Thermodynamic Parameters Research Articles

Synthesis, Characterization, Biological Potency, and Molecular Docking of Co2+, Ni2+, and Pd2+ Complexes Derived From Carbohydrazone Ligand and Its Application in Dye Removal

ABSTRACTAs a result of the Schiff base condensation reaction between carbohydrazide and 4‐aminoacetophenone, novel HL ligand [(Z)‐N′‐((Z)‐1‐(4‐aminophenyl)ethylidene)‐2‐(1‐(4‐aminophenyl)ethylidene)hydrazine‐1‐carbohydrazide] and three coordination compounds were successfully obtained with the formulas of [Co2(L)(Cl)3(H2O)].Cl, [Ni2(L)(Cl)2(H2O)2].Cl.H2O, and [Pd (HL)(Cl)(H2O)].Cl, the obtained structures were analyzed using analytical and spectroscopic techniques such as Fourier‐transform infrared (FT‐IR), NMR, UV–Vis, molar conductivity, elemental analysis, and magnetic susceptibility measurements. Additionally, thermal stabilities, kinetic, and thermodynamic parameters were estimated utilizing thermogravimetric analysis. The structures were confirmed through quantum chemical computations. The antioxidant, anticancer, and antimicrobial biological efficacies of the ligand and its metal chelates were assessed. The ligand shows optimistic results as an antioxidant, while Co2+ and Pd2+ complexes showed the highest antimicrobial activities. The DNA binding affinity and cleavage of the isolated compounds were evaluated. Furthermore, the fluorescence spectrum of ligand in the absence and presence of Co2+ was recorded in order to investigate the interaction affinity along with the limit of detection. Another application of this work is the removal of methylene blue and crystal violet dyes from wastewater and reusability, through an inventive synthesis of a cellulose‐based material “LDC” Schiff base.

Structural Aspects, Binding Interactions, Biological Activity of Co(II)‐ and Ni(II)‐N′‐(2‐fluorobenzoyl)benzo[d]thiazole‐2‐carbohydrazide Chelatess

ABSTRACTN′‐(2‐Fluorobenzoyl)benzo[d]thiazole‐2‐carbohydrazide (OFBBTCH, HL) and its chelates with Co(II) and Ni(II) have been synthesized and characterized by elemental analysis, liquid chromatography‐mass spectrometry (LC–MS), Fourier transform infrared spectroscopy (FT‐IR), ultra‐violet visible (UV–vis), nuclear magnetic resonance (NMR) spectroscopy, thermogravimetric analysis (TGA), and powder X‐ray diffraction. The conductance measurements reveal that the chelates are non‐electrolytic, and the spectral analysis indicates octahedral geometry of the chelates. The kinetic and thermodynamic parameters were obtained by Coats–Redfern relations, which shows positive Gibbs's free energy and negative entropy for both chelates. The equilibrium studies carried out by pH‐metry revealed the dissociation constant (pKa) of OFBBTCH as 8.13 and the formation of 1:1 and 1:2 Co(II)‐L and Ni(II)‐L complexes in solution. The CT‐DNA binding studies carried out by electron absorption, fluorescence quenching, steady state emissions and viscosity studies revealed hyperchromism and groove binding for HL and chelates. The Kb values calculated from electron absorption studies are 2.4 × 106, 4 × 106, and 9 × 106 M−1, from the fluorescence quenching studies Ksv values are 0.1722, 0.278, and 0.748 M−1, and Kapp values are 5.9 × 104, 1.3 × 105, and 2.9 × 105 M−1 for HL, Co(II)‐OFBBTCH and Ni(II)‐OFBBTCH, respectively. Bovine serum albumin (BSA) and human serum albumin (HSA) binding interactions were carried out by electron absorption and fluorescence quenching studies. The light switching properties of the chelates, the hydrolytic and oxidative cleavage of CT‐DNA, and the antioxidant properties were evaluated. Anti‐microbial studies carried out by pour plate method showed high activity for Ni(II)‐OFBBTCH chelate. Cytotoxicity of the compounds was performed for HeLa and MCF cell lines by MTT assay. Molecular docking studies revealed the docking of HL and Co(II)‐HL at the minor groove, and Ni(II)‐HL was docked at the major groove with hydrogen bonding.

Synthesis and Characterization of cellulose-derived superabsorbent hydrogel and its applications in the treatment of wastewater containing heavy metal ions

A cellulose xanthate (CX) based polymer hydrogel has been synthesized using free radical graft polymerization technique. Two monomers Acrylic Acid (AA) and Acrylonitrile (AN) were reacted with cellulose xanthate to synthesize the desired hydrogel CX-g-poly(AA-co-AN). The synthesized hydrogel has been characterized by various techniques viz. Thermo-gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy (UV), Field emission scanning electron microscope (FESEM) and Point zero charge (PZC). This hydrogel has been employed for the removal of toxic metal ions from wastewater. The maximum percentage removal has been found to be 97.5 (±4.87)% for Cu2+ ions and 96.1 (±4.80)% for Co2+ ions under optimum pH 6. The calculated adsorption capacities have been found to be 330.03 (±35.3) mg/g for Cu2+ ions and 325.73 (±22.4) mg/g for Co2+ ions using the Langmuir Adsorption isotherm model. The thermodynamic parameters depicted that the process was endothermic, and spontaneous. The adsorption kinetics data shows excellent fit with pseudo-second-order kinetic model. The synthesized hydrogel exhibits a high swelling ratio of 846.85 (±42.36) g/g and retention ratio of 50.12 (±2.50) % in distilled water. Also, the synthesized hydrogel showed good reusability, exhibiting percentage removal 83.2% for Cu2+ ions and 81.3% for Co2+ ions in the fifth cycle.

Nature of host–guest interaction of cyclic alcohols in β-Cyclodextrin: A molecular view of its structural features

Host- guest complexes are commonly found in several disciplines such as biochemistry, cosmetics, food, pharmaceuticals, and the environment. Studying the relationships between host and guest is essential in this context to understand their physicochemical behavior. This study aimed to examine the intermolecular interactions of cyclic alcohols within β-cyclodextrin (β-CD). The experimental spectroscopic results demonstrated the formation of the studied complexes. In this work, two orientations were used: orientation A (hydroxyl group toward the primary hydroxyl of β-CD) and orientation B (hydroxyl group toward the secondary hydroxyl of β-CD). The results indicate that regardless of the orientation used, the profile energy is thermodynamically favorable. However, there are differences in terms of greater or less stability in terms of the thermodynamic parameters studied. Physicochemical properties demonstrate that the host–guest complex forms spontaneously, and exothermic mode. The interaction between cyclic alcohols and β-CD in orientation A promotes a more pronounced deformation of the secondary edge of β-CD. Moreover, the arrangement of moleculesdemonstrates that intramolecular hydrogen bonds are less stable between the glycosidic units of β-CD. This arrangement may help or hinder the development of intermolecular hydrogen bonds.

Removal of cefuroxime from aqueous solution by biochars derived from antibiotic mycelial residue.

In China, antibiotic mycelial residue is categorized as hazardous waste. To achieve the harmless and resourceful disposal of cephalosporin, three types of biochars from cephalosporin mycelia residues, namely non-activated carbon (BC1), ZnCl2-activated carbon (BC2), and KOH-activated carbon (BC3), were respectively fabricated by high-temperature pyrolysis carbonization technology. These three kinds of biochars were characterized via iodine value, FTIR, and SEM, and the adsorption performance of the prepared biochars was investigated using cefuroxime (CXM) as the adsorption target. The results indicated that BC3 biochar possesses the most well-developed pores and the highest iodine value of 1367.41 mg/g; The most suitable dosage is 1.6 g/L, and the lower the pH, the more favorable the adsorption effect. The investigation of adsorption kinetics revealed that it conformed to the kinetic model of pseudo-second order, as well as the process of adsorption was governed by the chemical adsorption mechanism, the rate of adsorption was affected by the collective impact of the quantity of active sites present and the interaction strength between the CXM molecules and the biochar. The exploration of adsorption thermodynamics revealed that it aligned with the Langmuir model, the surface of biochar was relatively uniform, and the adsorption was mainly of low coverage; The calculation of thermodynamic parameters demonstrated that the adsorption was exothermic and spontaneous.

Removal of the nalidixic acid antibiotic from aqueous solutions using bovine serum albumin nanoparticles

The presence of antibiotic pollutants in water and wastewater can cause significant risks to the environment in different aspects. Therefore, antibiotics need to be removed from water. This study investigates the adsorption of nalidixic acid (NA), a common antibiotic, using bovine serum albumin nanoparticles (BSA NPs). These NPs were synthesized via desolvation technique and characterized using SEM, DLS, FT-IR, and UV-Vis spectroscopy. The effects of adsorbent dosage (0.02–0.9 mg), initial NA concentration (30–80 mg L− 1) and contact time (0.5–24 h) on adsorption efficiency were considered. Adsorption isotherms and kinetics were determined experimentally. The Freundlich isotherm best described the adsorption equilibrium, while the pseudo-second-order kinetic model accurately represented the adsorption process. Thermodynamic parameters confirmed the spontaneous and exothermic nature of NA adsorption onto BSA NPs. Under optimal conditions, BSA NPs achieved a removal efficiency of 75% for NA with a maximum adsorption capacity of 240 mg g− 1. These results demonstrate the potential of BSA NPs as an effective adsorbent for removing NA from aqueous solutions.

Corrosion kinetics of carbon steel in hydrochloric acid and its inhibition by recycling Salbutamol extracted from expired Farcolin drug

ABSTRACT Salbutamol, which has nontoxic properties, was effectively extracted from expired Farcolin and was evaluated as an inhibitor against carbon steel (CSt) dissolution in 1.0 M HCl solution. Some technologies were applied to determine the inhibition efficacy of Salbutamol such as weight loss (WL), potentiodynamic polarization (PP), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM). Also, FTIR, 1HNMR, and mass spectroscopy were used to clarify the structure of Salbutamol. The findings indicate that CSt can profit significantly from the recycling of Farcolin medicine and that Salbutamol may be extracted and employed as a CSt corrosion inhibitor. The efficiency of the inhibition improved with an increase in the dosage of salbutamol, polarization resistance and lowering corrosion current density, WL, and temperature. It’s reached 89.65% at a dose of 200 ppm using the EIS technology. The inhibition impact of Salbutamol was interpreted due to its spontaneous adsorption on the CSt/electrolyte interface, in accordance with Langmuir isotherm. Salbutamol was classified as a mixed inhibitor. In addition, how temperature affects the corrosion rate is considered by calculating and discussing some thermodynamic parameters.

EDTA‐modified cellulose from sago bark (Metroxylon sagu) for anionic and cationic dyes removal

AbstractThe present research employed ethylenediaminetetraacetic (EDTA) modified cellulose to remove basic violet 10 (BV10) and reactive orange 16 (RO16) dyes. The cellulose was obtained from sago bark which was solid waste of sago starch industries. Sago bark contains 56.86% cellulose so that it can provide significant amount of active site. The optimum condition was examined using batch method investigating some parameters including pH, initial dye concentration, contact time, and thermodynamics. The adsorption capacity of cellulose (Cell) itself was also investigated for the comparison. The characterization of adsorbent showed the presence of ester bond, amine groups and escalating of surface area and pores after EDTA modification. The adsorption capacity of EDTA‐modified cellulose (Cell‐EDTA) was 73.53 mg/g for BV10 and 22.42 mg/g for RO16. The adsorption of both dyes onto Cell‐EDTA followed Langmuir isotherm model and pseudo‐second‐order kinetic model. Thermodynamic parameters indicated that the adsorption process was spontaneous, endothermic and feasible. Desorption studies proved that NaOH was an effective desorbing agent of BV10 and RO16. Based on research, Cell‐EDTA was more favorable in cationic dye, basic violet 10 than anionic dye, reactive orange 16.

Assessing combustion characteristics of alternative fuels in a CI engine by use of a wavelet-based analysis of engine vibration signals

In the current work, a wavelet-based approach for assessing combustion performance of alternative fuels in compression-ignition engines, indicated that changes in cylinder pressure amplitude were reflected by commensurate changes in a proposed parameter, with a maximum of a 9% variation. The proposed parameter, the wavelet transform coefficient maximum amplitude (WMA), successfully accomplished this for various engine conditions. The wavelet transform coefficient standard deviation (WSD), a second proposed parameter, was able to track changes in the rates of pressure rise associated with changes in load conditions and fuel type, with a maximum variation in the parameter of 7%. The approach was assessed by testing six fuels in a test engine unit. Thermodynamic property data and vibration signal data were recorded for each of the fuels tested, at six loading conditions. Subsequently, combustion performance was evaluated using traditional thermodynamic parameters and using the WMA and WSD via a MATLAB based algorithm. Thus, it was surmised that the proposed approach can form the basis for a vibration-based assessment of alternative fuel combustion performance in reciprocating engines.

Investigations on the complexation and binding mechanism of bovine serum albumin with Ag-doped TiO2 nanoparticles.

It is essential to study the interactions between nanoparticles and proteins to better understand the biological interactions of nanoparticles. In this study, we studied the protein adsorption mode on the surface of Ag-doped TiO2 nanoparticles (NPs) using a model protein, bovine serum albumin (BSA). The mechanism of binding BSA to the Ag-doped TiO2 NPs was studied by applying fluorescence quenching, absorbance measurements, circular dichroism (CD) and Fourier transform infrared (FT-IR) spectroscopy techniques. The strong binding between BSA and Ag-doped TiO2 NPs was confirmed by a high value of binding constant (K = 2.65 × 105 L mol-1). We also studied the thermal stability of BSA in the presence of the Ag-doped TiO2 NPs. Thermodynamic parameters indicated that the adsorption of BSA on the Ag-doped TiO2 NPs was a spontaneous, natural and exothermic process. The effect of Ag-doped TiO2 NPs on the transportation function of BSA was also studied using a fluorescence spectroscopic technique. Fluorescence spectroscopic data suggested the existence of a strong interaction between BSA and the surface of the Ag-doped TiO2 NPs, which indicated that the binding affinities of some selected amino acids in BSA changed. This, in turn, clearly confirms that the Ag-doped TiO2 NPs affect the transportation capability of BSA in blood.

Thermodynamic and dielectric properties of hexagonal barium titanate near the phase transitions

The critical behavior of the thermodynamic quantities is studied for the two phase transitions near the transition temperatures (74 K and 222 K) in the hexagonal (h) BaTiO3. A linear relationship has been established between the variations of the frequency shifts and of the dielectric constant by using the literature data in h-BaTiO3. Temperature and pressure dependence of the mode Grüneisen parameters ( γp and γT ) are also described by a power-law formula as the other thermodynamic parameters near Tpt in h-BaTiO3. Our results show that they explain the observed behavior adequately, in particular soft-mode frequency, dielectric constant, thermal expansion, the excess specific heat and the entropy near Tpt in h-BaTiO3. Temperature dependence of the isobaric mode Grüneisen parameter ( γp ), enthalpy and the Gibbs free energy, which we have evaluated, can be compared with experiments in h-BaTiO3.

Analysis of molecular interactions of an aqueous benzoates with glycolic and lactic acid: spectroscopic, acoustic, and volumetric approach

Volumetric as well as Acoustic properties for the ternary liquid combination (water + sodium methyl p-hydroxybenzoate + glycolic acid/lactic acid) are evaluated at several temperatures using a Densimeter (DSA 5000 M) over the range of concentrations (0.000, 0.015, 0.025, 0.035) mol.kg−1. Several thermo-acoustical properties were computed utilizing the experimental data. These values were then used to derive several parameters, including the apparent molar volume( V∅ ); partial molar volume (V∅0); apparent molar isentropic compression (K∅,S); transfer properties(Δ V∅0, Δ K∅,s0 ); partial molar isentropic compression (K∅,s0); apparent molar expansibility ( E∅0 ) as well as its first derivative ( ∂Eϕ0/∂T ) P; and coefficient of thermal expansivity( αp ). The obtained results are explained by analyzing the several interactions that take place inside the liquid system by implementing the theory of co-sphere overlap. Utilizing these thermodynamical parameters, the interaction coefficients are computed to evaluate the ternary mixture corresponding to the interactions between solutes and solvents. FTIR spectrum analysis revealed the presence of H-bonds along with the other molecular interactions in the analyzed systems, as shown by the shifting of the O-H stretching band.

Deciphering Pathways and Thermodynamics of Protein Assembly Using Native Mass Spectrometry.

Protein oligomerization regulates many critical physiological processes, and its dysregulation can contribute to dysfunction and diseases. Elucidating the assembly pathways and quantifying their underlying thermodynamic and kinetic parameters are crucial for a comprehensive understanding of biological processes and for advancing therapeutics targeting abnormal protein oligomerization. Established binding assays, with limited mass precision, often rely on simplified models for data interpretation. In contrast, high-resolution native mass spectrometry (nMS) can directly determine the stoichiometry of biomolecular complexes in vitro. However, quantification is hindered by the fact that the relative abundances of gas-phase ions generally do not reflect solution concentrations due to nonuniform response factors. Recently, slow mixing mode (SLOMO)-nMS, which can quantify the relative response factors of interacting species, has been demonstrated to reliably measure the affinity (Kd) of binary biomolecular complexes. Here, we introduce an extended form of SLOMO-nMS that enables simultaneous quantification of the thermodynamics in multistep association reactions. Application of this method to homo-oligomerization of concanavalin A and insulin confirmed the reliability of the assay and uncovered details about the assembly processes that had previously resisted elucidation. Results acquired using SLOMO-nMS implemented with charge detection shed new light on the binding of recombinant human angiotensin-converting enzyme 2 and the SARS-CoV-2 spike protein. Importantly, new assembly pathways were uncovered, and the affinities of these interactions, which regulate host cell infection, were quantified. Together, these findings highlight the tremendous potential of SLOMO-nMS to accelerate the characterization of protein assembly pathways and thermodynamics and, in so doing, enhance fundamental biological understanding and facilitate therapeutic development. https://orcid.org/0000-0002-3389-7112.

Cleavage of DNA Substrate Containing Nucleotide Mismatch in the Complementary Region to sgRNA by Cas9 Endonuclease: Thermodynamic and Structural Features

The non-ideal accuracy and insufficient selectivity of CRISPR/Cas9 systems is a serious problem for their use as a genome editing tool. It is important to select the target sequence correctly so that the CRISPR/Cas9 system does not cut similar sequences. This requires an understanding of how and why mismatches in the target sequence can affect the efficiency of the Cas9/sgRNA complex. In this work, we studied the catalytic activity of the Cas9 enzyme to cleave DNA substrates containing nucleotide mismatch at different positions relative to the PAM in the “seed” sequence. We show that mismatches in the complementarity of the sgRNA/DNA duplex at different positions relative to the protospacer adjacent motif (PAM) sequence tend to decrease the cleavage efficiency and increase the half-maximal reaction time. However, for two mismatches at positions 11 and 20 relative to the PAM, an increase in cleavage efficiency was observed, both with and without an increase in half-reaction time. Thermodynamic parameters were obtained from molecular dynamics results, which showed that mismatches at positions 8, 11, and 20 relative to the PAM thermodynamically stabilize the formed complex, and a mismatch at position 2 of the PAM fragment exerts the greatest stabilization compared to the original DNA sequence. The weak correlation of the thermodynamic binding parameters of the components of the Cas9/sgRNA:dsDNA complex with the cleavage data of DNA substrates containing mismatches indicates that the efficiency of Cas9 operation is mainly affected by the conformational changes in Cas9 and the mutual arrangement of sgRNA and substrates.

The Dynamic Impact of Synthetic Dyes on the Physicochemical Parameters of Cationic and Anionic Surfactants

Introduction: The interaction of dyes (crystal violet, malachite green, and congo red) with cationic (cetrimide) and anionic surfactants (sodium dodecyl sulfate) in the aqueous medium were studied via conductometric and UV-visible spectroscopy. Method: The critical micelle concentration (CMC) of both cetrimide and SDS upsurges in all the selected dyes on increasing the temperature. Thermodynamic parameters like change in Gibb’s free energy of micellization (Δ G°m ), change in enthalpy of micellization (Δ H°m ) as well as change in entropy of micellization (Δ S°m ) were calculated by employing mass action model. Result: The Δ S°m values obtained are positive with Δ G°m and Δ H°m values being negative signified that the phenomenon of micellization is spontaneous as well as exothermic in nature. Moreover, the more negative Δ H°m in water as well as in the presence of dyes signify the presence of electrostatic forces of attraction between the oppositively charged dyes and surfactant moieties. UV-spectroscopy reveals that spectral changes occur because of the interaction of surfactants with dye molecules. Conclusion: By analyzing shifts in absorption peaks, changes in intensity, and alterations in band shape, insights into the nature of surfactant-dye complexes and their potential applications in various industries can be assessed. This understanding can help in the design and optimization of products and processes involving surfactants and dyes.

Analyzing the structural, optoelectronic, and thermoelectric properties of InGeX3 (X = Br) perovskites via DFT computations

The Electronic and optical properties of InGeX3(X = Cl, Br) were examined by adopting the density functional theory (DFT) approach. We applied the GGA + Trans-Blaha modified Becke–Johnson (TB-mBJ) technique to acquire the precise bandgap of 1.52 and 0.98 eV of the compounds InGeX3(X = Cl, Br) respectively which suggests the direct bandgap at (M-M). The stability of the material is confirmed by the formation energy (– 2.83 = Cl; – 2.35 = Br) and Mechanical stability. Primarily elastic constants were extracted for each of the materials under scrutiny, and these values then served to gauge all of the materials’ mechanical properties. The assessed Poisson’s and Pugh’s ratios for the materials InGeCl3 and InGeBr3 were verified to identify the degree of ductility. The quasi-harmonic Debye model additionally covers the temperature and pressure dependence on thermodynamic parameters, particularly volume, specific heat capacity (Cv) at constant volume, and the Gruneisen parameter (γ) in the range of 0–800 K and 0–5 GPa. It is anticipated that InGeCl3 and InGeBr3 will have static dielectric constants of 4.01 and 5.74, respectively. InGeX3(X = Cl, Br) also reveals significant absorption in the high UV spectrum. The thermoelectric properties have also been calculated vdata-element-id="9QNfR3VHbcMHX_W0fJCYp" data-element-type="html" style="display: initial; visibility: initial; opacity: initial; clip-path: initial; position: relative; float: left; top: 0px; left: 0px; z-index: 1 !important; pointer-events: none;" />ia boltztrap2 code using a k mesh of around 1,50,000 points.

Exploring conformational changes in β-lactoglobulin (β-LG) induced by silibinin: A comprehensive analysis of polyphenol-protein interaction

This study investigates the comprehensive characterization of the interaction between β-lactoglobulin (β-LG) and Silibinin using various spectroscopic techniques. Fluorescence quenching experiments at different temperatures (298, 303, 308, and 313 K) revealed substantive interactions between β-LG and Silibinin, as indicated by a reduction in fluorescence intensity and a red shift in emission maxima. Further analysis, including Stern-Volmer quenching constants (KSV), bimolecular quenching rate constants (kq), and thermodynamic parameters demonstrated static quenching mechanism and strong binding affinities (Ka range: 0.138–1.483 × 105 M−1) between BLG-Silibinin complex. Thermodynamic study suggested positive enthalpy and entropy changes (ΔHo=43.31 kcal mol−1; ΔSo=164.33 cal mol−1 K−1), suggesting a spontaneous reaction with negative ΔGo values (-5.66 to -7.30 kcal mol−1). Forster resonance energy transfer (FRET) measurements confirmed optimal distances (r and Ro) for FRET occurrence, endorsing the static quenching mechanism. Molecular docking supported these findings, showcasing a 1:1 stoichiometric binding ratio for β-LG: Silibinin. The β-LG and Silibinin complex is primarily stabilized by hydrogen bonds and hydrophobic interactions. Molecular dynamics simulations over 200 ns highlighted stability in the β-LG-Silibinin complex, indicated by RMSD convergence, consistent RMSF values, and compactness illustrated by Rg. Conformational changes in β-LG upon Silibinin binding were further confirmed through UV-Vis absorption spectroscopy, FTIR, far-UV CD, synchronous fluorescence, and 3D fluorescence analyses. Functionally, the antioxidant capacity of β-LG increased after complexation with silibinin as quantified by DPPH assay. These results collectively depict the intricate network of interactions between Silibinin and β-LG, shedding light on the molecular details of their binding and offering insights into potential functional implications in biological contexts.

Theoretical investigations of optoelectronic properties, photocatalytic performance as a water splitting photocatalyst and band gap engineering with transition metals (TM = Fe and Co) of K3VO4, Na3VO4 and Zn3V2O8: a first-principles study.

First-principles density functional investigations of the structural, electronic, optical and thermodynamic properties of K3VO4, Na3VO4 and Zn3V2O8 were performed using generalized gradient approximation (GGA) via ultrasoft pseudopotential and density functional theory (DFT). Their electronic structure was analyzed with a focus on the nature of electronic states near band edges. The electronic band structure revealed that between 6% Fe and 6% Co, 6% Co significantly tuned the band gap with the emergence of new states at the gamma point. Notable variations were highlighted in the electronic properties of Na3V(1-x)Fe x O4, Na3V(1-x)Co x O4, K3V(1-x)Fe x O4, K3V(1-x)Co x O4, Zn3(1-x)V2(1-x)Co x O8 and Zn3(1-x)V2(1-x)Fe x O8 (where x = 0.06) due to the different natures of the unoccupied 3d states of Fe and Co. Density of states analysis as well as α (spin up) and β (spin down) magnetic moments showed that cobalt can reduce the band gap by positioning the valence band higher than O 2p orbitals and the conduction band lower than V 3d orbitals. Mulliken charge distribution revealed the presence of the 6s2 lone pair on Zn, greater population and short bond length in V-O bonds. Hence, the hardness and covalent character develops owing to the V-O bond. Elastic properties, including bulk modulus, shear modulus, Pugh ratio and Poisson ratio, were computed and showed Zn3V2O8 to be mechanically more stable than Na3VO4 and K3VO4. Optimal values of optical properties, such as absorption, reflectivity, dielectric function, refractive index and loss functions, demonstrated Zn3V2O8 as an efficient photocatalytic compound. The optimum trend within finite temperature ranges utilizing quasi-harmonic technique is illustrated by calculating thermodynamic parameters. Theoretical investigations presented here will open up a new line of exploration of the photocatalytic characteristics of orthovanadates.

Computational Study of the Formation of Atmospheric Aerosol Precursors Under Ambient Conditions: A Case Study of the Interaction Between Sea Salt, Water, and Sulfuric Acid Molecules

ABSTRACTCluster formation has significant implications in atmospheric science and environmental chemistry. These clusters are characterized by complex interactions between their constituents, which influence their structure, stability, and growth. Experimental investigations are difficult for the initial stages of prenucleation cluster formation, which leads to larger aerosols. To understand the formation of clusters, the interactions between sea salts (NaCl, KCl, and MgCl2), water, and sulfuric acid molecules have been investigated. Each step has been comprehensively examined and thermodynamic parameters have been computed using DLPNO‐CCSD(T)/CBS//M06‐2X/6‐311++G(3df,3pd) to find the stabilities of the molecular complexes. Among all complexes, the binding energies of cluster (SS)1(W)1(SA)3 are found to be the lowest due to the formation of HCl, hydrogen bonding, and weak van der Waal forces. Sea salts have shown a more favorable interaction with H2SO4 compared to H2O molecules. The addition of H2SO4 increases the reactivity of the cluster (SS)1(W)n, while the addition of H2O molecules reduces the reactivity of the cluster (SS)1(SA)n. However, further addition of H2SO4 or H2O to the existing cluster (SS)1(W)n(SA)n increases the free energy of formation. Furthermore, the influence of temperature was also investigated, suggesting that complex formation is slightly more favorable at lower temperatures than at higher temperatures. The negative values of thermodynamic parameters indicate, that these complexes are spontaneous and exothermic over the colder regions.

Kinetic, equilibrium, and thermodynamic aspects of phenol adsorption onto acrylonitrile-divinylbenzene copolymer

Adsorption of phenol onto acrylonitrile-divinylbenzene copolymer (AN-DVB) was comprehensively investigated with the aspect of kinetic, equilibrium, and thermodynamic. The effect of adsorbent dosage, initial concentration, temperature, and pH were studied in batch adsorption process. Maximum phenol adsorption capacity was obtained at neutral pH of phenol solution (6.8), at room temperature (25 °C) and at higher initial concentrations (500 mg/L) as 117 mg/g. After examining two-parameter- and three-parameter-adsorption-isotherm models, experimental data were represented well by using Freundlich adsorption isotherm model at neutral pH. Due to the all possible interactions like hydrogen bonding, π-π stacking and hydrophobic ineractions have different strengths and energetic values, phenol adsorption at neutral pH (6.8) exhibited a heterogeneous multilayer process. On the other hand, Langmuir and BET models well represented the experimental data obtained beyond neutral pH due to the weakening of different interactions, hence, multilayer but more uniform adsorption occurred. Phenol adsorption followed pseudo-second-order kinetic model that shows the surface interactions play significant role on the adsorption rate. Analysis of Boyd's intraparticle and external diffusion kinetic models indicated that in addition to surface interactions, diffusion also controlled the adsorption rate at room temperature. Activation energy was calculated as 92.99 kJ/mol, which shows the strong interaction between phenol and AN-DVB. Adsorption enthalpy change and entropy change was calculated as −25.731 kJ/mol and −0.041 kJ/molK, respectively. Thermodynamic parameters indicated that adsorption process was exothermic and spontaneous in nature.