Partial Thermal Decomposition Research Articles

Full utilization of Cu single atoms on carbon nitride nanofibers for enhanced Fenton-like degradation of methylene blue

The utilization efficiency of single atoms is limited by the active sites being buried in support. To maximize atom utilization, Cu single atoms are anchored on the external surface of g-C3N4 nanofibers (CNNFs), which are fabricated by partial thermal decomposition and subsequent self-assembly in H2O. The abundant N and O-containing functional groups of CNNFs are vital for the loading of Cu. Benefited from the full utilization of Cu sites, CNNF-Cu exhibits excellent Fenton-like catalytic activity for Methylene Blue degradation. The reaction kinetic constant is more than 10 times higher than that of the traditional single-atom catalyst with Cu sites evenly distributed throughout the entire support. CNNF-Cu maintains most of its catalytic activity after five cycle tests, suggesting good stability. This work provides a convenient method to maximize the utilization of single metal atoms for catalytic applications.

Upcycling plastic waste into syngas by staged chemical looping gasification with modified Fe-based oxygen carriers

A novel staged approach, termed staged chemical looping gasification (SCLG) was proposed in this work, for the efficient upcycling of plastic waste into H2-rich syngas with exceptional carbon conversion reaching up to 99%. In such staged system, plastic was firstly pyrolyzed to generate hydrocarbon volatiles, followed by chemical looping reforming in the presence of oxygen carriers, and steam and air was also feed in sequence for carbon removal, syngas regulation and lattice oxygen recovery. A series of Fe-M-Al oxygen carriers (OCs, where M represents Mg, Ca, Mn, Mo, La, Ce) were synthesized and employed for SCLG of waste disposable masks. The performance and stability of these OCs were thoroughly investigated and compared in terms of H2 content and syngas production, while the physicochemical properties characterized by various techniques such as N2 isothermal adsorption-desorption, FESEM, XRD, TPO, and H2-TPR. Results showed that compared with the controlled FeAl sample, all the six modified OCs exhibited higher activity towards syngas production, due to the simultaneously enhanced both partial oxidation reactions and thermal decomposition reactions during the proposed SCLG process. However, the modifiers displayed different role for promoting gasification. Specifically, the addition of Ca significantly promoted the thermal cracking of plastic pyrolysis volatiles and lead to the deep extraction of carbon and H2, whereas the deposited carbon was further gasified into syngas in steam stage. As a result, Fe-Ca-Al showed the highest syngas yield and carbon conversion of 177.89 mmol/gOC and 99.03%, respectively. Fe-Mg-Al possessed relatively high CO selectivity, with the CO/(CO + CO2) ratio of 90.40%. The presence of MoO3 made the Fe-Mo-Al equipped with strong oxygen supply ability, leading to high content of oxygen-containing gases. Furthermore, the cycle stability of OCs was also conducted. The slight decrease in activity of Fe-Ca-Al was due to the metal sintering, whereas Fe-Mo-Al presented relatively stable syngas yield. The proposed staged chemical looping gasification with modified FeAl was demonstrated as a promising upcycling utilization of disposal plastic waste.

Nitrogen-doped CNTs enhance heterogeneous Fenton reaction for IOH removal by FeOCl: Role of NCNTs and mechanism

Heterogeneous Fenton has already been usedextensively to remove emerging contaminants, however, sluggish Fe(III)/Fe(II) circulation and high mass-transport resistance are its two major limitations. In this study, a novel heterogeneous N-doped carbon nanotubes loaded nano-FeOCl (NCF) catalyst was synthesized by partial thermal decomposition to enhance its catalytic performance. By incorporating NCNTs, the specific surface area of NCF was significantly increased in comparisontoFeOCl, which promotes the accumulation of contaminants on the catalyst surface. Similarly, the degradation rate constant (k) of IOH in the NCF/H2O2 system was observed 114 times greater than that of the FeOCl/H2O2 system. Besides not significantly increased k, excessive H2O2 substantially reduced H2O2 utilization. Electron paramagnetic resonance and electrochemical analysis reflected that the NCNTs facilitated the Fe(III)/Fe(II) circulation by improving electron transfer and enhanced •OH, O2•− and 1O2 availability by exerting a confinement effect. The major reactions assumed in IOH degradation include hydrogen atom abstract, amide hydrolysis, deiodination reaction, •OH radical adduct formation, and oxidation of C-OH. This study elucidates the degradation mechanism of IOH in the heterogeneous Fenton system with carbon-based co-catalysts and provides an efficient measure for removing emerging contaminants from the environment.

DBD plasma assisted synthesis of MO@Fe/Ce-MOFs with rich oxygen defects as efficient photocatalysts for nitrogen fixation

A series of metal oxide/ metal-organic frameworks (MOFs) composites (MO@Fe/Ce-MOFs) were synthesized by partial thermal decomposition of Fe/Ce-MOFs which were synthesized with dielectric barrier discharge (DBD) plasma. The heterojunction interface between MOFs and metal oxides can effectively promote the electron interface transfer. When Fe was introduced, the energy band of the catalysts became narrower, and the increase of oxygen defects concentration slowed down the recombination rate of photogenerated electrons and holes, which greatly improved the photocatalytic performance. MO@Fe/Ce-MOFs exhibited more efficient visible light photocatalytic performance than that of Fe/Ce-MOFs. MO@Fe/Ce-MOFs-b (the molar ratio of Fe to Ce is 1:3) formed an abundant oxygen defect that facilitated the photocatalytic nitrogen fixation reaction. For MO@Fe/Ce-MOFs-b, the NH4+ generation rate reached 299 μmol·L−1·h−1 after 2 h photoreaction under visible light with N2 and deionized water as solvent. Also, MO@Fe/Ce-MOFs-b showed high cyclic stability. After three repeated cycles, the NH4+ generation rate maintained about 95%. This work provided a new method for the preparation of MO@MOFs and emphasized the importance of oxygen defects in nitrogen fixation.

Mathematical Model and Numerical Method of Calculating the Dynamics of High-Temperature Drying of Milled Peat for the Production of Fuel Briquettes

Milled peat must be dried for the production of peat fuel briquettes. The current trend in the creation of drying technologies is the intensification of the dehydration process while obtaining a high-quality final product. An increase in the temperature of the drying agent, above 300 °C, significantly accelerates the reaching of the final moisture content of the peat. In the final stage, it is also accompanied by partial thermal decomposition of the solid phase. Its first stage, which is the decomposition of hemicellulose, contributes to a decrease in weight and an increase in the caloric content of the dry residue. The development of high-temperature drying modes consists of determining the temperature and velocity of the drying agent, wherein the duration of the material reaching the equilibrium moisture content will be minimal and the temperature of the material will not rise above the second-stage decomposition temperature of cellulose. This problem can be solved by the mathematical modeling of the dynamics of peat particles drying in the flow. The article presents a mathematical model of heat and mass transfer, phase transitions, and shrinkage during the dehydration of milled peat particles. The equations of the mathematical model were built based on the differential equation of mass transfer in open deformable systems, which, in the absence of deformations, turns into the known equation of state. A numerical method for implementing a mathematical model has been developed. The adequacy of the mathematical model is confirmed by comparing the results of numerical modeling with known experimental data.

Structure of two NH4BiF4 polymorph modifications. Ionic motion in NH4BiF4 and cubic products of its partial thermal decomposition

The conditions for the synthesis of two polymorph modifications of ammonium tetrafluorobismutate (III) from the heated water solution of ammonium fluoride (bifluoride) were studied with different BiF3:NH4HF2(NH4F) reagent concentrations. The crystal structure of monoclinic β–NH4BiF4 (a ​= ​8.1014(3), b ​= ​6.6208(2), c ​= ​8.1045(3) Å, β ​= ​111.003(1)°, sp.gr. P21/c) was determined for the first time. The structure of α–NH4BiF4 (a ​= ​8.3185(6), b ​= ​7.5902(6), c ​= ​6.4866(5) Å, β ​= ​93.687(1)°, sp.gr. P21/c) was refined. Both polymorph modifications have layered structures with a single nine-coordinated bismuth site. The thermal decomposition of NH4BiF4 was studied and two products of the decomposition having a cubic structure were isolated. The fluorine and ammonium mobility in obtained phases was probed with 1H, 19F NMR.

Fabrication of FeOCl/MoS2 catalytic membranes for pollutant degradation and alleviating membrane fouling with peroxymonosulfate activation

The combination of advanced oxidation (AOPs) and membrane separation technology provides a prospect for catalyst recovery and alleviation of membrane fouling. Herein, we prepared FeOCl/MoS2 catalysts for activating peroxymonosulfate (PMS) by a simple partial thermal decomposition method. Then, the FeOCl/MoS2 was immobilized onto a polyvinylidene fluoride (PVDF) membrane coated by polydopamine (PDA) through vacuum filtration. FeOCl/MoS2 can remove 96.9% of rhodamine B (RhB) within 5 min. Notably, with a pH range from 3 to 9, FeOCl/MoS2 exhibited high catalytic efficiency. Besides, the surface hydrophilicity of the PVDF membrane was significantly improved by the modification. The flux recovery rate (FRR) of the modified membrane reached 97.6%, which was 42.7% higher than that of the pristine membrane. With dead-end filtration, 72.2% of the pollutants can be removed. After 5 runs, the fabricated FeOCl/MoS2 membrane displayed good stability and high efficiency. The analysis of the mechanism showed that adding MoS2 to FeOCl can promote the reduction of Fe3+ to Fe2+ through the oxidation of Mo4+ to Mo6+. The active species in this system were identified as SO4-•, •OH, O2-•, and 1O2. SO4-• and 1O2 were dominant. This research provides a new strategy for the development and application of membrane separation technology.

Structure of Two Nh4bif4 Polymorph Modifications. Ionic Motion in Nh4bif4 and Cubic Products of its Partial Thermal Decomposition

Structure of Two Nh4bif4 Polymorph Modifications. Ionic Motion in Nh4bif4 and Cubic Products of its Partial Thermal Decomposition

Optical characterization by photoreflectance of GaN after its partial thermal decomposition

In the current study, we investigated the partial decomposition of GaN layers grown on SiN-treated sapphire substrate in an atmospheric pressure metal organic vapor phase epitaxy (AP-MOVPE) vertical reactor under N2 ambient at 1200 °C. Under these experimental conditions, we studied the decomposition of different coalescence degrees GaN layers and the early thermal decomposition stages of GaN films. By the help of the scanning electron microscope (SEM), the surface morphology of the decomposed GaN epilayers was examined. We demonstrated that the thermal decomposition leads to an irregular etching process, which was carried out step by step. The optical properties of the decomposed films were then studied by using the photoreflectance (PR) technique at room temperature and at 11 K. We determined a logarithmic relation between the built-in electric field in the surface of GaN layers and the stress value. A model is also proposed to extract the stress value from PR spectra. It should be noted also that by using the thermal decomposition process, the stress inside GaN layers can be reduced by a factor of 6.

A sensitive electrochemical sensor based on the partial thermal decomposition of MIL-53(Fe) and reduced graphene oxide for phenol detection

A sensitive electrochemical sensor based on the partial thermal decomposition of MIL-53(Fe) and reduced graphene oxide for phenol detection

Effect of Methylene Chain Length on the Thermodynamic Properties, Ferroelastic Properties, and Molecular Dynamics of the Perovskite-type Layer Crystal [NH3(CH2) n NH3]MnCl4 (n = 2, 3, and 4).

The structures and phase transitions of [NH3(CH2)nNH3]MnCl4 (n = 2, 3, and 4) crystals were confirmed through X-ray diffraction and differential scanning calorimetry (DSC) experiments. Thermodynamic properties, ferroelastic properties, and molecular dynamics of three crystals were studied as a function of the number (n) of CH2 groups in the alkylene chains. The loss in molecular weight due to a decrease in n marked the onset of the partial thermal decomposition. The thermal decomposition temperature, Td, increased with increasing length of the CH2 chain. While the ferroelastic twin domain walls for n = 2 and 4 were in the same direction at all temperatures, the domain walls for n = 3 were rotated by 45°, and the direction of extinction in phase II was rotated by 45° with respect to phases I and III. The 1H and 13C MAS NMR spectra of the three crystals were recorded as a function of temperature. With increasing length of the CH2 chain, the 1H spin relaxation time decreased, indicating that molecular motions were activated. These results provide insights into the thermodynamic properties and structural dynamics of the [NH3(CH2)nNH3]MnCl4 crystals and are expected to facilitate their potential applications.

Microstructure and Abrasive Wear Resistance of Metal Matrix Composite Coatings Deposited on Steel Grade AISI 4715 by Powder Plasma Transferred Arc Welding Part 2. Mechanical and Structural Properties of a Nickel-Based Alloy Surface Layer Reinforced with Particles of Tungsten Carbide and Synthetic Metal-Diamond Composite.

The article is the continuation of a cycle of works published in a Special Issue of MDPI entitled “Innovative Technologies and Materials for the Production of Mechanical, Thermal and Corrosion Wear-Resistant Surface Layers and Coatings” related to tests concerning the microstructure and mechanical properties of innovative surface layers made using the Powder Plasma Transferred Arc Welding (PPTAW) method and intended for work surfaces of drilling tools and machinery applied in the extraction industry. A layer subjected to tests was a metal matrix composite, made using powder based on a nickel alloy containing spherical fused tungsten carbide (SFTC) particles, which are fused tungsten carbide (FTC) particles and spherical particles of tungsten-coated synthetic metal–diamond composite (PD-W). The layer was deposited on the substrate of low-alloy structural steel grade AISI 4715. The results showed that the chemical composition of the metallic powder as well as the content of the hard phase constituting the matrix enabled the making of a powder filler material characterised by very good weldability and appropriate melting. It was also found that the structure of the Ni-WC-PD-W layer was complex and that proper claddings (characterised by the uniform distribution of tungsten carbide (WC)) were formed in relation to specific cladding process parameters. In addition, the structure of the composite layer revealed the partial thermal and structural decomposition of tungsten carbide, while the particles of the synthetic metal–diamond composite remained coherent. The deposited surface layer was characterised by favourable resistance to moderate dynamic impact loads with a potential energy of 200 J, yet at the same time, by over 12 times lower metal–mineral abrasive wear resistance than the previously tested surface layer made of cobalt-based composite powder, the matrix of which contained the hard phase composed of TiC particles and synthetic metal–diamond composite. The lower abrasive wear resistance could result from a different mechanism responsible for the hardening of the spherical particles of the hard phase susceptible to separation from the metal matrix, as well as from a different mechanism of tribological wear.

Ce-based heterogeneous catalysts by partial thermal decomposition of Ce-MOFs in activation of peroxymonosulfate for the removal of organic pollutants under visible light

Metal-organic framework (MOF) derivatives have drawn considerable attention for applications in various fields. In this work, spindle-shaped Ce-TCPPs were assembled by a rapid microwave-assisted hydrothermal method. After thermal treatment at low temperature under a N2 atmosphere, the Ce-TCPPs were partially pyrolyzed and converted to a novel CeO2/N-doped carbon/Ce-TCPP nanocomposite. Compared to completely decomposed materials, these partially decomposed heterogeneous catalysts exhibited significantly higher photocatalytic activation ability toward PMS for the removal of organic pollutants (e.g., rhodamine B, methylene blue, methyl orange, tetracycline and oxytetracycline). For the optimized sample thermal treated at 450 °C, a 100 mL RhB solution (10 mg/L) can be removed within 20 min with the assistance of PMS under visible light. The significantly enhanced activity can be attributed to the effective spatial separation of photogenerated electrons and holes in the formed Z-scheme CeO2/N-doped carbon/Ce-TCPP system. This work may provide useful guidance for the design and fabrication of MOF-derived photocatalytic systems for environmental remediation.

Efficient degradation of tetracycline by H2O2 catalyzed by FeOCl: A wide range of pH values from 3 to 7

Iron Oxychloride (FeOCl) was prepared by partial thermal decomposition and was studied as a heterogeneous Fenton catalyst to degrade tetracycline (TC). SEM, XRD, XPS technology were used to characterize its performance. The influencing factors of TC degradation efficiency were studied, including pH value, H2O2 content, catalyst dosage and initial TC concentration. The results showed that under the optimal conditions, the degradation rate of 60 mg L−1 TC reached 92.9% within 60 min of reaction. The degradation process follows a second-order kinetic equation. Compared with other iron-based catalysts, FeOCl exhibited better catalytic and degradation effects. Moreover, FeOCl/H2O2 system exhibited a wide pH range (from 3.0 to 7.0) for efficient degradation of TC and showed excellent stability and reusability. Meanwhile, based on the intermediates identified by HPLC-MS, two possible pathways for the degradation of TC were proposed. Further, the results of electron spin-resonance spectroscopy and radical quenching tests suggested that the ·OH formed in the FeOCl/H2O2 system was mainly responsible for the degradation of TC.

Incorporation of quartzite fines in the production of red ceramics

The ornamental stone sector produces a substantial amount of solid waste and effluents that are discarded in a disorderly manner, a fact that has prompted the need for research aimed at reuse. Considering the concepts of sustainable development and conscious mining, this study proposed the incorporation of quartzite residues in the production of ceramics (using soil as raw material) and aimed to reduce production prices, minimize environmental impacts, and obtain a higher quality of ceramic products (with less water absorption and greater resistance). Ceramic bricks were made in accordance with the following variables: replacement percentage (10% and 15%), compaction pressure (28 and 35 MPa), drying temperature (65 °C for 72 h and 110 °C for 24 h), and firing temperature (950 and 1100 °C). Technological tests evaluated the drying and firing linear shrinkage, firing specific weight, water absorption, and resistance to uniaxial compression. After determining the optimal conditions, a flexural tear test and microstructural characterization were also performed. The optimal conditions for making ceramic bricks were a replacement percentage of 15%, compaction pressure of 35 MPa, drying temperature of 65 °C (72 h), and firing temperature of 1100 °C. These results were favorable because of the partial thermal decomposition of the mineral phases with the recrystallization of mullite and cristobalite. The incorporation of the residue resulted in better quality ceramic products, placing them within the limits established for technological applications, whereas none of the compositions made entirely of clay met the technical specifications.

Thermal stability, cation dynamics, and ferroelastic domain walls in the α→β→γ phase transitions of perovskite (C2H5NH3)2MnCl4 crystals

Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) confirmed that the (C2H5NH3)2MnCl4 crystal undergoes α-β-γ phase transitions at approximately TC2 = 225 K and TC1 = 424 K, remains stable until 470 K, and displays a weight loss of 25.24% at around 579 K due to partial thermal decomposition. Cation dynamics near these temperatures was investigated by MAS 1H NMR and MAS 13C NMR experiments. The small changes in the 1H chemical shift for C2H5 near TC2 are consistent with the transition from the orthorhombic γ-phase to the orthorhombic β-phase. Also, the abrupt changes in NMR signals near TC1 correspond to structural change from the orthorhombic β-phase to the tetragonal α-phase. The 13C spin-lattice relaxation time in the rotating frame (T1ρ) below TC2 is shorter for CH3 than that for CH2, due to the greater mobility at the free end of the alkyl chain. In addition, the temperature-dependent ferroelastic domain structure was studied near the α-β phase transition. There was no noticeable temperature dependence in 1H and 13C T1ρ values at TC1 and TC2, whereas the change in the domain wall was prominent near TC1.

Thermodynamic, Physical, and Structural Characteristics in Layered Hybrid Type (C2H5NH3)2MCl4 (M = 59Co, 63Cu, 65Zn, and 113Cd) Crystals.

The thermal, physical, and molecular dynamics of layered hybrid type (C2H5NH3)2MCl4 (M = 59Co, 63Cu, 65Zn, and 113Cd) crystals were investigated by thermogravimetric analysis (TGA) and magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The temperatures of the onset of partial thermal decomposition were found to depend on the identity of M. In addition, the Bloembergen–Purcell–Pound curves for the 1H spin-lattice relaxation time T1ρ in the rotating frames of CH3CH2 and NH3, and for the 13C T1ρ of CH3 and CH2 were shown to exhibit minima as a function of the inverse temperature. These results confirmed the rotational motion of 1H and 13C in the C2H5NH3 cation. Finally, the T1ρ values and activation energies Ea obtained from the 1H measurements for the H‒Cl···M (M = Zn and Cd) bond in the absence of paramagnetic ions were larger than those obtained for the H‒Cl···M (M = Co and Cu) bond in the presence of paramagnetic ions. Moreover, the Ea value for 13C, which is distant from the M ions, was found to decrease upon increasing the mass of the M ion, unlike in the case of the Ea values for 1H.

Thermal property and structural molecular dynamics of organic–inorganic hybrid perovskite 1,4-butanediammonium tetrachlorocuprate

We investigate the thermal behaviour and physical properties of the crystals of the organic inorganic hybrid perovskite [(NH3)(CH2)4(NH3)]CuCl4. The compound's thermal stability curve as per thermogravimetric analysis exhibits a stable state up to ∼495 K, while the weight loss observed near 538 K corresponds to partial thermal decomposition. The 1H nuclear magnetic resonance (NMR) chemical shifts for NH3 change more significantly with temperature than those for CH2, because the organic cation motion is enhanced at both ends of the organic chain. The 13C NMR chemical shifts for the ‘CH2-1’ units of the chain show an anomalous change, and those for ‘CH2-2’ (units closer to NH3) are shifted sharply. Additionally, the 14N NMR spectra reflect the changes of local symmetry near TC (=323 K). Moreover, the 13C T1ρ values for CH2-2 are smaller than those for CH2-1, and the 13C T1ρ data curve for CH2-1 exhibits an anomalous behaviour between 260 and 310 K. These smaller T1ρ values at lower temperatures indicate that 1H and 13C in the organic chains are more flexible at these temperatures. The NH3 group is attached to both ends of the organic chain, and NH3 forms a N–H⋯Cl hydrogen bond with the Cl ion of inorganic CuCl4. When H and C are located close to the paramagnetic Cu2+ ion, the T1ρ value is smaller than when these are located far from the paramagnetic ion.

Quantitative investigation into the enhancing utilization efficiency of H2O2 catalyzed by FeOCl under visible light

FeOCl was prepared by a partial thermal decomposition method to effectively catalyze hydrogen peroxide under the visible light for the degradation of toxic organic wastewater. The combination of DRS and VB-XPS indicated that FeOCl is a narrow band gap catalyst with visible light absorption capacity (Eg =1.63 eV). The degradation rate constant of RhB in FeOCl/H2O2/Vis system is about 13.4 times that of FeOCl/H2O2 system. Compared to other heterogeneous Photo-Fenton systems, the oxidant utilization efficiency in FeOCl/H2O2/Vis system is higher. In addition, FeOCl has stable Photo-Fenton activity in a wide pH range (3.0–9.0). The content of Fe(II) increased after 5 cycles reaction through the ESR and XPS characterization, which proves that the electron transfer of Fe(III)/Fe(II) was improved during the reaction. After quantitative analysis of the ·OH generated in the reaction, the formation rate of ·OH in FeOCl/H2O2/Vis system is increased about 30% compared with FeOCl/H2O2/dark system. These results indicate that visible light excites FeOCl to generate produces photogenerated electron-hole pairs, accelerating the cycle of Fe(III)/Fe(II), promoting the production rate of ·OH, and enhancing the catalytic efficiency of FeOCl.

Ce(III) nanocomposites by partial thermal decomposition of Ce-MOF for effective phosphate adsorption in a wide pH range

A series of hierarchical micro/nano Ce-based composites were derived from Ce-MOF via thermal treatment in N2 atmosphere. Different from conventional complete decomposed materials, forming cerium oxide in air, Ce-MOF that calcinated in N2 at lower temperatures (400 °C or 500 °C) showed a partial thermal decomposition with high percent content of Ce(III). Even though the complete decomposed products held higher surface areas, the partial decomposed samples exhibited extremely higher phosphate uptake, with working capacity 2–4 times higher than that of ceria. The results implied a predominant effect of different valence states on phosphate removal by Ce-based materials, in which Ce(III) species were demonstrated playing the major role to form binding with phosphate. The maximum adsorption capacity (189.4 mg/g) was achieved by Ce-MOF-500(S) with wide applicable scope of pH ranging from 2 to 12 and great selectivity for phosphate in the presence of competing anions. Remarkably, Ce-MOF-500(S) described obvious enhanced phosphate adsorption ability under alkaline condition. This was due to the fact that the hydrolyzed Ce(III) species brought more active sites in the form of hydroxyl groups for ligand exchange with phosphate. Furthermore, based on the analysis of FTIR, XPS, XRD and zeta potential, electrostatic attraction, ligand exchange and surface precipitation were confirmed as the main adsorption mechanisms for partial decomposed samples, while electrostatic attraction was the main mechanism for complete decomposed samples.