Nitrogen Adsorption Isotherms Research Articles

Fabrication of high-surface-area, SiO2 supported polyimide carbon aerogel microspheres: electrochemical application

A series of polyimide (PI)/SiO2 aerogel microspheres were prepared by using polyamide acid salt and hydrolyzed tetraethyl orthosilicate based on the reverse-phase emulsion method. Then, PI/SiO2 aerogel microspheres were carbonized and etched to obtain carbon aerogel microspheres (CAMs). Scanning electron microscope, transmission electron microscope and nitrogen isothermal adsorption were used to characterize the micro-morphology and pore structure of the microspheres; and electrochemical workstation was used to test the electrochemical performance of the CAMs. The results showed that CAMs with different pore structures and specific surface area were obtained by adjusting the content of SiO2. Highest specific surface area of 1166.9 m2 g−1 and a total pore volume of 1.2369 cm3 g−1 were achieved at a SiO2 content of 50%. When used as the electrode materials for supercapacitors, these CAMs demonstrated a maximum specific capacitance of 125.1 F g−1 in a three-electrode system and a maximum capacitance of 53.3% at 30 A g−1. This article provides a new strategy for the preparation of CAMs with high specific surface area by using linear PI precursor and SiO2 support skeleton.

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.

The effect of impregnation ratio on the characteristics of activated carbon made from rubber fruit shells with KOH as the activation medium

The rubber fruit shell (RFS) activated carbon has been made using KOH as a chemical activating agent with several variations of the impregnation ratio (1:3, 1:4, and 1:5). To ascertain the impact of the impregnation ratio on the attributes of the produced activated carbon, analysis was carried out using thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) method, X-ray diffraction, and a field emission scanning electron microscope. In the impregnation ratio, 1:5 was carried out as the best result; the value for BET surface area and nitrogen adsorption isotherms were 160 m2/g and 62 cm3/g, where the average pore size diameter was 4.6 nm. Besides, this activated carbon also has around 78.40% carbon. According to the findings of this investigation, the impregnation ratio affects the performance of using KOH as an activator to produce activated carbon from rubber fruit shells. In addition, it could be indicated that the RFS has the potential to be an alternative source of relatively inexpensive activated carbon because the raw materials are available in large quantities.

Hard Carbon Reprising Porous Morphology Derived from Coconut Sheath for Sodium-Ion Battery

Seeking effective energy technology has become a herculean task in today’s world. Sodium-ion batteries play a vital role in the present energy tech market due to their entrancing electrochemical properties and this work is a breakthrough for developing sodium-ion batteries. As per recent reports, the preparation of anode materials seems to be very tedious in the realm of sodium-ion batteries. To remedy these issues, this work enlightens the preparation of hard carbon (HC) derived from coconut sheath (CS) by a pyrolysis process with different activating agents (KOH, NaOH, ZnCl2) and employed as an anode material for Sodium-ion batteries (SIBs). The prepared anode material was characterized for its thermal, structural, functional, morphological, and electrochemical properties. Additionally, the surface area and pore diameter of the as-prepared anode material was studied by nitrogen adsorption and desorption isotherm methods. The coconut sheath-derived hard carbon (CSHC) anode material delivered an initial charge capacity of 141 mAh g−1, 153 mAh g−1, and 162 mAh g−1 at a 1 C rate with a coulombic efficiency over 98.8%, 99.3%, and 99.5%, even after 100 cycles, respectively.

The influence of vacuum heat treatment on the pore structure of earlywood and latewood of larch

Abstract To investigate the changes in the pore structure of earlywood and latewood (EW and LW) in larch during the heat treatment process, this study applied nitrogen adsorption and mercury intrusion porosimetry (MIP) to measure wood pore characteristics. Wood samples were heat treated within a vacuum atmosphere at temperatures between 180 and 220 °C for 6 h. Analysis conducted on nitrogen adsorption isotherms indicated that the micropores and mesopores in the cell walls were present in both untreated and heat-treated EW and LW, and that the mesopores appeared as slit-shaped pores. More pores were detected in EW compared to LW, and these primarily absorbed in the range of 1.5–4 nm. Compared with the untreated wood, the total pore volume of treated wood decreased with increasing temperatures, with decreased pore volumes at 220 °C of 63 and 42% for EW and LW, respectively. The MIP results showed a greater porosity of EW compared to LW. Compared with the untreated wood, the porosity of heat-treated EW and LW first increased with increasing temperature, and then decreased at 220 °C. For treatment temperatures lower than 200 °C, heat treatment increased the proportion of macropores with pore sizes in the ranges of 100–1000 nm and 10,000–40,000 nm.

Design and fabrication of low-cost renewable carbon electrode materials and their thermo-kinetics for sustainable energy storage applications

Low-cost, abundant biomass is a promising raw material for future applications in energy storage when processed into renewable graphitic carbon. To date, there have been few studies performed on the kinetics of thermal decomposition of renewable carbon and its use in energy storage devices. Novel renewable graphitic carbon from Acer saccharum, sugar maple (SM) heartwood, and Arachis hypogaea, peanut outer shell (PS), are used as anodes in lithium-ion coin cell batteries, with steady specific capacities of 180 mAh/g and 220 mAh/g, respectively, and both retain 100% columbic efficiency for over 350 cycles. Cyclic voltammetry reveals the different charge storage kinetic mechanisms of the two. The voltammogram of SM contains an oxidation peak indicating Li ion intercalation suitable for battery application, while PS lacks a peak; thus, showing potential for function as a supercapacitor. A kinetic study is undertaken on six carbon sources to improve the understanding of the thermal degradation process leading to renewable graphitic carbon. Consistent results are shown across the various model-free methods, indicating that they can accurately describe the devolatilization process. The renewable graphitic carbons morphological features were studied by SEM, XRD, Raman and nitrogen adsorption isotherms. As SM and PS compare favorably to the electrodes they replace, renewable graphitic carbon has the potential for use in a wide variety of novel applications, such as organic thin film transistors, fuel cells, organic batteries, supercapacitors, and other bioelectronics.

Effect of preheating temperature on adsorption of N2 and Ar on graphene oxide

We measured the adsorption isotherms of nitrogen (N2) at 77 K and argon (Ar) at 87 K on graphene oxide (GO) preheated at mild temperatures. Pre-treating GO below 373 K does not significantly alter its composition and structure, giving small adsorption uptakes. Oxygen functional groups partially decompose on preheating GO at 423 K without changing the pore structure. Oppositely, the thermal treatment of GO at 463 K leads to a non-crystalline reduced GO (rGO) structure with large surface area. The comparative pore analysis using N2 and Ar adsorption showed N2 provide a more precise evaluation of GO porosity, despite IUPAC usual recommendation.

Adjuvant effect of mesoporous silica SBA-15 on anti-diphtheria and anti-tetanus humoral immune response

Routine immunization against diphtheria and tetanus has drastically reduced the incidence of these diseases worldwide. Anti-diphtheria/tetanus vaccine has in general aluminum salt as adjuvant in its formulation that can produce several adverse effects. There is a growing interest in developing new adjuvants. In this study, we evaluated the efficiency of SBA-15 as an adjuvant in subcutaneous immunization in mice with diphtheria (dANA) and tetanus (tANA) anatoxins as well as with the mixture of them (dtANA). The tANA molecules and their encapsulation in SBA-15 were characterized using Small-Angle X-ray Scattering (SAXS), Dynamical Light Scattering (DLS), Nitrogen Adsorption Isotherm (NAI), Conventional Circular Dichroism (CD)/Synchrotron Radiation Circular Dichroism (SRCD) Spectroscopy, and Tryptophan Fluorescence Spectroscopy (FS). The primary and secondary antibody response elicited by subcutaneous immunization of High (HIII) and Low (LIII) antibody responder mice with dANA, tANA, or dtANA encapsulated in the SBA-15 were determined. We demonstrated that SBA-15 increases the immunogenicity of dANA and tANA antigens, especially when administered in combination. We also verified that SBA-15 modulates the antibody response of LIII mice, turning them into high antibody responder. Thus, these results suggest that SBA-15 may be an effective adjuvant for different vaccine formulations.

Bimetallic MOF derived ZnCo2O4 nanocages as a novel class of high performance photocatalyst for the removal of organic pollutants

• ZnCo-MOF derived ZnCo 2 O 4 nanocages was facilely synthesized with the help of a hydrothermal technique. • The kinetic studies exhibited the 84.3, 87.9, and 89.5% of degradation of CV, MB, and RhB dye pollutants after the 180 min of irradiation at the rate constants (k) of 0.010, 0.011, and 0.012 min −1 , respectively. • The ZnCo 2 O 4 nanocages delivered the highest photocatalytic degradation percentage for RhB than other organic dye pollutants. • The extensive role of photogenerated holes and hydroxide radicals affecting to the dye degradation phenomena is confirmed by radical scavenger trapping experiments. Synthesis of metal oxides from Metal organic frameworks (MOFs) has taken center stage in the recent years due to its excellent structural behavior. Many MOF derived metal oxides such as ZnO, NiO, Co 3 O 4 , CuO, NiCo 2 O 4 , and CoFe 2 O 4 , etc., has been successfully synthesized using MOFs as templates. In this report, we have adopted the MOF assisted method to prepare ZnCo 2 O 4 (abbreviated as ZCO) nanocages using hydrothermal method were utilized to explore the photocatalytic removal of various organic contaminants like Methylene Blue (MB), Rhodamine B (RhB), and Crystal Violet (CV). The ZCO nanocages has been investigated to evaluate the structural properties by X-ray diffraction (XRD) studies. Morphological, microstructural, chemical compositional and optical characterizations have been carried out using FESEM, TEM, EDS, XPS, and UV–Visible spectrophotometer, respectively. The specific surface area and pore size of ZCO nanocages were confirmed from nitrogen adsorption and desorption isotherm analysis. Further, ZCO nanocages were utilized to explore the photocatalytic removal of various organic contaminants like MB, RhB, and CV. Moreover, ZCO nanocages showed remarkable photocatalytic performance for the removal of different dye pollutants. The kinetic studies exhibited the 84.3, 87.9, and 89.5% of removal of CV, MB, and RhB dye pollutants after the 180 min of irradiation at the 0.010, 0.011, and 0.012 min −1 rate constants (k), respectively. The extensive role of hydroxide radicals and photogenerated holes affecting to the organic pollutant degradation mechanism is studied by radical scavenger trapping experiments. In addition, its recyclability was also confirmed from stability study. Therefore, the present investigations offer a way to develop a MOF derived metal oxide for photocatalytic removal of various organic pollutants.

In English

For various adsorbents, especially nanoporous, there is an applicability problem of the Brunauer-Emmett-Teller (BET) method using nitrogen as a probe adsorbate. Therefore, the nitrogen adsorption (a(p/p0)) isotherms in several pressure ranges of the BET method at p/p0 = 0.05–0.3, 0.06–0.22, and narrower are analyzed for a large set (about 200 samples) of essentially different adsorbents such as fumed oxides (individual, binary and ternary, initial and modified), porous silicas, activated carbons and porous polymers. Graphitized carbon black ENVI–Carb composed of nonporous nanoparticles aggregated into microparticles is used as a standard adsorbent characterized by the standard area occupied by nitrogen molecule σm(N2) = 0.162 nm2. For initial nanooxides composed of nonporous nanoparticles, the standard value of σm = 0.162 nm2 results in the overestimation of the SBET values by ca. 10 % because of non-parallel-to-surface orientation of slightly polarized N2 molecules interacting with polar surface functionalities (e.g., various hydroxyls). For nanooxides modified by low- and high-molecular (linear, 2D and 3D polymers and proteins) compounds, the overestimation of SBET at σm = 0.162 nm2 could reach 30 %, as well as for some activated carbons. For adsorbents possessing nanopores (at half-width x or radius R < 1 nm) and narrow mesopores (1 nm < R < 3 nm), an overlap of monolayer and multilayer sorption (giving apparent underestimation of SBET at σm = 0.162 nm2) and non-parallel-to-surface orientation of the N2 molecules (causing σm lower than 0.162 nm2) could lead to various location of the normalized nitrogen adsorption isotherms (in the BET range) with respect to that for ENVI–Carb. It could be characterized by positive or negative values of the BET constant cBET. Two main criteria showing the inapplicability or applicability of the BET method (with nitrogen as a probe) related to the cBET values and a course of reduced adsorption a´(1- p/p0) vs. p/p0 in the BET range could not be in agreement for adsorbents, which are not pure nanoporous, but they are in agreement for pure nanoporous or meso/macroporous adsorbents

Physicochemical properties of porous activated carbon prepared from palm kernel shell through a low-cost activation protocol

Biomass-promoting routes for the synthesis of activated carbon (AC) have recently received considerable attention due to the advantages of this method: it is simple, cost-effective, and ecofriendly. This method is also an alternative way to avoid the unsafe practice of waste incineration. We describe the preparation of activated carbon from palm kernel shell (PKS) – an abundant biomass that is available in Africa and Asia. We investigated the effect of process variables such as impregnation ratio (ratio of H3PO4 to PKS) and carbonisation temperature (500–700 °C) on yield, microstructure, morphology, pore structure, and adsorption properties to optimise these parameters. Nitrogen adsorption isotherm analysis indicated that the AC was predominantly microporous in nature. Under optimal conditions, an AC with the highest surface area of 1560 m2/g was obtained. The aqueous adsorption test showed that the AC had significant removal capacity for methylene blue and iodine. The higher iodine value is consistent with the structural properties of the adsorbent, while the lower methylene blue value is consistent with the limited mesopore width. Considering the chemical and surface properties and adsorption properties of the AC produced, PKS has been shown to be an excellent precursor material for AC, thus solving the disposal problems associated with this biomass. Significance: AC significantly promotes adsorption and offers a low-cost and cleaner production method. PKS could serve as a dependable precursor for the synthesis of porous AC. This study provides useful information on how H3PO4-impregnated PKS influences the porosity of the resulting AC. Differences in porosity, yield, and morphology and Brunauer–Emmet–Teller surface area are achievable using AC from PKS.

Adsorption Isotherm of BET Nitrogen of Concretes with Consolidated Soil by Sugar Cane Molasses

Adsorption Isotherm of BET Nitrogen of Concretes with Consolidated Soil by Sugar Cane Molasses

Large-Scale Freeze-Thaw of Protein Solutions: Study of the Relative Contributions of Freeze-Concentration and Ice Surface Area on Stability of Lactate Dehydrogenase

Although bulk biotherapeutics are often frozen during fill finish and shipping to improve their stability, they can undergo degradation leading to losses in biological activity during sub-optimal freeze-thaw (F/T) process. Except for a few small-scale studies, the relative contribution of various F/T stresses to the instability of proteins has not been addressed. Thus, the objective of this study was to determine the individual contributions of freeze-concentration, ice surface area, and processing time to protein destabilization at a practical manufacturing-scale. Lactate dehydrogenase (LDH) in histidine buffer solutions were frozen in 1L containers. The frozen solutions were sliced into representative samples and assessed for the ice specific surface area (SSA) and extent of solutes freeze-concentration. For the first time to our knowledge, ice SSA was measured in dried samples from large-volume protein solutions using volumetric nitrogen adsorption isotherms. SSA measurements of the freeze-dried cakes showed that the ice surface area increased with an increase in the freezing rate. The ice SSA was also impacted by the position of the sample within the container: samples closer to the active cooled surface of the container exhibited smaller ice surface area compared to ice-cored samples from the center of the bottle. The freeze-concentrate composition was determined by measuring LDH concentration in the ice-cored samples. The protein distributed more evenly throughout the frozen solution after fast freezing which also correlated with enhanced protein stability compared to slow freezing conditions. Overall, better protein stability parameters correlated with higher ice SSA and lower freeze-concentration extent which was achieved at a faster freezing rate. Thus, extended residence time of the protein at the freeze-concentrated microenvironment is the critical destabilizing factor during freezing of LDH in bulk histidine buffer system. This study expands the understanding of the relative contributions of freezing stresses which, coupled with the knowledge of cryoprotection mechanisms, is imperative to the development of optimized processes and formulations aiming stable frozen protein solutions.

Facile synthesis of hierarchical core–shell heterostructured ZnO/SnO2@NiCo2O4 nanorod sheet arrays on carbon cloth for high performance quasi-solid-state asymmetric supercapacitors

We synthesized the hierarchical ZnO/SnO2@NiCo2O4 core–shell nanorod sheet arrays (NRSAs) grown on a flexible conductive carbon cloth (CC) substrate by a hydrothermal method. The amalgamation and formation mechanism were proposed. The as obtained ZnO/SnO2@NiCo2O4 core–shell heterostructures is investigated using X-ray diffraction, X-ray photoelectron spectroscopy, high resolution transmission electron microscopy, field emission scanning electron microscopy, and nitrogen adsorption and desorption isotherm analysis. The SnO2 layer which is conducting between ZnO and NiCo2O4 may effectively boost the electrical conductivity of the electrodes and also defend the ZnO from corrosion in the alkaline solution. Benefitting from the core–shell heterostructure formation, the hybrid ZnO/SnO2@NiCo2O4//CC electrode delivered a high specific capacity of 244.5 mA h/g, enhanced cycling stability with a 94.5% retention in specific capacitance even after 10,000 continuous charge–discharge cycles and good rate capability. To utilize the high specific capacity and ultra-long cycling stability, the PVA-KOH gel electrolyte based solid-state hybrid supercapacitor device was assembled with AC//CC as a negative electrode and ZnO/SnO2@NiCo2O4//CC as a positive electrode. The fabricated HSC device delivered a specific capacitance of 117.5 F/g with high energy density (41.7 Wh/kg) and power density (6400 W/kg) along with the outstanding capacitance retention of 94.6% even after 10,000 continuous charging and discharging cycles. With exceptional electrochemical performance, a facile and cost-effective preparation, such ZnO/SnO2@NiCo2O4//CC core–shell heterostructured electrode show a great potential for high-performance electrochemical supercapacitor applications in future.

MOF-Derived Co3O4 Nanoparticles Catalyzing Hydrothermal Deoxygenation of Fatty Acids for Alkane Production

Designing economical and nonprecious catalysts with a catalytic performance as good as that of noble metals is of great importance in future renewable bioenergy production. In this study, the metal–organic framework (MOF) was applied as a precursor template to synthesize Co3O4 nanoparticles with a carbon matrix shell (denoted as M-Co3O4). To select the synthesized optimal catalyst, stearic acid was chosen as the model reactant. The effects of catalyst dosage, methanol dosage, water dosage, temperature, and reaction time on catalytic efficiency were examined. Under the designed condition, M-Co3O4 exhibited high catalytic performance and the catalyst showed higher conversion of stearic acid (98.7%) and selectivity toward C8–C18 alkanes (92.2%) in comparison with Pt/C (95.8% conversion and 93.2% selectivity toward C8–C18). Furthermore, a series of characterization techniques such as scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nitrogen adsorption isotherms (Brunauer–Emmett–Teller (BET) method), and thermogravimetric analysis (TGA) was applied to investigate the physicochemical properties of the catalysts. Finally, we proposed that decarbonization (deCO) could be the presumably mechanistic pathway for the production of C8–C18 alkanes from the decomposition of stearic acid.

Composite material-based a clay for adsorption desalination and cooling applications

This paper studies improving the performance of an adsorption system by improving raw bentonite as an adsorbent. Acid treatment has been used for the pretreatment of raw bentonite. Then, a composite and activated adsorbents are prepared by bentonite impregnated in salt hydrates (CaCl2 and (NH4)2CO3). XRD, nitrogen adsorption isotherm, water vapor adsorption isotherm and kinetics are used to characterize raw and modified bentonite. Experimental results of adsorption isotherms and kinetics have been fitted using Dubinin–Astakhov equilibrium model and linear driving force model. MATLAB software has been used to solve a simulation model of an adsorption desalination system with and without heat recovery (HR). The effect of the modified adsorbents on the adsorption system performance has been investigated. The results illustrated that the surface area and pore volume of Bent/CaCl2 increased by about 200% and 500%, respectively, compared to raw bentonite. The Bent/CaCl2 was predicted to have the highest water uptake (0.82 kgH2O.kg−1). Bent/CaCl2 was predicted to have a SDWP of 11.5 m3.ton−1 per day with SCP 326 W.kg−1 and COP 0.52 at 85 °C desorption temperature. Also, the SDWP was predicted to achieve 26 m3.ton−1 per day with HR under the same conditions. The SDWP can be increased to 29 m3.ton−1 at 95 °C desorption temperature.

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Sol-gel processing of a covalent organic framework for the generation of hierarchically porous monolithic adsorbents

Synthesis and characterization of N-doped graphene oxide quantum dots/Fe-BDC composite for methylene blue decomposition

In this work, we functionalized FeBDC by dosing Nitrogen-doped graphene quantum dots in order to improve the photocatalytic performance over Methylene Blue (MB) degradation. The novelty of this research is that N-doped graphene quantum dots (NGQ) were prepared by microwave irradiation Glycerol-Urea-Citric acid mixture, in which Glycerol could expand the sp2 domain of the NGQ. The effect of NGQ dosage on crystalline phases and porous properties of NGQ/FeBDC were thoroughly studied using X-ray Diffraction, Fourier-transform Infrared spectroscopy, and Nitrogen adsorption isotherm measurement. The optimal catalyst was 4-NGQ/FeBDC, with the doping percentage of NGQ in NGQ/FeBDC composite being at 4%wt. of the precursors. Some of the noticeable improvements of the 4-NGQ/FeBDC over the original FeBDC sample included a larger BET surface area (141.8 m2 g−1), wider optical absorption edge, a smaller bandgap energy (2.42 eV), and faster degradation reaction. The optimal sample was able to completely decompose MB within 50 minutes and could be repeatedly exploited 4 times. The morphology of 4-NGQ/FeBDC particles was polyhedron shape with NGQ covering around, confirmed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images. Some parameters that affect MB degradation of the 4-NGQ/FeBDC would be investigated, covering light irradiation, H2O2 presence, initial pH of MB solution, and reusability. The regeneration procedure of the optimal photocatalysts as well as the electron transfer mechanism within the photocatalytic system would be proposed in this paper.

Soil pore structure changes induced by biochar affect microbial diversity and community structure in an Ultisol

The chemical mechanisms by which biochar addition affected soil microorganisms have been extensively studied. However, few studies investigated the effect of physical alteration induced by biochar application on microorganisms in soils. The study focused on how the pore structure affected microbial diversity and community structure in an Ultisol amended with straw-derived biochars. The nitrogen adsorption isotherm (NAI) and mercury intrusion porosimetry (MIP) were used to measure the soil pore characteristics. The bacterial and fungal community composition and diversity were analyzed by the sequencing of V4-V5 of 16 S rRNA gene and ITS1 gene, respectively. MIP results showed that biochar increased the total porosity, total pore volume, average pore diameter and the volumes of > 75, 30–75 and 5–30 µm pores in soils. The straw feedstock and pyrolysis temperature of biochar affected the microbial diversity and community structure in soils. The soil amended with RB550 had the highest Shannon diversity of bacteria and fungi, while the soil treated with CB350 had the highest bacterial abundance. The addition of biochar mainly increased the relative abundances of bacterial genera Actinospica, Ellin6067, Streptomyces and Massilia, while decreased the abundance of Pseudomonas, Methylobacterium and Nitrosospira. However, the fungal genera had a greater variation in biochar-amended soils. The > 5 µm pores in soils had positive effects on the microbial diversity and abundance. The bacterial genera that were acidophilic and aerobic had positive correlations with the volumes of > 75, 30–75 and 5–30 µm pores, especially Ellin6067, Flavisolibacter and Haliangium. Inversely, the genera that were facultative anaerobic (Methylobacterium, Pseudomonas and Nitrosospira) and anaerobic (Christensenellaceae_R-7_group) showed a positive correlation with the volume of < 5 µm pores or no obvious regularity. Most fungal genera tended to live in the larger pores of > 5 µm and could extend into smaller pores. Therefore, the pore characteristics largely determined the microbial community structure in the biochar-amended soils.

Effect of intercalated metal ions on the specific surface area and porosity of dibasic calcium silicate hydrate

This work aims to determine the influence of adsorbed Cu2+, Co2+, and Cr3+ ions on the porosity of synthetic calcium silicate hydrate by analyzing nitrogen adsorption and desorption isotherms. The calcium silicate hydrate sample was synthesized under saturated steam pressure at a 175 °C temperature when the duration of isothermal curing was 16 h. The intercalation of Cu2+, Co2+, or Cr3+ ions was based on the adsorption experiment at 25 °C temperature. It was obtained that after adsorption 100 mg of metal ions were intercalated in 1 g of the sample. The analysis of nitrogen adsorption-desorption isotherms showed, that the nature of intercalated metal ions strongly affects the specific surface area and porosity of adsorbent. It was calculated that the specific surfaces area of the adsorbent increases during adsorption of Cu2+ and Co2+ ions and decreases during adsorption of Cr3+ ions. During calcination, adsorbent and adsorbent with intercalated Co2+ ions became non-porous materials, while samples with intercalated Cr3+ and Cu2+ ions showed a different tendency. The classification of hysteresis loops and calculations by using the corrected Kelvin equation and Orr et al. scheme revealed that the shape of pores depends on the nature of adsorbate. The obtained results were confirmed by analysis of nitrogen adsorption-desorption isotherms as well as SEM and TEM analysis.