Isothermal Mode Research Articles

A modeling analysis on industrial radial-flow packed-bed reactors for the catalytic dehydrogenation of long-chain normal paraffins: Appraisal of the modeling approach

Catalytic dehydrogenation of long-chain normal paraffins is the most attractive route for producing of linear alkyl benzene. To make this happen, the radial-flow packed-bed reactors are employed as one of the most efficient currently available technologies. Simplifying assumptions that are sometimes imposed on reactor models to reduce the computational cost may also significantly decrease the accuracy of simulations. Here, it is decided to shed light on this matter by assessing the effect of typical model-simplifying assumptions on simulation results. To this end, one- and two-dimensional semi-homogeneous models are used to simulate an industrial-scale radial-flow packed-bed dehydrogenation reactor under isothermal and adiabatic conditions. Simulations are designed in four 1D isothermal, 1D adiabatic, 2D isothermal, and 2D adiabatic modes to compare different modeling strategies and investigate the effect of flow distribution on the reactor performance. An appropriate LHHW kinetics model is considered for paraffin dehydrogenation and the main associated side reactions over a commercial Pt-Sn-K-Mg/γ-Al2O3 catalyst. The model equations are solved numerically using the finite element method by COMSOL Multiphysics CFD software. The results show a 1–3 % discrepancy between the predictions of one- and two-dimensional models for feed conversion under isothermal and adiabatic conditions. In contrast, the comparison of isothermal and adiabatic results for each one- and two-dimensional models indicate a discrepancy of 33–36 %. Furthermore, the two-dimensional model shows a low non-uniformity in flow distribution under reaction conditions (∼ 0.175), which has a trivial negative effect on paraffin conversion.

Kinetics of thermal decomposition of methyl derivatives of 7<i>H</i>-difurazanofuxanoazepine and 7<i>H</i>-tryfurasanoazepine

The thermal stability of N-methyl derivatives of 7H-difurasanofuroxanoazepine and 7H-trifurazanoazepine in non-isothermal and isothermal modes has been studied. Formal-kinetic regularities of decomposition and temperature dependences of reaction rate constants have been determined. The thermal stability methyl, propargyl, cyanomethyl, allyl and amine derivatives of azepines is compared.

Prototype Alarm Integrating Pulse-Driven Nitrogen Dioxide Sensor Based on Holey Graphene Oxide/In2O3.

NO2 seriously threatens human health and the ecological environment. However, the fabrication of highly sensitive NO2 sensors with rapid response/recovery rates, low detection limits, and ease of integration remains a challenge. Herein, benefiting from the fast carrier transfer and rich active sites, holey graphene oxide (HGO) was adopted to functionalize the In2O3 nanosheet to construct NO2 gas sensors. Characterization and theoretical calculations established the merits of HGO decoration in the NO2 sensing. The optimal sample, 0.5 wt % HGO/In2O3-sheet, exhibited superior sensing properties, resulting in a 1.37-fold improvement in response to 1 ppm of NO2 compared to the GO/In2O3 counterpart. Gas-sensing kinetics analysis revealed its lower activation energy and higher kinetic rate constants. Importantly, pulsed-temperature modulation was employed to decouple the gas adsorption from surface activation processes, achieving an ultrahigh response of 2776 to 1 ppm of NO2 for the 0.5 wt % HGO/In2O3-sheet sensor. Compared to the isothermal mode, this strategy enhanced the response value by 1.6 times, reduced the response/recovery time by 33%/70%, and enabled the detection of NO2 concentrations as low as 1 ppb. Finally, an NO2 monitoring alarm system based on the 0.5 wt % HGO/In2O3-sheet sensor with pulsed-temperature modulation was demonstrated for hazard warnings.

Kinetics of Thermal Decomposition of N-Propargil Derivatives of 7<i>H</i>-Difurazanofuxanoazepine and 7<i>H</i>-Trifurasanoazepine

The thermal stability of the propargyl derivatives of 7H-difurazanofuroxanoazepine and 7H-trifurazanoazepine in isothermal and non-isothermal modes has been studied. Formal kinetic regularities of decomposition and temperature dependences of reaction rate constants are determined. The thermal stability of propargyl, cyanomethyl, allyl and amine derivatives of azepines is compared.

Creating a new polyaniline@oak acorn biocomposite to remove chromium ions from wastewater effectively

A novel biocomposite material, polyaniline@oak acorn (PANI@OA), was synthesized through a straightforward in situ chemical polymerization process. The resulting adsorbent was subjected to a comprehensive analysis using various techniques, including Fourier transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), specific surface area measurement (BET), and X-ray photoelectron spectroscopy (XPS). This thorough characterization provided a detailed understanding of the material’s structure and properties. The effectiveness of synthesized material in removing Cr(VI) ions from water was investigated in a controlled batch adsorption setup. The findings highlighted a firm reliance on physicochemical properties during adsorption. The adsorption behavior of Cr(VI) onto PANI@OA fits best with the pseudo-second-order kinetic model and closely follows the Langmuir isothermal mode. The maximum adsorption capacity of this composite material was accurately measured at 249.09 mg.g−1. We also found that PANI@OA can be easily regenerated using a NaOH solution. Thus, allowing it to be used repeatedly to eliminate Cr(VI) from water. These outcomes strongly suggest the practical feasibility of employing PANI@OA as a versatile, low-cost, and environmentally friendly composite for environmental remediation due to its adequate adsorption capacity for wastewater treatment.

The influence of nucleotide context on non-specific amplification of DNA with Bst exo- DNA polymerase

In recent years, nucleic acid amplification methods that proceed in isothermal mode and require the use of DNA polymerases with strand-displacement activity have become increasingly widespread. Among these, the most popular is the Bst exo- polymerase, but it tends to carry out nonspecific DNA synthesis through multimerization. This study shows the influence of the nucleotide sequence on the binding of Bst exo- with DNA and on the efficiency of multimerization initiation. On single-stranded trinucleotides (sst) and dinucleotide duplexes (dst), molecular docking revealed the preference for binding of the “closed” form of Bst exo- to purine-rich sequences, especially those containing dG at the 3′ end of the synthesized strand. The data obtainedin silicowere confirmed in experiments using oligonucleotide templates that differ in the structure of the 3′- and 5′-terminal motifs. It has been shown that templates with an oligopurine 3′-terminal fragment and an oligopyrimidine 5′-terminal part contribute to an earlier start of multimerization. The obtained data can be used at the stage of selecting optimal nucleotide sequences for isothermal amplification, ensuring more reliable results. Thus, to avoid multimerization, DNA templates and primers containing terminal dA and/or dG nucleotides should be excluded.

How Does Temperature Affect the Charge Transfer Process in Flow Electrode Capacitive Deionization?

In this study, we investigate how temperature variations, a key environmental factor, affect the charge transfer process in FCDI systems across seasonal variation and geographical distributions, which is crucial for optimizing FCDI performance but has not received adequate attention. Therefore, thermal-assisted FCDI systems were proposed by controlling the temperatures of the flow electrode and saline water to simulate the environmental conditions, and the temperature effects on the charge transport and desalting ability of FCDI were investigated. First, the isothermal mode was performed, where the flow electrode and saline water were controlled at the same temperatures (0-50 °C) to simulate the natural atmospheric temperature fluctuations and industrial circulating cooling water system. Experimental results showed a strong positive correlation between temperature and electrosorption dynamics. Elevated temperatures significantly improved ion electromigration and diffusion, thereby enhancing the electrosorption capacity of the FCDI device. On this basis, the nonisothermal mode was designed via maintaining the temperature of the flow electrode at 50 °C to improve the desalination performance of FCDI for saline water at different temperatures (0-50 °C). Finally, the East China seawater and industrial circulating cooling water were both desalted successfully to confirm the feasibility of the temperature field in the practical application of FCDI.

THERMAL TRANSFORMATIONS OF MALTENES AND OILS FROM HEAVY METHANE BASE CRUDES

The paper considers changes of composition of oils and maltenes during thermal cracking process. The oils and maltenes (mixture Oils+Resins) were isolated from crudes from two oil fields: Zyuzeevskoye (Republic of Tatarstan) and Zuunbayanskoye (Mongolia). Both crudes relate to methane type, but differ by content of saturated, aromatic hydrocarbons, resins, asphaltenes and sulfur. Cracking of oils and (O+R) mixtures was carried out at 450 °С for 120 min in isothermal mode. Data on the mass balance of process, composition of gaseous and liquid cracking products were obtained. It was shown the С1-С5 hydrocarbons are predominate in the composition of gaseous cracking products of oils and (O+R) mixtures. Independent of cracking object their content changes in a series: C1 > C2 > C3 > С4-С5. The dynamics of group hydrocarbon composition changes in thermolysates was studied. It was shown the thermal transformations of hydrocarbons steer in the direction of destruction reactions during cracking of oils with high content of saturated hydrocarbons, as it indicated by gaseous products yield. Condensation reactions are dominated during cracking of oils, in composition of which aromatic hydrocarbons are prevail. It was shown the addition of resins into the complex multicomponent mixture of hydrocarbons leads to directivity change of cracking free radical reaction behavior. Differences in structural-group characteristics of average resins molecules reflect not only on the yield of solid and gaseous cracking products of (O+R) mixture, but also affect on the directivity of hydrocarbons thermal transformations. Moreover it is impossible to exclude the effect of differences in the content of saturated and aromatic hydrocarbons in the composition of oils on the components thermal transformations during cracking process of (O+R) mixtures. For citation: Voronetskaya N.G., Pevneva G.S. Thermal transformations of maltenes and oils from heavy methane base crudes. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 59-67. DOI: 10.6060/ivkkt.20246708.4t.

Composition effects on equilibrium oxygen isotope fractionation factors between garnets and quartz/calcite/olivine: Implication from vibration frequencies of garnets at high temperatures and high pressures

Garnet-group minerals, with their wide range of compositions, play a significant role in Earth's crust and upper mantle, participating in various petrological and geochemical processes. Oxygen isotope fractionation factors between garnets and other minerals hold crucial implications in these contexts. In this work, vibration frequencies were measured via Raman spectra on five garnet mineral samples in the pyrope-almandine-spessartine ternary system and four synthetic pyrope-grossular solid solutions at temperatures up to 1000 °C and pressures up to 17 GPa. Isobaric (γiP) and isothermal (γiT) mode Grüneisen, as well as anharmonic (ai) parameters, were determined for the observed modes. Our study shows that the vibration bands tend to shift to lower frequencies with increasing temperature and to higher frequencies with increasing pressure. Moreover, the anharmonic correction has been found to contribute positively to equilibrium oxygen isotope fractionation β factors in garnets, typically within 0.5 ‰ above 1000 K. The 103∙lnβ(T) factors calculated from vibration spectra (considering Г points only) align closely with those from theoretical calculations (including all frequencies in the Brillouin zone). Contributions from phonon dispersion (including none-Г points) are typically smaller than the uncertainties propagated from frequency measurements. Additionally, the pressure effect on the oxygen isotope fractionation in garnet, evaluated from the isothermal Grüneisen parameters, is found to be insignificant under crustal and upper mantle conditions, consistent with thermodynamic expectations. Using published oxygen isotope fractionation β factors for quartz and calcite, the equilibrium oxygen isotope fractionation factors (103∙lnα) are calculated between garnets of diverse compositions and any of these phases as functions of temperature, pressure and fraction of garnet endmembers. Considering composition effects helps to reduce the discrepancies among experimental and empirical calibrations of oxygen isotope fractionation factors between garnet and quartz. As an example application, oxygen isotope fractionation factors 103∙lnα(P, T) between garnets and forsterite were calculated under upper mantle conditions. Our findings suggest that these fractionation factors are predominantly dependent on temperature and garnet compositions, with minor influence from pressure. Compared with our calculated fractionation factors between garnet and olivine, the oxygen isotope exchange equilibrium may have been reached in some in kimberlite and mantle xenolith samples between garnet and olivine. However, in other samples, the fractionation factors cannot be explained solely by the composition effect, likely due to metasomatism. Our results underscore the importance of considering garnet compositions when interpreting their oxygen isotope compositions.

Development of a sectionalizing method for simulation of large-scale complicated natural gas pipeline networks

By 2025, the total mileage of natural gas pipelines in China is expected to reach 163,000 km, placing urgent demands on the simulation technology for increasingly large-scale and more complicated pipeline networks. This paper describes the development of a new sectionalizing method, which is based on optimization strategy, for simulating large-scale and complicated natural gas pipeline networks. Based on analysis of the topological structures, the entire pipeline networks are decomposed into multiple sub-networks according to the connecting nodes between the adjoined pipelines. The sectionalizing method is then implemented by minimizing the residuals of conservation for continuity and momentum at the connecting nodes in isothermal mode. The hydraulic variables in each sub-network are obtained after the hydraulic variables at connecting nodes are updated. The calculation accuracy and efficiency of this sectionalizing method are demonstrated by comparison with a commercial software through three different test cases. It is shown that the maximum relative deviation of pressure of the method developed is within 2.5% of that calculated using the commercial software. In a 5 × 104 km test case with variable spatial step sizes, the computational efficiency is 2.1 to 3.2 times of that of the commercial software. The results of the three case studies suggest that this sectionalizing method is promising and suitable for application to large-scale complicate natural gas network simulation.

A cavitation enabled green leaching of metals from spent lithium-ion batteries

As the world dabbles with increasing quantities of spent lithium-ion batteries (LIBs) and the need to recover valuable metals therein, sustainable approaches to achieving this need have become a necessity. In this work, we present the findings of an ultrasound-assisted intensification of a leaching process for the recovery of cobalt, nickel, manganese and lithium from spent LIBs. Molasses, methanesulfonic acid and ultrasonication were used together to enhance the leaching of the metals. The influence of ultrasonic modes, namely, sonication under isothermal and non-isothermal conditions, and leaching parameters, such as temperature, sonication amplitude, time, solid-liquid ratio, and reductant dosage, were evaluated. The leaching of metals was found to be strongly dependent on amplitude, temperature, and time. Compared to conventional mechanical stirring, the application of ultrasonic waves improves the leaching of metals by ∼22–74 %, with the degree of enhancement dependent on the temperature and the metal. The non-isothermal sonication mode (sonication without temperature control) has a lower energy input yet can yield a similar leaching performance as sonication under controlled temperature (isothermal mode). The results suggest that the introduction of ultrasonic waves created cavitation bubbles, which caused solid fragmentation, enhanced the mass transfer and diffusion of the reactants, and formed products that led to significant improvements in the leaching efficiency.

Efficacy of thermal analysis in the detection of bacterial strains in periprosthetic joint infections

In musculoskeletal surgery, joint and periprosthetic infections are rare but significant complications with a high risk of morbidity. Rapid diagnosis, surgical intervention and definitive antibiotic therapy are key factors to the success of the treatment and the recovery of former limb function. In addition to the current diagnostic procedures, there is a need to introduce new, therapy-centered diagnostic procedures in view of the increase in antibiotic resistance. In our current study, we set out to demonstrate the practical utility of differential scanning calorimetry and the isoperibolic calorimetry in diagnostics of joint and periprosthetic infections. We have shown significant differences among the different grade of arthritis. Under experimental conditions, synovial fluid samples were artificially superinfected with the most frequently occurring bacteria at a concentration of 103–105 CFU mL−1 and monitored in isothermal mode at 37 °C. The isoperibolic tests clearly showed a specific, concentration-dependent representative curve (duration of proliferation and its maximum rates) for each bacterial strain of the study. In our opinion, the different thermal analytical methods can be useful in the diagnosis of septic inflammatory processes and, in the rapid selection of definitive antibiotic therapy.

Single-phase thermosyphon heat transport device, a future prospect for heat removal applications: An experimental comparison with heat pipe and two-phase closed thermosyphon

Over the years, the passive mode of heat transportation has gained immense popularity, which includes two-phase devices viz. Heat pipe (HP) and Two-phase closed thermosyphon (TPCT). But recently, the thermosyphon heat transport device (THTD) entered the pool, wherein the heat transfer fluid (HTF) in liquid phase transports heat by natural circulation (thermosyphon). Hence, to gauge their efficacy, in the present experimental investigation, the three devices (with the same geometry and HTF) are compared by imposing isothermal (40°C–90 °C) and isoflux (50–900 W) heating conditions.In isothermal mode, HP transports heat with a minimal temperature gradient compared to TPCT and THTD. The thermal resistance (TR) of TPCT and THTD is 5.4 to 10.1 times and 6.6 to 10.1 times respectively greater than HP. For isothermal temperatures below 80 °C, the TR of THTD is less than TPCT (viscous limit). Later the trend reverses as the TPCT outperforms, while THTD experiences HTF boiling. Further, the heat extracted by HP is 2.1 to 3.9 times and 3 to 3.5 times greater than TPCT and THTD respectively. Hence, its application is justified if cost is not a concern, while THTD (with high-temperature HTF) is suggested over TPCT on an economic basis. Even the isoflux mode showed a similar trend of TR. The system response (based on time constant) depicted both HP and TPCT have similar and nearly constant values over the heat load range, while in THTD, it decreases with an increase in heat load and approaches the other two. Hence, a high-temperature HTF would lead to competitive results. Further, concerning the heat transport distance, as the TR of THTD remained the same compared to the increment in TPCT, the application of the former is justified in long-distance heat transportation. Ultimately, HP is the front-runner, while TPCT and THTD perform on par depending on operating conditions and geometry.

Compressibility, thermal expansion and Raman scattering of synthetic whitlockite Ca9Mg(PO3OH)(PO4)6 at high pressures and high temperatures

Abstract In-situ X-ray diffraction and 16 Raman scattering of synthetic whitlockite, Ca9Mg(PO3OH)(PO4)6, have been systematically measured at high pressures and high temperatures, respectively. The results show that whitlockite is stable up to ~ 15 GPa at ambient temperature and undergoes a temperature-induced dehydrogenation to merrillite above 973 K at ambient pressure. The obtained pressure-volume data were fitted using a third-order Birch-Murnaghan equation of state to yield the isothermal bulk modulus as K0 = 79(4) GPa with pressure derivative K0' = 4.3(6). When K0' was fixed at 4, the refined isothermal bulk modulus was 81(1) GPa. The volumetric thermal expansion coefficient (αV) is equal to 4.05(8) × 10-5 K-1. The axial thermal expansion coefficients (αa and αc) are 1.07(5) × 10-5 K-1 and 1.91(6) × 10-5 K-1. Both compressibility and thermal expansion show an axial anisotropy. The effects of pressure and temperature on the Raman spectra of whitlockite have been quantitatively analyzed. The isothermal and isobaric mode Grüneisen parameters, and the intrinsic anharmonic mode parameters of whitlockite were calculated. Some amounts of OH--bearing whitlockite may be preserved and could be discovered in meteorites if whitlockite undergoes a low temperature process.

Polymerization of D,L-lactide in the presence of biocompatible catalyst bismuth subsalicylate

Polymerization of D,L-lactide was performed in bulk at 160°C in the presence of bismuth (III) subsalicylate catalyst. Kinetics of the reaction was studied by differential scanning calorimetry in isothermal mode at 160°C and catalyst concentrations of 2500, 5000, and 7500 ppm. It was shown that the catalyst has a high activity: under this conditions an equilibrium conversion of 96% was achieved in 20–30 min, and the molecular weight of the resulting poly(D,L-lactide) reached 118 kDa.

The performance of Adsorbing and Removing gaseous acetic acid by activate carbon

Currently, gaseous molecular contaminants (acetic acid) is one of the main factors that cause defects in semiconductors and wafers, reduce product yields in high-tech process plants. Propylene Glycol Monomethyl Ethyl Ether Acetate (PGMEA) is a versatile solvent with many applications. Solvents used in the solder mask process in the manufacture of printed circuit boards (PCBs). The diluent in photoresist and edge bead removers used in semiconductor and wafer fabrication is PGMEA, which forms acetate contaminants through an acid-catalyzed hydrolysis reaction. The concentration standard of acetic acid pollutants in clean rooms is 1ppb.In order to protect the expensive optical components, the acetic acid generated by PGMEA needs to be controlled.For this purpose, the activated carbon filter in the intake filter prevents acetic acid from contaminating the components and corroding the material. In this study, we used the commercially available activated carbon fabricated filter to adsorption of acetic acid. The effect of adsorption under different face velocity (0.03/0.06/0.09 m/s) and initial acetic acid concentrations (4/6/8/10 ppm) were measured according to the principle of ASHRAE 145.1standard. The experimental data are also evaluated for adsorption performance, adsorption capacity, kinetic model of acetic acid adsorption process, and isothermal model of acetic acid adsorption process.The results of the acetic acid adsorption experiment show that MM3000 activated carbon has the highest adsorption capacity and the longest adsorption saturation time than KPL activated carbon. The higher the inlet acetic acid concentration at a fixed wind speed, the shorter the saturation time and the higher the adsorption capacity; the faster the wind speed at a fixed acetic acid concentration, the shorter the saturation time and the higher the adsorption capacity.The Langmuir (R2) of the MM3000 sample is higher than the Freundlich’s coefficient of determination (R2), which indicates that the adsorption phenomenon of the MM3000 sample is more suitable to be described by the Langmuir isothermal adsorption mode, which is the adsorption of a single molecular layer on a homogeneous surface. The Freundlich R2 of the KPL sample is higher than the Langmuir’s coefficient of determination (R2), which means that the adsorption phenomenon of this KPL sample is more suitable to be described by the Freundlich isothermal adsorption mode, and it is a case of adsorption of multiple layers on an inhomogeneous surface. The adsorption of MM3000 activated carbon and KPL activated carbon is more suitable to be described by the proposed second-order adsorption kinetic model, which is a phenomenon of chemisorption.

Modeling the curing kinetics of two thermoset adhesives under varying temperature conditions

AbstractThis paper presents detailed curing kinetics models for two thermoset adhesives. The cure kinetics were characterized using differential scanning calorimetry in both anisothermal and isothermal modes. The Sestak–Berggren autocatalytic model was applied to describe the anisothermal cure kinetics of the two adhesives with the Malek and undetermined coefficients methods determining their kinetic parameters. The Kamal autocatalytic model was adopted for the isothermal curing processes with the Kenny analytical‐graphical method determining the kinetic parameters. A modified Kamal model was developed by introducing a concept of the maximum degree of cure (DOC) and temperature‐depended kinetic parameters to describe the isothermal cure kinetics of the adhesive with a typical exothermic peak, and an extended Kamal model was further proposed by adding an initial‐phase‐control term to the modified Kamal model to describe the isothermal cure kinetics of the adhesive with two exothermic peaks. The results showed that the presented curing kinetics models with the determined parameters can precisely predict the evolutions of the DOC of the two thermoset adhesives in both anisothermal and isothermal modes.

Preparation and crystallization behavior of Cu-Zr-Ti amorphous composite powders

Three Cu-Zr-Ti plate-like amorphous alloy composite powders were prepared by ball milling the corresponding alloy powders. Their crystallization behaviors are systematically investigated by non-isothermal and isothermal modes. The phase transition during the ball milling would be Cu51Zr14→amorphous+Cu51Zr14 for Cu70Zr15Ti15, Cu51Zr14+Cu→amorphous+Cu+Cu51Zr14→amorphous+Cu for Cu80Zr10Ti10, Cu+Cu3Ti→amorphous+Cu for Cu90Zr5Ti5, respectively. The crystallization temperature increases according to the sequence of Cu70Zr15Ti15, Cu80Zr10Ti10 and Cu90Zr5Ti5. The crystallization phases are Cu3Ti and Cu for the isothermal crystallized Cu70Zr15Ti15, the nonisothermal and isothermal crystallized Cu80Zr10Ti10, and the nonisothermal crystallized Cu90Zr5Ti5. The crystallization phases are Cu51Zr14, Cu3Ti and Cu for the nonisothermal crystallized Cu70Zr15Ti15, while Cu for the isothermal crystallized Cu90Zr5Ti5. The detailed crystallization mechanism of non-isothermal and isothermal modes are discussed.

Highly stable hybrid porous polymers containing polyhedral oligomeric silsesquioxane (POSS)/Dibenzo[g,p]chrysene and Dibenzo[b,d]thiophene units for efficient Rhodamine B dye removal

In this study, we employed the Heck reaction method to synthesize three types of hybrid porous organic/inorganic polymers (HPPs) incorporating octavinylsilsesquioxane (OVS) units. Specifically, we synthesized OVS-TBN-DBTH, OVS-TBN-THS, and OVS-TBN-THSO2 HPPs by reacting OVS with different brominated organic compounds, namely, 2,7,10,15-tetrabromodibenzo[g,p]chrysene (TBN-Br4)/2,8-dibromodibenzo[b,d]thiophene (DBTH-Br2), TBN-Br4/2,3,7,8-tetrabromothianthrene (THS-Br4), and TBN-Br4/2,3,7,8-tetrabromothianthrene-5,5,10,10-tetraoxide (THSO2-Br4). Based on thermal analysis (TGA), the onset decomposition temperatures (Td10) for these HPPs were as follows: OVS-TBN-DBTH at 575 °C, OVS-TBN-THS at 313 °C, and OVS-TBN-THSO2 at 490 °C. Additionally, these HPPs exhibited high char yields, with values of 83, 53, and 67 wt% for OVS-TBN-DBTH, OVS-TBN-THS, and OVS-TBN-THSO2 HPPs, respectively. Furthermore, when analyzed using nitrogen adsorption–desorption measurements, both OVS-TBN-DBTH and OVS-TBN-THSO2 HPPs demonstrated impressive specific surface areas (SBET) of up to 380 m2/g. In addition, the OVS-TBN-DBTH and OVS-TBN-THSO2 HPPs provide an adsorption capacity of 70.62 and 77.1 mg g−1 (qmax from Langmuir isothermal Mode) toward RhB dyestuff at room temperature. In this adsorption system, after calculation, the OVS-TBN-THS HPP could be inferred that the adsorption is a pseudo-first order adsorption model. The OVS-TBN-THS HPP and OVS-TBN-THSO2 HPP in the pseudo-secondary order model have a better representation of the adsorption system for rhodamine B. This study introduces an innovative method for developing HPPs as adsorbents for water treatment and purification.

Differential scanning calorimetry as a tool to assess the oxidation state of cold-pressed oils during shelf-life

AbstractCold-pressed oils are highly prone to the peroxidation process, which causes a rapid decline in quality. Thus, there is a need to develop instrumental methods instead of conventional chemical analysis consuming large quantities of harmful chemicals. Differential scanning calorimetry (DSC) is a valuable analytical tool for assessing the oxidative stability of oils. Cold-pressed flaxseed, camelina and hemp seed oils from different cultivars, which had been stored for six months in room conditions under natural light exposure, were tested. Chemical methods for measuring changes in oxidative stability during storage of oils included determination of peroxide value (PV), p-Anisidine value (p-AV), total oxidation value (TOTOX) value and acid value (AV). Parameters like oxidation induction time (OIT) in isothermal mode (120, 140 °C) and onset temperature (Ton) in non-isothermal mode (heating rate 2, 5 °C/min) were established from DSC curves. Data for OIT and Ton plotted against time showed a strong, significant (p ≤ 0.05) descending trend for all oils. However, flaxseed and hempseed oils revealed a more rapid deterioration during storage compared to camelina seed oils. All DSC results showed promising repeatability of the oxidative characteristics for three types of cold-pressed oils, regardless of their origins in different cultivars. However, the most suitable for monitoring the deteriorative changes in oils during storage was the isothermal test carried out at a temperature of 120 °C, for which the correlations with chemical indicators (PV, p-AV, TOTOX) were highly significant (p ≤ 0.0001). Linear discriminant analysis (LDA) based on the DSC results revealed, that the first discriminating function significantly separated the fresh oils from stored oils. The study showed that, based on a starting point defined for fresh oils, the DSC technique can be used to effectively and ecologically monitor the deterioration of oils by oxidation, instead of harmful chemical analyses.