Brunauer Emmett Teller Method Research Articles

Highly Sensitive Acetone Sensor Based on LaFeO3 Microspheres Prepared by Facile Hydrothermal Synthesis

This paper describes a gas sensor based on LaFeO3 nanoparticles for sensitive detection of low-concentration acetone. LaFeO3 nanoparticles were synthesized via a one-step hydrothermal reaction and subsequent annealing. The sample phases and morphologies were investigated by X-ray diffraction, scanning electron microscopy, and the Brunauer—Emmett—Teller method. The results show that the LaFeO3 nanoparticles were spherical with a loose porous structure. Gas sensors based on the LaFeO3 nanoparticles were prepared and their gas sensitivities were determined. In particular, the fabricated sensor based on LaFeO3 nanoparticles annealed at 600 °C showed an excellent response to acetone at 1–300 ppm, and high stability and selectivity. A response of 4.53 toward acetone gas down to 1 ppm at an operating temperature of 120 °C was obtained. This enhanced gas-sensing performance is attributed to a specific mesoporous structure of high roughness, a large surface area, and surface pores of an appropriate size. These properties enable more favorable conditions were provided for gas reaction.

Valorization of fluid petroleum coke for efficient catalytic destruction of biomass gasification tar

Large volumes of waste petroleum coke stockpiled in open yard not only represent a huge loss of valuable material but also pose a significant risk to the environment. This work proposed an innovative strategy for waste petroleum coke valorization by exploring its catalytic performance of biomass gasification tar destruction. Waste petroleum coke was firstly activated by potassium hydroxide (KOH) to obtain high specific surface area as well as low sulfur and ash contents. Petroleum coke derived catalyst showed superior performance than a commercial activated carbon derived catalyst for destruction of naphthalene as the tar model compound. The petroleum coke derived catalyst exhibited 99.1% naphthalene destruction efficiency at 800 °C but deactivated quickly under N2 atmosphere. Under H2 and steam atmospheres, the catalytic activities were 98.6% and 96.5% for 8 h, respectively. To study the correlation between catalytic performance and the structure of carbon catalyst, elemental analysis, scanning electron microscope (SEM) analysis, transmission electron microscope (TEM) analysis, X-ray powder diffraction (XRD) analysis, Brunauer-Emmett-Teller method (BET) analysis, Fourier transform infrared (FTIR) spectroscopy, temperature programmed oxidation (TPO) analysis and Raman spectroscopy were performed on both fresh and spent catalysts. Results demonstrated that the hydrogen-rich groups (small rings and amorphous carbon) and oxygen-containing groups may account for the good resistance to coke deposition under H2 and steam atmospheres.

Central Composite Design for Adsorption of Pb(II) and Zn(II) Metals on PKM-2 Moringa oleifera Leaves.

Biosorption is a very effective technique to eliminate the heavy metals present in the wastewater that utilize nongrowing biomass. The adsorption ability of the Periyakulam-2 (PKM-2) variety of Moringa Oleifera leaves (MOLs) to eliminate Pb(II) and Zn(II) ions from an aqueous solution was examined in this work. Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy, energy-dispersive X-ray (EDX) analysis, X-ray powder diffraction, and Brunauer–Emmett–Teller methods were used to characterize the PKM-2 variety of MOLs. The set of variables consists of the metal ion initial concentration, a dosage of the adsorbent, and pH were optimized with the help of the response surface methodology to get maximum metal removal efficiency of lead and zinc metals using the PKM-2 MOL biosorbent. A maximum Pb(II) removal of 95.6% was obtained under the condition of initial concentration of metal ions 38 mg/L, a dosage of the adsorbent 1.5 g, and pH 4.7, and a maximum zinc removal of 89.35% was obtained under the condition of initial concentration of metal ions 70 mg/L, a dosage of the adsorbent 0.6 g, and pH 3.2. The presence of lead and zinc ions on the biosorbent surface and the functional groups involved in the adsorption process were revealed using EDX and FTIR analysis, respectively. The adsorption data were evaluated by employing different isotherm and kinetic models. Among the isotherm models, Langmuir’s isotherm showed that the best fit and maximum adsorption capacities are 51.71 and 38.50 mg/g for lead and zinc, respectively. Kinetic studies showed accordance with the pseudo-second-order model to lead and zinc metal adsorption. Thermodynamic parameters confirmed (ΔG° < 0, ΔH° < 0, and ΔS° > 0) that the sorption mechanism is physisorption, exothermic, spontaneous, and favorable for adsorption. The results from this study show that the MOL of the PKM-2 type is a promising alternative for an ecofriendly, low-cost biosorbent that can effectively remove lead and zinc metals from aqueous solutions.

Folatereceptor-mediated delivery of 1-MDT-loaded mesoporous silica magnetic nanoparticles to target breast cancer cells.

Aims: The efficiency of mesoporous silica magnetic nanoparticles (MSMNP)as a targeted drug-delivery systemwas investigated. Methods: The superparamagnetic iron oxide nanoparticles (NP) were synthesized, coated with mesoporous silicaand conjugated with polyethylene glycol and methotrexate. Next, 1-methyl-D-tryptophan was loaded into the prepared nanosystems (NS). They were characterized using transmission electron microscopy, scanning electron microscopy, dynamic light scattering, vibrating sample magnetometer, x-ray powder diffraction, Fourier transform-infrared spectroscopyand theBrunauer-Emmett-Teller methodand their biological impacts on breast cancer cells were evaluated. Results: The prepared NSs displayed suitable properties and showed enhanced internalization by folate-receptor-expressing cells, exerting efficient cytotoxicity, which was further enhanced by the near-infrared radiation irradiation. Conclusion: On the basis of our findings, the engineered NS is a promising multifunctional nanomedicine/theranosticfor solid tumors.

On the BET Surface Area of Nanocellulose Determined Using Volumetric, Gravimetric and Chromatographic Adsorption Methods

Volumetric N2 adsorption at −196°C is generally accepted as “gold standard” for estimating the Brunauer-Emmet-Teller (BET) surface area of nanocellulose. It is unclear however, whether the BET surface area of nanocellulose obtained at such low temperatures and pressures is meaningful at an absolute sense, as nanocellulose is used at ambient temperature and pressure. In this work, a systematic evaluation of the BET surface area of nanocellulose using highly crystalline bacterial cellulose (BC) as model nanocellulose was undertaken to achieve a comprehensive understanding of the limitations of BET method for nanocellulose. BET surface area obtained using volumetric N2 adsorption at −196°C was compared with the BET surface area acquired from gravimetric experiments based on n-octane adsorption using dynamic vapour sorption (DVS) and n-octane adsorption determined by inverse gas chromatography (iGC), both at 25°C. It was found that the BET surface area calculated from volumetric N2 adsorption data was 25% lower than that of n-octane adsorption at 25°C obtained using DVS and iGC adsorption methods. These results supported the hypothesis that the BET surface area of nanocellulose is both a molecular scale (N2vs n-octane, molecular cross section of 0.162 nm2vs 0.646 nm2) and temperature (−196°C vs 25°C) dependent property. This study also demonstrates the importance of selecting appropriate BET pressure range based on established criteria and would suggest that room temperature measurement is more relevant for many nanocellulose applications.

Vitamin C-Assisted Fabrication of Aerogels from Industrial Graphene Oxide for Gaseous Hexamethyldisiloxane Adsorption

Volatile methyl siloxanes (VMSs) as a trace impurity in biogas decreases its energy utilization, and thus need to be removed. In this paper, a one-step hydrothermal reduction was performed to produce three-dimensional reduced graphene oxide aerogels (rGOAs) using industrial-grade graphene oxide (IGGO) as raw material and vitamin C (VC) as a reductant to facilitate the fabrication of rGOAs. The synthesis of rGOAs was a simple, green, and energy-efficient process. The developed rGOAs were characterized using the Brunauer–Emmett–Teller method, Raman spectrometry, scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction measurements and contact angle. The results obtained showed that rGOA-1 with a VC/IGGO ratio of 1/1 (m/m) exhibited a hierarchical porous structure and super-hydrophobicity, yielding a high specific surface area (137.9 m2 g−1) and superior water contact angle (143.8°). The breakthrough adsorption capacity of rGOA-1 for hexamethyldisiloxane (L2, a VMS model) was 11 times higher than that of IGGO. Low inlet concentration and bed temperature were considered beneficial for the L2 adsorption. Interestingly, rGOA-1 was less sensitive to water, and it was readily regenerated for reuse by annealing at 80 °C. The rGOAs have been demonstrated to have great potential for the removal of siloxanes from biogas.

Radiation‐initiated chitosan‐based double network hydrogel: Synthesis, characterization, and adsorption of methylene blue

AbstractA novel chitosan (CTS)‐based double network Poly(2‐acrylaMido‐2‐Methyl‐1‐propanesulfonic acid)/Polyacrylamide/CTS hydrogel was synthesized by irradiation initiated. Laponite RD (RD) was used as both dopant and the cross‐linking agent. Then the fabricated hydrogel was applied as an efficient adsorbent to remove the methylene blue (MB) in an aqueous solution. This hydrogel has both high strength and good adsorption properties for MB. The results from Brunauer–Emmett–Teller method confirmed that the hydrogel has a large specific surface area (96 m2/g) and developed pore structure, which is available for the contact between the adsorbent and dye molecules. In the adsorption process, the RD provides plenty of negative charges as adsorption sites for MB molecules. The influence of pH, temperature, and adsorbent dose on the adsorption performance was investigated in detail. The experimental data fit well with the pseudo‐second‐order kinetic model and Langmuir isotherm. Besides, the mechanical strength of the hydrogel was also investigated in this work.

Fabrication of attapulgite/magnetic aminated chitosan composite as efficient and reusable adsorbent for Cr (VI) ions.

An efficient composite was constructed based on aminated chitosan (NH2Cs), attapulgite (ATP) clay and magnetic Fe3O4 for adsorptive removal of Cr(VI) ions. The as-fabricated ATP@Fe3O4-NH2Cs composite was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Thermal Gravimetric Analyzer (TGA), Scanning Electron Microscope (SEM), Zeta potential (ZP), Vibrating Sample Magnetometer (VSM), Brunauer–Emmett–Teller method (BET) and X-ray photoelectron spectroscope (XPS). A significant improve in the adsorption profile was established at pH 2 in the order of ATP@Fe3O4-NH2Cs(1:3) > ATP@Fe3O4-NH2Cs(1:1) > ATP@Fe3O4-NH2Cs(3:1) > Fe3O4-NH2Cs > ATP. The maximum removal (%) of Cr(VI) exceeded 94% within a short equilibrium time of 60 min. The adsorption process obeyed the pseudo 2nd order and followed the Langmuir isotherm model with a maximum monolayer adsorption capacity of 294.12 mg/g. In addition, thermodynamics studies elucidated that the adsorption process was spontaneous, randomness and endothermic process. Interestingly, the developed adsorbent retained respectable adsorption properties with acceptable removal efficiency exceeded 58% after ten sequential cycles of reuse. Besides, the results hypothesize that the adsorption process occurs via electrostatic interactions, reduction of Cr(VI) to Cr(III) and ion-exchanging. These findings substantiate that the ATP@Fe3O4-NH2Cs composite could be effectively applied as a reusable adsorbent for removing of Cr(VI) ions from aqueous solutions.

Synthesis and characterization of bio catalyst prepared from dairy waste for lactic acid esterification

Abstract Dairy byproduct is known for its valuable chemical and nutritional content possessing high market potential. Notwithstanding, it is tractable to exploit its utilization. The waste generated is organic and having huge energy potential. The objective of current research is to synthesize novel catalyst from a dairy based solid waste called Ghee Residue by chemical activation process and deploy it for the production of iso-butyl lactate. Surface identity of catalyst was furnished using Brunauer-Emmet Teller (BET) method and Fourier Transform Infrared Spectroscopy (FTIR). Effect of variables like reaction time, temperature of reaction and loading of catalyst on lactic acid conversion were studied. In addition to this, reaction kinetics modelling was performed using 2nd order pseudo-homogeneous approach. It was inferred that, both internal as well as external resistance of mass transfer could not offer any influence on overall rate of reaction in this esterification. Optimum condition for esterification reaction was at 368 K with 3% catalyst loading giving the highest conversion around 74%. The energy of activation for the present system using synthesized catalyst was 41.5 kJ/mol and found to be lower in comparison with the other catalysts. Although, the activity of GRC declined gradually less than 10% from the activity of the several reaction cycle.

Ultra-hydrophobic aluminum foam development for potential application in continuous water-oil separation processes

Owing to their applicability as a selective barrier, porous materials with modified surfaces have been presented as alternatives for addressing oil spills in water. For this application, surface treatment seeks both maximization of surface area and formation of a low-energy layer. To achieve an effective selective barrier that is useful in the separation of oil-water mixtures, with future application in oil spill cleanup, this work presents aluminum foams treated with sodium hydroxide and immersed in dodecanoic acid to achieve pickling and reduction of surface energy, respectively. Treatment efficiency was evaluated using the Brunauer–Emmett–Teller method and contact angle measurements. Results were consistent with other hydrophobic materials. Pore sizes of 425 µm, 850 µm, and 1200 µm were used to evaluate separation of water and oil mixtures under static and dynamic conditions. Oil recovery efficiencies for all pore sizes were greater than 98%.

Mesoporous nanostructures of NiCo-LDH/ZnCo2O4 as an efficient electrocatalyst for oxygen evolution reaction

Increasing energy demands for pollution-free and renewable energy technologies have stimulated intense research on the development of inexpensive, highly efficient, and stable non-noble metal electrocatalysts for oxygen evolution reaction (OER). In this study, a superior OER performance was achieved using a tri-metallic (Zn, Co, Ni) high-performance electrocatalyst. We successfully fabricated a peony-flower-like hierarchical ZnCo2O4 through an additive-free hydrothermal reaction followed by heat treatment. Then NiCo-LDH (layered double hydroxides) nano-flakes was electrodeposited on the ZnCo2O4/GCE surface to prepare NiCo-LDH/ZnCo2O4/GCE which was used as electrode for OER. The structure and morphology of the catalysts were characterized by several techniques including Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping and Brunauer–Emmett–Teller method. The NiCo-LDH/ZnCo2O4 catalyst provided high catalytic activity toward OER under alkaline condition (1.0 M KOH) with a low overpotential of 260 mV to drive the benchmark current density of 10 mA cm−2 and Tafel slope of 62 mV dec−1, as well as long-term stability and high turnover frequency of 0.0641 s−1 at overpotential of 340 mV. The NiCo-LDH/ZnCo2O4 catalyst was found to perform significantly better than NiCo-LDH, ZnCo2O4, NiCo-LDH/Co3O4, Co3O4, and commercial RuO2 catalysts. The outstanding OER performance of NiCo-LDH/ZnCo2O4 catalyst, which may be attributed to the large specific surface area, accelerated mass and electron transport, and synergistic effect of multiple hybrid materials, makes it a promising catalyst for OER.

In-situ generation of platinum nanoparticles on LaCoO3 matrix for soot oxidation

The LaCo0.94Pt0.06O3 catalyst is reduced under 5% H2/Ar at different temperatures to get Pt/LaCoO3 with high catalytic activity for soot oxidation. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), X-ray photoelectron spectroscopy (XPS), H2-temperature programmed reduction (H2-TPR), O2-temperature programmed desorption (O2-TPD) and thermogravimetric analysis (TGA) were used to study the physicochemical properties of the catalyst. SEM and TEM results indicate that Pt nanoparticles (<10 nm) are grown homogeneously on the surface of the LaCoO3 matrix after in-situ reduction. XRD shows that the reduced catalyst has a high symmetrical structure. TGA results indicate that all reduced catalysts exhibit an excellent activity, especially the catalyst reduced at 350 °C (T10 = 338 °C, T50 = 393 °C, T90 = 427 °C). And perovskite is the primary active component. According to XPS study, the high symmetrical structure benefits the mobility of oxygen vacancy, and Pt nanoparticles induce the oxygen vacancy to move to its adjacent situation, resulting in more adsorbed oxygen on the surface of the reduced catalyst and increasing the activity. The possible reaction principle is also proposed.

Straw-Based Activated Carbon: Optimization of the Preparation Procedure and Performance of Volatile Organic Compounds Adsorption.

Straw is one of the largest agricultural biowastes and a potential alternative precursor of activated carbon. Activated carbon prepared from different types of straw have great differences in structure and adsorption performance. In order to explore the performance of different straw-based activated carbon in volatile organic compounds adsorption, five common straws were selected as potential source materials for the preparation of SAC. The straw-based activated carbons were prepared and characterized via a thermo-gravimetric analysis, scanning electron microscope and the Brunauer–Emmett–Teller method. Among the five straw-based activated carbons, millet straw-derived activated carbon exhibited superior properties in SBET, Smic and adsorption capacities of both toluene and ethyl acetate. Furthermore, the preparation process of millet straw activated carbon was optimized via response surface methodology, using carbonization temperature, carbonization time and impregnation ratio as variables and toluene adsorption capacity, ethyl acetate adsorption capacity and activated carbon yield as responses. The optimal preparation conditions include a carbonization temperature of 572 °C, carbonization time of 1.56 h and impregnation ratio (ZnCl2/PM, w/w) of 1.60, which was verified experimentally, resulting in millet straw activated carbon with a toluene adsorption capacity of 321.9 mg/g and ethyl acetate adsorption capacity of 240.4 mg/g. Meanwhile, the adsorption isothermals and regeneration performance of millet straw activated carbon prepared under the optimized conditions were evaluated. The descriptive ability of the isothermals via the Redlich–Peterson equation suggests a heterogeneous surface on millet straw activated carbon. Recyclability testing has shown that millet straw activated carbon maintained a stable adsorption capacity throughout the second to fifth cycles. The results of this work indicate that millet straw activated carbon may be a potential volatile organic compound adsorbent for industrial application.

Study on the Adsorption Properties of Graphene Oxide/Laponite RD/Chitosan Composites.

A novel Graphene oxide/Laponite RD/Chitosan ternary composite was synthesized by sol-gel method and freeze-drying method. The Laponite RD was silanized by 3-aminopropyltriethoxysilane (APTES). Graphene oxide (GO) was prepared by an improved Hummers method. Under the acidic conditions, self-assembly recombination was realized by electrostatic interaction between modified Laponite RD and GO. The results from Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy confirmed that the modified Laponite RD was successfully compounded with GO, and the composite is laminated and stacked. The results from BET (Brunauer–Emmett–Teller) methods found that the BET-specific surface area of the hybrid aerogel significantly increased with the increase of the doping content of the composite, and the specific surface area of the aerogel composite with 20% doping content reached 81 m2/g. The structure of aerogel is porous, and there are numerous holes in the interior, which is closely related to adsorption properties. Thermogravimetric analysis (TG) test was used to explore the change of thermal properties of hybrid aerogel materials, and it was found that the addition of composite increased the initial decomposition temperature and thermal stability of hybrid aerogel. Finally, the potential applications of aerogel were tested, such as methylene blue adsorption and CO2 adsorption.

Auto-combustion fabrication, structural, morphological and photocatalytic activity of CuO/ZnO/MgO nanocomposites

CuO/ZnO/MgO nanocomposites with various amounts of copper oxide (CuO = 0, 0.5, 1 and 2 mol) were fabricated by utilizing the separated white egg and auto-combustion method. The as-fabricated composites were heat treatment at 300 °C and 500 °C for a half-hour, separately. The calcined nanocomposites were examined utilizing various techniques such as X-ray diffraction (XRD), High-Resolution transmission electron microscopy (HR-TEM), Field emission scanning electron microscopy (FE-SEM), Diffuse reflectance spectroscopy (DRS), Fourier Transform Infrared Spectroscopy (FTIR) and UV–Visible spectrophotometer. The surface characteristics of the calcined CuO/ZnO/MgO nanocomposite were estimated employing the Brunauer Emmett Teller method (BET). Photocatalytic activities of the previous nanocomposites were investigated through the decomposition process of reactive red 195 dye with and without H2O2 under UV irradiation. The outcomes revealed that the crystallite size and surface area (SBET) of the calcined nanocomposites (S15, S25, S35 and S45 samples) ranged between 12- 42 nm and 9–20 m2/g, respectively. The particles of the fabricated nanocomposites have different sized and shapes which made the hexagonal and spherical structures. The maximum value of the percentage decomposition of reactive red 195 dye was detected to be 88% after 135 min without H2O2 over the obtained S15 sample. The degradation value of RR195 dye was determined to be 90% after 15 min in the presence of the fabricated S35 sample with H2O2.

Efficient Advanced Oxidation Process (AOP) for Photocatalytic Contaminant Degradation Using Exfoliated Metal-Free Graphitic Carbon Nitride and Visible Light-Emitting Diodes

The photocatalytic performance of metal-free graphitic carbon nitride (g-C3N4) was examined using visible light-emitting diodes (LEDs). A comparative and parametric study was conducted using the photocatalytic degradation of phenol as a model reaction. The g-C3N4 photocatalyst was synthesized from melamine using thermal condensation, followed by a thermal exfoliation that increases the catalyst surface area from 11 to 170 m2/g. Different characterization techniques, namely X-ray powder diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption using the Brunauer–Emmett–Teller method, ultraviolet-visible (UV–vis) spectroscopy, transmission electron microscopy, photoluminescence spectroscopy (PL), and zeta potential analysis, were used to characterize the photocatalyst. A comparison of the photodegradation experiments conducted with a full-spectrum xenon lamp and a custom-made single-wavelength LED immersion lamp showed that the photocatalyst performance was better with the LED immersion lamp. Furthermore, a comparison of the performance of exfoliated and bulk g-C3N4 revealed that exfoliated g-C3N4 completely degraded the pollutant in 90 min, whereas only 25% was degraded with bulk g-C3N4 in 180 min because the exfoliated g-C3N4 enhances the availability of active sites, which promotes the degradation of phenol. Experiments conducted at different pH have shown that acidic pH favors the degradation process. The exfoliated g-C3N4 has shown high photocatalytic performance in the photodegradation of other phenolic compounds, such as catechol, m-cresol, and xylenol, as well.

Hydrothermal synthesis and characterization of Ag2O/CeO2 modified 3D flower-like ZnO as the N-butanol-sensing

In this work, Ag2O/CeO2 modified 3D flower-like ZnO have been synthesized by a novel SDBS−PEG assisted hydrothermal route and the gas sensor fabricated from this material has prominent performance to n-butanol vapor. The 3D microporous ZnO flower-like structures with excellent adsorption property have been indicated by the images of field-emission electron microscopy (FESEM) and the analysis results of Brunauer-Emmett-Teller method (BET). The uniformly dispersed pure phase with high crystallinity existed has been verified by the X-ray diffraction (XRD) patterns combined with the Energy Dispersive Spectrometer (EDS) analysis. The X-ray photoelectron spectroscopy (XPS) further confirmed the co-existence of Ce3+/Ce4+, Ag/Ag+. Meanwhile, the gas sensor of the Ag2O/CeO2 modified ZnO (3 at% Ce, 1 at% Ag) showed the highest response to n-butanol of 100 ppm is 254 at 160 °C. It also exhibits good repeatability and satisfactory selectivity to target gases at 160 °C during gas sensing test. Even more importantly, a particular synergistic enhancement mechanism of Ag2O/CeO2 modified ZnO as the n-butanol-sensing has been explained. Employing SDBS/PEG micelles as structure-directing agent, the process of assembling 2D nanosheets into the 3D microporous ZnO flower-like structures has been discussed.

Insights into the mechanism of hydrogen peroxide activation with biochar produced from anaerobically digested residues at different pyrolysis temperatures for the degradation of BTEXS

The disposal of large amounts of biogas residue from anaerobically digested waste is a burden on environment protection. Porous biochars (BCs) were synthesized from biogas residue at three pyrolysis temperatures (300 °C, 550 °C, and 800 °C) and used to catalyze H2O2 for the degradation of benzene, toluene, ethylbenzene, xylene isomers (ortho, para, and meta), and styrene (BTEXS) to develop a new use for biogas residues. The prepared BCs were characterized through scanning electron microscopy, Brunauer–Emmett–Teller method, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy. Results showed that BC800/H2O2 had the highest BTEXS degradation performance over 6 h. The degradation kinetic data were most consistent with the pseudo-second-order model. The different catalytic effect of the three BCs pyrolyzed at different temperatures were attributed to the dominant active sites (C–O/C–OH/C=C/C=O groups, pyridinic N, and graphitic N) that induced the production of reactive oxygen species (ROS). ROS-quenching experiments indicated that the degradation of BTEXS by BC300/H2O2, BC550/H2O2, and BC800/H2O2 involved ∙OH, ∙O2−, and 1O2. ∙OH was the dominant ROS in BC300/H2O2 and BC550/H2O2, and 1O2 was the dominant ROS in BC800/H2O2. Our findings provided new insight into the different catalytic mechanisms for BC production at different pyrolysis temperatures and demonstrated that a porous BC catalyst with high utilization value could be prepared from biogas residue and could hold considerable potential for application in BTEXS treatment in the future.

Insight into the influence of defect sites in mixed phase of mesoporous titania nanoparticles toward photocatalytic degradation of 2‐chlorophenol: Effect of light source

AbstractThe impact of different light irradiation was studied on photocatalytic degradation of 2‐chlorophenol (2‐CP) using mesoporous titania nanoparticles (MTNs) prepared by microwave‐assisted methods. The photoactivity of MTNs was also compared with pretreated commercial TiO2 and Degussa P25 (P25). The reactions were conducted for 2.5 hr under UV‐A, UV‐C, sunlight, and visible light using a batch reactor. The catalysts were characterized by X‐ray powder diffractometer, UV–Vis diffuse reflectance spectroscopy, photoluminescence, Brunauer–Emmett–Teller method, field‐emission scanning electron microscopy, transmission electron microscopy, and X‐ray photoelectron spectroscopy. The characterization results confirmed that MTN consisted a composition of 21% rutile phase and 79% anatase phase with Ti3+ site defects (TSDs) and oxygen vacancies (OVs) in their structures because of their anionic surfactant nature, microwave heating, and high calcination temperature during the catalyst preparation. Besides, the photoactivity of MTN upon degradation of 2‐CP under sunlight has exhibited the best performance with 100% degradation followed by UV‐A, visible light, and UV‐C with degradation of 96, 52, and 39%, respectively. MTNs showed a remarkable performance due to their mixed‐phase crystalline structures as well as the formation of TSDs and OVs, which improved the charge migration, lowered the band gap energy, and reduced the rate of electron–hole recombination, thus succeeded to be activated under a wide range of light responses.

Occupational exposure during metal additive manufacturing: A case study of laser powder bed fusion of aluminum alloy

Occupational exposure during metal additive manufacturing (Laser Powder Bed Fusion) using an aluminum alloy (AlSi10Mg) was assessed. Background aerosols before manufacturing, powder sieving, machine loading, manufacturing, machine unloading, powder unpacking, and machine cleaning were analyzed. Measurements were taken simultaneously at the source, in the near field, and on the operator during five manufacturing cycles. Aerosol measurement devices and physico-chemical techniques were used to determine the particle number or mass concentration (DiSCmini, core particle counter and sampling cassette), particle size distribution (NanoScan, optical particle detector and impactor), and the shape/size and chemical compositions of the inhalable particles (laser diffraction, inductively coupled plasma spectroscopy, scanning electron microscopy, energy dispersive X-ray microanalysis, and Brunauer–Emmett–Teller Method). The laser powder-bed fusion machine emitted in the additive manufacturing room an inhalable fraction of 2.37 ± 0.35 mg/m3, with an aerosol number concentration ranging from 2 × 104 to 105 #/cm3 and a mass mean aerodynamic diameter of 318 nm. A relatively low concentration level was observed in the near field of the machine with an aerosol number concentration of ∼104 #/cm3. A higher concentration level on the operator was attained during the unpacking and cleaning steps, showing an inhalable fraction of 1.73 ± 0.30 mg/m3. Al and Mg nanoparticles were aerosolized at the source (inside the laser powder-bed fusion machine) with a particle size distribution of 153 nm for Al and 117 nm for Mg and an aerosol number concentration reaching ten times that of the background aerosol level. The number or mass concentration of particles in the room atmosphere was increased to double that of the background aerosol level at specific workstations during manufacturing. Metal additive manufacturing is a source of potential occupational exposure to airborne metal nanoparticles. Particle-counting instruments showed high numbers of nanoparticles and some important peaks of particles ranging from 10 nm to 10 µm or larger at specific work tasks in the Additive Manufacturing (AM) environment. A multimetric approach was used to characterize the particle emissions resulting from this type of additive manufacturing.