High BET Specific Surface Area Research Articles

Enhanced biobased carbon materials made from softwood bark via a steam explosion preprocessing step for reactive orange 16 dye adsorption

The growing textile industry produces large volumes of hazardous wastewater containing dyes, which stresses the need for cheap, efficient adsorbing technologies. This study investigates a novel preprocessing method for producing activated carbons from abundantly available softwood bark. The preprocessing involved a continuous steam explosion preconditioning step, chemical activation with ZnCl2, pyrolysis at 600 and 800 °C, and washing. The activated carbons were subsequently characterized by SEM, XPS, Raman and FTIR prior to evaluation for their effectiveness in adsorbing reactive orange 16 and two synthetic dyehouse effluents. Results showed that the steam-exploded carbon, pyrolyzed at 600 °C, obtained the highest BET specific surface area (1308 m2/g), the best Langmuir maximum adsorption of reactive orange 16 (218 mg g−1) and synthetic dyehouse effluents (>70 % removal) of the tested carbons. Finally, steam explosion preconditioning could open up new and potentially more sustainable process routes for producing functionalized active carbons.

Low energy synthesis of crystalline mesoporous aluminosilicate consisting of Na-P1 zeolite derived from coal fly ash

Worldwide every year massive amount of coal fly ash is being generated as by product in the power plants which creates economic, environmental and most importantly health problems. Usually coal fly ash is used in cement production worldwide. At present, in Bangladesh, about 95 % of fly ash remains still unutilized. The alkali activation of fly ash has become a top research topic as it is possible to synthesize low cost and ecologically sound mesoporous zeolite type materials. In the present work, to the best of our knowledge, for the first time in Bangladesh, synthesis and characterization of crystalline mesoporous (H3 type hysteresis) aluminosilicate consisting of Na-P1 zeolite with a high BET specific surface area and a high pore volume from coal fly ash based on hydrothermal alkali activation technique have been successfully done. This product has versatile applications like catalysis, gas separation, water softening, water purification, gas sensing etc. The variable of alkali concentration was studied which has the notable influence on the development of the framework of the pores. The untreated coal fly ash (CFA) and the synthesized modified fly ashes (MFAs) were tested by WDS-XRF, XRD, N2 physisorption, FE-SEM, FT-IR, XPS, EDAX-mapping, particle size analysis and other technologies. The BET specific surface area, total pore volume and average pore diameter of the CFA were only 3 m2/g, 0.01 cc/g and 6.3 nm respectively based on nitrogen gas physisorption technique, whereas, after alkali activation at a specific temperature and time, and then curing, significant and promising increased values of the said parameters of 45 m2/g, 0.11 cc/g and 9.8 nm were obtained respectively. In methylene blue dye adsorption experiment, MFA showed higher adsorption capacity (23.87 mg/g).

Sm2O3 micron plates/B4C/HDPE composites containing high specific surface area fillers for neutron and gamma-ray complex radiation shielding

In this study, a series of Sm2O3 micron plates/B4C/HDPE composites composed of synthesized Sm2O3 fillers (Sm2O3 micron plates) are prepared for shielding neutron and gamma radiation. The influence of micromorphology of Sm2O3 fillers on neutron and gamma radiation shielding properties of composites is investigated in detail. The XRD pattern reveals that the phase of synthetic Sm2O3 is cubic crystal systems, body-centered cubic lattices, and its space group is Ia 3‾ (206). SEM images and BET analyses reveal that the micromorphology of synthesized Sm2O3 is micron plates. The BET-specific surface area of the Sm2O3 fillers is increased with addition of urea content. The differential scanning calorimetry (DSC) curves reveal that Sm2O3 fillers increase the melting temperature of the composites, which is up to 138.6 °C. The thermogravimetric analysis (TGA) results reveal that the initial thermal degradation temperatures of the composites are all above 440 °C. The neutron and gamma radiation shielding tests show that Sm2O3 fillers with high BET-specific surface area (8.20 m2/g) and uniform size improve the neutron and gamma shielding rate of composites. A superior composite containing 10 wt% Sm2O3 (R = 1:25, R value represents the molar ratio of rare earth elements to urea)/20 wt% B4C/70 wt% HDPE has a neutron radiation shielding rate of 98.7% with a thickness of 15 cm under the 252Cf neutron source and a gamma radiation shielding rate of 72.1% with a thickness of 15 cm under 137Cs gamma source. And these lead-free and environment-friendly composites can be widely used in the neutron and gamma complex radiation fields.

Lignin-derived nitrogen doped hierarchical porous carbon spheres for highly efficient dichloromethane adsorption

Biomass-prepared porous carbon materials are promising solid adsorbents for the removal of volatile organic compounds (VOCs). However, their application is hindered due to the insufficient number of pores and poor surface activity. In this study, a lignin-derived nitrogen-doped hierarchical porous carbon sphere (NHPCS-0.5) with abundant surface active sites was synthesised through spray drying and carbonisation–activation methods. The optimised NHPCS-0.5 displayed a high BET specific surface area (2961 m2·g−1) and total pore volume (1.57 cm3·g−1), developed hierarchical porous distribution with micro-/meso-/macropores and satisfactory surface nitrogen content. Moreover, it exhibited an excellent dichloromethane adsorption capacity of 156 mg·g−1 and maintained 86% of initial capacity after five regeneration cycles, indicating an outstanding regenerative ability. The nitrogen introduction improved the micropore volume and adsorption capacity. Adsorption mechanism reveals that micropore filling and enhanced van der Waals interaction of carbon surface with dichloromethane molecule by N-containing functional groups played a vital role in adsorption, and mesopores contributed to the high adsorption rates. The above results indicate the potential of NHPCS-0.5 as an adsorbent for VOC removal and provide new ideas for the utilisation of lignin and design of carbon sphere materials.

Production and evaluation of activated carbon from Saudi Arabian Acacia Tortilis tree bark by microwave and low temperature activation process

In the present work, activated carbon was produced from Acacia Tortilis tree bark, utilizing phosphoric acid chemical activation, and microwave irradiation (AC-MWI). Activated carbon was also produce by conventional phosphoric acid chemical activation and low temperature carbonization (AC-CA). Characterization of produced activated carbons performed by proximate analysis adopting ASTM standard procedures. BET-specific surface area, total ash content, bulk density, moisture content, pH, pore volume and iodine number were determined. Comparison of characteristics for both carbon, with the characteristics of AC available in the literature and commercially available in the market was performed. Comparison showed that activated carbon produced from Acacia Tortilis tree bark is well comparable with the reported characteristics of AC in literature and commercially available in market. It was found that AC-MWI has higher BET-specific surface area than AC-CA (836 m2/g and 687 m2/g respectively). Results depict that there is an increase of 22.3% in microspores component and 21.7% BET- specific surface area obtained in AC-MWI as compared to AC-CA. Similarly, the corresponding pore volume obtained (4.97 cm3/g and 4.07 cm3/g respectively) demonstrating better values as compared to the commercial ACs (<1 cm3/g). Additionally, it was found that AC can be produced by microwave irradiation in about 48.5% less time when compared to conventional low temperature heating. The adsorption study of produced ACs was performed using methylene blue as a contaminant. Study showed that MB removal rate initially increased with increase in contact time, which decreased with time until steady state was reached. Adsorption data of MB was fitted to Freundlich, Langmuir and Temkin adsorption isotherm models. All models show reasonable correlation, however, Freundlich isotherm is best to describe the MB adsorption on AC-MWI based on correlation coefficient R2 value (0.9985). The results revealed the feasibility of microwave heating for preparation of high surface area activated carbons from Acacia Tortilis tree bark.

Production and evaluation of activated carbon from Saudi Arabian Acacia Tortilis tree bark by microwave and low temperature activation process

In the present work, activated carbon was prepared from Acacia Tortilis tree bark, utilizing phosphoric acid chemical activation, and microwave irradiation (AC-MWI). Activated carbon was also prepared by conventional phosphoric acid chemical activation and low temperature carbonization (AC-CA). Characterization of the activated carbons were performed by proximate analysis adopting ASTM standard procedures. BET-specific surface area, total ash content, bulk density, moisture content, pH, pore volume and iodine number were determined. Comparison of characteristics for both carbons, with the characteristics of AC available in the literature and commercially available in the market was performed. Comparison showed that activated carbon produced from Acacia Tortilis tree bark is well comparable with the reported characteristics of AC in literature and commercially available in market. It was found that AC-MWI has higher BET-specific surface area than AC-CA (836 m2/g and 687 m2/g respectively). Results depict that there is an increase of 22.3% in microspores component and 21.7% BET- specific surface area obtained in AC-MWI as compared to AC-CA. Similarly, the corresponding pore volume obtained (4.97 cm3/g and 4.07 cm3/g respectively) demonstrating better values as compared to the commercial ACs (<1 cm3/g). Additionally, it was found that AC can be produced by microwave irradiation in about 48.5% less time when compared to conventional low temperature heating. The adsorption study of produced ACs was performed using methylene blue as a contaminant. Study showed that MB removal rate initially increased with increase in contact time, which decreased with time until steady state was reached. Adsorption data of MB was fitted to Freundlich, Langmuir and Temkin adsorption isotherm models. All models show reasonable correlation, however, Freundlich isotherm is best to describe the MB adsorption on AC-MWI based on correlation coefficient R2 value (0.9985). The results revealed the feasibility of microwave heating for preparation of high surface area activated carbons from Acacia Tortilis tree bark.

Acidic ionic liquid-functionalized ordered mesoporous polymers: Highly efficient solid acid catalysts for water-medium organic reactions

Strong acidic ionic liquid-functionalized mesoporous organic material (MPOM-T-AIL) has been created by quaternary ammonization of mesoporous organic material (MPOM) with 1,3-propane sultone and subsequent strong acid (H2SO4 or HSO3CF3) acidification. The novel supporting material, MPOM, had high nitrogen content and was synthesized by direct high-temperature (400–550 °C) polymerization of an easily prepared and low cost protic salt [pPDA][2HSO4], which was obtained by simple neutralization of p-phenylenediamine with two equivalents of H2SO4. MPOM-T-AIL possesses high BET specific surface area, ordered and uniform mesoporosity, hydrophobic property, and highly active acidic ionic liquid components. Catalytic tests in the water-medium Prins reactions and acetalization of benzaldehyde with ethylene glycol showed that MPOM-T-AIL exhibits much better catalytic activities and reusabilities than commercially available solid acid catalysts Amberlyst 15 and H-ZSM-5, and mineral acid H2SO4. Additionally, MPOM-T-AIL significantly improved the catalytic selectivity of the water-medium Prins reaction, which was strongly related to its hydrophobic property. MPOM-T-AIL with excellent catalytic performance is a promising new solid acid catalyst for various acid-catalyzed reactions.

Synthesis of sustainable rice husk ash-derived nickel-decorated MCM-41 and SBA-15 mesoporous silica materials for hydrogen storage

To promote sustainability, it is essential to make use of biomass waste to create resources that can be transformed into mesoporous materials like silicates. These materials can be used as effective adsorbents for solid-state H2 storage systems. To meet the requirements of these systems, materials must be inexpensive, possess high specific surface areas, have proper pore arrangements, and exhibit reasonable H2 uptake. In this study, sustainable rice husk ash-derived MCM-41-RHA and SBA-15-RHA mesoporous silica materials were developed. These materials were engineered with different levels of Ni loading (2.5–10 wt%) and are used for H2 storage. The prepared MCM-41-RHA and SBA-15-RHA materials have a high BET-specific surface area of 1092.6 m2/g and 539.2 m2/g, respectively, with a mesopore distribution. The best results were observed for samples with a Ni loading of 5 wt%, such as MCM-41-RHA-Ni5 and SBA-15-RHA-Ni5, which demonstrated the highest H2 uptake of 3.64 wt% and 2.48 wt%, respectively, at 77 K and 1 bar. This was due to the strong interaction between the adsorbent and split over hydrogen despite the decrease in the BET-specific surface area after the incorporation of Ni. The enhanced interaction was evidenced by the increased isosteric heat of adsorption observed for MCM-41-RHA-Ni5 and SBA-15-RHA-Ni5, ranging from 21.1 to 8.1 kJ/mol, in contrast to the range of 6.9 to 4.1 kJ/mol for the pristine MCM-41-RHA and SBA-15-RHA. After five successive H2 uptake/release cycles, more than 92 % of the initial capacity was retained. This study presents a sustainable and cost-effective RHA-derived mesoporous silica material decorated with Ni- nanoparticles for solid-state H2 storage.

Facile Preparation of a Novel HfC Aerogel with Low Thermal Conductivity and Excellent Mechanical Properties.

Aerogels emerge as captivating contenders within the realm of high-temperature thermal resistance and thermal insulation. Nevertheless, their practical applications are usually constrained by their inherent brittleness when subjected to rigorous conditions. Herein, employing hafnium dichloride oxide octahydrate (HfOCl2·8H2O) as the hafnium source and resorcinol-formaldehyde (RF) as the carbon precursor, hafnium carbide (HfC) aerogels are fabricated via the sol-gel method complemented with carbothermal reduction reaction. Investigations are conducted into the effects of various molar ratios, duration, and temperatures of calcination on the microstructural features and physico-chemical characteristics of the as-prepared HfC aerogel. The aerogel shows a high BET-specific surface area (601.02 m2/g), which is much larger than those of previously reported aerogels. Furthermore, the HfC aerogel exhibits a low thermal conductivity of 0.053 W/(m·K) and a compressive strength of up to 6.12 MPa after carbothermal reduction at 1500 °C. These excellent thermal insulation and mechanical properties ensure it is ideal for the utilization of high-temperature thermal resistance and thermal insulation in the fields of aerospace.

Optimization of electrochemical performance for double network electrically conductive aerogel-based supercapacitor electrode

In order to improve the energy density and optimize the electrochemical performance of supercapacitors, a new double network calcium alginate/polyaniline (CA/PANI) aerogels were designed in this study, in which sodium alginate (SA) cross-linked by Ca2+ was the first network and the phytic acid cross-linked PANI was the second network. Due to the strong hydrogen bonds between PANI and CA, and the ionic cross-linking between CA molecular chains, CA/PANI aerogels can form a stable porous network structure with excellent performance, such as high BET specific surface area (330 m2/g) and high conductivity (2.66 S/cm). The aerogel further used as a supercapacitor electrode showed enhanced capacitive performance (463 F/g at 0.5 A/g). After repeated 10,000 galvanostatic charge/discharge tests, more than 84% of the initial capacitance could be maintained, while the capacitance retention of PANI was only 45%. Therefore, this aerogel showed great potential as an electrode material for supercapacitors.

Mesoporous Zn2SnO4 for efficient sensing of ethylene glycol vapor

Within this study, mesoporous Zn2SnO4 nanostructures have been prepared by a facile and eco-friendly hydrothermal method. Through X-ray diffraction analysis, a polycrystalline zinc tin oxide structure is recognized with a cubic inverse spinel phase crystal structure. By Field emission scanning electron microscopy method, various morphologies based on the hydrothermal time ranging from the cubic-like morphology, irregular hexagonal plates, and large quantity of microspheres to the truncated octahedron have been observed. By the aid of Energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy analyses, the atomic ratio and characteristic vibration peaks of Zn2SnO4 have been evaluated. By the help of Brunauer–Emmett–Teller analysis, specific surface area, mean pore diameter, and total pore volume were measured. The nanostructured Zn2SnO4 prepared in 36 h hydrothermal treatment (as a selected sample) showed a higher BET specific surface area (9.10 m2/g) and total pore volume (0.078 cm3/g) than the other samples. The gas-sensing performance of the samples was investigated towards different vapors. The optimum operating temperature (270 °C), transient response, response/recovery times, and long-term stability (eight months) of the samples have been evaluated. For the selected sample, appreciable sensing response (92.92 toward 100 ppm ethylene glycol), the ultra-fast response time (1 s), excellent selectivity (about 6–23 times more than other tested vapors) and excellent long-term stability (the response decay of about 10% after eight months) has been perceived which makes it a promising gas sensor. It seems that the selected sample has shown relatively better performance for two reasons: Firstly, high crystalline quality (largest crystallite size and lowest strain value) which can affect the combination or separation of adsorbed oxygen species on the surface of the material. Secondly, the higher specific surface area and the relatively larger total pore volume can lead to more gas adsorption sites leading to further narrowing of the depletion layer and resulting in a high and very fast response.

Deciphering the role of pristine and Ni ions substituted Co3O4 nanoparticles with altered structural, magnetic and dielectric traits towards elevated photosensing and photocatalytic activity

ABSTRACT Pure and nickel (Ni) doped cobalt oxide nanoparticles were employed by the co-precipitation method to present the structural, optical, and photocatalytic characteristics of NixCo3-xO4 nanoparticles (x = 0, 0.05, 0.1, and 0.3) for organic pollutant photodegradation. X-ray diffraction (XRD) was employed on NixCo3-xO4 samples with particle sizes ranging from 14 to 22 nm, confirming the occurrence of cubic phase. In addition, particle size was calculated by Debye Scherrer, Williamson-Hall (W-H) and Halder methods, respectively. The Fourier transform infrared (FTIR) analyses of all samples characterised the inherent lattice vibrations of spinel structures octahedral and tetrahedral sites, respectively. FESEM image depicts irregular-shaped clusters and EDX confirmed the presence of Ni, Co and O elements. The mesoporous nature of the pores and high BET specific surface area indicated the presence of several active sites, proving their viability as photocatalysts. UV-Vis spectrophotometer was utilised to measure the optical properties, which included recording absorption spectra and computing optical parameters. The photocatalytic activities of the pure Co3O4 and NixCo3-xO4 photocatalysts were studied by the degradation of a series of four dyes (Congo Red, Tartrazine, Rhodamine B, and Methylene Blue) solution under visible light irradiation. Compared to pure cobalt oxide, Ni-incorporated Co3O4 exhibits a substantially higher photocatalytic efficiency that increases with Ni doping concentration. The photocatalysts displayed superior recycling stability, retaining high performance after three cycles. The photosensing properties were investigated under UV light, and a considerable photocurrent enhancement was observed. As a result, it is illustrated that Ni-doped cobalt oxide NPs are a potential material for the fabrication of photosensitive devices.

Ppb-Level Hydrogen Sulfide Gas Sensor Based on the Nanocomposite of MoS2 Octahedron/ZnO-Zn2SnO4 Nanoparticles.

Hydrogen sulfide (H2S) detection is extremely necessary due to its hazardous nature. Thus, the design of novel sensors to detect H2S gas at low temperatures is highly desirable. In this study, a series of nanocomposites based on MoS2 octahedrons and ZnO-Zn2SnO4 nanoparticles were synthesized through the hydrothermal method. Various characterizations such as X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectrum (XPS) have been used to verify the crystal phase, morphology and composition of synthesized nanocomposites. Three gas sensors based on the nanocomposites of pure ZnO-Zn2SnO4 (MS-ZNO-0), 5 wt% MoS2-ZnO-Zn2SnO4 (MS-ZNO-5) and 10 wt% MoS2-ZnO-Zn2SnO4 (MS-ZNO-10) were fabricated to check the gas sensing properties of various volatile organic compounds (VOCs). It showed that the gas sensor of (MS-ZNO-5) displayed the highest response of 4 to 2 ppm H2S and fewer responses to all other tested gases at 30 °C. The sensor of MS-ZNO-5 also displayed humble selectivity (1.6), good stability (35 days), promising reproducibility (5 cycles), rapid response/recovery times (10 s/6 s), a limit of detection (LOD) of 0.05 ppm H2S (Ra/Rg = 1.8) and an almost linear relationship between H2S concentration and response. Several elements such as the structure of MoS2, higher BET-specific surface area, n-n junction and improvement in oxygen species corresponded to improving response.

Adsorption of methylene blue from textile industrial wastewater using activated carbon developed from Rumexabyssinicus plant

Methylene blue (MB) is abundantly found in textile industrial effluent which can cause severe health problems for public and environmental ecology. Therefore, this study aimed to remove MB from textile wastewater using the activated carbon developed from Rumexabyssinicus. The adsorbent was activated using chemical and thermal methods, and then it was characterized by SEM, FTIR, BET, XRD, and pH zero-point charge (pHpzc). The adsorption isotherm and kinetics were also investigated. The experimental design was composed of four factors at three levels (pH (3, 6, and 9), initial MB concentration (100, 150, and 200 mg/L), adsorbent dosage (20, 40, and 60 mg/100 mL), and contact time (20, 40, and 60 min)). The adsorption interaction was evaluated using response surface methodology. The characterization of a Rumexabyssinicus activated carbon was found to have multiple functional groups (FTIR), an amorphous structure (XRD), crack with ups and down morphology (SEM), pHpzc of 5.03 and a high BET-specific surface area of 2522 m2/g. The optimization of MB dye removal was carried out using the Response Surface methodology coupled with the Box Behnken approach. The maximum removal efficiency of 99.9% was recorded at optimum conditions of pH 9, MB concentration of 100 mg/L, the adsorbent dosage of 60 mg/100 mL, and contact time of 60 min. Among the three adsorption isotherm models, the Freundlich isotherm model was the best fit with an experimental value at R2 0.99 showing the adsorption process was heterogeneous and multilayer whereas the kinetics study revealed that pseudo-second-order at R2 0.88. Finally, this adsorption process is quite promising to be used at an industrial level.

An investigation of the influence of nanofibers morphology on the performance of QCM-based ethanol vapor sensor utilizing polyvinylpyrrolidone nanofibers active layer

Quartz crystal microbalances (QCMs) coated by polyvinylpyrrolidone (PVP) nanofibers with controlled morphology have been made for ethanol vapor detection. We used electrospinning to deposit PVP nanofibers of different morphologies (spherical-beaded, spindle-beaded, and pure nanofiber) on a QCM surface to study the effect on sensor performance. BET characterization revealed that the spherical-beaded nanofiber had the highest BET-specific surface area than the other morphologies, which improves the QCM sensor sensitivity, limit of quantification (LOQ), limit of detection (LOD), and sensor response. QCM coated with spherical-beaded nanofiber showed improved sensitivity of 2.632 Hz/ppm, lower LOD and LOQ of 0.018 ppm and 0.061 ppm, and better response compared to those coated with spindle-beaded and pure nanofiber. Based on adsorption isotherm models, Freundlich adsorption isotherm was found to be the most suitable for describing ethanol vapor adsorption on the sensor. The high sensitivity of the sensor to ethanol vapor was attributed to hydrogen bonding interactions between the sensor and the ethanol molecules. This study shows that the QCM-based sensor performance can be improved by modifying the morphology of nanofibrous coating layer.

Polyimide and polystyrene‐based activated carbon nanofibers with tubular structure for supercapacitor

AbstractPolyimide (PI) and polystyrene (PS) blend electrospun fibers are prepared by electrospinning method. PI and PS are not completely compatible due to the difference of solubility and surface energy in electrospinning precursor, so PI/PS electrospun fibers have some phase separations along the electric field direction under the high‐voltage electrostatic force. PI with high carbon conversion served as carbon nanofibers, PS with low carbon conversion served as porogenic sacrificial agent, so PI/PS‐based activated carbon nanofibers derived from PI/PS electrospun fibers with well‐controlled opening tubular structure are obtained via thermally induced phase separation process. The morphology and electrochemical performance of activated carbon nanofibers are investigated by structural analysis and electrochemical measurements. The relationships among pores structure, electrolyte character and electrochemical performance of activated carbon fibers are extensively evaluated. Activated carbon nanofibers derived from PI/PS (mass ratio = 1:2) electrospun fibers with nano scale opening tube wall structure show a small charge transfer resistance and the short electric double layers forming time, but also suitable average pore diameter (3.74 nm), high BET specific surface area (952.5 m2 g−1) and average pore volume (0.532 cm3 g−1). Then, a comprehensive electrochemical performance can also be achieved in organic electrolyte: high energy density (31.80 Wh kg−1), good power density (3094.05 W kg−1) and low internal resistance (1.24 Ω). The findings reveal a guideline for the preparation of polymer‐based hierachical porous and opening tubular structure activated carbon nanofibers for electrochemical energy conversion and storage devices.

Study of phytotoxicity, remarkable photocatalytic activity, recycling process and energy consumption cost of TiO2 quantum dots photocatalyst for photodegradation of Coomassie brilliant blue R dye

The phytotoxicity experimental assessment revealed that the water used in the germination of Lycopersicon esculentum tomato seeds which was treated with TiO2 quantum dots, TDs1 (2.7 nm), TDs2 (3.1 nm) and TiO2 (Degussa) respectively, had no impact on the germination process. TiO2 quantum dots with a high BET Specific surface area of 462.3 m2/g for TDs1 (2.7 nm) and 338.22 m2/g for TDs2 (3.1 nm) were synthesized through the sol-gel method using TiCl4 in different polar solvents. The structure, shape, and size of the prepared TDs samples have been characterized by techniques such as XRD, FE-SEM, HRTEM, and EDX, confirming no additional phases or impurities in TDs. The optical band gaps of TDs samples were determined from their diffuse reflectance spectral data using Kubelka-Munk Equation. Photocatalytic activities of 91 and 89% were achieved in the mineralization of Coomassie brilliant blue R (CBBR), a model commercial dye, under direct sunlight and xenon lamp irradiation, respectively. The reactive species on the photodegradation mechanism for the TDs prepared samples were determined by different trapping agents. The photocatalytic activity of the TDs samples remained strong after eight repetitions with a Xenon photoreactor and direct solar light. The assessment of the photodegradation efficiency of CBBR dye in terms of its beneficial influence on energy consumption (EE/O) and price estimates has been reported.

Green and Fast Strategies for Energy-Efficient Preparation of the Covalent Organic Framework TpPa-1.

Three synthesis procedures for the covalent-organic framework (COF) TpPa-1 are studied with the purpose of setting up the most promising one in a fast and green way, leading to a more environmentally friendly and sustainable process. With conventional heating, good crystallinity and a high BET specific surface area (SSA) of up to 1007 m2 ⋅ g-1 are achieved at 170 °C for 3 days using water as the quintessential green solvent. However, the application of microwave radiation in the synthesis for this crystalline porous polymer allows reaction times to be shortened to 30 min while maintaining structural and textural properties (BET SSA of 928 m2 ⋅ g-1 ) and obtaining yields close to 98 % (vs. 90 % in the hydrothermal synthesis). The water-assisted mechanochemical synthesis is also an environmentally friendly synthetic approach; with heating at 170 °C in a two-step process (10+10 min), high crystallinity is achieved, a BET SSA of 960 m2 ⋅ g-1 and a yield of 98 % for TpPa-1.

Co,N,S co-doped hollow carbon with efficient oxidase-like activity for the detection of Hg2+ and Fe3+ ions

Most nanozymes have limited catalytic ability, and constructing high performance nanozymes is important and challenging. Metal-carbon hybrid materials obtained by integrating transition metals into carbon can not only generate rich active sites, but also enhance their electrical conductivity. Heteroatom doping is shown to be an efficient strategy to improve the catalytic activity of carbon-based nanozymes. Here, by taking advantage of the structural merits of MOFs-derived porous carbon materials combined with sulfur doping strategy, the Co,N,S co-doped hollow carbon material, i.e. Co-N/S-HCN, was fabricated by pyrolyzing a thiomalic acid (TA) modified zeolitic imidazolate framework (ZIF-67@TA) in a nitrogen atmosphere. It exhibits hollow dodecahedron shape with rich defects, high BET specific surface area of 240.75 m2/g and pore volume of 0.27 cm3/g. The electrochemical characterization reveals the doping of S reduces the charge transfer resistance of the Co-N-HCN, accelerates electron transfer rate, and finally boosts its catalytic activity. The Co-N/S-HCN shows superior oxidase-like activity and can convert colorless 3,3′,5,5′-tetramethylbenzidine (TMB), o-phenylenediamine and 2,2′-azo-bis (3-ethylbenzothiazolin-6-sulfonic acid) diammonium salt into visible color substrates without hydrogen peroxide. The oxidase-like activity of Co-N/S-HCN was 2.1 times that of Co-N-HCN. The quenching trials revealed the generation of O2•−, •OH and 1O2 during catalytic TMB oxidation by Co-N/S-HCN. The Co-N/S-HCN oxidase-like nanozyme exhibited good affinity to TMB with a Km value of 0.25 mM and Vmax of 4.19 × 10−7 M s−1. In terms of Soft-Hard Acid-Base principle, Hg2+ combines easily with the sulfur. Thus, the introduction of Hg2+ ions can restrain TMB oxidation catalyzed by Co-N/S-HCN, thereby inhibiting the color reaction. In addition, the addition of 8-hydroxyquinoline can restrain TMB oxidation catalyzed by Co-N/S-HCN, resulting in a decrease in absorbance at 652 nm. However, the color reaction recovers in the presence of Fe3+, resulting in an increase in absorbance at 652 nm. In terms of above fact, a colorimetric sensing platform for determining Hg2+ and Fe3+ ions was established and successfully used for detecting Hg2+ in water samples and Fe3+ in liquors. This work offers a different way to prepare nanozymes with efficient oxidase-like activity and is of great significance for detecting heavy metal ions in environmental and food samples.

Zeolitic imidazolate framework-8 modified bacterial cellulose/sodium alginate composite aerogel for efficient removal of tetracycline hydrochloride

Antibiotics released in the water pose a serious threat to human and ecological health. Therefore, it is of great importance to effectively remove antibiotics from wastewater. In this study, recyclable bacterial cellulose/sodium alginate/zeolitic imidazolate framework-8 (BC/SA/ZIF-8) aerogel composites were prepared by chemical cross-linking and in situ growth in freeze-drying. The successful preparation of the composite aerogel was confirmed by scanning electron microscope (SEM), Fourier Transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. The results reveal that BC/SA/ZIF-8 aerogel composite has significantly high BET specific surface area of 165.24 m2/g than that of BC/SA at 7.39 m2/g. The BC/SA/ZIF-8 composite aerogel exhibited excellent adsorption performance for tetracycline hydrochloride, with a maximum adsorption capacity of 746.27 mg/g. The adsorption process followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm model. Moreover, the reusability test on BC/SA/ZIF-8 composite aerogel revealed an insignificant decline in adsorption after six cycles. Therefore, BC/SA/ZIF-8 composite aerogel has a high potential as a novel and recyclable adsorbent for efficient removal of tetracycline hydrochloride from water.