurements in rapid multiple adsorption–desorption cycle control. Adsorption and desorption cycling of the CaCl2-NH3 adducts is realized in a custom-made setup. Iron wires and waste red mud are investigated as potential inductive materials. Material performance is evaluated after 1, 2 and 1000 cycles using differential scanning calorimetry, thermogravimetry, scanning electron microscopy and specific surface area. Waste red mud shows good inductive potential. No material degradation is observed after 1000 cycles in all cases. Samples heated using waste red mud have a higher maximum absorption capacity (0.304 versus 0.154 gNH3/gCaCl2) and desorption enthalpy (716 versus 460 KJ/ kgCaCl2) compared to the ones heated using iron wires. This is found to be related to the average specific surface area of samples containing red mud, which is almost double that of iron ones. We hope the concept presented here can stimulate research in the direction of inductive heating while simultaneously generating new utilization pathways for waste red mud.

Characteristics and Factors Influencing Pore Structure in Shale Oil Reservoirs of Different Lithologies in the Jurassic Lianggaoshan Formation of the Yingshan Gas Field in Central Sichuan Basin

Shale in the Jurassic Lianggaoshan Formation in central Sichuan exhibits strong heterogeneity. The study of the pore structure characteristics of different lithologies is crucial to the selection of the target interval. Shale samples of the Lianggaoshan Formation from well YS5 in the central part of the Sichuan Basin were analyzed using scanning electron microscopy, low-temperature nitrogen adsorption, high-pressure mercury injection (HPMI), and large -field splicing method -based scanning electron microscopy (LFS-SEM) to elucidate the pore structure characteristics of shale and their influencing factors. The mineral composition of the reservoir in the study area was diverse, primarily consisting of clay minerals, followed by quartz and calcite. The reservoir space comprised intergranular, granular, and organic matter pores, and oil was observed to fill the reservoir space. Reservoir characteristics varied with the lithological properties. In clayey shale, intergranular pores located in clay mineral particles and pores between pyrite and natural fractures were mainly observed, with a bimodal distribution of pore size and peak distribution of 10–50 nm and >100 nm. The storage space of ash-bearing shale mainly consisted of intragranular pores and intergranular (crystalline) micropores, with pore sizes primarily concentrated in the 10–50 nm range. The storage space in silty shale mainly developed in clastic mineral particles such as quartz, followed by clay mineral intergranular pores with a relatively wide distribution of sizes. Pores were mainly inkbottle-shaped and slit-type/plate-type pores, with an average specific surface area of approximately 6.9046 m2·g−1 and an average pore volume of approximately 0.0150 cm3·g−1. The full-pore capillary pressure curve was established using a combination of gas adsorption–desorption tests and HPMI. The fractal dimension of the sample pore structure was calculated, and a significant linear correlation was found between clay mineral content and the fractal dimension. Thus, the pore structure characteristics were mainly controlled by the content and distribution of clay minerals.

Release performance and kinetic behavior of volatile products from controlled pressure pyrolysis of oil shale in nitrogen atmosphere

The gas injection parameters such as temperature, pressure and duration during the in-situ pyrolysis of oil shale are important factors that affect the pore evolution and product release characteristics of oil shale. This paper takes Huadian oil shale as a sample, uses pressurized thermogravimetry and pressurized fluidized bed experimental device to explore the influence of temperature, pressure and time on the evolution of pore structure under high-pressure nitrogen injection conditions, and analyzes the influence mechanism of pore structure evolution on the release and kinetic behavior of volatile products. The results show that in the range of 623–673 K, the effective oil recovery of oil shale pyrolysis under high pressure increases from 30.5 to 96.0% with the extension of temperature and pyrolysis time, and the average activation energy is 346.8 kJ/mol, which is higher than the activation energy of 306.6 kJ/mol under normal pressure pyrolysis. Under high pressure, the release process of volatile products is inhibited, resulting in the intensification of the secondary reaction of products and the reduction of olefin content. In addition, the primary pores of kerogen are prone to coking reaction and collapse of plastic structure, so that some large pores become microporous structure, and the average pore size and specific surface area are reduced.

Effect of thermal annealing on kaolin from the Amazon region, aiming at the production of geopolymer

In the focus of environmental problems and climate change, research for alternative materials becomes essential. In this sense, research on geopolymers is very relevant, due to its sustainability characteristics linked to mechanical and physical properties. Metakaolin is a geopolymer precursor and obtained from kaolin, whose characteristics, which are specific to each region, impact on the characteristics of metakaolinite, which in turn influences the production of geopolymer. Characteristics of metakaolin from the Amazon region are not well known, with few publications, despite the importance of the region in the international context in terms of natural resources and environmental. In order to contribute to this research, the present investigation analyses the effect of thermal annealing temperature on kaolin and verifies the suitability of metakaolin as a precursor of geopolymer products. The kaolin in natura was benefited by wet sieving and thermally treated in the range 600 °C to 800 °C. Samples were characterized by XRD, with phases quantification and amorphous fraction obtained by Rietveld method, XRF, TG/DTG, specific surface area, laser granulometry, FTIR, SEM and EDS. An average specific surface area of 1.32 m2/g was identified for kaolin treated at 700 °C, where the amorphous fraction is 91.6% which has almost reached saturation, varying slightly to 800 °C as thermal annealing temperature. Considering environmental aspects and the energy savings, one may state that samples treated at 700 °C may efficiently be used as geopolymer precursor material. The vibration of the O–H bond in kaolinite treated at temperatures greater than 650 °C was not identified. Results suggest that the metakaolinite obtained from Amazon kaolin is indicated for geopolymer production.

Effect of Rice Husk Ash on the Properties of Alkali-Activated Slag Pastes: Shrinkage, Hydration and Mechanical Property.

In this paper, rice husk ash (RHA) with different average pore diameters and specific surface areas was used to replace 10% slag in the preparation of alkali-activated slag (AAS) pastes. The effect of RHA addition on the shrinkage, hydration, and strength of AAS pastes was studied. The results show that RHA with a porous structure will pre-absorb part of the mixing water during paste preparation, resulting in a decrease in the fluidity of AAS pastes by 5-20 mm. RHA has a significant inhibitory effect on the shrinkage of AAS pastes. The autogenous shrinkage of AAS pastes decreases by 18-55% at 7 days, and the drying shrinkage decreases by 7-18% at 28 days. This shrinkage reduction effect weakens with the decrease in RHA particle size. RHA has no obvious effect on the type of hydration products of AAS pastes, whereas RHA after proper grinding treatment can significantly improve the hydration degree. Therefore, more hydration products are generated and fills the internal pores of the pastes, which significantly improves the mechanical properties of the AAS pastes. The 28 day compressive strength of sample R10M30 (the content of RHA is 10%, RHA milling time is 30 min) is 13 MPa higher than that of blank sample.

Microstructure and oxidation resistant of Si–NbSi2 coating on Nb substrate at 800°C and 1000°C

The Si–NbSi2 composite coating with a smooth surface was successfully prepared on Nb substrate by hot dip silicon-plating (HDS) technology. The composite coating is composed of Si outer layer, NbSi2 interlayer and Nb5Si3 interfacial layer. And the average surface roughness (RSa) and specific surface area growth rate (Sdr) are only 0.275 μm and 2.85%, respectively. The cyclic oxidation test shows that the Si–NbSi2 composite coating has a very excellent oxidative resistance after oxidation at 800 °C for different times. After oxidation for 40 h, the Δm/S and oxide layer thickness of the coating are only 3.72 mg/cm2 and 8 μm, respectively. After oxidation at 1000 °C for 20 h, the coating surface is almost completely covered by a dense SiO2 layer, the Δm/S and oxide layer thickness of the coating are 7.28 mg/cm2 and 15 μm, respectively. The Si–NbSi2 composite coating presents good self-healing ability and excellent oxidation resistance, which can significantly prolong the service life of bare Nb in oxidation environment.

Spherical Attapulgite/Silica Aerogels Fabricated via Different Drying Methods with Excellent Adsorption Performance.

Dye wastewater has caused great harm to the environment, which is an urgent problem to be solved. As typical three-dimensional porous materials, aerogels have attracted great interest in dye wastewater treatment. In this work, spherical attapulgite/silica (ATP/SiO2) gels were initially prepared by easily scalable sol-gel dripping methods and then dried to aerogels with three drying techniques, namely, supercritical CO2 drying (SCD), freeze-drying (FD), and ambient pressure drying (APD). The effect of the drying techniques and heat-treated temperature on the physical characteristic, morphological properties, microstructure, and chemical structure of the spherical ATP/SiO2 aerogels were investigated. The macroscopic morphology of the spherical ATP/SiO2 aerogels was homogeneous and integrated without local cracking. The average pore diameter and specific surface area of the spherical ATP/SiO2 aerogels prepared by the three drying techniques were in the range of 6.8-8.6 nm and 218.5-267.4 m2/g, respectively. The heat treatment temperature had a significant effect on the pore structure and the wetting properties of the aerogels. The 600 °C heat-treated aerogels were subjected to adsorption tests in methylene blue (MB) solution (60 mg/g, 100 mL), which exhibited a great adsorption capacity of 102.50 mg/g. Therefore, the resulting spherical ATP/SiO2 aerogels possessed multipath preparation and exhibited an efficient adsorption performance, with the potential to be applied as an adsorbent for dye wastewater.

Investigation of behaviours of diclofenac adsorption onto different adsorbents of carbon- aerogel by the kinetic and isotherm non-linear models

ABSTRACT The application of eco-friendly, economically justifiable and reusable materials in removing pollutants from the aqueous solutions has received much attention. Therefore, in the present study, three adsorbents (carbon/aerogel (CA), carbon/aerogel/nickel (CAN) and carbon/aerogel/magnetite (CAM)) were used to remove diclofenac from the aqueous solutions. The various techniques such as brunauer-emmett-teller (BET), thermogravimetric (TGA), fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to investigate the structure and main composition of the target adsorbents. The average size and specific surface area for CA, CAN and CAM adsorbents were obtained (6.5 nm and 714.93 m2 g−1), (1.61 nm and 734.32 m2 g−1) and (1.65 nm and 1193.9 m2 g−1), respectively. The maximum amount of the adsorbed pollutant on CA, CAN and CAM adsorbents were determined to be 60 mg g−1 (based on Sips), 101.9 mg g−1 (based on Langmuir) and 78 mg g−1 (based on Khan), respectively. The experimental data obtained for CA, CAN and CAM showed the best fit with Sips, Langmuir and Khan isotherms, respectively. In addition, the best kinetic models to express the adsorption characteristics of CA, CAN and CAM adsorbents were pseudo-first order, pseudo-first order and pseudo-second order, respectively. The performances of the CAN and CAM adsorbents were investigated for six consecutive cycles. The efficiency of CA, CAN and CAM adsorbents in diclofenac adsorption in the first and sixth cycles were (84% and 55%), (90% and 67%) and (88% and 63%), respectively.

Multiscale structural control of thiostannate chalcogels with two-dimensional crystalline constituents

Chalcogenide aerogels (chalcogels) are amorphous structures widely known for their lack of localized structural control. This study, however, demonstrates a precise multiscale structural control through a thiostannate motif ([Sn2S6]4−)-transformation-induced self-assembly, yielding Na-Mn-Sn-S, Na-Mg-Sn-S, and Na-Sn(II)-Sn(IV)-S aerogels. The aerogels exhibited [Sn2S6]4−:Mn2+ stoichiometric-variation-induced-control of average specific surface areas (95–226 m2 g−1), thiostannate coordination networks (octahedral to tetrahedral), phase crystallinity (crystalline to amorphous), and hierarchical porous structures (micropore-intensive to mixed-pore state). In addition, these chalcogels successfully adopted the structural motifs and ion-exchange principles of two-dimensional layered metal sulfides (K2xMnxSn3-xS6, KMS-1), featuring a layer-by-layer stacking structure and effective radionuclide (Cs+, Sr2+)-control functionality. The thiostannate cluster-based gelation principle can be extended to afford Na-Mg-Sn-S and Na-Sn(II)-Sn(IV)-S chalcogels with the same structural features as the Na-Mn-Sn-S chalcogels (NMSCs). The study of NMSCs and their chalcogel family proves that the self-assembly principle of two-dimensional chalcogenide clusters can be used to design unique chalcogels with unprecedented structural hierarchy.

Preparation of activated carbon fibers (ACF) impregnated with metallic silver particles from cotton-woven wastes and its performance as an antibacterial agent

Although activated carbon has been the subject of numerous research applications in water treatment, purification, catalysis, etc., its production is mainly focused on granular and powder presentations due to the commonly used raw materials (e.g., wood, phenolic resin, etc.). Herein, we report an easily established methodology for preparing activated carbon fibers (ACF) using cotton-woven wastes as raw material under chemical activation with H3PO4. We tested different experimental conditions between the activating agent and the cotton fabrics using a randomized-block experimental design with the specific surface area of the activated fibers as the response variable. A highly microporous structure was obtained with an average specific surface area of 1060 m2/g and pore size of 17 Å. The fibers were later impregnated with metallic silver particles using an immersion process in AgNO3 solutions followed by drying and a thermal decomposition to promote the nucleation and precipitation of non-regular shaped silver particles with sizes on the micro and nanoscale within the fiber’s porous. The novel material showed a strong antibacterial effect and a complete inhibition of bacterial culture growth with silver contents as low as 200 ppm. • Cotton-woven wastes are suitable precursors for activated carbon fibers production. • Esterification of cellulose-based raw materials is the activation mechanism. • Production of activated carbon fibers with a specific surface area up to 1200 m 2 /g. • Considerably dimension and structural stability reduction from the original fiber. • High antibacterial activity due to the presence of metallic silver microparticles.