Values Of ΔH Research Articles

Kinetico‐Mechanistic Studies of Cu(II)‐Mediated Cyclization of Imines via C−H Bond Activations

AbstractHerein, we focus on the kinetico‐mechanistic studies of a carboxylate and Cu(II)‐assisted synthesis of imidazo[1,5‐a]pyridines encompassing C(sp3)−H amination and cyclization of imines coupled with C(sp2)−H cyanation using time‐resolved UV‐Vis reaction monitoring and ex‐situ analyses. Thus, kinetic studies have been carried out, providing a proof of the elementary steps involved, allowing for batch analysis of the compounds present in solution via MS. The experimental data obtained are consistent with the formation of a cyclometalated complex (k1) involving a C(sp3)−H bond cleavage followed by a reductive elimination/proton abstraction event (k2), both showing high enthalpy‐demanding transition states. The two processes show a well‐defined Eyring behavior with values of ΔH≠ and ΔS≠ within the expected range. Further insights on the intermediate fast C(sp2)–cyanation are also presented together with control reactions.

Exploring the adsorption of Catechol and Resorcinol onto Croton caudatus activated carbon: An integrated experimental and theoretical approach

The present work aimed to examine the process for adsorption of Catechol (CT) and Resorcinol (RS) onto activated carbon that was obtained from Croton caudatus biomass (CAB). Using a batch method, the maximum removal efficiencies of 99.23 % for CT and 98.68 % for RS was achieved at adsorbent dosage-0.2 g L-1, reaction time-60 min; concentration-100 mgL-1 CT and 80 mgL-1 RS; and pH 6.0 CT and pH 4.0 RS, respectively. A maximum equilibrium adsorption of 56.05 mgg-1 and 61.85 mgg-1 was achieved at pH 6.0 and pH 4.0 for CT and RS. The adsorption behavior of both adsorbates on activated carbon were best described by the Langmuir model (correlation coefficients (R2) = 0.996 for CT and 0.995 for RS) and the pseudo-second order kinetic model. The values of ΔG, ΔS, and ΔH suggest that the adsorption process is spontaneous and endothermic. Additionally, the adsorption process is easily reversible, enabling the reuse of the adsorbate even after fifth cycle. Further, density functional theory (DFT) simulations demonstrated that the CT and RS adsorption onto the AC adsorbent is favorable. Among the oxygen functional groups analysed, the carboxyl group showed the greatest effect on the adsorption process, exhibiting the most negative adsorption energy at -44.869 (CT) and -45.082 kJmol-1 (RS), respectively. Therefore, the activated carbon derived from CAB has significant potential for effectively removing phenolic contaminants from wastewater.

Chitosan-NiFe2O4 Nanocomposite Synthesis for Effective Removal of Pb(II) and Zn(II) from Aqueous Solution

The purpose of present work is to synthesize and investigate the use of chitosan-based nanobiocomposites integrated with magnetic nanoparticles (NiFe2O4) for the adsorptive removal of Pb(II) and Zn(II) ions from aquatic media. The research is focused on addressing the urgent global problem of heavy metal pollution, especially in aquatic environments, with effective and sustainable solutions. Chitosan nanoparticles are prepared using an ionic gelation method, which are then used to synthesize a magnetic nanobiocomposite via ultrasonication and chemical co-precipitation with Ni and Fe precursors. The structural, morphological, and elemental properties of the resultant chitosan-NiFe2O4 nanobiocomposite (Fe/Ni@Chitosan NCs.) are characterized using XRD, FTIR, and Electron Microscopy (TEM and FE-SEM). The adsorption tests were conducted in a batch system, with varying contact times, pH levels, adsorbent dosages, and temperatures. The experimental adsorption of Pb(II) and Zn(II) ions showed a good fit with model of Langmuir. The nanocomposite's computed Langmuir maximum adsorption capacity (qmax) values were (91.0581, 90.7080) mg/g for Pb(II) at pH (4.0±0.01) and Zn(II) at pH (6.0±0.01), respectively, at a temperature of 45°C. The thermodynamic assessment involved the determination of change of Gibbs free energy (ΔG), change of enthalpy (ΔH), and entropy ΔS. The observation of a positive ΔH value implies that the interaction between Pb(II) or Zn(II) adsorbed by Fe/Ni@Chitosan NCs is endothermic. On the other hand, a negative ΔG value suggests that the adsorption of these two ions occurs spontaneously.

Corrosion Inhibition and Adsorption Behaviour of Centrosema pubescens Leaf Extract for Copper in HCl Solution

Study’s Excerpt In this study, Centrosema pubescens leaf extract (CPE) has been confirmed as eco-friendly and efficient green inhibitor for copper corrosion in hydrochloric acid. Detailed thermodynamic analysis, revealed that CPE adsorption follows a Freundlich isotherm model. SEM-EDX and FTIR characterizations confirmed the formation of a protective layer confirming the potentials of the plant extracts in sustainable corrosion prevention. Full Abstract The anti-corrosion behaviour of Centrosema pubescens leaf extract (CPE) on copper in 1.5 M hydrochloric acid was investigated using weight loss method at different temperatures, followed with scanning electron microscopy (SEM) surface characterization connected with energy dispersive X-ray spectroscopy (EDX). The Fourier transform infrared spectrum of CPE was obtained. CPE inhibition effectiveness depends on the temperature and its concentration. CPE restrains the copper corrosion with 94.26 % inhibition efficiency at 1.0 g/L of CPE and at 303 K. For the CPE-inhibited system, a higher activation energy (Ea) value (range of 31.09 to 38.70 kJmol-1) compared to 20.34 kJmol-1 of the blank solution was obtained. The reaction process is spontaneous and endo thermic, as indicated by the ΔH, ΔS and ΔG values calculated. CPE adsorption behaviour fitted best into Freundlich isotherm.

Ibuprofen Removal by Aluminum-Modified Activated Carbon (AC@Al) Derived from Coconut Shells

In this study, a new composite adsorbent consisting of aluminum-modified activated carbon (abbreviated hereafter AC@Al) was synthesized for the removal of the Ibuprofen compound (IBU), a non-steroidal anti-inflammatory drug (NSAID). Coconut shells were used as a source material for activated carbon, which was then modified with AlCl3 to improve its properties. Adsorbent dosage, pH and initial IBU concentration, as well as contact time and temperature, are some of the factors affecting adsorption that were investigated in this work. Specifically, at pH 2.0 ± 0.1 with the application of 0.5 g/L of AC@Al in 100 mg/L of IBU, more than 90% was removed, reaching 100% with the addition of 1.0 g/L of the adsorbent. The IBU kinetic data followed the pseudo-second-order kinetic model. Non-linear Langmuir, Freundlich, Sips and Redlich–Peterson isotherm models were used to interpret the adsorption. According to the correlation coefficient (R2), the Langmuir model was found to best match the experimental data. The maximum adsorption capacity (Qmax) according to the Langmuir model was found to be as high as 2053 mg/g. The positive values of ΔH0 (42.92 kJ/mol) confirmed the endothermic nature of the adsorption. Due to the increasing values of ΔG0 with temperature, the adsorption of IBU onto AC@Al proved to be spontaneous. Also, the adsorbent was regenerated and reused for five cycles. This study shows that AC@Al could be used as a cost-effective adsorbent.

Removal of Ibuprofen from Aqueous Solutions by Using Graphene Oxide@MgO

In this study, a new composite adsorbent, namely magnesium oxide modified graphene oxide (hereafter abbreviated GO@MgO), was prepared for the removal of Ibuprofen (IBU), a non-steroidal anti-inflammatory drug (NSAID) compound. Graphene oxide was modified with MgO to improve its properties. Several factors important for the evolution of the adsorption process were investigated, such as the dose of the adsorbent, the pH, and the initial IBU content, as well as the duration of the procedure and temperature. According to the results obtained, it was found that at pH 3.0 ± 0.1, by applying 0.5 g/L GO@MgO to 100 mg/L IBU, more than 80% was removed, reaching 96.3% with the addition of 1.5 g/L adsorbent in 24 h. After 30 min, the equilibrium was reached (77% removal) by adding 0.5 g/L of GO@MgO. This study proves that GO@MgO is capable of economical and efficient adsorption. The IBU kinetic data followed the pseudo-second-order kinetic model. Langmuir and Freundlich isotherm models were used to interpret the adsorption, but the Freundlich model described the adsorption method more accurately. The positive values of ΔH0 (14.465 kJ/mol) confirm the endothermic nature of the adsorption. Due to the increase of ΔG0 values with temperature, the adsorption of IBU on GO@MgO is considered to be spontaneous.

Synthesis and characterization of guar gum xanthate derivative super adsorbent hydrogel for the capturing of heavy metal ions from wastewater

The Guar Gum Xanthate based hydrogel GGmX-g-poly(AA-co-HEMA) has been successfully synthesized by using the graft copolymerization of two monomers, acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) hydrogel. The synthesis follows the free-radical graft polymerization method. UV-visible spectroscopy (UV), Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Point zero charge (PZC), and field emission scanning electron microscopy (FESEM) were employed for the characterization of the synthesized hydrogel. This hydrogel has shown a high swelling ratio of 430.2 g/g and retention of 75.82% in distilled water which is a notable result. By using GGmX-g-poly(AA-co-HEMA) hydrogel, the maximum percentage of heavy metal ions removal from wastewater was found to be 98.5(±1.5)% and 97.1(±1.5) at optimum pH 6 and 6.5 for Cu2+ and Ni2+ solutions respectively. The Langmuir adsorption isotherm fits best for the adsorption data indicating a monolayer adsorption with maximum adsorption capacity of 423.72 (±26.1) mg/g and 404.85 (±31.4) mg/g for Cu2+ and Ni2+ ions respectively. The pseudo-second-order kinetic model provides the most accurate depiction of adsorption kinetics with rate constant 9.1 × 10−4 (±1.37×10−4)g/(mg.min) for Cu2+ and 8.3 × 10−4 (±1.24×10−4)g/(mg.min) for Ni2+ ions, respectively. The negative ΔG value (-4.75 kJ/mol for Cu2+ and −3.26 kJ/mol for Ni2+ ions) and positive value of ΔH (57.55 (±5.41) kJ/mol for Cu2+ and 40.60(±5.37) kJ/mol for Ni2+ ions) suggested the process to be spontaneous, endothermic, and feasible. It has been found that the hydrogel has excellent regenerative capacity with the % adsorption has been found to be 84.8% for Cu2+ and 82.4% for Ni2+ ions for the fifth cycle.

Synthesis and characterization of allyl mannitol cross-linker based novel hydrogel for capturing of toxic metal ions from aqueous solution

ABSTRACT Three grades of allyl-mannitol cross-linker-based hydrogel (AMCLHs hydrogel) have been synthesized with the help of acrylic acid and acrylamide monomers using a free radical co-polymerization technique. The three prepared grades of AMCLHs hydrogel have been referred to as AMCLHs-1, AMCLHs-2, and AMCLHs-3, respectively. The prepared AMCLHs hydrogels have been characterized by several analytical techniques viz. Fourier transform infrared (FTIR) spectroscopy, thermogravimetric (TG) analysis, point of zero charge (ΔpHPZC), analysis, and scanning electron microscope (SEM) analysis, respectively. The synthesized hydrogels have been utilized for the elimination of Cu2+ and Co2+ ions from wastewater. The properties of prepared AMCLHs hydrogels, i.e. swelling and water retention ratio have been studied in distilled water under optimized conditions. The maximum swelling ratio of the best grade of hydrogel (AMCLHs-1) has been found to be 400.5 g/g with the water retention ratio of 75.09% during 24 h. These findings indicate the AMCLHs-1 hydrogel has remarkable swelling and water retention capacity. The maximum metal ion removal efficiency of AMCLHs-1 hydrogel from aqueous solutions has been found to be 96.6% for Cu2+ and 94.2% for Co2+ ions under optimum conditions. The experimental data fitted well with the Langmuir and Freundlich adsorption models, revealing maximum adsorption capacities of 431.03 mg/g for Cu2+ ions and 414.93 mg/g for Co2+ ions, respectively. In addition, the rate for the adsorption of Cu2+ and Co2+ ions onto AMCLHs-1 hydrogel follows both Pseudo first and second-order kinetic models. The negative ΔG values indicate that the adsorption process occurs spontaneously, while positive ΔH values suggest that the adsorption process is exothermic in nature. The prepared AMCLHs hydrogel is reusable and exhibits high desorption efficiency with 87.63% for Cu2+ and 85.21% for Co2+ metal ions even after the fourth cycle. Overall, AMCLHs hydrogel is a cost-effective and reusable adsorbent that possesses a significant potential for heavy metal ion removal from aqueous solutions.

Binding characteristics of the major kratom alkaloid, mitragynine, towards serum albumin: Spectroscopic, calorimetric, microscopic, and computational investigations

Mitragynine (MTG) is a prominent indole alkaloid that is present abundantly in Mitragyna speciosa, commonly referred to as kratom. MTG has garnered significant attention due to its selective agonistic characteristics towards opioid receptors and related analgesic effects. In the circulatory system, the in vivo efficacy of MTG is dictated by its interaction with plasma proteins, primarily human serum albumin (HSA). In the present study, we utilized a broad methodology that included spectroscopic, calorimetric, microscopic, and in silico approaches to characterize the interaction between MTG and HSA. Alterations in the UV absorption spectrum of HSA by the presence of MTG demonstrated a ground-state complexation between the protein and the ligand. The Ka values obtained for the MTG–HSA interaction were in the range 103–104 M−1 based on analysis of fluorescence and ITC data, respectively, indicating an intermediate binding affinity. The binding reaction was thermodynamically favorable as revealed by ΔH, ΔS, and ΔG values of −16.42 kJ mol−1, 39.97 J mol−1 K−1, and −28.34 kJ mol−1, respectively. Furthermore, CD spectroscopy results suggested MTG binding induced minimal effects on the structural integrity of HSA, supported by computational methods. Changes in the dimensions of HSA particles due to aggregation, as observed using atomic force microscopy in the presence of MTG. Competitive drug displacement results seemingly suggested site III of HSA located at subdomain IB as the preferred binding site of MTG, but were in inconclusive. However, docking results showed the clear preference of MTG to bind to site III, facilitated by hydrophobic (alkyl and pi-alkyl) and van der Waals forces, together with carbon hydrogen bonds. Additionally, the MTG–HSA complexation was demonstrated to be stable based on molecular dynamics analysis. The outcomes of this study shed light on the therapeutic potential of MTG and can help in the design of more effective derivatives of the compound.

Synthesis of magnetic spinal ferrite CrFe2O4 nanoparticles and uses them to remove lead and cadmium ions from aqueous solutions

Abstract This study deals with the preparation of a magnetic ferrite CrFe2O4 by the sol–gel auto-combustion method, using the lemon juice extract as a fuel for the reaction and preventing the precipitation of the components. The prepared nanocomposite was diagnized using various techniques such as FT-IR, XRD, FE-SEM, EDX, Zeta Potential and (BET). X-ray diffraction patterns verified the state of phase purity and the particle size of 33.9 nm. Additionally the study examined the synthesized compound as an adsorbent surface for lead and cadmium ions from their aqueous solutions. The mathematical formulae of the Langmuir and Freundlich isotherms were applied to the actual adsorption data utilising the findings from the temperature effect studies. As a result, the Freundlich equation yielded a more correlated linear link than the Langmuir isotherm. The thermodynamic results showed that the lead and cadmium ions adsorption were endothermic according to the positive (ΔH) values, whereas the lead and cadmium ion adsorption process were spontaneous with negative (ΔG) values. Positive values of (ΔS) indicate an increase in the randomness of the adsorption process. The current study also comprises the practical application of eliminating lead and cadmium ions from marine waters collected from two sites: Al-Faw Al-Kabir Port (Eastern Breaker) and Khor Al-Zubair (berth 13), by means of the prepared surface. The results indicate the removal percentage of the prepared surface for lead was (91.72%) for the first location and (86.00%) for the second location, whereas the removal percentage of cadmium was (85.52%) for the first site and (89.10%) for the second site.

Optimizing oxytetracycline removal from aqueous solutions using activated carbon from barley lignocellulosic wastes with isotherms and thermodynamic studies

The excessive presence of antibiotics such as Oxytetracycline (OTC) in the wastewater has increased health problems due to their toxic impact on the aquatic ecosystem. Therefore, their removal has become an important topic. This study aims to produce high surface area-activated carbon derived from low-cost and environmentally friendly barley lignocellulosic wastes to remove OTC from aqueous solutions. The synthesized barley wastes-activated carbon (BW-AC) was characterized using Fourier-Transform Infrared spectroscopy, Thermal Gravimetric Analysis, X-ray diffraction analysis, N2 adsorption/desorption isotherms, and Scanning Electron Microscopy. A Central Composite Design under the Response Surface Methodology (CCD-RSM) was applied to optimize the operational parameters (adsorbent dosage, pH, OTC initial concentration, and contact time) affecting the adsorption capacity as the response factor. The optimum condition of OTC adsorption by BW-AC was the adsorbent dosage of 16.25 mg, pH of 8.25, initial concentration of 62.50 mg/L, and contact time of 23.46 min. An analysis of variance (ANOVA) was performed to investigate the significance of the designed quadratic model and evaluate the parameters interactions. The linear regression coefficient (R2) of 0.975 shows a good correlation between predicted and actual results. The adsorption isotherms were used to determine the contaminant distribution over the adsorbent surface, and the equilibrium data was best described by the Freundlich isotherm due to the R2 value of 0.99 compared to other isotherms and β parameter of 0.23 in Redlich-Peterson equation. Moreover, the n value of 1.25 in Freundlich equation and E value of 0.31 in Dubinin–Radushkevich equation indicates a physical nature of adsorption process. According to the equations results, the maximum adsorption capacity of BW-AC for OTC removal was 500 mg/g, based on the Langmuir isotherm equation. In addition, the thermodynamic studies indicated an endothermic process based on the 0.31 value of ΔH° and spontaneous nature due to the negative amount of ΔG° within the temperature range of 288–318 K. Consequently, the prepared BW-AC can be deemed as a highly effective adsorbent with a large surface area, resulting in significant capacity for removing OTC. This synthesized BW-AC can serve as an environmentally friendly adsorbent for affordable wastewater treatment and is poised to make valuable contributions to future research in this field.

Assessment of dissociation enthalpies of methane hydrates in the absence and presence of ionic liquids using the Clausius-Clapeyron approach

The Clausius-Clapeyron (CC) equation is generally preferred to obtain dissociation enthalpies (ΔH) of hydrate-forming systems due to its ease of use. The application of other direct and indirect methods becomes more problematic if complex additives such as ionic liquids (ILs) are also present in the system. In this work, around 400 equilibrium data points for methane hydrates in the presence of over 80 ILs were collected from the literature in the temperature and pressure ranges of (272.10 – 306.07) K and (2.48 – 100.34) MPa, respectively. The ΔH of methane hydrates in the absence and presence of ionic liquids (ILs) have been calculated using the CC equation. The compressibility factor (z), required to calculate ΔH at each phase equilibrium condition has been obtained from three different approaches viz., Peng-Robinson (PR) equation of state, Soave-Redlich-Kwong (SRK) equation of state and Pitzer (Pz) correlation. The results were compared to the experimentally reported dissociation enthalpy (54.5 ± 1.5 kJ.mol−1) of methane hydrates. The role of the compressibility factor along with the slope of the equilibrium data set and the temperature/pressure range in determining the outcome of the CC equation has been discussed. The effect of molar mass, molar volume, and hydrate suppression temperature of the ILs on the ΔH of methane hydrates has been explored. The tested ILs do not show a systematic and significant influence on enthalpies, rather they show a large scattering in the ΔH values, which might mask any existing subtle effect of the ILs on the dissociation enthalpies. Therefore, this approach should be dealt with care to obtain molecular-level insights.

Kinetic and thermodynamic analysis of engineered alginate–chitosan hydrogel based scaffolds for drug delivery applications

The synthesis of stimulus–responsive hydrogel–based scaffolds has been extensively investigated for controlled drug delivery applications. This study focused on synthesizing alginate and chitosan–based scaffolds for potential use in releasing antibiotic antimycotic solution (AAS) drugs. The controlled release of AAS from AAS–loaded alginate–chitosan scaffolds was investigated under distinct temperatures viz. 37 °C, 25 °C, and 10 °C, labeled as scaffolds A, B, and C, respectively. Porosity assessment revealed consistent and substantial mean porosity percentage of 95.06 ± 2.01 % across all scaffolds. The lower temperature of 10 °C significantly contributed to a gradual and consistent cumulative release of 91.67 ± 1.47 %, compared to 37 °C (94.07 ± 1.89 %) and 25 °C (92.75 ± 1.51 %). The Korsmeyer–Peppas model exhibited high R2 values (0.98, 0.97 to 0.99) for scaffolds A, B, and C, indicating its suitability for describing the in–vitro release of AAS. Furthermore, the obtained release exponent values (0.60, 0.65, and 0.72 for scaffolds A, B, and C, respectively) suggest non–Fickian diffusion as the primary mechanism governing drug release. The release was also pH–dependent, with slower release at acidic (pH 3) and faster release under basic conditions (pH 8) due to varying swelling ratios. Evaluation of thermodynamic parameters viz. Ea, ΔG, ΔH and ΔS, using the rate constant of the Korsmeyer–Peppas model, revealed positive values of ΔH > 0 and ΔS > 0, indicating the prevalence of hydrophobic interactions in the release process.

Uptake of selected heavy metals from contaminated waters utilizing cost-effective and environmentally friendly biosorbents prepared from the residues of a traditionally fermented Ethiopian alcoholic beverage (Tella)

In the current study, the adsorption capacity of Tella residues (residues of fermented alcoholic beverage) for quantitative uptake of Cu(II), Cd(II), Zn(II) and Pb(II) was evaluated. Chemical treatment of the local beer residue (LBR) has improved the removal efficiency of the adsorbent, which was achieved at pH = 5, 1.0 g adsorbent, 50 mg/L initial concentration, 180 min contact time and agitation speed of 100 rpm. The adsorption was found to fit the Langmuir adsorption isotherm model, and the theoretical equilibrium capacities were well fitted with the experimental equilibrium capacities, resulting in chemical adsorption (chemisorptions) on the adsorbent surface while the equilibrium kinetics follows the pseudo-second-order. The adsorption capacity (Qo) of LBR decreases in the following order: Zn(II) > Cu(II) > Pb(II) > Cd(II) as metal concentration ranged from 20-200 mg/L. Thermodynamic parameters, including standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°) were calculated to predict the nature of adsorption. The negative values of ΔG° and the positive value of ΔH° indicate that the adsorption process was spontaneous and endothermic. Adsorption capacities were found to increase when the temperature ranged from 25-60 °C. Thus, the findings suggest a promising application of LBR as an alternative low-cost novel adsorbent for the removal of toxic heavy metals from wastewater.

Harnessing the power of ternary nanocomposites: Iron oxide, multiwalled carbon nanotubes, and bentonite for superior ciprofloxacin adsorption

Water contamination from antibiotics can have detrimental effects on one’s health. Consequently, treating the polluted water is required to fix this issue. Fe3O4-multiwalled Carbon Nanotubes (MWCNTs)-Bentonite nanocomposite has been successfully prepared using a customized co-precipitation process. The synthesized nanocomposite was used as an adsorbent to extract the ciprofloxacin from aqueous solutions. The synthesized nanocomposite was examined using several characterization methods. Scanning electron microscopy demonstrates that the Fe3O4 nanoparticles and bentonite are well-decorated on MWCNTs. The nanocomposite exhibits a high BET surface area of 221.577 m2/g and a pore volume of 0.411 cm3/g. According to the analysis, the average pore diameter was found to be 3.717 nm. Additionally, the adsorption model agreed with the Jovanovic model, which had a 137.35 mg/g adsorption capacity, with a χ2 of 2.161, and a good nonlinear R2 value of 0.999. Moreover, adsorbent was found to be highly stable even after 4 cycles. The ΔS and ΔH values were found to be positive, which suggested an endothermic process. The synthesized nanocomposite proved to be a viable option for water treatment applications, and there is no literature available on CIP antibiotic adsorption using Fe3O4-MWCNT-Bentonite nanocomposite.

Remediation of fenitrothion pesticide from the aquatic environment by porous Graphitized 3D carbon material: Their antimicrobial activity

This work sought to optimize the elimination of organophosphate from the watery surroundings by a Porous Graphitized 3D Nitrogen-Doped Carbon material (NDC) derived from freeze-dried sponge-based hydrogel, employing response surface methodology using Box-Behnken architecture (BBA). The Porous Graphitized 3D Nitrogen-Doped Carbon materials were prepared at 500 °C (NDC-500) and 900 °C (NDC-900) carbonization temperatures; among these, NDC-900 was found to be micropore rich and can be used as a potential adsorbent for effective remediation of organophosphate fenitrothion pesticide from the aquatic environment. Various characterization techniques include Field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller, N2 adsorption–desorption isotherms studies (BET), and Fourier transform infrared spectroscopy (FTIR) were used to characterize the NDC-900. It revealed that the surface area of NDC-900 is appreciably large,2346.54 m2/g, and has a considerable pore volume of 1.59 cm3/g. Furthermore, the synthesized porous carbon-based material depicted acceptable profitable benefits with a remuneration of 600 $t−1. The as-prepared material undergoes a hydrothermal reaction with silver nitrate to form silver-doped carbon material, which displays excellent antimicrobial activity. The impact of four critical parameters, including initialfenitrothion(FE) concentration, NDC-900 mass, pH, and temperature, were maximized by a quadratic model. Analysis of variance demonstrated that the findings were trustworthy. According to the Pareto analysis, preliminary FE concentration had the most impact on eliminating FE among the four chosen parameters. The optimum variables for FE remediation were 40.01 mg L−1 preliminary FE concentration, 14.99 mgL−1 NDC-900 dosage, 35.62 °C temperature, and solution pH 7.91. The predicted FE remediation effectiveness of 99.91 % is in excellent accord with the experimental result of 99.88 % under ideal circumstances. The effectiveness of FE adsorption on NDC was comprehensively assessed by employing kinetic models, particularly those that follow the pseudo-first-order kinetic models. Additionally, the Langmuir isotherm model was used to match the adsorption process precisely. A physisorption mechanism was shown to be involved in the entire process. Furthermore, the study was done to understand better how NDC-900 and FE interact. The interplay might transpire via many pathways, such as H-bonding and pore filling. There has never been evidence of how well NDC-900 works as an adsorbent to eliminate FE from sewer water samples. However, our research is the first to accomplish this. The findings show that the optimum adsorption capacity of FE onto NDC, 616 mg. g−1, can only be attained at a pH of 7. The derived values of (ΔH°), (ΔS°), and (ΔG°) for FE suggested that the process was exothermic and spontaneous when employing NDC-900 as an adsorbent. Furthermore, NDC-900, in combination with Ag (silver), shows excellent antibacterial and antifungal activity. The regeneration outcomes showed that FE remediation effectiveness efficiency was still sustained at 80 % during five iterations of the adsorption–desorption process. Consequently, NDC-900 is a viable adsorbent for the effective and quick adsorption of FE from water.

A new three-dimensional modeling of fluorescence excitation-emission measurements to explore the interaction of hydroxychloroquine and DNA, and to quantify their binding constant

A new three-dimensional chemometric approach was introduced to explore the interaction of hydroxychloroquine (HCQ)-calf thymus deoxyribonucleic acid (DNA) and quantify binding constant using fluorescence excitation and emission measurements. The fluorescence excitation-emission spectra were recorded after gradual titration of HCQ with DNA. Then, the excitation and emission curves and relative concentrations of the drug and drug-DNA complex were quantitatively estimated using a three-dimensional model called Parallel Factor Analysis (PARAFAC) to a cubic fluorescence data array. The interaction of HCQ and DNA was predicted by applying newly modified Stern-Volmer equations to the relationship between the actual DNA concentration, and the HCQ concentration in the relative concentration profile of the PARAFAC model. In the PARAFAC application, the binding constants of the HCQ-DNA complex at 288, 298, and 310 K were found as 6.78 × 103, 5.07 × 103, and 3.74 × 103 L mol−1, respectively. From the temperature studies, the thermodynamic parameters (ΔS0= 3.528 J mol−1 K−1, ΔH0= −20.099 kJ mol−1 and ΔG0=-21.11, −21.12, and −21.19 kJ mol−1 at 288, 298, and 310 K, respectively) were calculated. The drug-DNA interaction is spontaneous due to negative ΔG0 values. The positive ΔS0 and negative ΔH0 values revealed the major role of the electrostatic force on the binding of HCQ to DNA. Assay results obtained from the proposed three-way modeling were compared to those provided by the traditional spectrofluorimetric method.

Synthesis of a BODIPY-quinoline dyad probe and studies of its biophysical interactions with fibrinogen/HSA by spectral and computational methods

A new BODIPY-based quinoline dyad probe (Bdq) was synthesized and its binding affinity with fibrinogen (Fib) and human serum albumin (HSA) was examined using steady-state/three-dimensional (3D) fluorescence and UV–vis absorption as well as molecular docking method. Fluorescence titration assays indicated that protein intrinsic emission was quenched by Bdq with a combined (static and dynamic) mechanism to form a non-fluorescent complex. 3D spectra showed that the two proteins undergo conformational changes when they interact with Bdq. Based on Förster’s non-radiative energy transfer; r, binding distances were found as 3.64/3.47 nm for Fib/HSA. The negative values of both ΔH (−62.27 kJ/mol) and ΔS (−83.03 J/mol K) parameters pointed out van der Waals forces/hydrogen bonds with Fib and also positive values of both ΔH (240.0 kJ/mol) and ΔS (920.0 J/molK) showed hydrophobic interactions with HSA of Bdq. Molecular docking also gave consistent results supporting the experimental binding types.

Determination of surface acidity of mixed oxide of silicon and titanium by calorimetric titration

Silica-titania mixed oxide with catalytic and adsorption properties has been of great academic and industrial interest. Metal oxides supported on silica have been used as a matrix for immobilizing electron transfer mediators, generating materials with diverse properties. The characterization of the surface acidity of these materials is essential and has been carried out using various techniques, including IR spectroscopy and calorimetry. However, no single technique completely analyses the present acidic sites. This study used calorimetric titration to investigate a mixed oxide containing titanium and silica, prepared by the sol-gel method, and its interaction with pyridine. The results showed that thermal treatment increased the enthalpy values (ΔH), indicating water removal from the matrix surface. The presence of pyridine resulted in a decrease in ΔH values, suggesting a preferential occupation of the stronger acidic sites. After thermal treatments between 473 and 573 K, the solids exhibited similar ΔH values, indicating a homogenization of the surface acidic sites. Calorimetric analysis revealed that the acidic sites were occupied in descending order of strength, with the strongest sites being filled initially. The increase in temperature did not result in new acidic sites but rather in greater occupation of the existing ones. Correlation between calorimetric and infrared data is suggested as the next investigation step. Thus, the results of this study contribute to a deeper understanding of the physicochemical properties, especially regarding their surface acidity, with the potential for more effective and controlled practical applications of this silica-titania mixed oxide in catalysis and adsorption.

Carbonaceous Shape-Stabilized Octadecane/Multi-Walled Carbon Nanotube Composite Materials for Enhanced Energy Storage and Electromagnetic Interference Shielding.

Developing materials for efficient energy storage and effective electromagnetic interference (EMI) shielding is crucial in modern technology. This study explores the synthesis and characterization of carbonaceous shape-stabilized octadecane/MWCNT (multi-walled carbon nanotube) composites, utilizing activated carbon, expanded graphite or ceramic carbon foam, as shape stabilizers for phase change materials (PCMs) to enhance thermal energy storage and EMI shielding, for energy-efficient and advanced applications. The integration of octadecane, a phase change material (PCM) with carbonaceous stabilizers ensures the material's stability during phase transitions, while MWCNTs contribute to improved thermal storage properties and EMI shielding capabilities. The research aims to develop novel composites with dual functionality for thermal storage and EMI shielding, emphasizing the role of carbon matrices and their MWCNT composites. SEM and CT microtomography analyses reveal variations in MWCNT incorporation across the matrices, influenced by surface properties and porosity. Leaching tests, infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) confirm the composite's stability and high latent heat storage. The presence of nanotubes enhances the thermal properties of octadecane and ΔH values almost reached their theoretical values. EMI shielding effectiveness measurements indicate that the composites show improved electric properties in the presence of MWCNTs.