Conditions Of Thermal Decomposition Research Articles

Synergistic on engineering layered N-doped carbon/MXene heterostructure: A potential scaffold for simultaneous electrochemical detection of Cu2+ and Hg2+ ions

The presence of heavy metal ions (HMIs) like Cu2+ and Hg2+ in natural water and foods is a major health and environmental concern. Thus advanced electrochemical sensors are required to monitor these ions. Herein, we introduce a nitrogen-rich carbon-MXene composite (layered N-doped carbon/MXene) as an electrochemical sensor suitable for the simultaneous detection of Cu2+ and Hg2+. Synthesizing 2D/2D heterostructure interfaces using controlled thermal decomposition conditions with the incorporation of quaternary nitrogen from choline chloride and the formation of hydrogen bonds of urea within the MXene (Ti3C2Tx) provided active surfaces area that is suitable for the detection of Cu2+ and Hg2+. The intermediate structure of layered N-doped carbon/MXene, had a nitrogen content of ∼6 %, maximized sensitivity for Cu2+ and Hg2+. The layered N-doped carbon/MXene composite exhibited excellent electrochemical sensing for Cu2+ and Hg2+ in 0.1 M acetate buffer at low sensing potentials. The limits of detection (LODs) of layered N-doped carbon/MXene were 0.019 and 0.056 µM with a sensitivity of 114.54 and 64.317 µA µM−1 cm−2 for Cu2+ and Hg2+, respectively. Furthermore, the layered N-doped carbon/MXene heterostructure exhibited high selectivity for Cu2+ and Hg2+ in the presence of potentially interfering common metal ions. This study introduces a promising advanced material for rapid Cu2+ and Hg2+ detection in food and environmental applications.

FIXATION OF THE OPTICAL FIBER IN THE CONNECTOR USING HYDROGEL

A method of fastening optical fiber in a quartz connector with a sodium polysilicate hydrogel obtained in a cylindrical gap between the connector and the fiber due to the alkaline decomposition of quartz surfaces of parts was developed. The conditions of thermal decomposition of the hydrogel are determined and it is shown that the decomposition of the hydrogel with the formation of a cellular structure is possible at temperatures below the temperature of thermal decomposition of the polymer coating of the fiber. The conditions for obtaining and thermal properties of the hydrogel are determined. Conclusions are drawn about the suitability of the proposed method for fixing optical fiber in a quartz connector.

INVESTIGATION OF THE POSSIBILITY OF PROCESSING KAOLIN CLAYS OF THE SUVOROV DEPOSIT TO OBTAIN COAGULANTS

The mineral and chemical compositions of the Suvorov depositkaolin clay have been studied using X-ray phase and atomic emission spectrometry with induction plasma. The conditions of thermal calcination and decomposition of kaolin clay with sulfuric and hydrochloric acids are optimized: the calcination temperature is 650-700 °C; the calcination duration is 60-90 minutes. The extraction degree of Al2O3 from calcined clay into sulfuric acid solutions was 92-94%, into hydrochloric acid solutions — 76-78%. The effect of different flocculants on the separation of liquid and solid phases is investigated. It is shown that the use of polyacrylamide increases the filtration rate by 1.5—2 times. The coagulating properties of aluminum sulfate and hydroxochlorides were studied: oxidizability, color, concentration of aluminum and iron in the treated water. The tested coagulants can be effectively used in the purification of drinking and wastewater at low and high temperatures in a wide pH range of treated waters.

Noncatalyzed Reduction of Nitriles to Primary Amines with Ammonia Borane.

The preparation of primary amines from nitriles has been a subject of continuing interest, and many different methods have been reported for this process. We report in this paper an alternative method for transforming nitriles into primary amines. In this work, a wide range of nitriles were reduced to primary amines by 1.2 equiv of ammonia borane under thermal decomposition conditions without any catalyst and the corresponding primary amines were isolated in good to excellent yields. The reactions are environmentally benign with H2 and NH3 generated as byproducts. The reactions are also tolerant of many functional groups. Nitriles are likely reduced by the in situ-generated aminodiborane, the application of which in organic synthesis has never been reported before. By using our protocol, primary amines containing multifluorinated aromatic rings, which are greatly important in pharmaceutical synthesis and have rarely been prepared via catalytic processes, were successfully prepared.

POTENTIAL USE OF BIOCHAR IN WASTEWATER TREATMENT OPERATIONS AND SOIL IMPROVEMENT

Biochar is produced through thermochemical decomposition, so called as pyrolysis, of different biomass groups in the presence of little or no oxygen. Resultant material is highly stable material with excellent surface characteristics and pore structure and is also rich in functional groups. Such properties of the material are largely influenced by pre- and post-treatments and thermal decomposition conditions. Various methods have been used for thermal decomposition of biomass, such as pyrolysis thermal carbonization, torrefaction and microwave heating at different temperatures and for different durations. Biochar has recently started to be used for wastewater treatment and water pollution control purposes. It is also used to improve soil properties including aggregate stability, water holding capacity and organic matter content. It is a new, economic and environment friendly material to be used in wastewater treatments technology and soil improvement. In this study, biochar production technologies and properties of resultant materials were summarized and potential use of biochar in wastewater treatments operations and for soil improvement were assessed in detail.

Experimental Study on Optimization of Phosphogypsum Suspension Decomposition Conditions under Double Catalysis.

Phosphogypsum (PG) is not only a solid waste discharged from the phosphate fertilizer industry, but also a valuable resource. After high-temperature heat treatment, it can be decomposed into SO2 and CaO; the former can be used to produce sulfuric acid, and the latter can be used as building materials. In this paper, the catalytic thermal decomposition conditions of phosphogypsum were optimized, and the effects of the reaction temperature, reaction atmosphere, reaction time and carbon powder content on the decomposition of phosphogypsum were studied. The research shows that the synergistic effect of carbon powder and CO reducing atmosphere can effectively reduce the decomposition temperature of phosphogypsum. According to the results of the orthogonal test under simulated suspended laboratory conditions, the factors affecting the decomposition rate of phosphogypsum are temperature, time, atmosphere and carbon powder content in turn, and the factors affecting the desulfurization rate are time, temperature, atmosphere and carbon powder content in turn. Under laboratory conditions, the highest decomposition rate and desulfurization rate of phosphogypsum are 97.73% and 97.2%, and the corresponding reaction conditions are as follows: calcination temperature is 1180 °C, calcination time is 15 min, carbon powder content is 4%, and CO concentration is 6%. The results of thermal analysis of phosphogypsum at different temperature rising rates show that the higher the temperature rising rate, the higher the initial temperature of decomposition reaction and the temperature of maximum thermal decomposition rate, but the increase in the temperature rising rate will not reduce the decomposition rate of phosphogypsum.

Characteristics of moisture release from layers of forest fuels with typical fire extinguishing agents

Typical fire extinguishing agents were considered: water, bischofite solutions, bentonite slurries, and foaming agent emulsions (with a mass fraction of 5% and 10%). The heating temperature range of 150-400 ?? was chosen to correspond to the conditions of rapid thermal decomposition of forest fuels. The experimental research findings suggest that the rates of moisture release depend exponentially on the heating temperature. It was established that the rates of moisture release in the above temperature range may differ significantly for the forest fuels and fire extinguishing agents under study. Conditions were identified when the general approximation equations, presented in this paper, can be used to predict the vaporization characteristics of firefighting liquids.

Optimization and Validation of Rp-Hplc Stability-Indicating Method for Determination of Efavirenz and its Degradation Products

Stability is considered one of the most important criteria in pharmaceutical quality control. With this objective a stability-indicating high performance liquid chromatographic (HPLC) method has been established for analysis of Efavirenz in the presence of the degradation products generated in the stress degradation study. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal decomposition. Extensive degradation was found to occur in alkaline medium and under thermal stress. Minimum degradation was observed under acidic medium, in the photolytic conditions and oxidative stress. Successful separation of drug from degradation products formed under stress conditions was achieved on a C-8 column using acetonitrile: potassium dihydrogen phosphate (pH 2.9, 25mM) - (60:40% v/v) as the mobile phase. The flow rate was 1 mL min -1 and the detector was set at in a range of wavelength be- tween 220nm to 390nm. The method was validated for linearity, range, precision, accuracy, limit of quantification and limit of detection. Because the method effectively separates the drugs from their degradation products, it can be used as stability-indicating method.

A straightforward approach to high purity sodium silicide Na4Si4.

Sodium silicide Na4Si4 is a reductive and reactive source of silicon highly relevant to designing non-oxidic silicon materials, including clathrates, various silicon allotropes, and metal silicides. Despite the importance of this compound, its production in high amounts and high purity is still a bottleneck with reported methods. In this work, we demonstrate that readily available silicon nanoparticles react with sodium hydride with a stoichiometry close to the theoretical one and at a temperature of 395 °C for shorter duration than previously reported. This enhanced reactivity of silicon nanoparticles makes the procedure robust and less dependent on experimental parameters, such as gas flow. As a result, we deliver a procedure to achieve Na4Si4 with purity of ca. 98 mol% at the gram scale. We show that this compound is an efficient precursor to deliver selectively type I and type II sodium silicon clathrates depending on the conditions of thermal decomposition.

Optimization of Thermal Decomposition Conditions of Bone to Achieve the Highest Percentage of Crystalline Phase in Bone Char using Gene Expression Programming and Artificial Neural Network

Bone char (BC) is one of the most common adsorbent with extensive applications in the removal of pollutions. The adsorption capability of BC is proportional to the crystalline index, i.e, the atomic ratio of Ca/P. This study is an attempt to model the crystalline index of BC that by thermal decomposition of natural bone using artificial neural network (ANN) and genetic expression programming (GEP). In this regard, 100 various experimental data used to construct the ANN and GEP models, separately. Through the data collection step, heating rate, the type of precursor, calcination temperature, and residence time selected as the inputs for the preset output as Ca/P ratio. The results reveal that the minimum amount of Ca/P ratio are at the heating rate 10 °C/min, HNO3 1.6 M as activation agent, calcination temperature 1000 °C, and residence time 2 h. R squared indices is used to compare the performance of extracted models. Finally, the best ANN uses to investigate the effect of each practical variable by sensitivity analysis and revealed that the residence time is the most effective parameter on the crystalline index while acid activation is of secondary importance.

Thermodynamic foundations of wood’s operational properties

The paper shows trends in the study of building materials. Thermodynamic approaches to analysis of the condition of building materials as a thermodynamic system, including in thermal decomposition conditions, are described. As part of the experimental part, the proposed methods analysed the effect of phosphorus organic materials on the fire danger of wood. The correlation of thermodynamic criteria (Gibbs energy) and identified physical and chemical behaviors of modified wood has been revealed.

Studying the toxicity effects of coated and uncoated NaLuF4: Yb3+, Tm3+ upconversion nanoparticles on blood factors and histopathology for Balb/C mice’s tissue

In this study, upconversion nanoparticles were synthesized in less than 6 h under thermal decomposition conditions by changing pH and synthesis temperature. The washing process removed the hydrophobic species on the surface of nanoparticles. Then the nanoparticles were coated by calcium carbonate () and were loaded with curcumin (Cur) as a drug model in one synthesis step. The effects of toxicity of uncoated and coated nanoparticles were investigated on normal cells, blood factors, and histopathology of the tissue in Balb/C mice. The most of synthesized nanoparticles had spherical shape considering the results from the SEM and TEM. The results of the DLS analysis showed that the hydrodynamic diameter of the uncoated and coated nanoparticles was 49.52 and 59.37 nm, respectively. By injecting nanoparticles into human blood, there was not seen a significant difference in the number of red blood cells, white blood cells, hemoglobin, and blood platelets with the treatment of the control group. Besides, cell biocompatibility studies in fibroblast cell lines showed that the toxicity of uncoated nanoparticles increased at concentrations higher than 250 Also, cytotoxicity increases significantly with increasing the time of 24, 48, and 72 h. The coated samples did not represent the toxicity effect. The results of cellular changes induced by the addition of uncoated and coated nanoparticles showed that the cells change from spherical to Spindle after treatment with Which indicates a lack of toxicity. Histopathological examination of vital organs in mice receiving did not show any pathological damage compared to the control group.

Preparation of LaNiO3 perovskite by oxalate and carbonate precursor method for utilization as catalyst for high-temperature decomposition of N2O

The mixed oxide LaNiO3 with perovskite structure was prepared by two relatively new and unconventional methods including preparation and thermal decomposition of mixed metal oxalate or carbonate precursors. The intermediates were prepared by reaction in a highly concentrated suspension (paste). The thermal decomposition conditions of these intermediates were described, and the final calcination temperatures were determined, which were done using thermal analysis methods and X-ray diffraction. During the decomposition of mixed carbonates, one-phase LaNiO3 is produced directly, and in case of decomposition of oxalates, a mixture of LaNiO3 and La2O3 is produced due to the formation of La2O2CO3 during the heating. Catalytic decomposition of nitrous oxide at high temperature (650–930 °C) and high loading (GHSV = 350,000 h−1) has shown high LaNiO3 activity, even at lower temperatures. The results were compared with the same compound obtained by co-precipitation and by solid-state reaction. Methods of preparation based on decomposition of oxalate and carbonate intermediates lead to the preparation of materials with appropriate composition, morphology, specific surface and high catalytic activity.

Modulating the photoluminescence of europium oxide nanoparticles by controlling thermal decomposition conditions

Europium oxide nanoparticles are emerging as one of the most important oxide phosphors for a variety of applications. Currently, thermal decomposition is the most powerful approach to prepare europium oxide nanoparticles with narrow size and morphology distribution. However, an understanding of the relationship between thermal decomposition conditions on the corresponding photoluminescence (PL) performance of europium oxide nanoparticles remains unexplored so far. In this study, europium oxide nanoparticles were prepared through thermal decomposition under different conditions by controlling the concentration precursor or the solvent used for thermal decomposition and the PL properties of as-prepared europium oxide nanoparticles were investigated. The obtained PL spectra infer the coexistence of Eu3+ and Eu2+ emission centers in the as-prepared europium oxide nanoparticles. More importantly, it is evidenced that the control of the thermal decomposition conditions appears an effective way to modulate the relative fraction of Eu2+ and Eu3+ emission centers, which confers the PL emission of europium oxide nanoparticles from blue to red.

Stability Profiling of Amodiaquine under stress Degradation Conditions

Degradation Product is an impurity which results from a chemical change in the drug substance during storage and/or manufacture of the new drug product due to some environmental changes or by reaction with an excipient and/or the immediate container closure system. Impurity development may be either during formulation or upon aging of both API’S and formulated API’S in medicines. The objective of the current investigation was to study the stress degradation behaviour of Amodiaquine under different ICH recommended stress conditions by HPLC method. The anti-malarial drug Amodiaquine, when subjected to stress degradation conditions of hydrolysis, oxidation, photolysis and thermal decomposition prescribed by ICH guideline Q1A (R2), it is found that, the drug Amodiaquine (API) was stable. The method was established using column C18 Hypersyl BDS (250* 4.6) mm, 5µ, mobile phase as monobasic potassium phosphate PH 2.5 with orthophosphoric acid and methanol. Method was isocratic and composition 22: 78 (A: B), at a flow rate of 1.2ml/ min. To facilitate the development of analytical methodology, in order to obtain a better understanding of active pharmaceutical ingredient (API) and drug product (DP) stability, and also to provide information about degradation pathways and degradation products, this process is very useful. These types of studies will provide information about the degradation products that could form during storage and transportation.

Structural study of dehydration mechanisms of NH4Th(NO3)5·9H2O

The new pentanitrate thorium compounds NH4Th(NO3)5·nH2O were synthesized and their crystal structures were determined by X-ray diffraction analysis: space group P21/n, a = 10.5476(5), b = 14.0444(7), c = 15.5287(8)Å, β = 109.4999(7)°, Z = 4; R = 0.0246 (NH4Th(NO3)5·9H2O); space group P212121, a = 8.7039(4), b = 11.9985(6), c = 16.3531(8) Å, Z = 4; R = 0.0259 (NH4Th(NO3)5·5H2O). Features of structural changes in the dehydration were revealed. Conditions of thermal decomposition of the thorium compound were established using differential scanning calorimetry. The compound was investigated by IR spectroscopy and its bands are assigned.

Study of forced degradation behavior of pramlintide acetate by HPLC and LC–MS

Pramlintide acetate (Symlin®), a synthetic analogue of the human hormone amylin. It was approved in March 2005 as a subcutaneous injection for the adjunctive treatment of patients who have type 1 or 2 diabetes mellitus. The objective of current investigation was to study the degradation behavior of pramlintide acetate under different ICH recommended stress conditions by HPLC and LC–MS. Pramlintide acetate was subjected to stress conditions of hydrolysis (acidic or alkaline), oxidation, photolysis and thermal decomposition. Extensive degradation products were observed under the hydrolysis, oxidation or thermal stress conditions, while minimal degradation was found in the photolytic conditions. Successful separation of drug from the degradation products was achieved by the validated chromatography (RP-HPLC and SCX-HPLC) methods. Subsequent to isolation, the molecular weight of each component was determined by LC–MS. The LC–MS m/z values and fragmentation patterns of 4 impurities matched with the predicted degradation products of pramlintide acetate.

Combined production of synthetic rutile in the sulfate TiO2 process

Abstract This paper describes a novel process for preparation of synthetic rutile using an intermediate, sulfated ilmenite from the sulfate TiO 2 process as the feedstock. The synthetic rutile can be obtained by selective thermal decomposition of the sulfated ilmenite, followed by targeted leaching for removal of various impurities. The results of the decomposition unit showed that almost all the TiOSO 4 in the sulfated ilmenite decomposed to TiO 2 , while the iron component mainly existed in the form of sulfates in the optimal thermal decomposition conditions, i.e., a roasting temperature of 540 ° C and a roasting time of 120 min under air flow or in stagnant air or a roasting temperature of 510 ° C and a roasting time of 120 min under nitrogen flow. The thermal decomposition can be divided into three stages. The sulfates of titanium and iron in the sulfated ilmenite were first decomposed to TiO 2 and water-insoluble FeOHSO 4 , respectively, at a temperature less than 500 ° C. The FeOHSO 4 was further converted into water-soluble Fe 2 O(SO 4 ) 2 at 500–560 ° C. Finally, the Fe 2 O(SO 4 ) 2 was decomposed to Fe 2 (SO 4 ) 3 and Fe 2 O 3 at a temperature above 560 ° C. The water-soluble metal sulfates, the water-insoluble FeOHSO 4 /Fe 2 O 3 and the SiO 2 in the TiO 2 -containing slag can be removed through leaching by using water, dilute sulfuric acid and sodium hydroxide, respectively. The results showed that 70–85% of the iron, as well as a majority of the magnesium, calcium, etc. impurities, could be leached by water, and up to 92% of the total iron could be removed after the subsequent acid leaching in a 15 wt% H 2 SO 4 solution, while the silicon removal reached 65% in a 5 wt% NaOH solution. A synthetic rutile with a TiO 2 content over 90 wt% and total MgO + CaO less than 1 wt% was obtained under the optimal conditions listed above. The present process can be integrated with the sulfate TiO 2 process, producing titania pigment and synthetic rutile simultaneously. The advantages of the TiO 2 beneficiation process include the moderate reaction conditions, the capability of recycling the H 2 SO 4 completely and the recovery of a large part of the iron, as well as comprehensive utilization of the waste sulfuric acid discharged from the sulfate TiO 2 production process.

TG-DTG-DSC, FTIR, DRIFT and Py-GC-MS studies of thermal decomposition for poly(sodium acrylate)/dextrin (PAANa/D) – new binder BioCo3

TG-DTG-DSC, FTIR, DRIFT, and Py-GC-MS studies have been conducted to determine the effect of the thermal decomposition conditions and structure of foundry binder BioCo3 in the form of a composition poly(sodium acrylate)/dextrin (PAANa/D) on the progress of degradation in terms of processes occurring in foundry sands in contact with liquid metal. TG-DTG-DSC curves of the composition allowed us to determine the temperature range in which they do not undergo degradation, by which they do not lose their binding properties. With temperature increasing, physical and chemical changes occur that are related to the evaporation of solvent water (20–110°C), followed by the release of constitution water, and finally intermolecular dehydration (110–230°C). In this temperature range, processes that are mainly reversible take place. Within a temperature range of 450–826°C, polymer chains are decomposed, including the decomposition of side chains. Within a temperature range of 399–663°C, polymer composition decomposition can be observed (FTIR, DRIFT), and gas products are generated from this destruction (Py-GC-MS).

Preparation of synthetic rutile via selective sulfation of ilmenite with (NH 4 ) 2 SO 4 followed by targeted removal of impurities

Abstract This paper describes a novel, facile chemical pathway for preparing synthetic rutile from ilmenite. The pathway consists of two primary units, i.e. , selectively sulfating ilmenite, which was realized via roasting ilmenite with (NH 4 ) 2 SO 4 followed by selective thermal decomposition of the sulfated ilmenite, and targeted leaching of the impurities. The effects of the process parameters were systematically investigated. The results showed that the optimum sulfation conditions were a mass ratio of (NH 4 ) 2 SO 4 to ilmenite of 14, temperature of 360 °C, and time of 120 min with a sulfation ratio of ~ 95%. The optimum thermal decomposition conditions were 480 °C in N 2 atmosphere, and nearly all TiOSO 4 were decomposed with co-decomposition of FeSO 4 of 23%. For acid leaching, the optimum conditions were 2.5 wt% HCl, 98 °C and 120 min. Under those conditions, 94.2% iron was removed with a TiO 2 dissolution loss 2 was removed in 5 wt% NaOH at 102 °C for 1 h. A synthetic rutile with a TiO 2 content > 92 wt% and total MgO + CaO 4 mixed with TiOSO 4 under N 2 was inhibited due to its oxidation to a higher thermal stability Fe 2 (SO 4 ) 3 by oxygen emitted from the decomposition of TiOSO 4 . At the same time, TiOSO 4 decomposition was promoted due to the immediate in situ consumption of oxygen by FeSO 4 . The synergetic effect might be responsible for the enhanced selectivity of sulfated ilmenite thermal decomposition.