Thermodynamic Parameters Research Articles

Theoretical study of the anharmonic effect on the main reactions in the combustion mechanism of methanol

The harmonic and anharmonic rate constants, kinetic and thermodynamic parameters of the important reactions of the combustion mechanism of CH3OH are calculated from 300 K to 4000 K. Furthermore, the effect of pressure and tunneling effect are considered in this paper. The calculations indicate that the bimolecular reaction exhibits a particularly obvious anharmonic effect than the unimolecular reaction. The calculated anharmonic rate constants are more in line with other theoretical or experimental results. In summary, these calculations complement the basic database of methanol, thereby improving the accuracy of the combustion reaction mechanism.

Methylene blue dye elimination from synthetic wastewater by modified adsorbent produced from Foeniculum vulgare waste: Thermodynamic, equilibrium, and kinetic studies

In the current investigation, seeds of the Foeniculum vulgare plant were acquired from the KSA, Tabuk City, and its powder was chemically modified by four different reagents. The four resulting samples were identified by SEM and IR techniques and inspected for methylene blue (MB) dye adsorption. The influence of MB concentration, adsorbent dose, solution pH, temperature, and contact time on adsorption performance was examined. This adsorption's kinetic, isothermal, and thermodynamic parameters were correspondingly studied. The idyllic adsorbent was established to be the modified sample with oxalic acid, which removed 90.15 % of the MB dye. It was also shown that the MB adsorption matched well with the kinetically 2nd -order model. The findings of the experiment fit better with the model of Langmuir isotherm than the other models. The negative values of each ΔG°, ΔH°, and ΔS° indicate the adsorption of MB is an exothermic and spontaneous process. The very law value of adsorption enthalpy proves the physisorption adsorption. The very high maximum adsorption capacity (qmax) values of this adsorption (892.857, 684.932, 487.805 mg g−1), the stability and availability and of this oxalic acid modified adsorbent suggest it will be highly valued in the field of water decontamination.

Supreme capture of Europium(ΙΙΙ) by silica-hyperbranched poly(ethylene imine) composites from aqueous solutions − A mechanistic study

Two bio-inspired variations of the sol–gel technique produced silica-hyperbranched poly (ethylene imine) (PEI) composite nanoparticles (NP) and xerogels (XG). Both methods are performed in ambient conditions and do not require toxic organic solvents or high temperatures. We have investigated the removal efficiency of trivalent europium by these two hybrid species in near-neutral aqueous solutions. The adsorption kinetics and isotherms, including data fitting with the pseudo-first and second order kinetic, and the Langmuir isotherm model are presented and discussed. Thermodynamic parameters indicate exothermic reaction (–180 kJ/mol for NP and –192 kJ/mol for XG, respectively) In addition, spectroscopic (Fourier Transform Infra-Red FTIR, Fluorescence Spectroscopy FS, X-ray Photoelectron Spectroscopy XPS) and microscopic techniques (Scanning Electron Microscopy SEM coupled with Energy Dispersive X-ray analysis EDX), as well as ζ-potential and Dynamic light scattering (DLS) measurements, have been employed to evaluate the interaction mechanism between the surface active moieties and Eu(III). The extremely high and homogeneous dispersion of the amino and silicate groups of the composites has led to the highest capacity value (22 mmol/g or 3343 mg/g and 14 mol/g or 2128 mg/g for the two distinct forms of the nanoparticles and the xerogels, respectively) reported up to today implying a potential application for lanthanide recovery. The adsorption data along with the spectroscopic and microscopic indicate that the adsorption is well described by the Langmuir isotherm model and is based on the formation of inner- and outer-sphere complexes between Eu(III) the amine and −Si-O− moieties.

Measurement of thermal conductivity of thermally reactive materials for use in pyrolysis models

AbstractPyrolysis models are used in the fire science field to simulate the thermal decomposition of materials. These models require knowledge of the kinetic and thermodynamic parameters of an assumed reaction mechanism, and the thermophysical properties of the virgin material and product species. Standard test methods exist for measuring the thermal conductivity of nonreactive materials, but to date no suitable method exists that is compatible with contemporary pyrolysis models and is applicable to thermally reactive materials. In the present study, a modified methodology was presented and evaluated to address this need. The methodology involves a preliminary assessment of thermal stability, followed by a series of tests including: thermogravimetric analysis, differential scanning calorimetry, and laser flash analysis. Once a reaction mechanism has been identified, gram‐scale samples of the virgin and stable product species are isolated and independent measurements of thermal conductivity of those species are obtained. The methodology was applied to eucalyptus fiber hardboard, for which a complete set of property data for pyrolysis modeling was obtained. A pyrolysis experiment was then conducted, and that experiment was simulated using a pyrolysis model parameterized with the measured property data. Model predictions of the mass loss rate and temperature rise of a hardboard sample exposed to radiant heat flux of 35 and 60 kW m−2 were found to be a good match to measurements. These results demonstrate the suitability of the property data, the pyrolysis model, and the utility of this approach. This work will serve as a basis for property determination in future pyrolysis studies.

Superior adsorptive uptake of methylene blue pollutant by nanobiochar- impregnated-layered double hydroxides

Design and assembly of novel, sustainable, ecofriendly and low-cost nanobiosorbents by facile and green approaches are generally aimed to apply in remediation of toxic and nonbiodegradable pollutants from aquatic systems. Hence, the current study is directed to synthesize a novel nanobiosorbent by a facile solid–solid and microwave-assisted approach for direct impregnation of derived nanobiochar from pomegranate peels waste feedstock (PPNC) onto magnesium (II) aluminum (III)-layered double hydroxide (MgAl-LDH) for the generation of MgAl-LDHs@PPNC. This was initially characterized by several techniques to confirm the morphological and structural features. The particle size range was identified (13.47–41.78 nm) and the concluded elemental compositions were Al (9.49 %), Mg (19.33 %), C (25.4 %), and O (45.78 %) according to the energy-dispersive X-ray (EDX) analysis. The Fourier Transform-infrared (FT-IR) study denoted to several incorporated surface functionalities as –COOH, –OH, metal–O and others functionalities. MgAl-LDHs@PPNC exhibited a good surface area 275.57 m2g−1, while the zero-charge point was also detected at 6.0. Some experimental impacting conditions were testified and optimized by the batch removal system of methylene blue dye pollutant (MBDP) by MgAl-LDHs@PPNC. The concluded optimum conditions were figured out at pH 7.0, 15 min reaction duration, 25 mg nanobiosorbent dosage and 25 °C reaction temperature. Related expressions to isotherm and kinetic investigations were testified to confirm the most correlated experimental data to both Freundlich and pseudo-2nd-order expressions. Thermodynamic parameters were additionally computed to refer to the exothermal spontaneity trends in adsorptive reaction of MBDP onto MgAl-LDHs@PPNC. The evaluated nanobiosorbent is therefore, labeled with high stability to providing highly acceptable efficiency at 82.7–99.2 % (5 mgL−1) by the first-fifth regeneration processes. MgAl-LDHs@PPNC was finally afforded excellent removal uptake of MBDP (5 mgL−1) from real contaminated waters giving 93.17–98.27 %.

Thermokinetic study of tannery sludge using combustion and pyrolysis process through non-isothermal thermogravimetric analysis

Sludge from the tannery is produced in enormous amount. This work has investigated the thermal analysis behaviour of the tannery sludge by use of the thermogravimetric analysis (TGA). The TGA experiments is carried out in both air and nitrogen environment at the varied heating rates of 5, 10, 20 and 40 °C/min from the temperature range of 30–900 °C. In the assessment of kinetic parameters, the model fitting (Combined kinetics) method was employed. It was investigated that thermal degradation of the tannery sludge sample occurred in three stages. Majorly the conversions were observed in stage II for both in air and nitrogen environment. The activation energy (Ea) value for the combustion is 165.9 kJ/mol while for the pyrolysis the Ea value is obtained as 65.2 kJ/mol from the conversion range between 0.2 and 0.8 which is a promising approximation supported by a strong R2 value of 0.9719 and 0.93 for combustion and pyrolysis respectively. It is estimated from the master plots that six ideal models A1/2, A1/3, A1/4, F3, F4 and D5 were probably in approximation with the linear fitted data for both air and nitrogen. Various thermodynamic parameters which include the ΔH, ΔG and ΔS are also complimented that indicates the formation of activated complex and non-spontaneity of the reaction. The detailed thermokinetic study of the tannery sludge in combustion and pyrolysis offers a novel approach to understanding how this waste material decomposes under different temperature conditions. This holistic perspective contributes valuable insights into waste management practices, environmental impacts, resource recovery, and process optimization within the leather industry. Furthermore, the optimization of leather production processes on a large scale can minimize waste generation and enhance energy efficiency, strengthening the competitiveness and sustainability of the leather industry.

Preparation of poly(methacrylic acid) grafted on SiO2-NH2/PSF composite membranes for amlodipine removal

Firstly, the SiO2 microspheres were prepared by Stӧber method, and then modified by 3-Aminopropyltrimethoxysilane (KH-540) to introduce –NH2 onto the microspheres. Then, SiO2-NH2 microspheres were mixed into polysulfone casting solution, and SiO2-NH2/PSF composite membrane was prepared by the phase conversion method. On this basis, the functional adsorbent SiO2-NH2/PSF-g-PMAA was prepared by grafting polymerization of methacrylic acid (MAA) as a functional monomer using –NH2/S2O8 2− surface initiation system. The samples were characterized by Fourier infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), the Brunauer–Emmett–Teller (BET) and weighing method. The adsorption properties of amlodipine (ADP) by functional adsorbents were investigated, and the adsorption mechanism was further studied. The results show that the adsorption reaches equilibrium at 180 min, and the adsorption kinetics can be well fitted by the pseudo-second-order model. The adsorption capacity of SiO2-NH2/PSF-g-PMAA for amlodipine in methanol with 1.4 mg/mL at 15 °C is 137 mg/g. The adsorption ability increases with the decrease of ionic strength and temperature via the hydrogen bond and ionic interactions, and the adsorption of ADP by SiO2-NH2/PSF-g-PMAA is consistent with the D-R adsorption isotherm model. Thermodynamic parameters imply that adsorption is a spontaneous and exothermic process.

Scale effects on rotating detonation rocket engine operation

Rotating detonation rocket engines are propulsive devices employing detonation waves moving circumferentially around an annular channel that consume axially fed propellants. Theoretically, this provides benefits with respect to combustion pressure gain and thermodynamic efficiency when compared to deflagration-based combustors. To facilitate size scaling of these devices, the relationships between geometric parameters, performance, and wave dynamics have been investigated with gaseous methane-oxygen propellant. Empirical relations were derived between combustor geometry, fueling conditions, and engine operation, as well as correlation to thermodynamic parameters calculated with chemical kinetics codes. The radius of curvature effects were explored in annular combustors having outer diameters of 25 mm, 51 mm, and 76 mm with a fixed gap width of 5 mm. The injectors were scaled to have same oxidizer-to-fuel injector port area ratio, impingement distance, and injector-to-gap area ratio. Larger combustors had higher wave counts during operation at a given mass flux and equivalence ratio. Combustor axial pressures were found to be more dependent on propellant mass flux and equivalence ratio than geometry. Mass flux and the inner-to-outer radius ratio, the latter of which was related to other geometric ratios, dictated the operating mode transition thresholds and the number of resulting waves, respectively.

Surface Plasmon Resonance Allows to Correlate Molecular Properties with Diffusion Coefficients of Linear Chain Alcohols.

Every biological and physicochemical process occurring in a fluid phase depends on the diffusion coefficient (D) of the species in solution. In the present work, a model to describe and fit the behaviour of D as a function of structure and extensive thermodynamics parameters in binary solutions of linear chain organic molecules is developed. Supporting experimental and computational evidences for this model are obtained by measuring D for a series of n-alcohols through a novel surface plasmon resonance method and molecular dynamics simulations. This allows to propose a kind of combined analysis to explain the dependence of D on various thermodynamic and structural parameters. The results suggest that for small linear systems in the range from 0 to 200 g mol-1 and under the assumption that the diffusive activation energy is a linear function of mass, D is strictly dependent on the molecular shape and on the relative strength of the solute-solvent intermolecular forces represented by a parameter named R. The newly proposed approach can be utilized to characterize and monitor progressive changes in physicochemical properties for any investigated species upon increasing the dimension of the aggregate/molecule along a certain direction.

The Binding Mechanism Between Cyclodextrins and Anticancer Drug Noscapine: A Spectroscopic and Molecular Docking Study.

In this paper the binding of noscapine (NOS) as an anticancer drug with poor bioavailability and low solubility with beta and methyl-beta cyclodextrins (β-CD and M-β-CD) as the biocompatible drug carriers were discussed using ultraviolet-visible, fluorescence and nuclear magnetic resonance spectroscopy, as well as molecular docking. The absorption of NOS changed when it was bound to both cyclodextrins, resulting in a hyperchromic shift. It formed a 1:1 stoichiometry inclusion complex with both cyclodextrins according to the Benesi-Hildebrand equation. The binding affinity was larger in NOS-M-β-CD (5.9 (± 0.66) × 103 M- 1) than NOS-β-CD (3.7 (± 0.22) × 103 M- 1) complex. The fluorescence emission band of NOS at 408nm was quenched when NOS was complexed with β-CD, and enhanced in the presence of M-β-CD, while the shoulder at 350nm was enhanced selectively when NOS was complexed with M-β-CD. The fluorescence quenching of NOS with β-CD showed a negative deviation from the Stern-Volmer. The thermodynamic parameters have been estimated with the help of the Van't Hoff equation in different temperatures, and a dynamic mechanism was proposed for quenching. Also, both ΔH and ΔS have positive values thus the main interactions result in hydrophobic forces. Moreover, the negative value of ΔG indicates that the bonding process is spontaneous. 1H NMR chemical shift changes were observable for NOS and both CDs protons due to the chemical environment changes of some nuclei upon complexation. The molecular docking results revealed that the 1:1 inclusion complex possesses a good molecular shape complementarity score for their most probable structures, and indicated that the M-β-CD inclusion system gave the higher complexation efficiency. The binding energy values for β-CD and M-β-CD were determined to be -6.7 and - 9.5kcal/mol, respectively. These findings suggest the same as the result of experimental tests that the NOS-M-β-CD complex is more stable than the NOS-β-CD complex.

Molecular analysis of recombinant collagenase from Bacillus siamensis strain Z1: Gene Cloning, expression and in-silico characterization

This study focuses on gene cloning, expression, biochemical and analytical characterization along with structural and functional characterization of collagenase followed with molecular docking, dynamics study and Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA). The collagenase gene identified from the genome of the novel collagenase Bacillus siamensis strain Z1 is introduced into E.coli DH5α, subsequently expressed in E.coli BL21 (DE3) withisopropyl β −d – 1 − thiogalactopyranoside(IPTG) induction and further affinity purified yielding in ∼ 89.4 kDa recombinant collagenase which demonstrated alkali characteristics and thermostability determined by thermodynamic parameters. Recombinant collagenase revealed good stability when exposed to diverse biochemical components. The recombinant collagenase identity was confirmed through matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) showing specific mass peaks and via N-terminal sequence analysis as MTAVNQTISK. Moreover, the concluded N-terminal amino acid sequence from Edman degradation displayed significant resemblance. The structural and functional analysisof recombinant collagenase was analysed by Circular dichroism (CD), Proton nuclear magnetic resonance (1H NMR) spectrometry and Thermogravimetric analysis (TGA). The recombinant collagenase also showed gelatin liquefaction ability. The collagenase gene sequence is also assessed for structural and functional characterizations by using various computational tools and revealed its classification in U32 family peptidase. A Grand average of hydropathicity index (GRAVY) score of −0.295 and instability index of 37.22 was obtained. Homology model of collagenase gene was generated by employing SWISS-MODEL and structure analysis by Ramachandran plot. Molecular docking of modelled collagenase with four different substrates was carried out by PyRx and Autodocking. Highest docking score of −12.7 kcal/mol was obtained for Alaska pollock hydroxyproline containing marine collagen peptide (APHCP). Subsequently, Molecular dynamics and simulations for highest score docked complex was assessed using GROningenMAchine for Chemical Simulations (GROMACS).

Effect of molecular crowders on ligand binding kinetics with G-quadruplex DNA probed by fluorescence correlation spectroscopy

Guanine-rich single-stranded DNA folds into G-quadruplex DNA (GqDNA) structures, which play crucial roles in various biological processes. These structures are also promising targets for ligands, potentially inducing antitumor effects. While thermodynamic parameters of ligand/DNA interactions are well-studied, the kinetics of ligand interaction with GqDNA, particularly in cell-like crowded environments, remain less explored. In this study, we investigate the impact of molecular crowding agents (glucose, sucrose, and ficoll 70) at physiologically relevant concentrations (20% w/v) on the association and dissociation rates of the benzophenoxazine-core based ligand, cresyl violet (CV), with human telomeric antiparallel-GqDNA. We utilized fluorescence correlation spectroscopy (FCS) along with other techniques. Our findings reveal that crowding agents decrease the binding affinity of CV to GqDNA, with the most significant effect—a nearly three-fold decrease—observed with ficoll 70. FCS measurements indicate that this decrease is primarily due to a viscosity-induced slowdown of ligand association in the crowded environment. Interestingly, dissociation rates remain largely unaffected by smaller crowders, with only small effect observed in presence of ficoll 70 due to direct but weak interaction between the ligand and ficoll. These results along with previously reported data provide valuable insights into ligand/GqDNA interactions in cellular contexts, suggesting a conserved mechanism of saccharide crowder influence, regardless of variations in GqDNA structure and ligand binding mode. This underscores the importance of considering crowding effects in the design and development of GqDNA-targeted drugs for potential cancer treatment.

Ultrafast and efficient extraction of heparin via cationic brush magnetic adsorbents

Heparin is a highly sulfated polysaccharide used extensively as an anticoagulant. However, conventional heparin extraction processes remains time-consuming and inefficient. We report cationic brush magnetic adsorbents by grafting poly(3-acrylamidopropyl) trimethylammonium chloride-co-N‑isopropylacrylamide random copolymers onto the surface of Fe3O4 for ultrafast and efficient heparin extraction. The fabricated adsorbent demonstrated an excellent adsorption capacity of 169.36 mg g−1 and a record-breaking adsorption rate towards heparin due to the introduction of N‑isopropylacrylamide, providing more adsorption sites and larger transport channels for the macromolecule heparin to access active sites. In addition, the adsorption capacity and rate for crude heparin were significantly better than those of commercial resin. Thermodynamic parameters implied that the heparin adsorption was spontaneous and endothermic process. The adsorption mechanism can be described by the synergistic effect of electrostatic attraction and hydrogen bond. This study paved an innovative approach to simultaneously enhance the adsorption rate and capacity of the adsorbent for polysaccharide.

Synthesis of green ceramic adsorbent for the treatment of tire factory effluent containing lead, zinc, aluminum, cobalt, iron and manganese ions

In this study, a novel nano-composite ceramic adsorbent was synthesized and characterized for the removal of heavy metal ions from industrial wastewater. The adsorbent was prepared using low-cost materials including clay and human hair, and hydroxyapatite nanoparticles derived from bovine bones. The synthesis method, material properties, and adsorption performance were thoroughly investigated wed XRD, FT-IR, FE-SEM and, BET. The adsorption process was optimized using Design Expert software, resulting in optimal conditions of pH 6.5, adsorbent mass of 22.5 g, temperature of 44.5 °C, initial concentration of 281 mgL−1, and retention time of 192 min. Thermodynamic parameters indicated that the adsorption process was spontaneous, endothermic, and followed the Freundlich isotherm model. The adsorption mechanism involved ion exchange, physical and chemical surface adsorption, facilitated by the unique surface properties of the nano-composite adsorbent. Moreover, the adsorbent exhibited high regeneration efficiency, with up to 73 cycles of reuse without a decrease in removal efficiency.

Investigation on Heterostructured SeO2–TiO2 Nanofluoroprobe for Highly Selective and Sensitive Detection of a Neonicotinoid Insecticide, Imidacloprid in Soil and Water Matrixes

Heterostructured SeO2–TiO2 nanoparticles were used as a highly sensitive and selective fluoroprobe for the detection and determination of neonicotinoid insecticide imidacloprid. The sonication-assisted co-precipitation technique was used to create nanoparticles, which were then characterized using UV–Vis, SEM–EDS, HRTEM, XRD, and TGA. These analyses revealed that the nanoparticles had globular morphology, a crystallite size of 14 nm, a bandgap of 2.45 eV, and stability at high temperatures. Fluorescence emission at 548 nm wavelength exhibits high sensitivity and selectivity for imidacloprid over other pesticides with complete fluorescent quenching at 2 × 10–4 M concentration of imidacloprid. Stern–Volmer equation and thermodynamic parameters applied to the experimental data over a temperature range of 20–50 °C provide the Ksv value in the range of 1.56 × 105 to 2.69 × 105 M−1 and indicate strong interactions, dynamic, spontaneous, and endothermic quenching process. Furthermore, the excellent salient features and notably the unaffected performance even in the presence of various anions, fertilizer, and binary mixture of pesticides often sprayed on plants, will pave the way for the development of rapid, affordable, selective fluoroprobe for onsite monitoring of imidacloprid. The reliability for determination is also examined for spiked soil samples to develop a hybrid SeO2–TiO2 nanoparticles fluoroprobe as a simple alternative to existing techniques for the detection of imidacloprid.Graphical

Experimental and computational explorations for the inhibitive performances of synthesized green surfactants against the corrosion of copper in nitric acid

The inhibitory characteristics of two recently synthesized biosurfactants based on amino acids, namely sodium N-hexadecyl glycine (I) and sodium N-hexadecyl valine (II), concerning copper corrosion in 1.0 M HNO3 were studied at variance of temperatures. FTIR analysis was utilized to identify the chemical structures of both synthesized biosurfactants. Various techniques were employed in this study. According to the results, the synthesized biosurfactants were played as proficient inhibitors for copper corrosion and their inhibition efficiencies (% IEs) were concentration- and structure-dependent with respect to them. At a concentration of 400 mg/L of the synthesized biosurfactants and at 298 K, the average% IE was found to be 90% for biosurfactant I and 85% for biosurfactant II. The gained higher% IEs were suggested to as a result of the potent adsorption of these biosurfactants on the surface of copper and the type of adsorption was discovered to be physical and followed Langmuir adsorption isotherm. The obtained findings signified that the synthesized biosurfactants exhibited mixed-type and interface-type inhibitors. The thermodynamic and kinetic parameters were assessed and discussed. Furthermore, the kinetics of corrosion of copper as well as its inhibition were also investigated. The density functional theory (DFT) and molecular dynamics (MD) simulations emphasized the inhibitory mechanism of the examined biosurfactants and proved the adsorption of the biosurfactants’ molecules on the copper surface. Theoretical modeling also demonstrated that the biosurfactant I exhibited a greater% IE compared to biosurfactant II. The experimental results gained from all employed measurements are largely reliable with each others and are in a good consistent with the theoretical studies signifying the validity of these results.

Computational Assessment of the Phytochemicals of Panax ginseng C.A. Meyer Against Dopamine Receptor D1 for Early Huntington's Disease Prophylactics.

A herb, Panax ginseng C.A. Meyer has been used traditionally for the treatment of various diseases. In this work, its chemical components have been explored by computational methods for the possibility of therapeutic potential against early Huntington's disease. The molecular docking calculations against dopamine receptor D1 (PDB ID: 7X2F) involved in pathogenesis of early Huntington's disease gave the binding affinities (kcal/mol) of schizandrin (-10.530), ergosterol (-10.124), protopanaxadiol (-9.650), panaxydol (-9.399), diphenhydramine (-9.358), and panasenoside (-9.358). The values for native ligand (-7.748) and some selected drugs, Nefazodone (-9.880), Risperidone (-9.752), and Haloperidol (-9.712) were higher revealing weaker interactions. The stability assessment of top protein-ligand adducts in terms of various geometrical and thermodynamical parameters extracted from 200 ns molecular dynamics simulations pointed to schizandrin, protopanaxadiol, and panasenoside as hit molecules. The minimal translational and rotational motion of the docked ligands at orthosteric pocket of the receptor at near physiological conditions hinted at the probability of it restricting or inhibiting over-activation of DRD1. The sustained thermodynamic spontaneity of complex formation reaction augmented the inferences derived from spatial results. The phytochemicals from Panax ginseng could be used in the prophylactics of early Huntington's disease and recommendation is made for further evaluation by experimental work.

Biophysical studies of human serum albumin with cocaine and cocaethylene: Understanding the drug-protein interaction in simulated physiological conditions

In this study, HSA was used as a transport protein model to simulate the transport dynamics and availability of cocaine (COC) and its pharmacologically active metabolite, cocaethylene (CE). In the interaction studies between the alkaloids and HSA, the binding constant (Kb) values were higher for CE (2.92 to 8.33 × 104 M−1) than COC (1.15 to 3.77 × 104 M−1) at different temperatures. Thermodynamic parameter calculations indicate that COC preferentially interacts through van der Waals forces and hydrogen bonds, while CE interacts hydrophobically. Competition studies using the ANS probe confirmed the more hydrophobic characteristics of CE. Synchronized fluorescence indicated that both compounds preferentially interact in the microregion of the Trp214 residue. Based on 3D fluorescence, UV–vis, and circular dichroic results, changes in the secondary structure of the protein were confirmed. Studies to assess the HSA binding site were carried out using warfarin (site I), diazepam (site II), and digitoxin (subdomain IIIB) as markers, and it was verified that both compounds interact preferentially at the site I. Finally, based on the 1H NMR and theoretical studies, it was possible to propose the alkaloid epitope in the interaction with HSA. In conclusion, when compared to COC, CE presented greater HSA protein affinity, justifying its longer plasma lifetime and increasing the drug’s effects on the body.

Efficient CO2 capture using a novel Zn-doped activated carbon developed from agricultural liquid biomass: Adsorption study, mechanism and transition state

A Zn-doped carbon was prepared and used as an effective CO2 adsorbent. This carbonaceous material was developed from olive mill wastewater (OMWW) by an innovative process using thermal shock flash pyrolysis followed by zinc chloride impregnation at ambient temperature. The developed Zn-doped carbon is highly porous (1406.56 m2.g−1), thermally stable and rich in active sites. The Temkin isotherm and the pseudo-second order kinetic model best describe the adsorption of CO2 on the developed material, and the storage capacity is of 370.41 mg g−1 (293 K). Thermodynamic parameters showed favorable, exothermic, and orderly adsorption. Two new isotherms, based on the number of layers formed at the surface, developed by advanced statistical modelling, were adapted and used to understand the mechanism in depth. The analysis of the results showed that CO2 adsorption occurs through the appearance of double layers on the adsorbent surface. Adapted models showed: only one molecule was adsorbed per surface active site, a very low degree of aggregation of CO2 molecules before adsorption and the molecules were adsorbed in a parallel orientation. The activation parameters showed a rapid and physical adsorption with a drop in entropy at the transition state. The mechanisms involved were governed by thermodynamic control with the possibility of easy desorption at high temperature. Zn-doped carbon is an ecological approach to reduce CO2 emissions on the globe.

Study on the adsorption performance of zeolite imidazole frameworks materials for Co(II) and Mn(II) in solution

Abstract The radionuclides 60Co and 54Mn are the main activation products produced in the operation of nuclear power facilities. Wastewater with these radionuclides must be treated to meet standards before being discharged. A variety of zeolite imidazole frameworks (ZIFs) materials were synthesized at room temperature, and the adsorption effect of ZIF-67 was found to be the best through adsorption experiments on Co(II) and Mn(II). The thermal stability test and structural characterization of ZIF-67 were carried out. At the same time, the influence of the initial pH value, adsorption time, and initial concentration of the solution on the adsorption of Co(II) and Mn(II) by ZIF-67 was investigated. The results show that: ZIF-67 has a microporous structure with a BET surface area of 1,035.72 m2/g. In addition, ZIF-67 has good thermal stability, under the condition of pH = 6, a temperature of 303 K and the initial concentration of 500 mg/L. The saturated adsorption capacity for Co(II) and Mn(II) reached 230.25 mg/g and 338.75 mg/g, respectively. ZIF-67 exhibits good selective adsorption performance for Co(II) and Mn (II) in high concentration interfering ion solutions and multi-ion solutions. The adsorption process of ZIF-67 was analyzed by kinetics, thermodynamics, isotherms, and adsorption diffusion models. The analysis of thermodynamic parameters shows that the adsorption process of ZIF-67 to Co(II) and Mn(II) is spontaneous and endothermic. The pseudo-second-order kinetic model, Langmuir isotherm model, and Boyd model are more in line with the adsorption process of Co(II) and Mn(II) by ZIF-67. It shows that the active sites on the surface of ZIF-67 are evenly distributed, and the adsorption process is single-molecule chemical layer adsorption. In addition, the liquid film diffusion dominates the adsorption rate during the adsorption process of Co(II) and Mn(II) by ZIF-67.