Derivative Thermal Gravimetry Research Articles

Protein‐Based Polymeric Metal–Nanocomposite Derived From Egg Albumin: A Highly Effective Antimicrobial Agent Against Bacteria

ABSTRACTThe synthesis of four distinct protein‐based metal nanocomposites has been fabricated by employing egg albumin and zinc metal through a simple, straightforward two‐step method. The Fourier transform infrared (FTIR), X‐ray diffraction (XRD), and scanning electron microscopy (SEM) analyses confirmed the successful incorporation of zinc nanoparticles into the protein matrix and revealed an irregular microporous structure with average crystallite sizes of less than 100 nm. Thermal stability was assessed via thermogravimetric (TG) and derivative thermal gravimetry (DTG) analysis, revealing a notable increase in thermal stability in a high‐temperature range (300°C°C–700°C), suggesting remarkable stability at elevated temperatures. Antimicrobial efficacy against both gram‐positive (B. cereus and Lactobacillus spp.) and gram‐negative bacteria (E. coli and K. pneumoniae) was evaluated using paper disk diffusion, pour plate, and minimum inhibitory concentration (MIC) methods. All samples exhibited antibacterial efficacy, with zone of inhibition (ZOI) diameters ranging from 12 to 35 mm, and demonstrated a bactericidal effect by eliminating 93 to 98% of bacteria within 8 to 20 h at their MICs. Notably, protein–ZnO–PANI exhibited potent antimicrobial activity against all four bacterial strains and among all the samples, demonstrated higher antimicrobial activity than the unpolymerized nanocomposites. The disk diffusion study confirmed that a concentration of 25 μg/mL of protein–ZnO–PANI resulted in ZOI measurements of 25 mm and 35 mm, whereas MIC values of 300 μg/mL and 200 μg/mL were observed against Bacillus cereus and E. coli, respectively, and killed 95% of B. cereus and 98% of E. coli within 24 h. Based on the obtained results, a plausible mechanism was also proposed.

Effects of potassium on hydrothermal carbonization of sorghum bagasse

Hydrothermal carbonization (HTC) reacts with biomass in water at a high temperature and pressure to produce hydrochar with a higher heating value (HHV) and lower ash content than dry torrefaction. The high potassium content in biomass can promote thermochemical conversion; however, it lowers the melting temperature of the ash, causing slugging and fouling. Therefore, this study, investigated the effect of potassium on the HTC of sorghum bagasse by comparing the removal of potassium by washing with the addition of K2CO3. Consequently, the ash content was the highest in the potassium-added hydrochar and was 3.81% at a reaction time of 2 h. Elemental analysis showed that the lower the potassium content, the higher the carbon content, and the hydrochar with potassium removed by water washing at a reaction time of 3 h had the highest carbon content at 68.3%. Fourier transform infrared spectrometer showed dehydration and decarboxylation reactions due to HTC, but no significant differences were observed between the potassium concentrations. The mass yield decreased with increasing potassium content, and was 27.2% for the potassium-added hydrochar after 3 h. This trend was more pronounced with increasing reaction temperature. On the other hand, HHV was not affected by the potassium content. Therefore, the energy yield was similar to the weight yield. Thermal gravimetry and derivative thermal gravimetry (TG-DTG) analysis showed that higher potassium tended to accelerate the decomposition of lignin and decrease the oxidation temperature.Graphical

Strength development of dredged sludge with different sodium hydroxide contents

Granular blast furnace slag (GS) is a glassy substance formed when the slag melted in blast furnace ironmaking is not crystallized within time. An alkaline activator can show high hydraulic hardness in an alkaline environment. Using industrial wastes such as GS and fly ash (FA) to solidify dredged sludge (DS) is an economical and environmentally friendly solution. This study investigates the effectiveness of sodium hydroxide (SH) on the strength development of cement-bound industrial waste to stabilize DS. The effects of SH content on strength, atterberg limits, cohesion, and internal friction angle were analyzed. In addition, microstructural analysis was carried out by scanning electron microscopy (SEM) and x-ray diffraction experiments (XRD). Thermal gravimetry (TG) and derivative thermal gravimetry (DTG) was carried out to analyze the decomposition properties of the stabilized soil. The results show that SH's content significantly affects the solidified DS, and the UCS of stabilized soil increases with the increase in SH content. In addition, the SH content had no noticeable effect on the cohesion between particles. However, with the increase of SH content, the internal friction angle increased significantly, improving the solidified DS's shear strength.

Characterization of Five Collagenous Biomaterials by SEM Observations, TG-DTA, Collagenase Dissolution Tests and Subcutaneous Implantation Tests.

Collagenous biomaterials that are clinically applied in dentistry have dermis-type and membrane-type, both of which are materials for promoting bone and soft tissue formation. The properties of materials supplied with different types could affect their biodegradation periods. The purpose of this study was to characterize five of these products by four different methods: scanning electron microscopy (SEM) observation, thermogravimetry-differential thermal analysis (TG-DTA), 0.01 wt% collagenase dissolution test, and subcutaneous implantation test in vivo. SEM micrographs revealed that both dermis and membranous materials were fibrous and porous. The membranous materials had higher specific derivative thermal gravimetry (DTG) peak temperatures in TG-DTA at around 320 °C, longer collagenase dissolution time ranging from about 300 to 500 min, and more longevity in mice exceeding 9 weeks than the dermis materials. There existed a correlation between the peak temperature in TG-DTA and the collagenase dissolution time. It was considered that higher cross-link degree among collagen fibrils of the membrane-type collagenous materials might account for these phenomena. The experimental protocol and numerical results obtained could be helpful for selection and future development of fibrous collagenous biomaterials in clinical use.

Mesoporous Ionically Tagged Cross-Linked Poly(vinyl imidazole)s as Novel and Reusable Catalysts for the Preparation of N-Heterocycle Spiropyrans.

Herein, two novel mesoporous cross-linked poly(vinyl imidazole)s with sulfonic acid tags, [PVI-SO3H]Cl (1) and [PVI-SO3H]FeCl4 (2), were prepared and characterized by a variety of techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, elemental mapping, energy dispersive X-ray analysis, transmission electron microscopy, thermal gravimetry, derivative thermal gravimetry, and N2 adsorption–desorption isotherms (Brunauer–Emmett–Teller). In addition, magnetic properties of poly(vinyl imidazole) sulfonic acid iron(IV) chloride [PVI-SO3H]FeCl4 (2) as an ionically tagged magnetic polymer were investigated using a vibrating sample magnetometer. The presented polymers, [PVI-SO3H]Cl (1) and [PVI-SO3H]FeCl4 (2), were successfully applied as reusable and efficient catalysts for the preparation of N-heterocycle spiropyrans. The described catalysts were recycled and reused with a marginal decrease in their catalytic activities. The desired products were prepared under mild and green conditions. The structures of the obtained products were confirmed by various analysis techniques.

Synthesis of cross-linked PVA membranes embedded with multi-wall carbon nanotubes and their application to esterification of acetic acid with methanol

The present study focused on the performance enhancement of cross-linked PVA membrane using citric acid as the cross-linking agent, and by incorporation of treated multi-wall carbon nanotubes (TCN). Hybrid membranes were synthesized and applied as a separation element in a membrane reactor to improve the esterification of acetic acid with methanol in which Amberlyst 15 was used as the catalyst. The properties of the membranes were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electronic microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), derivative thermal gravimetry (DTG), differential scanning calorimetry (DSC), and tensile test. Moreover, swelling of prepared membranes at 25°C was found for a quaternary feed solution. Results showed that the acid conversion rate was improved with the increasing TCN content of the membranes. It was also indicated that the hybrid membranes had good separating properties for removing water from the reaction mixture. The final conversion of acid was increased from 52.30% to 99.25% using the membrane with 2wt.% TCN instead of the pure membrane at optimized condition and 4h of operation. The operating conditions were optimized as the initial methanol to acetic acid molar ratio of 4:1, reaction temperature of 70°C and catalyst loading of 15wt.% relative to acetic acid.

Synthesis and characterization of new 1-(α-aminoalkyl)-2-naphthols using pyrazine-1,4-diium trinitromethanide {[1,4-DHPyrazine][C(NO2)3]2} as a novel nano-structured molten salt and catalyst in compared with Ag–TiO2 nano composite

Pyrazine-1,4-diium trinitromethanide {[1,4-DHPyrazine][C(NO2)3]2} as a green and novel nano-structured molten salt catalyzed the synthesis of new 1-(α-aminoalkyl)-2-naphthol derivatives via the one-pot three-component condensation reaction between 2 or 4-aminopyridine, aromatic aldehydes and β-naphthol at room temperature under solvent-free conditions in comparison with Ag–TiO2 nano composite. Some advantages of the offered method are excellent cost effectiveness, catalytic efficiency, recycle and reusability of the catalyst. Pyrazine-1,4-diium trinitromethanide {[1,4-DHPyrazine][C(NO2)3]2} was fully characterized by IR, 1H NMR, 13C NMR, mass, thermal gravimetry (TG), derivative thermal gravimetry (DTG), differential thermal (DTA), X-ray diffraction patterns (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis.

The removal of hydrogen sulfide in solution by ferric and alum water treatment residuals

This work investigated the characteristics and mechanisms of hydrogen sulfide adsorption by ferric and alum water treatment residuals (FARs) in solution. The results indicated that FARs had a high hydrogen sulfide adsorption capacity. pH 7 rather than higher pH (e.g. pH 8–10) was favorable for hydrogen sulfide removal. The Yan model fitted the breakthrough curves better than the Thomas model under varied pH values and concentrations. The Brunauer–Emmett–Teller surface area and the total pore volume of the FARs decreased after the adsorption of hydrogen sulfide. In particular, the volume of pores with a radius of 3–5nm decreased, while the volume of pores with a radius of 2nm increased. Therefore, it was inferred that new adsorption sites were generated during the adsorption process. The pH of the FARs increased greatly after adsorption. Moreover, differential scanning calorimetry analysis indicated that elemental sulfur was present in the FARs, while the derivative thermal gravimetry curves indicated the presence of sulfuric acid and sulfurous acid. These results indicated that both oxidization and ligand exchange contribute to the removal of hydrogen sulfide by FARs. Under anaerobic conditions, the maximum amount of hydrogen sulfide released was approximately 0.026mgg−1, which was less than 0.19% of the total amount adsorbed by the FARs. The hydrogen sulfide that was released may be re-adsorbed by the FARs and transformed into more stable mineral forms. Therefore, FARs are an excellent adsorbent for hydrogen sulfide.

BET, TG–DTG, FT-IR, SEM, iodine number analysis and preparation of activated carbon from acorn shell by chemical activation with ZnCl2

Activated carbons were produced from acorn shell by chemical activation with zinc chloride (ZnCl2) at 600°C in N2 atmosphere and their characteristics were investigated. The effects of activation temperature, duration time, impregnation concentration of agent and impregnation time were examined. Adsorption capacity was demonstrated with BET and iodine number. The obtained activated carbons were characterized by measuring their porosities and pore size distributions. BET surface area of the best produced activated carbon was 1289m2/g. The surface chemical characteristics of activated carbons were determined by FT-IR spectroscopic method. The microstructure of the produced activated carbons was examined by scanning electron microscopy (SEM). Thermal gravimetry (TG) and derivative thermal gravimetry (DTG) analysis of produced activated carbon was carried out.

Thermal Behaviors of Ferrocenyl-Terminated Hyperbranched Polyester

The first to the fourth generation (G1–G4) of ferrocenyl-terminated hyperbranched polyesters (HBPE-CP-Fe) were successfully synthesized by esterification between ferrocene carboxylic and hyperbranched polyester(HBPE).The molecular structures of HBPE-CP-Fe were characterized by FTIR, 1H NMR and 13C NMR techniques. The thermal properties and the structure of thermal decomposition segments were investigated by thermal gravimetry (TG)-derivative thermal gravimetry (DTG), differential scanning calorimetry (DSC), FTIR and element analysis techniques. G1–G4 HBPE-CP-Fe are more thermally stable than G1–G4 HBPE and the incorporation of ferrocene could efficiently improve the thermal stability of HBPE. The thermal degradation of HBPE-CP-Fe is multi-stage process between 240 and 500 °C and the mass loss of the HBPE-CP-Fe seems to stop further at the temprerature above 500 °C with the final weight losing rate of 78.6%. The left residua is carbon and iron elements. A possible thermolysis mechanism is proposed as that the thermal decomposition might contain some complicated subsequent reactions including the scission of weak links of ester bands, the formation of intermediate composites and the degradation of the ferrocene.

The thermolysis behavior of Ag/PAMAMs nanocomposites

Ag/polyamidoamine (PAMAM) nanocomposites were produced by photoreduction of relevant metallic salts in different generations of PAMAM (PAMAMs) methanol solutions under room temperature and ambient pressure. The obtained Ag nanoparticles were quite uniform in size with a diameter of about 15 nm. Thermogravimetric analysis (TGA) results showed that the amount of Ag nanoparticles could well affect the thermal stability of PAMAMs. As the mass ratio of Ag nanoparticles to PAMAMs increased, the weight-losing ratios decreased. Meanwhile, TGA curves also indicated that the thermal behavior of Ag/PAMAMs was greatly different in the two stages of low (130~280 °C) and high temperature (280~450 °C) range; the loading of Ag nanoparticles mainly influences the thermal stability of PAMAMs in high temperature region (280~450 °C). Moreover, the multistage decomposition profile of derivative thermal gravimetry curves suggested that there might contain some intermediate Ag/PAMAMs type of composites.

Thermal Decomposition of Chloromethylated Poly(styrene)-PAN Resin and Its Complexes with Some Transition Metal Ions

The complexes formed by the chemically modified chloromethylated poly(styrene)-PAN (CMPS-PAN) as a resin chelating ion exchanger were characterized by infrared and potentiometry. The thermal degradation of pure CMPS-PAN resin and its complexes with Au3+, Cr3+, Cu2+, Fe3+, Mn2+ and Pt4+ in air atmosphere has been studied using thermal gravimetry (TG) and derivative thermal gravimetry (DTG). The results showed that four different steps accompany the decomposition of CMPS-PAN resin and its complexes with the metal ions. These stages were affected by the presence of the investigated metal ions. The thermal degradation of CMPS-PAN resin in the presence of the ions showed different stability of the resin in the following decreasing order: Au3+>Pt4+>Mn2+>Cu2+>Cr3+>Fe3+. On the basis of the applicability of a non-isothermal kinetic equation, the decomposition process was a first-order reaction. The activation energy, Ea, the entropy change, ΔS *, the enthalpy change, ΔH * and the Gibbs free energy of activation, ΔG * were calculated by applying the theory of the reaction rates. The effect of the different central metal ions on the calculated thermodynamic activation parameters was discussed.

Properties’ improvement of epoxy resin using prepolymers prepared from diisocyanates and 3,9-dihydroxyethyl-3 ′,9 ′-dibenzyl-1,5,7,11-tetraoxaspiro(5,5)undecane

The prepolymers were prepared by the reaction of 3,9-dihydroxyethyl-3′,9′-dibenzyltetraoxaspiro(5,5)undecane ( 2) with 4,4′-diphenylenemethane diisocyanate (MDI) or hexamethylene diisocyanate (HDI) for improving the properties of the epoxy resin. The volume changes of the curing system was measured. The effects of the prepolymers on the conversion of epoxy group and thermal stability of the epoxy resin were studied. Glass transition temperature ( T g) of the modified matrix slightly decreased as the content of the prepolymers in the resin system increased. Two peaks appeared on derivative thermal gravimetry (DTG) curves of the modified epoxy resin. The one at the lower temperature was due to the decomposition of the polymeric linkages produced from the prepolymers, the other belonged to the decomposition of epoxy resin. The thermal stability of the modified matrix decreased because of the prepolymers as modifiers. However, the residual carbon of the modified matrix had an increasing tendency with quantity of prepolymer added. The strength of the modified matrix slightly decreased, but the elongation increased. When the mixture of E-51, prepolymers and BF 3-H 2NEt were used as adhesives, the tensile strength and shear strength were improved. The factors influencing the adhesive strength were investigated

Solidification/stabilization of arsenic salts: Effects of long cure times

Leachability of As III and As V from various solidification-stabilization ( S S ) binders has been studied over a period of four years. Type I portland cement (OPC), both alone and mixed with a number of additives, results in toxicity characteristic leaching procedure (TCLP) leachabilities of ≤ 3 mg l −1 for arsenite and ≤ 2 mg l −1 for arsenate. There is no appreciable change in leachability after 3 years of cure, compared with 28 days of cure. The combination of OPC and Class F fly ash as a binder results in substantially degraded performance, as measured by TCLP leachability. Furthermore, the OPC-FA-As mixtures show increasing leachability with time. These solidified products have been studied using powder X-ray diffraction (XRD), derivative thermal gravimetry (DTG) and solid-state magic angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR). The As V salt, NaCaAsO 4 · 7.5H 2O, is identifiable by XRD in many of these samples, particularly when sodium arsenate is the model As waste, but even when sodium arsenite is the original form of As. The OPC-FA mixtures show substantial respeciation during long curing times. There is evidence for formation of strätlingite from XRD, and there is substantial conversion of octahedrally coordinated aluminum, which is the predominant form at 28 days, to tetrahedrally coordinated aluminum at longer cure times, as shown by NMR. These matrix changes are correlated with increased leachability, although direct cause and effect cannot be established. These results emphasize the importance of long-term testing to identify specific combinations of S S binders and wastes that are prone to undergo respeciation, and consequent leachability changes, after long cure times.

SUPERCRITICAL EXTRACTION OF ISRAELI MISHOR ROTEM OIL SHALE 1. BATCH EXTRACTION WITH TOLUENE

ABSTRACT Recovery of organic material from Israeli Mishor Rotem oil shale with toluene under supercritical conditions was investigated. The rate of solubilization, change of structural aspects and molecular weights of solubilized products with time were investigated. Experiments to recover organic material from shale were performed in a stainless steel high pressure autoclave. Shale Sample was charged in a sintered glass crucible suspended from the cap of the autoclave; toluene was the solvent in all experiments. Solvent/shale ratio was 20; experimental temperature was 34O°C. The gaseous products were analyzed by gas chromatography. Molecular weights of the organic material recovered was measured by gel permeation chromatography technique. FTIR spectra of the organic material recovered and fractions isolated by extractive and chromatographical methods were measured. The amount of kerogen remaining in the spent shale was determined by oxidative derivative thermal gravimetry. A steady state in the productio...