Thermogravimetry Mass Spectrometry Research Articles

Effective extraction of nickel and cobalt from sintered nickel alloy via reduction roasting and leaching

In this work, a carbothermic reduction technique is developed to improve the extraction of valuable metals from sintered nickel alloys by atmospheric acid leaching. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS) analyses indicate that NiO in the sintered nickel alloy and the NiO coated by Ni2O3 hinders further dissolution of nickel. Nickel oxides can be transformed into easily leached metallic nickel by carbothermic reduction. The reduction roasting was investigated and optimized by thermodynamic analysis, thermogravimetry-mass spectrometry, XRD, and response surface methodology (RSM). The results show that the leaching efficiencies of nickel and cobalt are respectively increased from 80.34% and 69.92% to 98.65% and 96.71% after the reduction roasting under the optimized conditions: 935 °C of temperature, 50 min of time, and 29.9% of carbon dosage. The leaching of nickel was optimized by single-factor test method and the optimum conditions have been established as: 150 g/L of H2SO4 concentration, 25% of H2O2 dosage, 10 mL/g of liquid–solid ratio, 400 rpm of stirring speed, 80 °C of temperature, and 80 min of time. The kinetic analysis of leaching process shows that the activation energies of nickel and cobalt leaching are 20.71 kJ/mol and 16.33 kJ/mol, respectively, indicating that the leaching process is an internal diffusion control process. This study provides a feasible and effective approach to extract nickel from sintered alloys.

Analysis of the catalytic pyrolysis of shale gas oil‐based drill cuttings via TG‐MS

AbstractBACKGROUNDShale gas oil‐based drill cuttings are receiving increasing attention because of their hazards and contamination. In this study, two catalysts (Fe2(SO4)3 and a synthesised catalyst) were used to study the pyrolysis products, possible reaction mechanisms, and kinetic characteristics via thermogravimetry‐mass spectrometry (TG‐MS) analysis.RESULTSThe results indicate that the synthesised catalyst, YAP‐3, exhibited an improved catalytic effect on the pyrolysis of drill cuttings with a good conversion rate. The reaction activation energy during the pyrolysis was reduced from 9.6 to 1.4 kJ/mol. In addition to hydrocarbons, the pyrolysis products contained nitrogen oxides and other compounds.CONCLUSIONA comparison of the peak temperature range and response intensity of the same substance with the same mass‐to‐charge ratio (m/z) showed that YAP‐3 significantly promoted the formation of pyrolysis products. This study provides theoretical support for the catalytic pyrolysis treatment of shale gas drill cuttings. © 2023 Society of Chemical Industry.

Alterations promoted by acid straightening and/or bleaching in hair microstructures.

Human hair is a biopolymer constituted mainly of keratin intermediate filaments, lipids, pigments and water. Cosmetic treatments usually interact with the hair at the molecular level, inducing changes in its components and modifying the physicochemical and mechanical properties of the fibers. Here, the effect of acid straightening on the morphology and ultrastructure of Caucasian hair was investigated by a group of complementary experimental methods: wide-, small- and ultra-small-angle X-ray scattering; high-resolution 3D X-ray microscopy; quasi-elastic neutron scattering and inelastic neutron scattering; thermogravimetry-mass spectrometry; and differential scanning calorimetry (DSC). X-ray diffraction patterns showed that acid straightening associated with a flat iron (∼180°C) changed the cortex of the fiber, shown by denaturation of the intermediate filaments (measured by DSC). The increase in the spacing of the lipid layers and the observation of the dehydration behavior of the fiber provided indications that water may be confined between these layers, while neutron spectroscopy showed alterations in the vibration mode of the CH2 groups of the lipids and an increase of the proton (H+) mobility in the hair structure. The latter may be associated with the extremely low pH of the formulation (pH ≃ 1). Additionally, this investigation showed that bleached hair (one-time bleached) is more damaged by the action of acid straightening than virgin hair, which was shown by a threefold increase in the percentage of total porosity of the tresses. The obtained results demonstrate that the investigation approach proposed here can provide very important thermodynamic and structural information on induced changes of hair structure, and certainly can be applied for the evaluation of the action mode and efficiency of cosmetic treatments.

Thermal characterization of leathers tanned by metal salts and vegetable tannins

In this work, the thermal properties of vegetable (mimosa), metal salt (chromium) and mixed (chromium-mimosa and aluminum-myrobalan) tanned bovine leathers were studied to understand the thermal decomposition processes with the aim of possible utilization of various leather wastes by thermal conversion. Thermogravimetry/mass spectrometry (TG/MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) measurements were carried out to compare the thermal behavior and reveal interactions between the leather and various tannins. Bovine parchment was used as an untanned reference material. The tanning agent ratios were estimated by determination of ash, nitrogen and protein contents of the samples. It was found that ash yield is a good indicator for the inorganic content, while the protein content is inversely proportional to the total tannin content in leathers. The thermal decomposition of the samples as a function of the temperature was performed using TG/MS. The differences between the samples are clearly recognizable on the thermogravimetric curves and the mass spectrometric evolution profiles of the products. Among the tanning agents, chromium had the largest impact on the thermal decomposition process. Therefore, additional TG/MS experiments were carried out on chromium-treated parchment samples and the catalytic effect of chromium was demonstrated on the evolution curves of several products. It was established that hydrolysis of the amide bonds of the polypeptide chain was retarded resulting in less ammonia formation, and higher yield of water. On the other hand, higher amounts of hydrogen cyanide and other nitriles were released in the presence of chromium sulfate. The decomposing chromium sulfate released oxygen beside sulfur dioxide, which dehydrogenated certain amino acid residues leading to the enhanced formation of nitriles and water. The volatile compounds of the decomposition were determined by Py-GC/MS at 400 and 600 °C. The diketopiperazines (DKPs) dominated the pyrograms at both temperatures, but the ratio of gaseous and other products of smaller molecular mass was increased at higher pyrolysis temperature and in the presence of metal tanning agents. The chromium-treated parchment samples were also studied by Py-GC/MS. The relationship between the chromium content and the formation of certain decomposition products has been confirmed. Principal component analysis (PCA) was performed using the Py-GC/MS data of leathers and parchment. The PCA results show clear separation between the chromium-tanned, vegetable-tanned and mix-tanned leathers as well as parchment.

Cotton-Based Activated Carbon Fiber with High Specific Surface Area Prepared by Low-Temperature Hydrothermal Carbonization with Urea Enhancement

The traditional preparation method of activated carbon fiber is high-temperature carbonization and activation. In this experiment, cotton-based activated carbon fiber was prepared by urea-enhanced low-temperature hydrothermal carbonization and activation method. A specific surface area of 2304.8 m2/g of activated carbon fiber prepared by low-temperature hydrothermal carbonization with urea enhancement was the maximum reported using biomass as a raw material, which was higher than that of activated carbon fibers prepared by other biomass raw materials. X-ray photoelectron spectroscopy and elemental analysis studies have shown that the form of N transformed and decomposed during the high-temperature process, leading to the separation of C–N. Thermogravimetry mass spectrometry characterization analysis found that K2CO3 of low-temperature hydrothermal-assisted KOH activation may fully react with the N-containing group produced during the carbonization process to generate NH3, which lead to the formation of more pore structures in the carbon materials. The adsorption capacity of activated carbon fiber activated by hydrothermal-assisted KOH for iodine could reach up to 2254.8 mg/g. This process provides a new idea for the preparation of high-performance activated carbon fibers.

Structure phase engineering strategy through acetic acid coupling to boost hydrogen evolution reaction performance of 2H phase MoS2 at wide pH range

The semiconductor phase molybdenum disulfide (2H-MoS2) with poor hydrogen evolution reaction (HER) performance restricts the further improvement of hydrogen production. Herein, an acetic acid coupled structure phase engineering (SPE) strategy is developed to synthesize a homogeneous and orderly cobalt molybdenum composite structure. The resulting CoS2/MoS2 complexes reveal excellent HER activity with a low overpotential of 80, 95, and 135 mV at 10 mA cm−2 in 0.5 M H2SO4, 1 M KOH, and 1 M PBS. Fourier transform infrared spectroscopy (FT-IR) and thermogravimetry mass spectrometry (TGA-MS) results illustrate that acetic acid is successfully coupled at the interface between CoS2 and MoS2. Results from density functional theory demonstrate that the π-π conjunction formed by acetic acid coupling can work as a bridge to help electrons transfer from cobalt to molybdenum. More importantly, the method can be extended to the synthesis of other composite materials with the similar structure.

Effects of hafnium sources and hafnium content on the structures and properties of SiBNC–Hf ceramic precursors

AbstractThe synthesis of SiBNC–M (M is metal element) multinary ceramic precursors has mainly been through chemical modification of the SiBNC ceramic precursors with the introduction of the metal element/compound. This misses the simplicity, efficiency, and combined benefits of single reactor synthesis routes. We herein adopt a one‐pot method to synthesize SiBNC–Hf ceramic precursors (PBSHZ) from different Hf sources, and with varying Hf content. The starting materials include hafnium tetrachloride, hafnium dichloride, trichlorosilane, hexamethyldisilazane, and boron trichloride. Fourier transform infrared spectroscopy (FT‐IR), nuclear magnetic resonance (NMR), X‐ray photoelectron spectroscopy (XPS), and thermogravimetric analysis are employed to characterize the structures and properties of the PBSHZ. The results reveal the successful incorporation of Hf into the precursors. Compared to the hafnium tetrachloride source, the precursor synthesized from hafnium dichloride yields more ceramics and shows better solubility, due to fewer Hf–Cl bonds available for reaction. Meanwhile, there is a positive correlation between the rise in the Hf content of PBSHZ and the ceramic yield. However, the solubility and processability of the precursors decline, due to the multiplication of the cross‐linking degree in the molecular structure. Further FT‐IR, NMR, XPS, and thermogravimetry–mass spectrometry (TG–MS) analysis indicate a full polymer‐to‐ceramic transformation at 1000°C pyrolysis temperature. At this point, the SiBNC–Hf ceramics mainly consist of an Si–B–N skeleton, HfN, and free carbon.

Thermal studies of novel heat-resistant 3,6-dinitropyrazolo[4,3-c]pyrazole-based energetic materials

1,4-Bis(2′,4′,6′-trinitrophenyl)−3,6-dinitro[4,3-c]pyrazole (DTNBDNP) is a newly developed heat-resistant explosive exhibiting superior properties to most traditional heat-resistant energetic materials with a significantly high thermal decomposition temperature of 410 °C. Detailed thermal behaviors and nonisothermal decomposition kinetics of DTNBDNP and 1,4-bis(2′,4′-dinitrophenyl)−3,6-dinitro[4,3-c]pyrazole (DDNBDNP) were investigated using a differential scanning calorimeter (DSC), and the thermal safety was evaluated by different criteria, including the self-accelerating decomposition temperature and critical temperature of thermal explosion. Their thermodynamic functions were also obtained based on the specific heat capacity data determined using a micro-DSC method. Further studies on the thermal decomposition mechanism were carried out through condensed-phase thermolysis/Fourier transform infrared (in situ FTIR) spectroscopy and the combination of differential scanning calorimetry–thermogravimetry–mass spectrometry–Fourier transform infrared spectroscopy (DSC–TG–MS–FTIR) techniques. The experimental results prove that the decomposition of DTNBDNP and DDNBDNP is most likely to begin with a ring-opening reaction of the fused-heterocycle backbone. In addition, the main gaseous products, including NO, CO2, N2O, and NO2, are released from the decomposition of DTNBDNP and DDNBDNP.

Study on the multiple roles of CaO on nitrogen evolution mechanism of protein inside sewage sludge pyrolysis

The aim of this study was to clarify the multiple influence mechanisms through which Ca influences the emission of NOx precursors (NH3 and HCN) during sewage sludge pyrolysis and to establish a scientific correlation between the mechanisms and temperatures. In this study, the effects of CaO on pyrolysis kinetics and NOx precursor emission temperature of deashed sludge were estimated using Thermogravimetry-mass spectrometry. Based on this, the NH3 and HCN evolution pathways were investigated at these nitrogen emission temperatures by employing sludge protein model compounds in a self-designed all-quartz pyrolysis system. Results showed that the addition of CaO reduced the activation energy of sludge pyrolysis by approximately 0–40 kJ/mol. CaO promoted the retention of nitrogen in char and the conversion of nitrogen into gas phase while hampering its migration to tar. The Ca-fixed nitrogen in char reacted with NH3/HCN to form CaCxNy, such as CaCN2 and CaN2. Notably, results revealed the overwhelming effects of temperature on nitrogen evolution. Specifically, CaO was found to affect only the dominant reaction at the target temperature. At lower temperatures (255–350 °C), CaO promoted the conversion of protein-N to NH3 and inhibited nitrile-N decomposition to HCN in char. In contrast, at comparatively higher temperatures (490–750 °C), CaO inhibited the production of NH3 by promoting the hydrogenation of heterocyclic-N in char and the dimerization of amino acid molecules in tar, while CaO increased HCN release by promoting the dehydrogenation of amine-N in tar and ring opening of heterocyclic-N to form nitrile-N and subsequently HCN. These results would guide NOx control for obtaining energy from nitrogen-rich solid waste for industrial applications and the targeted regulation of NH3 (carbon-free hydrogen-rich fuels) utilization.

Predicting Pyrolysis of a Wide Variety of Petroleum Coke Using an Independent Parallel Reaction Model and a Backpropagation Neural Network

In this work, the pyrolysis behavior and gaseous products of petroleum coke were investigated by nonisothermal thermogravimetric analysis (TGA) and thermogravimetry-mass spectrometry (TG-MS). Then, the pyrolysis kinetics of six kinds of petroleum coke (Fushun (FS), Fuyu (FY), Wuhan (WH), Zhenhai (ZH), Qilu (QL), and Shijiazhuang (SJZ)) were determined by an independent parallel reaction (IPR) model, and the kinetic parameters (activation energy and preexponential factor) were obtained. In addition, an efficient backpropagation neural network (BPNN) was developed to predict the thermal data of six kinds of petroleum coke. The BPNN-predicted thermal data were used to calculate the kinetic parameters based on the IPR model, and the results were compared with the ones calculated using experimental data. The results showed that the pyrolysis process of six kinds of petroleum coke was divided into three stages, of which stage II (250-900 °C) had the significant mass loss, corresponding to the devolatilization of petroleum coke. MS fragmented ion intensity analysis indicated that the main pyrolysis products were methane CH x (m/z = 13, 14, 15, and 16), aliphatic hydrocarbon C3H5, H2, CO, CO2, and H2O. The thermal data predicted by the IPR, BPNN, and BPNN-IPR (BPNN combined with IPR) models were in good agreement with the experimental data. Most importantly, it was concluded that the BPNN-predicted data can be further applied to calculate the kinetic parameters using the IPR kinetic model.

Enhanced catalytic activity and ignition characteristics of three-dimensional ordered macroporous FeCo2O4 through controlled synthesis

To improve the combustion performance of solid propellants relies on efficient combustion catalyst with large specific surface area and high density of active sites. In this work, three-dimensional ordered macroporous FeCo2O4 (3DOM-FeCo2O4) with four different pore diameters was successfully prepared using polymethyl methacrylate (PMMA) colloidal crystals as a template. Differential scanning calorimetry (DSC) study shows that 3DOM-FeCo2O4 with a pore diameter of 176 nm has the best catalytic performance on the thermolysis of ammonium perchlorate (AP). The decomposition peak temperature and apparent activation energy were reduced by 116.5 ℃ and 26.1 kJ/mol, respectively. Thermogravimetry/mass spectrometry (TG/MS) was used to analyze the catalytic mechanism. The result indicates that 3DOM-FeCo2O4 can accelerate the electron transfer from ClO4– to NH4+ to form HClO4 and NH3 and the transformation from O2 to superoxide ion(O2–), thus providing active sites for intermediate products of AP and catalyzing the decomposition of AP. Furthermore, the heat release and ignition tests of thermites using 3DOM-FeCo2O4 as the oxidant were carried out. The thermite with a pore diameter of 215 nm exhibits higher heat release and better ignition characteristic compared to the thermites with other pore diameters.

Self-Plasticized PVC Prepared by Introducing Fatty Acid to the PVC with Triglycidyl Isocyanurate as an Intermediate Bridge.

The phthalate-free self-plasticization of poly(vinyl chloride) (PVC) conforms to the concept of green chemistry. In this work, phthalate-free, biocontaining, self-plasticized PVC with nonmigration (4-an-TG-X-PVC; X = R, P, or O) was prepared by covalent attachment of ricinoleic acid, palmitic acid, and oleic acid, respectively, to the PVC matrix with 4-aminothiophenol and triglycidyl isocyanurate (TGIC) as intermediate bridges. 4-Aminothiophenol and TGIC acted as the nucleophilic reagent and the thermally stable substance, respectively. The 4-an-TG-X-PVC was observed by diverse characterization methods. Specifically, Fourier transform infrared spectra, 1H nuclear magnetic resonance, gel permeation chromatography, and migration stability tests proved the successful synthesis of 4-an-TG-X-PVC. Compared to the neat PVC, the mechanical property of 4-an-TG-X-PVC is better. The glass transition temperature (Tg) of PVC is 81.24 °C, while that of 4-an-TG-X-PVC decreased to 41.88, 31.49, and 46.91 °C. The 4-an-TG-X-PVC showed higher elongation at break and lower tensile strength than neat PVC. Simultaneously, the thermal property of 4-an-TG-X-PVC got a boost. Thermogravimetry–infrared and thermogravimetry–mass spectrometry showed that 4-an-TG-X-PVC released less HCl than neat PVC in a thermal environment. Discoloration experiments demonstrated that 4-an-TG-P-PVC had better heat stabilization and better color than 4-an-TG-O-PVC and 4-an-TG-R-PVC. This work provides a viable solution to the dependence on phthalates, reduced human health and ecological risks, and endowed PVC with improved thermal stability and nonmigration performance.

A novel application of thermogravimetry-mass spectrometry for polystyrene quantification in the PM10 and PM2.5 fractions of airborne microplastics

Microplastics have appeared as emerging pollutants due to the diverse applications of plastics in today's world. Growing evidence points to the negative impacts that airborne microplastics have on human health, as they can enter the human body through respiration. Our aim was to quantify polystyrene airborne microplastics in smaller fractions, thoracic (PM10) and alveolar (PM2.5), as they have scarcely been studied. In this work, we proposed a methodology based on thermogravimetric analysis coupled with mass spectrometry that requires minimal sample preparation and does not limit particle size. We applied this methodology to quantify the airborne polystyrene in PM10 and PM2.5 fractions in mass units of microplastics per m3 of air in an urban and agricultural region during the summer of 2021. The mean concentrations of polystyrene found in the PM10 and PM2.5 fractions were 2.09 and 1.81 ng m−3, respectively. Therefore, the majority of airborne polystyrene microplastics are found in the alveolar fraction which, is associated with severe cardiopulmonary and respiratory diseases. According to air mass backward trajectories, it was noted that the main sources of these emerging pollutants could be related to local agricultural practices.

Study on the thermal decomposition mechanism of Mg(NO3)2·6H2O from the perspective of resource utilization of magnesium slag

ABSTRACT The magnesium slag (magnesium nitrate hydrate Mg(NO3)2·6H2O) produced in the nitric acid leaching process of laterite nickel ore can be effectively recycled by thermal decomposition. To this end, this study placed great emphasis on disclosing the thermal decomposition mechanism of Mg(NO3)2·6H2O. Firstly, thermal decomposition paths of Mg(NO3)2·6H2O were revealed through Thermogravimetry-Mass Spectrometry, Differential Scanning Calorimetry and powder X-ray diffraction. It was found that the thermal decomposition of Mg(NO3)2·6H2O was a multistep endothermic reaction involving two dehydration stages and one denitration stage. The two dehydration stages were characterized by the evolution of H2O, with the formation of magnesium nitrate dihydrate and anhydrous magnesium nitrate. The denitration stage was characterized by the simultaneous evolution of O2 and NO2, with the formation of MgO. The conventional kinetic analysis was not suitable for describing such complex multistep reaction behaviour. Thus, the kinetic rate data (dα/dt-T) for the overall reaction were separated into those for three contributing stages by mathematical peak deconvolution. Then, the complete kinetic interpretations of the separated reaction stages for Mg(NO3)2·6H2O pyrolysis were achieved by the Friedman method and the master plots method. Finally, the original experimental α-T curves were successfully simulated using the resulting kinetic triplets.

Unveiling the mechanisms of carbon conversion and loss in biochars derived from characteristic lignocellulosic biomass

The relationship between biomass components and carbon retention or loss in biochars is unclear. In this study, four characteristic feedstocks were pyrolyzed into biochar, and the conversion and stability of carbon in biochar were studied in detail. Thirteen kinds of ion fragments were detected by thermogravimetry - mass spectrometry (TG-MS), among which H2O, CO2 and CO were the main gas products. In addition, the presence of lignin slowed that the pyrolysis of biomass and produced more CO, which eventually led to more aromatic biochar. The carbon retention of lignin, cellulose and xylan during pyrolysis was 78.7 %, 41.7 % and 40.2 %, respectively. Carbon retention calculations showed that lignin was a major contributor to the formation of biochar (40.1–53.2 %). In the K2Cr2O7 oxidation experiment, the carbon stability of sunflower and cotton stalk char was relatively poor, which was consistent with the results of thermal stability. Spectral characterization analysis showed that biomass with low lignin content generated more unstable carbon during pyrolysis, which was more likely to be lost or converted in an oxidized environment. These findings are meaningful for guiding in biochars preparation and avoiding their environmental risks.

Green emitting β$\ubeta$‐SiAlON:Eu2+ phosphors derived from chemically modified perhydropolysilazanes

AbstractWe report the first synthesis of β‐SiAlON:Eu2+ phosphors from single‐source precursors, perhydropolysilazane (PHPS), chemically modified with Al(OCH(CH3)2)3, and EuCl2. The reactions occurring during the precursor synthesis and the subsequent thermal conversion of polymeric precursors into β‐SiAlON:Eu2+ phosphors have been studied by a complementary set of analytical techniques, including infrared spectroscopy, gas chromatography–mass spectrometry, thermogravimetry–mass spectrometry, X‐ray diffraction (XRD), photoluminescence spectroscopy, and scanning electron microscopy. It has been clearly established that Al(OCH(CH3)2)3 immediately reacted with PHPS to afford N–Al bonds at room temperature, whereas N–Eu bond formation was suggested to proceed above 600°C accompanied by the elimination of HCl up to 1000°C in flowing N2. The subsequent 1800°C‐heat treatment for 1 h under an N2 gas pressure at 980 kPa allowed converting the single‐source precursors into fine‐grained β‐SiAlON:Eu2+ phosphors. XRD analysis revealed that the Al/Si of .09 was the critical atomic ratio in the precursor synthesis to afford single‐phase β‐SiAlON (z = .55). Moreover, Eu2+‐doping was found to efficiently reduce the carbon impurity in the host β‐SiAlON. The polymer‐derived β‐SiAlON:Eu2+ phosphors exhibited green emission under excitation at 460 nm and achieved the highest green emission intensity at the critical dopant Eu2+ concentration at 1.48 at%.

Preparation of a Chitosan-Lead Composite Carbon Aerogel and Its Catalytic Thermal Decomposition Performance on Ammonium Perchlorate.

Chitosan-lead (CS-Pb) carbon aerogels were prepared by ionic cross-linking and high-temperature carbonization using chitosan (CS) as the carbon precursor. The obtained carbon aerogels were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), and X-ray photoelectron spectroscopy (XPS). The obtained aerogels have a 3D structure and a large surface area, which can effectively prevent the agglomeration phenomenon of metals. Differential thermal analysis (DTA) was used to analyze the catalytic performance of a carbon aerogel for ammonium perchlorate (AP). The results showed that the CS-Pb carbon aerogel reduced the peak temperature of AP pyrolysis from 703.9 to 627.7 K. According to the Kissinger method calculations, the Ea of AP decomposition decreased about 27.2 kJ/mol. The TG data at different warming rates were analyzed by the Flynne-Walle-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods, which are two of the isoconversion methods, and the activation energies of AP and AP+CS-Pb-3.5 were calculated. Between the conversion degrees (α) of 0.1 and 0.9, the Ea values obtained by the two isoconversion methods are similar and have a certain match. Also, the two isoconversion methods confirm Kissinger's calculation. Finally, thermogravimetry-mass spectrometry (TG-MS) was used to monitor the gases generated during the thermal decomposition of the AP+CS-Pb-3.5 system in real time.

Chemical route for synthesis of β-SiAlON:Eu2+ phosphors combining polymer-derived ceramics route with non-hydrolytic sol-gel chemistry

We report the synthesis of β-SiAlON:Eu2+ phosphors from novel single source precursors in which strictly controlled chemical composition is established at molecular scale. The two-step synthesis occurs by the chemical modification of perhydropolysilazane (PHPS) with Al(OCH(CH3)2)3 and AlCl3 in xylene at room temperature to 140 °C to introduce Al in the PHPS network while controlling the oxygen content followed by the reaction of EuCl2 with the Al-modified PHPS upon heat-treatment. Gas chromatography-mass spectrometry and thermogravimetry-mass spectrometry analyses revealed that PHPS reacted with Al(OCH(CH3)2)3 and AlCl3 via the formation of Al-N bonds. Moreover, AlCl3 reacted with nitrogen-bonded Al alkoxide residue to release 2-chloropropane in an analogy to the non-hydrolytic sol-gel reaction between metal alkoxide and metal chloride. Subsequently, AlCl3 acted as a Lewis acid catalyst to promote the Friedel-Craft alkylation between xylene solvent and the 2-chloropropane formed in-situ to afford dimethylcumene. On the other hand, EuCl2 reacted with silylamino moiety to form Eu-N bonds at around 850 °C. β-SiAlON:Eu2+ phosphors were successfully synthesized by pyrolysis of the precursors under flowing N2 or NH3 at 1000 °C, followed by heat treatment at 1800 °C for 1 h under a N2 gas pressure at 980 kPa. The polymer-derived β-SiAlON:Eu2+ (z = 0.55, Eu2+ 0.37 at%) exhibited green emission under excitation at 410 or 460 nm, and the green emission intensity under the excitation at 410 nm was found to be increased by reducing the carbon and chlorine impurities through the polymer-derived ceramics route investigated in this study.

Microplastics in dyeing sludge: Whether do they affect sludge incineration?

Microplastics (MPs), as emerging contaminant detected in dyeing sludge (DS), inevitably affected the subsequent treatment and disposal of DS. However, the effect of MPs on the predominant disposal path (incineration) of DS remains far from explicit. This study used thermogravimetry-mass spectrometry (TG-MS) method to explore the effect of representative MPs, polyethylene terephthalate (PET) and polyvinyl chloride (PVC), on combustion characteristics, gas evolution and kinetics on DS combustion. Results showed that PET inhibited the whole combustion of DS by physical barrier. Relatively, PVC delayed the combustion of light volatile but promoted heavy volatile and char reaction due to HCl catalyst. Generally, MPs deteriorated the combustibility, burnout performance and combustion stability of DS. MPs aggravated HCl and gaseous N emissions. Noticeably, the interactions between DS and PVC accelerated the emissions of gaseous pollutants, especially under high dose condition. DAEM and FWO models could well describe the combustion kinetic of DS containing MPs. MPs led to an increase in activation energy of DS, namely, it deteriorated the combustion efficiency of DS. The combustion mechanisms could be divided into two stages: (1) diffusion (D3) stage: melted MPs blocked the gas channels, (2) chemical reaction (F3): the residual chars were thermally stable.

Release of nitrogen during thermochemical conversion of Shenhua bituminous coal under Ar, CO2, and air atmospheres

AbstractCoal thermochemical conversion processes unavoidably generate gaseous pollutants, endangering the environment or influencing synthetic processes downstream. In order to display the differences in release behaviours of nitrogen among different coal thermochemical conversion stages, the nitrogen release characteristics of Shenhua bituminous coal under Ar, CO2, and air atmospheres were investigated using X‐ray photoelectron spectrum (XPS) and thermogravimetry‐mass spectrometry (TG‐MS). Results indicate that the reaction atmosphere has an important influence on nitrogen release. The total released mass of nitrogen when using 100 g raw coal in the whole experiment under Ar, CO2, and air atmospheres is 0.54, 0.64, and 0.75 g, respectively. The organic forms of nitrogen in raw coal and coal char are pyridine nitrogen (N‐6), pyrrole nitrogen (N‐5), quaternary nitrogen (N‐Q), and nitrogen oxide (N‐X). While in the coal ash, the sub‐peaks of N‐Q and N‐X disappear entirely, leaving only N‐5 and N‐6 sub‐peaks. The released nitrogen‐containing gas consists of NH3, HCN, NO, and NO2 during experiments in CO2 and air atmospheres. However, only NH3 and HCN are detected during experiments in the Ar atmosphere. The revolution characteristics of NH3 and HCN under Ar and CO2 atmospheres are similar.