Particle Specific Surface Area Research Articles

Mapping of density-dependent material properties of dry manufactured snow using 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

Despite the significance of snow in various cryospheric, polar, and construction contexts, more comprehensive studies are required on its mechanical properties. In recent years, the utilization of 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 has yielded valuable insights into snow analysis. Our objective is to establish a methodology for mapping density-dependent material properties for dry manufactured snow within the density range of 400–600 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} utilizing 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 step-wise, quasi-static, mechanical loading. We also aim to investigate the variations in the structural parameters of snow during loading. The three-dimensional (3D) structure of snow is captured using 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 with 801 projections at the beginning of the experiments and at the end of each loading step. The sample is compressed at a temperature of − 18 o\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {^o}$$\\end{document}C using a constant rate of deformation (0.2 mm/min) in multiple steps. The relative density of the snow is determined at each load step using binary image segmentation. It varies from 0.44 in the beginning to nearly 0.65 at the end of the loading, which corresponds to a density range of 400–600 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}. The estimated modulus and viscosity terms, obtained from the Burger’s model, show an increasing trend with density. The values of the Maxwell and Kelvin–Voigt moduli were found to range from 60 to 320 MPa and from 6 to 40 MPa, respectively. Meanwhile, the viscosity values for the Maxwell and Kelvin–Voigt models varied from 0.4 to 3.5 GPa-s, and 0.3–3.2 GPa-s, respectively, within the considered density range. In addition, Digital Volume Correlation (DVC) was used to calculate the full-field strain distribution in the specimen at each load step. The image analysis results show that, the particle size and specific surface area (SSA) do not change significantly within the studied range of loading and densities, while the sphericity of the particles is increased. The grain diameter ranges from approximately 100 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}m to nearly 400 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}m, with a mode of nearly 200 μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}m. The methodology presented in this study opens up a path for an extensive statistical analysis of the material properties by experimenting more snow samples.

Effects of explosion puffing on the native structural organization and oil adsorption properties of starch

The effects of explosion puffing (EP) on the native structural organization (i.e., thermal properties, crystalline structure, short-range order, granule morphology and powder properties) and oil adsorption properties of puffed starch (PS) were investigated. The results showed that EP treatment could decrease the melting enthalpy of starch double helices and increase the V-type crystallinity. The highest V-type crystallinity (24.7 %) was obtained when the puffing pressure was 0.4 MPa and the starch:ethanol:water ratio was 1:2:1 (w/w). By controlling the puffing conditions, EP treatment can alter the morphology, and increase the particle size, flowability and specific surface area of PS. The high amorphous proportion and porous sheet structure of PS resulted in the highest oil adsorption capacity when the starch:ethanol:water ratio was 1:1:1 (w/w). Pearson correlation analysis showed that oil adsorption capacity was significantly and positively correlated with the 1022/995 cm−1 value and V-type crystallinity, but negatively correlated with bulk density and angle of repose. Furthermore, oil retention capacity was strongly dependent on V-type crystallinity. These findings demonstrated that EP is an innovative technology with the potential to enhance the V-type crystallinity and adsorption performance of starch.

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.

Kinetic studies of ignition of coal char particle suspension in hot air

Coal ignition has been a focal point in the pursuit of improved energy efficiency and reduced emissions. This study focuses on investigating the kinetic characteristics of char ignition within a closed reactor. The combustion process is modeled using a one-step global reaction in a quiescent air environment. The results show that particle ignition time increases with equivalence ratio and particle size, while decreases with gas initial pressure and initial temperature. Particle ignition temperature is minimally affected by the particle size, slightly influenced by the gas initial pressure and initial temperature, but substantially influenced by the equivalence ratio. In the fuel-rich condition, the coal char combustion exhibits a thermal runaway stage, primarily driven by the escalating particle temperature, followed by a decaying stage, mainly influenced by the depleting oxygen mass fraction. The dominant kinetic factors affecting the heat release rate (HRR) peak are detailly investigated: the HRR peak shows an initial increase and subsequent decrease with the equivalence ratio, which is mainly controlled by the total particle number and particle temperature; Particle size affects the HRR peak through altering the total particle specific surface area, i.e., the product of the particle number and the particle diameter squared; the gas initial pressure and temperature all affect the HRR peak through directly altering the gas density. Additionally, larger retention coefficient leads to faster particle ignition and higher HRR peak. These findings provide valuable insights into the regulations of coal combustion processes, particularly in scenarios involving elevated pressure and temperature, such as coal/mine explosions.

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.

A study on the preparation of V2O5 from NH4V3O8 based on thermal decomposition including the thermal decomposition temperature effect, mechanism and kinetics

This study extensively investigated the thermal decomposition process of NH4V3O8, examining how varying temperatures affect the physicochemical properties of the products, as well as exploring the mechanism and kinetics of the process. Through XRD and SEM analysis, the study identified the phase compositions, crystal structures, and micromorphology of the thermal decomposition products. It also systematically investigated the effects of temperature on particle size and specific surface area, identified the lowest thermal decomposition temperature, and proposed the reaction equations. Additionally, by employing FT-IR analysis and DFT calculation, the study revealed the molecular-level thermal decomposition mechanism of NH4V3O8. Finally, the study calculated the kinetic parameters of NH4V3O8 thermal decomposition using the Kissinger and Kissinger-Crane methods and established the rate equation. These findings not only provide practical guidance but also serve as theoretical references for the thermal decomposition of other metal ammonium salts.

Evaluating methodological parameters to quantify particle size of organic soil material with laser diffraction

AbstractThe recognition that texture is a “master soil property” points toward the need for actual quantification of particle size in organic soil material. Using a multi‐wave particle size analyzer, fibric and sapric soil samples were circulated in deionized water through a closed aqueous loop at 9.6 L min−1, and the following methodological parameters were investigated: pre‐treatment, circulation time, and refractive index. Our results show that pre‐treatment for organic soil samples is dependent upon the degree of decomposition; the intact and dispersed PSDs for fibrous samples were similiar, whereas the PSDs for sapric samples showed a shift from 500–2000 (intact) μm to 5–100 (dispersed) μm. Circulation time was investigated using mean particle diameter and specific surface area. We demonstrated that as circulation time increased, the mean particle diameter decreased and the specific surface area increased out to 30 min as mechanical dispersion and/or fragmentation of organic particles occurred. However, circulation time after 5 min is not significantly different in terms of mean particle diameter. To investigate refractive index, 12 optical models were created. When determined across all intact samples, uncertainty was low within individual bins, with a maximum value of 0.07 ± 0.04% v/v. For dispersed samples, uncertainty increased within the silt sized region and had a maximum value of 0.17 ± 0.07% v/v. This study demonstrates that the particle diameter of organic soil material can be measured by LD with comparable certainty as that of mineral soil material using the methodological approach used in this study.

Sol-Gel-Controlled Size and Morphology of Mesoporous Silica Microspheres Using Hard Templates.

Mesoporous silica microspheres (MPSMs) represent a promising material as a stationary phase for HPLC separations. The use of hard templates provides a preparation strategy for producing such monodisperse silica microspheres. Here, 15 MPSMs were systematically synthesized by varying the sol-gel reaction parameters of water-to-precursor ratio and ammonia concentration in the presence of a porous p(GMA-co-EDMA) polymeric hard template. Changing the sol-gel process factors resulted in a wide range of MPSMs with varying particle sizes from smaller than one to several micrometers. The application of response surface methodology allowed to derive quantitative predictive models based on the process factor effects on particle size, pore size, pore volume, and specific surface area of the MPSMs. A narrow size distribution of the silica particles was maintained over the entire experimental space. Two larger-scale batches of MPSMs were prepared, and the particles were functionalized with trimethoxy(octadecyl) silane for the application as stationary phase in reversed-phases liquid chromatography. The separation of proteins and amino acids was successfully accomplished, and the effect of the pore properties of the silica particles on separation was demonstrated.

Effect of aggregate size on water distribution and pore fractal characteristics during hydration of cement mortar based on low-field NMR technology

The influence of aggregate size (AS) on the hydration of cement mortar is very important for improving the quality and stability of cement mortar. This study aims to study the effect of AS on water distribution and pore structure characteristics on the early-age hydration of cement mortar by low-field NMR technology. The hydration degree and fractal dimension of the hydration process were calculated by the T2 spectrum. The water distribution models at different times and locations during the hydration process were established based on the MRI bitmap data. The variation law of water volume at different locations was studied. The results indicate that: In the process of hydration, some of the water is consumed by the hydration reaction, and some of the water oozes out. The water in the large pores flows to the small pores under the action of hydrostatic pressure. AS affected the uniformity of the cement mortar at the initial state, and the gradation of the sand could improve the uniformity. The smaller AS was, the more complex the pore water distribution and changed during hydration. The bleeding mass was directly proportional to the porosity and inversely proportional to the specific surface area of particles. The effect of porosity on bleeding mass was more significant than AS. Pore fractal dimension was negatively correlated with aggregate diameter. In the initial stage, when the aggregate composition became complex, the change of fractal dimension with time also became complex. The fractal dimension increased gradually with the increase of hydration time. The gel pores (G) did not have fractal characteristics from beginning to end, capillary pores (C) and transition pores (T) had fractal characteristics after a particular time of hydration reaction. Although the air-voids (A) had fractal characteristics from beginning to end, they were not continuous.

Structure optimization and selection of catalyst particle for highly efficient gas oil hydrodenitrogenation

In this work, a single particle model and particle-resolved reactor model are established at particle and reactor scales for HDN process of gas oil. In the aspects of optimal particle shape and size selection, the specific surface area of particle plays a decisive role at particle scale, while the interaction between reaction and diffusion resulting from the bed bulk density and total particle surface area is more crucial at reactor scale. In terms of selecting the optimal pore structure, the optimal pore diameter and porosity are found to be nonlinear correlated with particle specific surface area at particle and reactor scales, and the deviation is within an acceptable range. The optimal pore structures of HDN catalyst with given particle shape and size could be derived from the obtained correlation in the single particle model instead of the particle-resolved reactor model to greatly reduce the computational resources and time consumption.

Scrutinizing the CO Chemical Capture Path in Li2MnO3 Samples with Different Microstructural Properties

Hydrothermal and ball-milling procedures combined with the solid-state reaction method were proposed as alternative synthesis routes to modify microstructural Li2MnO3 powders. All these materials were compared against Li2MnO3 prepared by following the solid-state reaction method only. To totally understand the effect of the synthesis routes proposed, the modified samples were structurally and microstructurally analyzed and subsequently subjected to the CO chemisorption process. Li2MnO3-modified samples exhibited important differences and improvements during the CO chemisorption process, in comparison to the powders obtained through the solid-state reaction method, associated with important variations on their microstructural features. Specifically, the sample prepared by the hydrothermal bottom-up approach and labeled as HSS700 showed the best CO chemisorption. This result was explained based on its crystal and particle sizes, morphology, and specific surface area. Moreover, the whole analysis performed on all the samples allowed one to determine that the solid–gas interphase controls the CO chemisorption over the CO-Li2MnO3 kinetics.

Microemulsion nanoreactor applied for the synthesis of iron-based catalysts for carbon nanotube formation

Catalysts play an important role in the production of carbon nanotubes, and the preparation of catalysts has always been a hot topic. In this study, microemulsion nanoreactor was constructed and applied for the first time to prepare carbon nanotube catalysts. The natural “pool” formed with the oil phase as an external substance and the surfactant as the boundary provides a reactor stable at the nanometer level for the co-precipitation reaction of Fe (NO3)3•9H2O and Al (NO3)3•9H2O, and the precipitation reaction is more uniform and sufficient. The active ingredient of the catalyst has better dispersion. Carbon nanotubes are nucleated with the active ingredient as the site and have a smaller and uniform diameter. Moreover, we want to control the size of the reactor by changing the surfactant concentration. The best performance was obtained when the surfactant content is 14 %, with the hydration diameter of microemulsion prepared of about 50 nm, the particle size and specific surface area of catalyst of about 60 nm and 255.97 m2/g. The diameter of carbon nanotubes grown under the catalyst was mainly distributed between 6 and 13 nm, with low defect degree. The results show that the reverse microemulsion method has unique advantages in the preparation of nano-scale materials, and this study provides a reference for the preparation of carbon nanotubes catalysts using microemulsion nanoreactor.

A study on the preparation and characterization of pigment quality from mill scale steel wastes.

Every day, significant quantities of solid wastes are generated in steel companies which causes environment pollution. These waste materials differ from one steel plant to other depending upon the steelmaking processes adopted and pollution control equipment installed. The most common type of solid wastes originated in steel plant are hot metal pretreatment slag, dust, GCP sludge, mill scale, scrap, etc. At present, various efforts and experiments are being carried out in order to make use of 100% solid wastes products in order to reducing cost of disposal, saving raw materials and conserving energy. Then, the purpose of our paper is the access to reuse potential of the steel abundant mill scale for sustainable industrial applications. This material is a very valuable industrial waste due to its richness in iron (about 72% Fe), chemical stability, and variable usage in multiple fields which implies that it can bring social and environmental benefits. This work aims to recover Mill scale and reuse it to synthesize three iron oxide pigments; hematite (α-Fe2O3, red color), magnetite (Fe3O4, black color), and maghemite (γ-Fe2O3, brown color). To achieve this objective, Mill scale needs to be refined and granted to react with sulfuric acid to obtain ferrous sulfate FeSO4.xH2O which is used to produce hematite by calcination between 600 and 900°C, then, magnetite by reduction of hematite using a reducing agent at 400°C and maghemite from a thermal treatment of magnetite at 200°C. It was shown within the experiments that the mill scale contains between 75% and 86.66% of Fe and a uniform distribution of particles size with a low span. That gave red particles size (0.18-0.193µm) and specific surface area SSA: 6.12m2/g, black particles sizes (0.2-0.3µm) and SSA 4.92m2/g, brown particles size (0.18-0.189µm) and SSA 6.32m2/g. The results revealed that the mill scale was successfully converted into pigments with good qualities. So, it is recommended to work from the beginning at synthesis hematite by copperas red process and then magnetite and maghemite in order to control shape of magnetite and maghemite (spheroidal) to get the best results economically and environmentally.

Effects of multiwalled carbon nanotube and Bacillus atrophaeus application on crop root zone thermal characteristics of saline farmland

Presently, the effects of crop roots on crop root zone thermal characteristics are poorly understood, and new fertilizers are rarely considered from the perspective of changing crop root zone thermal characteristics. This study explored the effect of applying two new fertilizers, multiwalled carbon nanotubes (MWCNTs) and Bacillus atrophaeus (B. atrophaeus), on the crop root zone thermal characteristics of saline farmland soils through in situ measurements. The results showed that MWCNTs and B. atrophaeus could indirectly affect crop root zone thermal characteristics by changing the crop root growth. Combined application of MWCNTs and B. atrophaeus could promote both to induce positive effects, promote crop root growth, and significantly alleviate the adverse effects of soil salinization. The thermal conductivity and heat capacity of the shallow root zone were reduced due to the presence of crop roots, while the opposite was true in the deep root zone. For example, the thermal conductivity of the 0–5 cm rich root zone in the MWCNT treatment was 0.8174 W m−1 ·K−1, and the thermal conductivity of the poor root zone was 13.42% higher than that of the rich root zone. MWCNTs and B. atrophaeus can also change the spatial distribution of soil moisture, soil salt, and soil particle size characteristics by influencing the root-soil interactions and indirectly affecting crop root zone thermal characteristics. In addition, MWCNTs and B. atrophaeus could directly affect the root zone thermal characteristics by changing the soil properties. The higher the soil salt content was, the more obvious the effect of the MWCNTs and B. atrophaeus on the crop root zone thermal characteristics. The thermal conductivity and heat capacity of the crop root zone were positively correlated with the soil moisture content, soil salt content and soil particle specific surface area and negatively correlated with the soil particle size and the fresh and dry root weights. In summary, MWCNTs and B. atrophaeus significantly affected crop root zone thermal characteristics directly and indirectly and could adjust the temperature of the crop root zone.

Synthesis of Nanocrystalline Yttrium Oxide and Evolution of Morphology and Microstructure during Thermal Decomposition of Y2(C2O4)3·10H2O

A study of the morphology and evolution of the microstructure during thermal decomposition of Y2(C2O4)3·10H2O was conducted, and the stages and factors having the greatest impact on particle size and specific surface area were identified. The effect of the yttrium oxalate hexahydrate phases on the course of decomposition was also investigated. The evolution of the morphology and microstructure of decomposition products was explained from the analysis of volume shrinkage at various stages of the reaction. The formation of oxycarbonate is accompanied by the largest shrinkage during the reaction. At this stage, there is a significant increase in the specific surface area to 60–90 m2/g. Conversely, the morphology and microstructure of the particles during the transformation of oxycarbonate into yttrium oxide change insignificantly. Yttrium oxide powders obtained from the monoclinic and triclinic hexahydrate phases have the same specific surface area, but different morphology and bulk density due to pseudomorph formation. The carbon formed during thermolysis was shown to affect the specific surface area of the decomposition product. Two methods for producing yttrium oxide with high specific surface area have been proposed, and nanocrystalline yttrium oxide with a specific surface area of 65 m2/g was obtained.

Studi pengaruh penggilingan kondisi kering dan basah terhadap kinetika dan karakteristik distribusi ukuran butir bijih sulfida kompleks galena sfalerit – Uji pendahuluan

Grinding is generally carried out in wet conditions, but issues regarding water conservation and high-water treatment costs encourage the application of grinding in dry conditions. Both produce products with certain characteristics that affect the success of the next process. Grinding of P100 6 mesh (3.36 mm) ore was performed using steel ball media with dry and wet grinding with 33.33% solids for 5, 10, 15, 20, 25, and 30 minutes. Particle size distribution of the grinding product was obtained from the wet sieving process and the -200 mesh (-75µm) ore particles were analyzed using a laser diffraction particle size analyzer. The Alyavdin grinding kinetics equation model was used to study the kinetics of ore grinding behavior and the particle size distribution and its characteristics consisting of uniformity index, size modulus and fractal dimension were studied using the logistic, Rosin-Rammler (RR) and Gates-Gaudin-Schuhmann (GGS) equation model. Equivalent particle size (EPS) and specific surface area (SSA) observations were carried out on the -200 mesh (-75µm) grinding product. Grinding in dry condition is more effective in reducing the size of complex galena-sphalerite sulphide ore, indicated by high grinding rate with the highest K value of 0,135/minute, high cummulative % undersize, low size modulus, high uniformity index, high fine particle and high SSA compared to wet grinding. Alyavdin's kinetics model can describe the grinding kinetics of galena sphalerite complex sulfide ore, while the particle size distribution follows the logistic equation model.

Two-stage chemical-biological oxidation process for low-grade refractory gold concentrate with high arsenic and sulfur

In order to cost-effectively exploit and utilize the low-grade refractory gold ore resource with high arsenic and sulfur and reuse the ferric iron resources remained in the bio-oxidation waste solution, a two-stage oxidation process combining secondary high-temperature oxidation of the bio-oxidation solution with subsequent bio-oxidation was proposed for treating such resource. Scanning electron microscopy and laser particle sizer were used to analyze the oxidized residue, and the results demonstrated that the material surface was destroyed and the particle specific surface area was increased accordingly. Moreover, chemical analysis revealed that the nitrogen element content in concentrate was also increased greatly after oxidation. As a result, microbial adsorption behavior and growth rate were significantly improved and accelerated in the bio-oxidation stage. Specifically, 16S rRNA gene analysis indicated that the activity and proportion of iron-oxidized microorganism Leptospirillum genus in community was improved obviously after chemical oxidation. Therefore, the bio-oxidation efficiency of the concentrate was significantly increased in this stage. Consequently, the extraction levels of As, Fe and S elements in this process were 97.9 ± 0.9 %, 71.5 ± 4.8 % and 64.3 ± 1.6 % respectively, which were significant increased by 30.8 ± 0.8 %, 40.2 ± 1.6 % and 35.6 ± 3.8 % compared to the values in one-stage bio-oxidation. In the meantime, the gold and silver extraction yields by cyanidation in this process were increased from 61.5 ± 1.0 % and 58.1 ± 1.2 % of one-stage bio-oxidation process to 92.2 ± 1.2 % and 89.8 ± 2.8 %, respectively.

Photocatalytic Hydrogen Generation from Aqueous Methanol Solution over n-Butylamine-Intercalated Layered Titanate H2La2Ti3O10: Activity and Stability of the Hybrid Photocatalyst

The stability of platinized n-butylamine-intercalated layered titanate H2La2Ti3O10 during the process of photocatalytic hydrogen production from aqueous methanol under UV irradiation has been thoroughly investigated by means of XRD, CHN, TG, 13C NMR, BET, SEM and GC-MS analysis. It was revealed that n-butylamine completely abandons the interlayer space and transforms into n-butyraldehyde within 3 h of the reaction, while the particle morphology and specific surface area of the photocatalyst are preserved. The resulting solid phase contains carbon in at least two different oxidation states, which are attributed to the intermediate products of methanol oxidation bound to the perovskite matrix. The activity of the photocatalyst formed in this way is stable in time and strongly depends on the medium pH, which is not typical of either the parent H2La2Ti3O10 or TiO2. An approximate linear equation φ ≈ 29−2∙pH holds for the apparent quantum efficiency of hydrogen production in the 220–340 nm range at 1 mol. % methanol concentration. In the acidic medium, the photocatalyst under study outperforms the platinized H2La2Ti3O10 by more than one order of magnitude. The variation in methanol concentration allowed a maximum quantum efficiency of hydrogen production of 44% at 10 mol. % to be reached.

Photo-Fenton-like degradation of direct blue 15 using fixed bed reactor containing bimetallic nanoparticles: Effects and Box–Behnken optimization

This study involved the treatment of textile wastewater contaminated with direct blue 15 dye (DB15) using a heterogeneous photo-Fenton-like process. Bimetallic iron/copper nanoparticles loaded on bentonite clay were used as heterogeneous catalysts and prepared via liquid-phase reduction method using eucalyptus leaves extract (E-Fe/Cu@B-NPs). Characterization methods were applied to resultant particles (NPs), including SEM, BET, and FTIR techniques. The prepared NPs were found with porous and spherical shapes with a specific surface area of particles was 28.589 m 2 /g. The effect of main parameters on the photo-Fenton-like degradation of DB15 was investigated through batch and continuous fixed-bed systems. In batch mode, pH, H2O2 dosage, DB15 concentration, and UV intensity were investigated. In contrast, the flow rate, E-Fe/Cu@B-NPs height, DB15 concentration, and UV intensity were examined in the fixed-bed column. The response surface methodology based on the Box–Behnken design (BBD) was used to optimize both studied systems. The batch results showed that 100 mg/L of DB15 was completely degraded within 60 min with optimum pH 3.5, H 2 O 2 dosage of 7.5 mmol/L, and UV intensity of 15 W/m 2 . The kinetic study indicated that the DB15 degradation was fitted to the second-order kinetic model. The optimized parameters for the fixed-bed system were determined as 1mL/min, 1 cm, 100 mg/L, and 15 W/m 2 for flow rate, E-Fe/Cu@B-NPs height, DB15 concentration, and UV intensity. • The bentonite-supported Fe/Cu nanoparticles were synthesized by the green method. • The nanoparticle has a spherical shape with a specific surface area of 28.6 m 2 /g. • A heterogeneous catalyst was used in the photo-Fenton-like process. • Batch and fixed-bed techniques used for degradation of dye-contaminated wastewater. • The second-order kinetic model fitted the dye degradation.

Efficient uranium(VI) adsorbing bioinspired nano-sized hydroxyapatite composites: synthesis, tuning, and adsorption mechanism.

The production of large amounts of uranium-containing wastewater and its potential hazards has stimulated green and efficient material removal of uranium (VI). Inspired by the natural mineralization of bone, a facile and eco-friendly biomimetic synthesis of nano-hydroxyapatite (HAP) was carried out using chitosan (CS) as a template. It was found that the reaction temperature and the amount of precursors influence the particle size, crystallinity and specific surface area of the CS/HAP nanorods, and consequently their U(VI) adsorption efficiency. Moreover, the synthesized CS/HAP-40 with smaller particle size, lower crystallinity, and larger specific surface area show a more efficient U(VI) removal compared with CS/HAP-55 and CS/HAP-55-AT. It has a maximum adsorption capacity of 294.12mg·g-1 of the CS/HAP-40. Interestingly, the U(VI) removal mechanism of CS/HAP-40 in acidic (pH = 3) and alkaline (pH = 8) aqueous solutions was found to be different. As one of the main results, the U(VI) adsorption mechanisms at pH 8 could be surface complexation and ion exchange. On the contrary, three different mechanisms could be observed at pH 3: dissolution-precipitation to form chernikovite, surface complexation, and ion exchange.