Nitrogen Desorption Isotherms Research Articles

Pore Structure and Heterogeneity Characteristics of Coal-Bearing Marine–Continental Transitional Shales from the Longtan Formation in the South Sichuan Basin, China

Marine–continental transitional shale has become a new field for shale gas exploration and development in recent years. Its reservoir characteristics analysis lags significantly behind that of marine shale, which restricts the theoretical research on the accumulation of marine–continental transitional shale and the progress of exploration and development. The shale pore system is complex and has strong heterogeneity, which restricts the fine evaluation and optimization of the reservoir. Based on nitrogen adsorption–desorption experiments, the morphology and structural characteristics of coal-bearing shale pores were analyzed, and then the micro-pore structure heterogeneity was quantitatively characterized based on fractal theory and nitrogen adsorption–desorption data, and the relationship between pore structure parameters and their influence on fractal characteristics were discussed. The hysteresis loop of nitrogen desorption isotherm mainly belongs to type B, indicating ink bottle, flat plate, and slit are the main pore shapes. The pore size distribution curves are left unimodal or multimodal, with the main peak around 4 nm and 20–60 nm. Smaller pores develop a larger specific surface area, resulting in a high value of fractal dimension (2.564 to 2.677). The rougher the pore surface and the larger the specific surface area provide an adequate adsorption site for shale gas adsorption and aggregation. Thus, fractal characteristics conduced to understand the pore structure, heterogeneity, and gas-bearing property of coal-bearing shale.

Facile preparation of sulfonated covalent triazine frameworks for effectively detection of six carcinogenic aromatic amines in cigarette smoke

FDA reported a HPHCs (Harmful and Potentially Harmful Constituents) list for tobacco products and tobacco smoke in 2012, which contained six carcinogenic aromatic amines (AAs). In this work, a sulfonated covalent triazine frameworks (CTF-SO3H) material was synthesized and used as a solid phase extraction (SPE) absorbent for highly effective enrichment and determination of six carcinogenic AAs in cigarette mainstream smoke (MSS), coupled with HPLC-MS/MS technique. The CTF-SO3H material was prepared with a rapid and facile method, which was superior to the general methods. The characterization with Nitrogen adsorption and desorption isotherm experiment, High resolution transmission electron microscopy (HTEM), etc, indicated that the CTF-SO3H material possessed sulfonic acid groups and abundant microporous structure. And the CTF-SO3H material showed good enrichment effect for AAs due to the synergistic effect of π-π stacking and electrostatic interactions. Limits of detection (LODs) of 6 AAs with the developed method were in the range of 0.01–0.11 ng cig−1. Recoveries of 6 AAs were between 80.40% and 106.00%, while the intra-day and inter-day precisions were good (i.e. RSDintra ≤ 6.40%, RSDinter ≤ 9.90%). Commercial cigarette MSS samples were analyzed with the developed method, and a commercial cation exchange SPE column was chosen for comparison. Results obtained by two methods showed a good consistency. However, the CTF-SO3H material needed less dosage, even could be reused for 4 times. Thus, the developed method not only showed high enrichment efficiency, but also was economical.

Mesoporous silica particles by aerosol spray synthesis; solid core and porous shell structure study

Mesoporous silica core shell particles are materials of high interest especially due to pharmaceutical and catalytic applications. In the current work we presented the synthesis of uniformly porous and solid core porous particles by aerosol spray pyrolysis route according to the principles of EISA, by a one step process. The particles are evaluated morphologically by TEM and by nitrogen adsorption and desorption isotherms for pore size distribution and pore connectivity, validating the effect of synthesis parameters on the core size, surface area and porosity of the uniformly porous and core-shell structures. Three different surfactants Brij-58, CTAB, P123 at various concentrations and combinations as well as three different core type compositions of NaCl, CeO2 and, Ce0.8Zr0.2O2 have been evaluated for the controlled synthesis of silica core-shell particles by a scalable synthesis method.

Bi-metalic ZIFs(Zn-M) (M: Co, Ni) for photocatalytic removal of organic pollutants in aqueous solutions

In this study, we successfully synthesised bi-metallic ZIF(Zn-M) of 2-methyl imidazole with a second metal (cobalt or nickel) binding to the ZIF network. All ZIF samples were synthesised at room temperature and characterised by using XRD, FT-IR, SEM, DRS, and nitrogen adsorption and desorption isotherms. The materials have high crystallinity with a large surface area. The materials’ photocatalytic ability was examined via the degradation of indigo carmine under a sun-light simulator. The second metal enhanced the photon harvesting ability of ZIF(Zn) because the materials can absorb photons in both UV and visible regions. Of the two catalysts, ZIF(Zn-Co) exhibited high photocatalytic ability when it removed 100% of indigo carmine from an aqueous solution. The catalyst adsorbed 45% of indigo carmine after 2 h and entirely degraded the remaining dye dring 1.5 h of solar irradiation. While Co2+ increased the catalyst’s surface area, Ni2+ reduced it, leading to lower photocatalytic efficiency.

Preparation, Characterization, and Antibacterial Activity of Silver Nanoparticle-Decorated Ordered Mesoporous Carbon

In this study, Ordered Mesoporous Carbon (OMC) was prepared using resol as a carbon precursor and F127 as a soft template. Small-angle X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) images, and nitrogen adsorption and desorption isotherms revealed that OMC possessed ordered hexagonal mesostructures (p6m) with an ordered pore size of 3.2nm, a high specific surface area (SBET) of 539m2/g, and a large total pore volume (Vtotal) of 0.44cm3/g. Subsequently, silver nanoparticles synthesized from an aqueous AgNO3 solution using glucose as a reducing agent and starch as a stabilizing agent were decorated on OMC, producing Ag/OMC. XRD analysis revealed that the composite contained silver crystals. In addition, the content and size of silver nanoparticles in Ag/OMC were 0.71wt% (AAS) and around 25-50nm (TEM), respectively. Due to the surface cover of silver nanoparticles, SBET and Vtotal of Ag/OMC slightly decreased to 417m2/g and 0.38cm3/g, respectively. Both agar and broth dilution techniques were used to evaluate the antibacterial activity of the material against Staphylococcus aureus. Ag/OMC with a Minimum Inhibitory Concentration (MIC) of 25.0μg/mL is a potential candidate for use against Staphylococcus aureus.

High performance hybrid supercapacitor based on hierarchical MOF derived CoFe2O4 and NiMn2O4 composite for efficient energy storage

We have synthesized the hierarchical FeCo-MIL-88 (FC-MOF) derived CoFe2O4 and NiMn2O4 (CFO@NMO) composite using a hydrothermal route. The combination and formation process were presented. The prepared composite of CFO@NMO is studied using XRD, XPS, FESEM with EDS, HRTEM, and nitrogen adsorption and desorption isotherm. The formation of composite with CoFe2O4 (CFO) and NiMn2O4 (NMO) may effectively boost the conductivity thereby enhance the performance of electrochemical activity. Benefitting from the formation of composite, the hybrid CFO@NMO electrode achieved a high specific capacity (i.e., 353.6 mAh/g), 86.1 % retention in capacity after 5000 galvanostatic charging and discharging (GCD) cycles. To utilize the advantages of ultra-long cycling stability and high specific capacity, the aqueous electrolyte-based hybrid supercapacitor (HSC) device with AC//NF as a negative electrode and CFO@NMO//NF as a positive electrode was fabricated. The assembled HSC device provided a specific capacitance 312.8 F/g, 88.4 % retention in capacitance after 10,000 GCD cycles along with high energy density (90.3 Wh/kg) and power density (12.9 kW/kg). An easy and cost-effective preparation of CFO@NMO composite with outstanding supercapacitor performance demonstrates an excessive potential for utilization in the near future.

Recycling of tobacco wastes in the development of ultra-high surface area activated carbon

Activated carbons are vital for remediation processes such as water treatment. Nevertheless, some commercial versions have poor characteristics, such as low surface area and efficacy in removing contaminants. This work accessed the production of highly developed surface area activated carbons for environmental purposes and the recycling of tobacco wastes as an alternative precursor. Important parameters were tested, such as activation temperature (700, 800, and 900 °C) and mass ratio of chemical agents (KOH and ZnCl2, 3:1, 4:1, and 5:1 m:m). Activated carbons were evaluated using mathematical models of nitrogen adsorption and desorption isotherms (BET and BJH) and infrared spectroscopy (FT-IR). KOH was more effective than ZnCl2 as a chemical modifier, resulting in products with a greater surface area. Activation with KOH at 900 °C and a mass ratio of 4:1 resulted in a surface area of 3294 m2 g −1 and functional groups OH, CH, CO, CC, and CO, i.e., resulting in a promising adsorbent for contaminant sorption/removal processes. The developed methodology results in tobacco-based activated carbon with an extremely high surface area. Thus, tobacco wastes are excellent alternatives for producing KOH-activated carbons, besides being an ecological alternative to tobacco wastes destination.

Development of MOF Based Recyclable Photocatalyst for the Removal of Different Organic Dye Pollutants

The preparation of metal organic frameworks (MOFs) has come to the forefront in recent years because of their outstanding physical and chemical properties. Many MOFs such as Zn, Co, Ni, Fe, and Ag, etc., have been successfully synthesized. In this work, we followed the solvothermal assisted route to synthesize Ag-MOF (abbreviated as AMOF) nanosheets and then applied them as a photocatalyst to remove different organic pollutants, namely methyl orange (MO), crystal violet (CV), and methylene blue (MB). Chemical composition, optical properties, morphology, and microstructural analysis were analyzed using XPS, UV-visible spectrophotometer, FESEM, TEM, and EDS, respectively. The structural properties of AMOF nanosheets were studied by X-ray diffraction (XRD). Nitrogen adsorption and desorption isotherm analysis were utilized to evaluate the specific surface area and pore size of the AMOF nanosheets. Further, AMOF nanosheets showed notable photocatalytic performance for various dye pollutants degradation. The results confirmed 74.5, 85.5, and 90.7% of MO, CV, and MB dye pollutants removal after 120 min of irradiation with the rate constants (k) of 0.0123, 0.0153, and 0.0158 min-1, respectively. The effect of superoxide radicals (O2-) and photogenerated holes (h+) on the organic dye pollutants removal was investigated using radical scavenger trapping studies. Moreover, the stability study also confirmed the recyclability of the photocatalyst. Therefore, the findings of this research present a realizable method to grow AMOF photocatalyst for successful degradation of various dye pollutants.

A facile method for synthesizing MOF derived ZnCo2O4 particles on MXene nanosheets as a novel anode material for high performance hybrid supercapacitors

MXene (MX) is a capable material for future generation supercapacitor devices. But, the attraction between active functional groups and hydrogen bonds on the surface of MX make the interlayer agglomerate obviously. In this work, we present a ZnCo-MOF (ZCM) derived ZnCo2O4 (ZCO) particles to adsorb on the (MX) nanosheets and form a mesoporous structure which may provide the flexible ion diffusion pathways. The as obtained MXene@ZnCo2O4 (MX@ZCO) composite is investigated using XRD, XPS, HRTEM, FESEM, and nitrogen adsorption and desorption isotherm analysis. The ZCO particles not only provide activation sites for free movement of charges but also help to avoid the agglomeration of MX nanosheets. Benefitted from this novel composite structure, MX@ZCO holds a great specific capacity of 260 mAh g−1 at the current density of 1 mA g−1. Further, the MX@ZCO electrode exhibits a good cyclic stability of 78.9% even after 5000 cycles at the current density of 10 mA g−1, which can be ascribed to excellent electronic conductivity and short ion transport path. Furthermore, the fabricated aqueous HSC device with MX@ZCO/NF as a positive electrode and AC/NF as a negative electrode revealed a high energy density of 63.8 Wh kg−1 at power density of 3512.2 W kg−1, along with the outstanding capacitance retention of 91.3% even after 15,000 GCD cycles. This work offers an excellent approach for the preparation of MX and ZCO composite material as an electrode for hybrid supercapacitors.

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.

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.

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.

Adsorption of Metformin on Activated Carbon Produced from the Water Hyacinth Biowaste Using H3PO4 as a Chemical Activator

Water hyacinth biomass was used for the synthesis of activated carbons in the process of chemical activation with H3PO4, followed by controlled carbonization. The study investigates the effect of various impregnation weight ratios of H3PO4 and dry hyacinth (0.5–3.0), as well as different carbonization temperatures (T = 400–800 °C), on the surface characteristics of the produced activated carbons (AC). The activated carbon obtained with an impregnation ratio of 1.5 and a carbonization temperature of 600 °C (1.5 AC/600) showed the highest values of specific surface area of 1421 m2 g−1, representing a selected adsorbent for metformin removal. The chosen sample was characterized by elemental analysis, adsorption–desorption isotherms of nitrogen at −196 °C, via FTIR spectroscopy and the SEM method. The modeling of the experimental adsorption data showed that metformin adsorption: (i) can be best described by the Langmuir isotherm model, with the value of qmax = 122.47 mg g−1; (ii) led the pseudo-second order kinetic model; and (iii) is a spontaneous (ΔG° = −3.44 kJ mol−1) and endothermic (ΔH° = 8.77 kJ mol−1) process. A desorption study has shown that 92% of metformin was successfully desorbed in the presence of a 0.1 MHCl/ethanol mixture (volume ratio 2:1). The recovery of the adsorbent of 84%, after five successive cycles, indicated that the 1.5 AC/600 has potential to be applied in the real systems for water treatment.

Synthesis and Characterization of 2,4-Dichlorophenoxypropanoic Acid (2,4-DP) Herbicide Interleaved into Calcium-Aluminium Layered Double Hydroxide and the Study of Controlled Release Formulation

The commonly used herbicide in agriculture, namely 2,4-dichlorophenoxypropanoic acid (2,4-DP), is an anionic herbicide used to interleave into the interlayer of calcium-aluminum layered double hydroxide (Ca-Al LDH) employing co-precipitation method to form a new nanohybrid labeled as CAL-2,4DP. The LDH compound serves as a host in supporting the herbicide’s controlled release formulation. The effective interleave was investigated by employing a powder X-Ray Diffraction (XRD) pattern at 0.025 M nanocomposite, which revealed that the basal spacing has increased from 8.0 Å to 23.8 Å. The ATR-FTIR spectra further supported the interleaving, where the nitrate peak (NO−) diminished, and the carboxylate ion (COO−) band appeared at 1653 cm−1. The percentage loading of CAL-2,4DP was 71.26%, calculated from the carbon content in the sample. The BET analysis shows that CAL-2,4DP was a mesoporous material relying on nitrogen-desorption isotherms. The release of 2,4-DP ions into the aqueous solutions followed the order of PO43− > CO32− > Cl− with a percentage of 83, 65, and 30%, respectively. This work indicates the successful interleaving process of the 2,4-DP anion and the potential of CAL-2,4DP as an eco-friendly agrochemical that can be beneficial for farmers in minimizing herbicide usage to the environment.

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.

Synthesis of Titanium Dioxide by Sol-Gel Method and Comparison with Titanium Dioxide Pure

This paper study the synthesis of the TiO2 nanoparticles using the sol-gel method and TiCl4 as raw material (TiO2 sol-gel) and characterize it and TiO2 pure by Powder X-Ray Diffraction (XRD), both samples show they are anatase phase with high crystallinity and purity. Fourier transform infrared spectrum (FTIR) both samples it showed in the graph that TiO2 pure, TiO2 sol-gel various frequency vibrations which are shown by different peaks formed, The specific surface area and porosity of the TiO2 pure (46.962 m²/g) and TiO2 sol-gel (38.264 m²/g) were evaluated by using the nitrogen adsorption and desorption isotherms by using Brunauer-Emmett-Teller (BET) method. Using Ocean Optio USB- 2000 spectrometer for optical properties which are related to the absorption spectrum but using diffuse reflectance spectrum in the state of the Kubelka-Munk remission function replaces the Lambert-Beer law.

Adsorption of CdII by synthetic zeolite under multi-factor using response surface methodology

The remediation of heavy metal contamination was urgent owing to their toxicity and non-biodegradability. In this study, a synthetic zeolite originated from natural low-grade molybdenum ore (NMO) was used to adsorb CdII from wastewater under simulated multi-environmental factors. X-ray diffraction spectroscopy proved that faujasite was successfully synthesized. The specific surface area of the synthetic zeolite was up to 652.3 m2/g, based on the nitrogen adsorption and desorption isotherms. X-ray photoelectron spectroscopy confirmed that ion-exchange was a major mechanism of CdII adsorption. Batch adsorption experiments showed that synthetic zeolite has an excellent adsorption capacity for CdII at pH above 4. The theoretical maximum adsorption capacity was 249.63 mg/kg, as evidenced by the adsorption model fitting. Systematic adsorption experiments showed that the quadratic regression model can be used to predict the CdII adsorption amount of synthetic zeolite (predicted r² = 0.9027) under six environmental factors. The fitted results showed a decreasing influence on adsorption capacity in the following order: CdII concentration > adsorbent dosage > CaII concentration > NaI concentration > pH > Temperature. In all, the synthetic zeolite has a great potential for treating CdII-containing wastewater. Especially the application could be optimized with the predicted adsorption based on the response surface plots.

Photocatalytic activity of the visible-light-driven spherical Ag2S modifying the CdS synthesized by the facile chemical methods for the degradation of methylene blue and rhodamine B

Semiconductor photocatalyst is a simple, efficient, low-cost, and green solution for dealing with the environmental crisis. To suppress the recombination of electrons and holes and the photocorrosion of the CdS synthesized via a controllable chemical precipitation method without using any surfactants or templates, the CdS–Ag2S heterostructure was synthesized by a facile ion exchange technique. The CdS and CdS–Ag2S photocatalysts were characterized, and the results confirmed the formation of Ag2S particles on the surface of CdS spheres. Based on the optical properties of the CdS–Ag2S heterostructure compared with those of the pure CdS, investigated by ultraviolet–visible diffuse reflectance spectra (UV–Vis DRS) and photoluminescence (PL), the greater absorption capacity, narrower band gap (2.02 eV), and more efficient transfer and separation of charge carriers were observed. The value of the specific surface area of CdS–Ag2S (415.93 m2/g) was studied via the nitrogen adsorption and desorption isotherms. Accordingly, it is higher than the specific surface area of the bare CdS (33.385 m2/g) due to having more active sites. The photocatalytic activities of CdS and the CdS–Ag2S heterostructure were evaluated by the degradation of the dyes of methylene blue (MB) and rhodamine B (RhB), and the uncolored organic contaminant of phenol. The photodegradation of MB, RhB, and phenol by CdS increased from 80%, 67%, and 61%–98%, 90%, and 81% by CdS–Ag2S, respectively, within 180 min under the visible light irradiation. Furthermore, the CdS–Ag2S heterostructure exhibited a suitable stability after being used in three cycles. The efficiencies of sunlight and visible light irradiation for photodegradation of MB and RhB were compared. The effects of the initial concentration of the dyes, concentration of the catalyst, pH, and the presence of Cl− and CO32− ions (available in the wastewater containing dyes) on the photodegradation of MB and RhB by the CdS–Ag2S heterostructure were also investigated. The electrochemical impedance spectroscopy (EIS) measurement revealed that the CdS–Ag2S heterostructure accelerated the photogenerated transfer of charge carriers. The present work has recommended a new approach using the chemical precipitation and ion exchange to synthesize 3-dimensional CdS–Ag2S spheres with an excellent photocatalytic performance. A proper mechanism was suggested to investigate the photocatalytic process of the CdS–Ag2S heterostructure. Also, the radical trapping experiment was carried out via various scavengers to distinguish the role of the active species of O2•-, OH•, h+, and e−, respectively. Finally, the kinetics of the photodegradation of MB and RhB could be studied by Langmuir-Hinshelwood model explained as pseudo-first-order.

Synthesis and Characteristic Properties of Crosslinked Chitosan with Epichlorohydrin for Nitrate Removal from Water.

In this study, we prepared chitosan beads cross-linked with epichlorohydrin (CB-ECH) to improve the removal of nitrate in groundwater. It was confirmed that CB-ECH exhibited higher thermal stability and well-developed nano-pores compared to the pure chitosan beads (CB) by the thermogravimetric analyzer, nitrogen gas adsorption and desorption isotherm, and field emission scanning microscopy analysis. The CB-ECH showed a higher nitrate adsorption amount than the pure CB. Nitrate adsorption behaviors of CB-ECH were further investigated using adsorption isotherm, adsorption kinetics, adsorption energy distribution, and Gibbs free energy distribution models. The adsorption equilibrium and kinetics of nitrate ion on CB-ECH were well explained by the Sips isotherm and homogeneous surface diffusion model, respectively. It was also found from the AED analysis that the CB-ECH represent the heterogeneous adsorption behaviors for nitrate.

Influence of Structure on Catalytic Properties of La0.7Sr0.3BO3 (B = Mn, Fe, Ni) Perovskite Catalysts in Total Oxidation Reaction of M-Xylene

In this study, the influence of structure on catalytic properties of La0.7Sr0.3BO3 (B = Mn, Fe, Ni) perovskite catalysts in total oxidation reaction of m-xylene was studied. Perovskite oxides of La0.7Sr0.3BO3 (B = Mn, Fe, Ni) were prepared by sol-gel citrate method. Structural properties of these materials were determined by various physico-chemical methods such as X-ray diffraction method (XRD) with Rietveld analytical method using Fullprof program, infra - red spectroscopy method (IR), temperature - programmed desorption of oxygen (TPDO) method and nitrogen adsorption and desorption isotherms method (BET). Obtained results show that there is a close relationship between the structural properties and catalytic activity of these materials: the catalyst that has the more of structural distortion, the larger of specific surface area, the greater of the amount of chemically adsorbed oxygen on the catalyst and the less durable of B-O link that has the higher of catalytic activity in total oxidation recation of m-xylene. Perovskite of La0.7Sr0.3MnO3 has structural features the best, so it has the highest of catalytic activity in total oxidation recation of m-xylene.