Thermodynamic Studies Research Articles

Molecular recognition of peptides and proteins by cucurbit[n]urils: systems and applications.

The development of methodology for attaching ligand binding sites to proteins of interest has accelerated biomedical science. Such protein tags have widespread applications as well as properties that significantly limit their utility. This review describes the mechanisms and applications of supramolecular systems comprising the synthetic receptors cucurbit[7]uril (Q7) or cucurbit[8]uril (Q8) and their polypeptide ligands. Molecular recognition of peptides and proteins occurs at sites of 1-3 amino acids with high selectivity and affinity via several distinct mechanisms, which are supported by extensive thermodynamic and structural studies in aqueous media. The commercial availability, low cost, high stability, and biocompatibility of these synthetic receptors has led to the development of myriad applications. This comprehensive review compiles the molecular recognition studies and the resulting applications with the goals of providing a valuable resource to the community and inspiring the next generation of innovation.

Uptake of ofloxacin antibiotic from aqueous solution on Co3O4/SBA-15 adsorbent by an adsorption process: Evaluation of isotherm, kinetics, and thermodynamic studies

Uptake of ofloxacin antibiotic from aqueous solution on Co3O4/SBA-15 adsorbent by an adsorption process: Evaluation of isotherm, kinetics, and thermodynamic studies

The high adsorption performance of banana (Musa ABB Cv. Kluai ‘Namwa’) beaded materials modified with zinc and magnesium oxides for cadmium removal

Wastewater contaminated with cadmium is a concern because of its toxicity, persistence, and bioaccumulation to the environment, ecosystem, and human health, so it is required to remove cadmium(II) ions before releasing them to receiving water. Banana powder beads (BPB), banana powder doped ZnO beads (BPZB), banana powder doped MgO beads (BPMB), and banana powder doped ZnO + MgO beads (BPZMB) were synthesized as the novel cadmium adsorbents, and their characterizations, cadmium adsorption performances, cadmium adsorption patterns and mechanisms, thermodynamic study, and reusability were investigated. BPMB had the highest specific surface area of 16.60 m2/g and the smallest pore size of 1.69 nm than other materials. BPB was an amorphous structure, whereas BPZB, BPMB, and BPZMB were crystalline structures presenting their specific metal oxide peaks of ZnO or MgO. They were coarse surfaces and had a spherical shape consisting of C, O, Ca, Cl, and Na. Their main functional groups were O–H, C–H, C=O, C–O, and N–H. The points of zero charge of BPB, BPZB, BPMB, and BPZMB were 5.37, 6.75, 9.87, and 9.43. The cadmium removal efficiencies of BPB, BPZB, BPMB, and BPZMB were 89.18%, 96.62%, 99.59%, and 97.85%, and their qm values were 90.09, 232.56, 454.55, and 303.03 mg/g, respectively. Thus, the metal oxide helped to improve material efficiency, especially MgO. The Freundlich and pseudo-second-order kinetic models were good fit models for describing their adsorption patterns and mechanisms. The increasing temperature affected to decrease their cadmium adsorptions. They could be reused in more than 3 cycles of more than 73% of cadmium adsorption. The electrostatic interaction played an important role in describing their cadmium adsorptions. Therefore, BPBM was a good cadmium adsorbent for application in industrial wastewater treatment since it had a higher performance of cadmium adsorption than other materials.

KINETIC AND THERMODYNAMIC STUDY OF GOURD SEEDS OIL EXTRACTION (Cucurbita pepo)

Our interest has been imphasized in this paper on oil extraction of gourd seeds because these are widespread in all the country (DRCongo) and are reputed to have excellent cure properties against prostate. They prevent also diabetes cardiac fits, cerebral vascular accident, lived complaints and menopause symptoms. We need of course to solve the problem of home technology for underdeveloped countries where the transfer of technology is made impossible by the so called the developed countries wishing to maintain the rest of the world in timeless impoverishment. In this paper the kinetic and the thermodynamic study of extraction shows for the former aspect (kinetic aspect) how to calculate the kinetic constant ( k ) which will allow to size the reactor of production of gourd seeds oil in large quantities because the reactor volume is directly proportional to the desired volumic debit of produced oil per hour and for the later aspect (thermodynamic aspect) the released energy accompagning the extraction ( exothermic phenomenon) can be used for example to produce mechanical work or electrical work, it can be also converted to strengthen the production. The proposed kinetic method is original, it supports the name of its founder (KUNYIMA method).

A Sustainable Solution for the Adsorption of C.I. Direct Black 80, an Azoic Textile Dye with Plant Stems: Zygophyllum gaetulum in an Aqueous Solution.

The presence of pollutants in water sources, particularly dyes coming by way of the textile industry, represents a major challenge with far-reaching environmental consequences, including increased scarcity. This phenomenon endangers the health of living organisms and the natural system. Numerous biosorbents have been utilized for the removal of dyes from the textile industry. The aim of this study was to optimize discarded Zygophyllum gaetulum stems as constituting an untreated natural biosorbent for the efficient removal of C.I. Direct Black 80, an azo textile dye, from an aqueous solution, thus offering an ecological and low-cost alternative while recovering the waste for reuse. The biosorbent was subjected to a series of characterization analyses: scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), and infrared spectroscopy (IR) were employed to characterize the biosorbent. Additionally, the moisture and ash content of the plant stem were also examined. The absorption phenomenon was studied for several different parameters including the effect of the absorption time (0 to 360 min), the sorbent mass (3 to 40 g/L), the pH of the solution (3 to 11), the dye concentration (5 to 300 mg/L), and the pH of the zero-charge point (2-12). Thermodynamic studies and desorption studies were also carried out. The results showed that an increase in plant mass from 3 to 40 g/L resulted in a notable enhancement in dye adsorption rates, with an observed rise from 63.96% to 97.08%. The pH at the zero-charge point (pHpzc) was determined to be 7.12. The percentage of dye removal was found to be highest for pH values ≤ 7, with a subsequent decline in removal efficiency as the pH increased. Following an initial increase in the amount of adsorbed dye, equilibrium was reached within 2 h of contact. The kinetic parameters of adsorption were investigated using the pseudo-first-order, pseudo-second-order and Elovich models. The results indicated that the pseudo-first-order kinetic model was the most appropriate for the plant adsorbent. The isotherm parameters were determined using the Langmuir, Frendlich, Temkin, and Dubinin-Radushkevich models. The experimental data were more satisfactory and better fitted using the Langmuir model for the adsorption of dye on the plant. This study demonstrated that Zygophyllum gaetulum stems could be employed as an effective adsorbent for the removal of our organic dye from an aqueous solution.

Desulfurization of simulated and commercial liquid fuel on nano-ZnO fabricated walnut shells.

The current investigation involved the development of activated carbon, juglans regia activated carbon (JRACs), from walnut shells, scientifically known as Juglans regia. The ZnO nanorods were loaded on the activated carbon and referred to as ZnO@JRACs. Desulfurization efficiency was assessed through batch adsorption and compared to commercial activated carbon known as DARCO. The materials were characterized using PXRD (powder X-ray diffraction), FTIR (Fourier-transform infrared spectroscopy), ICP-AES (inductively coupled plasma atomic emission spectroscopy), BET (Brunauer-Emmett-Teller) surface area analysis, TEM (transmission electron microscopy) imaging, and TGA (thermal gravimetric analysis). The findings indicated that the materials have oxygen functionalities, a porous morphology, and a substantial specific surface area (BET) of 1269.92 m2/g for ZnO@JRACs. Zn atom concentration in the ZnO@JRACs surface was determined to be 1.16 atomic percent using ICP-AES. Desulfurization experiments were conducted on three liquid fuels, namely a single component model fuel, MSF (multicomponent simulated fuel), and commercial fuel (kerosene), under optimized conditions (8g/L adsorbent dosage in 10mL of fuel, 15min of contact time at room temperature). The conditions effectively removed ~ 98.9% of dibenzothiophene (DBT) from the single component model fuel. The observed order for adsorption capacity is as follows: ZnO@JRACs (63.6mgg-1) > JRACs (46.3mgg-1) > DARCO (26.1mgg-1). The analysis of multicomponent simulated fuel (MSF) using gas chromatography-flame photometric detector (GC-FPD) revealed significant removal percentages for different types of thiophenic sulfur. Specifically, the removal percentages were ~ 46.2%, 97.6%, and 99.4% for benzothiophene, dibenzothiophene, and 4, 6-dimethyldibenzothiophene, respectively. Kinetic studies have shown that the adsorption process is governed by a pseudo second-order reaction. Additional thermodynamic studies were conducted to further investigate the mechanism of adsorption. The spent synthesized composite ZnO@JRACs were thermally regenerated and can be reused for up to four cycles.

Modeling of adsorptive treatment of lead (II) ions contaminated effluents using cashew nut shell alkali activated carbon: Batch kinetic, isothermal and thermodynamic studies

The numerical study of the decontamination of lead(II) ions-rich effluent employing activated carbon derived from cashew nut shell was the central focus of this work. Chemical activation with zinc chloride (ZnCl2) was used to produce powdered activated carbon at optimized activation conditions of impregnation ratio (0.531), activation temperature (1083 K) and activation time (63min). The physiochemical properties of raw and activated cashew nut shell were determined using Fourier transform infrared spectroscopy, scanning, X-ray diffractor (XRD), scanning electron microscopy (SEM), and Brunauer-Emmet-Teller (BET) analyses. Batch adsorption experiments were performed at varied process conditions of temperature (303–323) K, contact time (5–80min), and initial lead(II) ion concentrations (100–400 mg.L−1). The adsorption behavior of the batch–type operation was mathematically described in the form of non-linear parabolic partial differential equations (PDE’S) incorporating film, pore and surface diffusion mechanisms. The batch mathematical model was solved by implementing a custom MATLAB program-OkiyNwabannebatch and calibrated to predict the desired response (percentage removal) using measured adsorption data. The equilibrium adsorption, kinetics and thermodynamics of lead(II) ions adsorption onto activated cashew nut shell were also assessed using nonlinear isotherm, kinetic and thermodynamic models. Sensitivity analysis unveiled that temperature with sensitivity value of 37.31 % had a predominant effect on the model performance. The simulated equilibrium data was well explicated by the Freundlich model for lead(II) ions adsorption onto activated cashew nut shell. The pseudo-second order kinetic model best reproduced the simulated adsorption data for lead(II) ions uptake by cashew nut shell adsorbent. Likewise, the kinetic data followed Boyd model, indicating that the adsorption process is controlled by external (film) diffusion for the uptake of lead(II) ions by alkali activated cashew nut shell. Thermodynamic analysis using the Gibbs and Van’t Hoff’s models indicated that lead(II) ions adsorption by modified cashew nut shell is spontaneous and exothermic. The physical nature of the adsorption process was elucidated from the low values of the isosteric heats of adsorption (ΔHX) evaluated (<80 kJ mol−1). This study showed that zinc chloride activated cashew nut shell has good potential to be used as a cost-effective and efficient adsorbent for the uptake of lead(II) ions from aqueous solution.

Selective adsorption of cationic dye by κ-carrageenan-potato starch bio-hydrogel: Kinetics, isotherm, and thermodynamic studies

An eco-friendly κ-carrageenan/potato starch bio-hydrogel is designed for the efficient removal of methylene blue (MB) dye from water. The incorporation of potato starch was successfully confirmed through XRD, FT-IR, and SEM analysis, while TGA highlighted the hydrogel's thermal stability. Batch adsorption experiments demonstrated excellent MB removal efficiency, with a maximum adsorption capacity of 116.1 mg/g under optimal conditions (initial dye concentration: 100 mg/L, contact time: 180 min, temperature: 20 °C, adsorbent dosage: 1.6 g/L, and pH: 11). FT-IR analysis indicated that electrostatic interactions and hydrogen bonding primarily govern the adsorption process. The adsorption followed pseudo-second-order kinetics and fitted well with the Langmuir isotherm model. Thermodynamic studies revealed that the adsorption was exothermic and spontaneous. A key feature of this bio hydrogel is its selective affinity for the cationic dye MB, in a mixture with Acid Orange (AO) and other cationic dyes (Rhodamine B (Rh B) and crystal violet (CV)). The adsorbent also demonstrated impressive reusability, maintaining 93 % of its efficiency after five cycles, highlighting its potential for sustainable and cost-effective water treatment.

Sn-doped n-type GaN freestanding layer: Thermodynamic study and fabrication by halide vapor phase epitaxy

Results of a thermodynamic study of Sn doping and fabrication of a Sn-doped GaN freestanding layer with high structural quality by halide vapor phase epitaxy (HVPE) are described in this paper. Thermodynamic analysis revealed that SnCl2 and/or SnCl act as Sn precursors through the reaction between Sn metal and HCl gas. The equilibrium partial pressures of SnCl2 and SnCl increase with the input HCl partial pressure. To generate Sn precursors effectively, it is desirable that the reaction between Sn metal and HCl gas occurs in the inert gas ambient. On the basis of results of the thermodynamic study, the Sn-doped GaN freestanding layer with a Sn concentration of 5.7 × 1019 cm−3 is fabricated by removing the GaN seed substrate after HVPE growth. The Sn-doped GaN freestanding layer has high crystal quality, and the lattice constants along the c- and a-axes of the Sn-doped GaN freestanding layer are larger than those of the GaN seed substrate because of the high electron density and the size effect of Sn atoms.

Thermodynamics and Kinetic Study for Removal of Orange-G Dye from Aqueous Solution by Nano Composite

In this study, where graphene oxide was prepared by Hummer method, while copper oxide was prepared in the green way using (capparies spinosa) plant extract as a reducing agent, these oxides were diagnosed as well as the binary nanocomposite by several techniques including Fourier Transform Infrared Spectroscopy (FTIR), X-rays diffraction , and field Emission scanning electron microscopy (FESEM), after that the superimposed (GO/CuO) was used to adsorbent the orange G dye ( Orange - G) from its aqueous solutions, A number of factors affecting adsorption were studied (equilibrium time, surface weight, pH, concentration effect, temperature). The results showed that the ideal time for adsorption of the orange dye (orange-G) on the surface of the nanocomposite (GO/CuO) was (30min), the best ideal weight for dye removal was (0.05gm), the best concentration was (20ppm), and the best acid function was (pH=2). After that, the adsorption kinetics were also studied by applying the pseudo first and second order of adsorption. The results showed that the adsorption process follows the false second-order kinetics. The thermodynamic functions of the removal process were also studied, and it was found that the value of (DH) is negative for the surface of the composite (GO/CuO) with dye. Meaning the adsorption process is exothermic, and that the DG0 has negative value, meaning that the adsorption processes occur spontaneously. positive DS0 values indicate that the molecules are becoming less bound

Modeling of performance and thermodynamic study of a gas turbine power plant

The efficiencies and performance of gas turbine cycles are highly dependent on parameters such as the turbine inlet temperature (TIT), compressor inlet temperature (T1), and pressure ratio (Rc). This study analyzed the effects of these parameters on the energy efficiency, exergy efficiency, and specific fuel consumption (SFC) of a simple gas turbine cycle. The analysis found that increasing the TIT leads to higher efficiencies and lower SFC, while increasing the To or Rc results in lower efficiencies and higher SFC. For a TIT of 1400 ℃, T1 of 20 ℃, and Rc of 8, the energy and exergy efficiencies were 32.75% and 30.9%, respectively, with an SFC of 187.9 g/kWh. However, for a TIT of 900 ℃, T1 of 30 ℃, and Rc of 30, the energy and exergy efficiencies dropped to 13.18% and 12.44%, respectively, while the SFC increased to 570.3 g/kWh. The results show that there are optimal combinations of TIT, To, and Rc that maximize performance for a given application. Designers must consider trade-offs between efficiency, emissions, cost, and other factors to optimize gas turbine cycles. Overall, this study provides data and insights to improve the design and operation of simple gas turbine cycles.

Effective removal of Calcium and Magnesium Ions from boiler feed Water using Polyacrylonitrile supported titanium tungstovanadate composite ion exchange nanofiber

&lt;p&gt;&lt;em&gt;&lt;strong&gt;​​​​​​&lt;/strong&gt;&lt;/em&gt;&lt;span style="font-family:&amp;quot;Times New Roman&amp;quot;,&amp;quot;serif&amp;quot;;font-size:12.0pt;line-height:150%;"&gt;The challenge posed by the presence of calcium ions (Ca&lt;sup&gt;2+&lt;/sup&gt;) in process streams is attributed to its adverse effects on the heat transfer efficiency of process equipment. In this study, a novel electrospun nanofibrous composite was synthesized by combining polyacrylonitrile (PAN) with well-dispersed Titanium tungestovanadate (TWV) cation exchanger. Homogeneous precipitation technique was employed to synthesize nano-titanium (IV) tungstovanadate (TWV) cation exchanger. Various synthesis parameters, including reactant volume ratio, amount of precipitating agent and reaction temperature, were optimized to achieve the highest ion exchange capacity (IEC). The prepared ion exchange material exhibited an ion exchange capacity (IEC) of 2.39 meq.g&lt;sup&gt;-1&lt;/sup&gt; for Na&lt;sup&gt;+&lt;/sup&gt; ions. The incorporation of the prepared nanoparticles into nanofibers conferred the sorption capabilities of the composite. The nanofibers' morphologies and structures were analyzed using Fourier transform infrared (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). Batch sorption experiments were carried out to investigate the sorption properties. Controlled experiments were conducted to investigate the impact of various factors, including solution pH, temperature, dosage, contact time, and the initial concentration of the hard water. The results indicated that the optimum adsorption conditions that gave the highest percentage of removal 99%, 98% for Ca&lt;sup&gt;2+&lt;/sup&gt; and Mg&lt;sup&gt;2+&lt;/sup&gt;&amp;nbsp; ions respectively were 50 mg of adsorbent dosage, 500 ppm of Ca&lt;sup&gt;2+&lt;/sup&gt; and Mg&lt;sup&gt;2+&lt;/sup&gt;&amp;nbsp; solution =7, and a contact time of 30 min at room temperature .The &amp;nbsp;kinetic data were fitted to pseudo second order model. Furthermore, the thermodynamic study suggested that the adsorption on PAN/TWV NF was endothermic and spontaneous.&lt;/span&gt;&lt;/p&gt;

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.

Adsorption technique using new semi-IPN hydrogels for high removal of methylene blue dye from aqueous solutions

ABSTRACT Six new semi-IPN hydrogels using 2-acrylamido-methylpropane-1-sulfonic acid (AMPS) and Gelatin at different ratios through redox polymerization were prepared. Methylene-bisacrylamide and glutaraldehyde were used as the crosslinking agents for AMPS and Gelatin, respectively. The hydrogels’ swelling ratios and surface morphologies were analyzed using SEM for characterization. Porosity and specific surface area using the Brunauer–Emmett–Teller technique. DSC and Tg were also used for the thermal analysis of the prepared hydrogels, which show trans-glass temperature (Tg) higher than their raw materials AMPS and Gelatin. The prepared hydrogels were used to eliminate the cationic dye MB from the water-based solutions with an initial concentration of 600 ppm. The study discovered that the N9 and N10 hydrogels were extremely effective at removing a certain dye from aqueous solutions with an optimum pH level of 11 and an optimum temperature of 65°C. Both N9 and N10 achieved high removal efficiencies, reaching equilibrium at 90 min, whereas the other hydrogels required 120 min. N9 performed slightly better at 1078.919 mg/g and N10 at 1057.404 mg/g. The adsorption behavior of the two hydrogels followed the Langmuir model. The hydrogels exhibited pseudo-second-order kinetics. The thermodynamic study cleared that the adsorption of MB dye was endothermic and spontaneous. Results also showed that the adsorption of dyes with hydrogels N9 and N10 is chemisorption in nature. Desorption studies were conducted using 0.1 M HCl and NaOH. HCl was found to be the best eluent for dye recovery.

Crystal violet removal from waste water by sulfonated poly (glycidyl methacrylate) nano-adsorbent: optimization by response surface methodology, isotherms, kinetics, and thermodynamics studies

Crystal violet removal from waste water by sulfonated poly (glycidyl methacrylate) nano-adsorbent: optimization by response surface methodology, isotherms, kinetics, and thermodynamics studies

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.

Harnessing Moringa oleifera root powder (MORP) for the sustainable remediation of heavy metal contaminated water.

Heavy metal environmental pollution is rapidly increasing due to the increase in industrialization and urbanization. Industrial processes, such as paint production, mining, and raw materials producing industries release effluents rich in heavy metals, like Pb2+, Cd2+, Cu2+, and Cr3+. These heavy metals are dangerous because they persist in nature, are non-biodegradable and they have high tendency to accumulate in the environment and in living organisms who are exposed to them. This work studied the removal of heavy metals (Cu, Pb, Cr, and Cd) from aqueous solution using Moringa oleifera root powder (MORP) as the adsorbent. The MORP was characterized by SEM, FTIR, BET, and XRD. Batch adsorption experiments carried out investigated the effects of adsorbate concentration, adsorbent dosage, agitation time, pH and temperature on adsorption. The optimum parameters are: contact time (90 min); pH (9); adsorbent dose (0.6); metal ion concentration (30 mg L-1) for Cr and 40 mg L-1 for the rest; and temperature (50 °C) for Cu and Pb, and 70 °C for Cr and Cd. These experimental data were analyzed with 5 isotherm models (Temkin, Flory-Huggins, Langmuir, D-R and Freundlich). The result obtained fitted best to Temkin isotherm in comparison to others. Kinetic studies revealed that the pseudo-second order kinetic model best described the adsorption (with high R2 values ranging from 0.9810-0.9976) compared to pseudo-first order and intra-particle diffusion kinetics model. Results of the thermodynamic study showed that the sorption process was endothermic for Cu and Pb, but exothermic for Cd and Cr. The adsorbent showed good adsorptive tendencies toward the ions studied, and could be applied on an industrial scale for the remediation of metal contaminated water.

Reduction of 2,4-dichlorophenoxy acetic acid herbicide toxicity from aqueous media by adsorption: Experimental and theoretical study using DFT method

This work studies the possibility of reducing the toxicity of water laden with 2,4-dichlorophenoxy acetic acid (2,4-D) using a commercial activated carbon (AC). Multiple structural and textural characterization techniques including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM/EDS), point of zero charge (pHzpc) determination, Boehm titration, iodine number, Methylene blue index, and BET analysis measurements were performed on the commercial AC. Various parameters affecting adsorption were studied and well-known isotherms models in their linear and non-linear forms were applied for fitting equilibrium data. The kinetic data was analyzed using intraparticle diffusion, pseudo-first and second-order kinetic models. Density functional modeling (DFT) of 2,4-dichlorophenoxyacetic acid was used to investigate the origin of the reactivity. The AC surface area was found to be 1017 m2⋅g−1. A contact time of 30 min, an AC dose of 4 g⋅L−1 and a pH of 6.2 resulted in a maximum adsorption capacity of 235.55 ± 6.43 mg⋅g−1. The thermodynamic study revealed that the adsorption process was physical, spontaneous and endothermic. The adsorption process was governed by second-order kinetics and controlled by intraparticle diffusion.

Development of synergistic antifungal in situ gel of miconazole nitrate loaded microemulsion as a novel approach to treat vaginal candidiasis

Limited solubility is the main cause of the low local availability of anti-candidiasis drug, miconazole nitrate (MN). The study’s objective was to develop and characterize microemulsion (ME) based temperature-triggered in situ gel of MN for intravaginal administration to enhance local availability and antifungal activity. The solubility of MN was initially studied in different oils, surfactants, and co-surfactants. Then, pseudo-ternary phase diagrams were constructed to select the best ratio of various components. The ME formulations were characterized by thermodynamic study, droplet size, polydispersity index (PDI), viscosity, and in-vitro antifungal mean inhibition zone (MIZ). Selected MEs were incorporated into different in situ gel bases using a combination of two thermosensitive polymers (poloxamer (PLX) 407 and 188), with 0.6% of hydroxypropyl methylcellulose (HPMC K4M) and gellan gum (GG) as mucoadhesive polymer. ME-based gels (MG) were investigated for gelation temperature, gelation time, viscosity, spreadability, mucoadhesive strength, in vitro release profile, and MIZ test. Furthermore, the optimum MG was assessed for in vivo animal irritation test and FESEM investigation. Tea tree oil, lavender oil, tween 80, and propylene glycol (PG) were chosen for ME preparation for the optimal formulation; formulation ME7 and ME10 were chosen. After incorporation of the selected formulation into a mixture of P407 and P188 (18:2% w/w) with 0.6% mucoadhesive polymer, the resultant MG formulation (MG1) revealed optimum gelation temperature (33 ± 0.01℃) and appropriate viscosity with enhanced sustained release (98%) and retention through sheep vaginal mucosa, MG1 exhibited a better MIZ compared to the 2% MN gel formulation and the marketed MN product, and no rabbit vagina irritation. In conclusion, the miconazole nitrate-loaded MG-based formula sustained the duration of action and better antifungal activity than the marketed miconazole nitrate formulation.

Insight into the molecular mechanism of organic pollutants’ adsorption on magnetic ZIF-8 synthesized via a transformational route

This study presents the synthesis of Fe3O4@Zeolite Imidazolate Framework-8 (Fe3O4@ZIF-8), a novel magnetic core–shell adsorbent engineered for enhance adsorption of organic pollutants. The process begins with the formation of spherical magnetite aggregates (i.e., Fe3O4) via a solvothermal method, using polyacrylic acid for stabilization and capping. A ZIF-8 shell is then grown through a sol gel process followed by reaction with 2-methylimidazole, resulting in a crystalline shell approximately 60 nm thick. Characterization techniques, including energy dispersive X-ray analysis and X-ray diffraction, confirm the successful preparation of Fe3O4@ZIF-8. The adsorption capabilities were evaluated using methylene blue (MB) and diclofenac sodium (DCF) as model pollutants. Fe3O4@ZIF-8 demonstrated rapid removal efficiencies, with 98 % removal of MB (6.01 × 10-4 mg·g−1·min−1) and DCF (4.43 × 10-4 g·mg−1.min−1) within 15 and 30 min, respectively, significantly outperforming conventional activated carbon. Thermodynamic studies indicate that the adsorption processes are spontaneous; enthalpic changes drive MB adsorption, while DCF is influenced by entropic factors. Molecular modeling reveals preferential adsorption behaviors on different ZIF-8 facets, with stronger interactions for MB due to π-π stacking and hydrogen bonding. These findings underscore the potential of Fe3O4@ZIF-8 as an effective adsorbent for water purification, highlighting its substantial adsorption capacity (73.2 mg·g−1 for MB and 53.8 mg·g−1 for DCF), stability, and reusability.