جستجوی مقالات مرتبط با کلیدواژه « thermodynamics » در نشریات گروه « شیمی »

This study investigated the adsorption of alizarin red (AR) from aqueous solutions using Epichlorohydrin-Modified Walnut Shells (EMWS). Through static adsorption experiments, the impact of contact time (tc), initial pH of the solution, solution concentration (c0), and temperature (T) on the adsorption of AR onto the EMWS was examined. The optimum values of tc and pH were determined to be 360 min and 3.51, respectively. The adsorption capacity of the EMWS for AR increased when c0 and T were increased. Non-linear fitting of the equilibrium data was performed using the Langmuir, Freundlich, and Temkin isotherms. AR adsorption was well explained by the Langmuir isotherm with the qm of 81.44 mg/g at 323 K. To simulate the adsorption kinetics, various models including pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich models were employed. The results indicated that it followed the PSO kinetic model (k = 4.56 × 10 -4 g / (mg·min), qe = 18.84 mg/g and R2 = 0.9808). Moreover, the Elovich model confirmed the occurrence of chemisorption. According to thermodynamic investigations, the adsorption of AR is found to be spontaneous (ΔG﹤0) and endothermic (ΔH = 12.24 kJ/mol) while exhibiting an increase in entropy (ΔS = 58.5 J / (mol.K)). The results indicated that EMWS showed great potential as an affordable and efficient adsorbent for treating AR wastewater.

This study aims to examine histamine adsorption using Takari natural sand-based SiO2@BSA as the silica source. Silica was extracted using the hydrothermal and coprecipitation methods and then modified into SiO2@BSA adsorbent using the ultrasonication method. After that, the adsorbent was used to adsorb histamine. The results showed that the mass ratio of SiO2 and BSA to the histamine adsorption was 1:0.02 (qe=11.39 mg/g), with optimum adsorption pH of 5 (qe= 12.33 mg/g) and a contact time of 60 minutes (qe=12.36 mg/g). The percentage of histamine removal was 96%. The kinetic model was pseudo-second order type 1 with an adsorption rate constant of 6.3x103 g/mg, while the isotherm model was Langmuir with R2=0.997; qe=18 mg/g. Thermodynamic parameters indicated that the adsorption process was exothermic with a high degree of randomness, and the histamine adsorption by silica-based SiO2@BSA adsorbent from natural sand occurred chemically.

The performance of the electrochemical oxidation of wastewater contaminated with Astrazon Red Violet 3RN Dye on Ti/IrO₂/RuO₂ was evaluated under a range of significant process variables: support electrolyte type and concentration, initial dye concentration, pH, current density, and temperature. ARV-3RN dye removal efficiency was over 90% at the high concentrations of NaCl (≥ 5.0 mM) and lower pH values (3.0 ≤ pH≤ ~7.5). At the same time, the temperature increases promoted faster degradation and less energy consumption except at 10°C temperature. While the increase in the initial dye concentration had a negative effect on the removal efficiency (from 99.84% to 65.02%), energy consumption increased from 2.5 kW-h/m3  to 3.25 kW-h/m3. Although the change in applied current density did not cause a significant difference in the removal efficiency (from 99.34% to 92.79%), it caused the energy consumption to increase from 3.10 kW-h/m3 to 25.767 kW-h/m3. Electrooxidation kinetics were evaluated using Pseudo-zero-order, Pseudo-first-order, and pseudo-second-order models. Kinetic data fitted best Pseudo-first-order model. The activation energy (Ea) of the EAOP process calculated using the Arrhenius equation is 13.707 kJ/mol. Thermodynamic parameters ΔH°, ΔS°, and ΔG° evaluated by Eyring's equation calculated 11.196 kJ/mol, -0.1244 kJ/mol, and 47.662 for 293 K, respectively.

This study focuses on investigating the complexation process between N,N'-bis(salicylidene)ethylenediamine (Salen) and the metal complex [Cu(PDTC)2] in a dimethyl sulfoxide (DMSO) solvent. The kinetics and thermodynamics of the substitution reaction were examined. The [Cu(PDTC)2] complex and the Salen ligand were synthesized using a reported method, and their absorption spectra displayed characteristic peaks consistent with previous findings. The kinetics of the Cu(II) complex were studied under pseudo-first-order conditions in DMSO, with varying concentrations of Salen and a constant concentration of the [Cu(PDTC)2] complex. Reactions were carried out at temperatures of 25 °C, 30 °C, and 35 °C. By conducting temperature-dependent studies, the activation parameters (activation energy, activation entropy, and activation enthalpy) were determined. The substitution reaction was monitored through absorption spectra measurements, revealing a reduction in the absorption peak at 435 nm and the appearance of a new absorption peak at 360 nm. The rate constants obtained for the substitution reactions of salen at 25 °C fell within the range of 0.16x10-1 1/min to 5.66x10-1 1/min, which was higher compared to previous investigations due to the size of the substituted ligand. The reaction was found to follow the first-order kinetics with respect to [Cu(PDTC)2] and salen, indicating a second-order overall reaction. Increasing temperature resulted in higher values of kobs and k2. The calculated activation parameters revealed a positive activation entropy, implying a dissociative mechanism, and a positive activation enthalpy, indicating an endothermic nature of the substitution reaction.

The adsorption of an anionic dye (ARS) on raw typha grass (RAW-TG) was studied using an equilibrium batch approach. To test their impact on the ARS removal, the operational parameters of contact time (15 minutes), starting dye concentration (120 mg/L), adsorbent dosage (0.02 g), and pH (8) were tuned. Among the physical properties that were looked at were the RAW-TG's bulk density (0.397 g/cm3), pore volume (1.253 cm3), and moisture content (17.80 %). To better characterize the adsorbent, it was further studied using scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and point of zero charges (PZC) techniques. To numerically model equilibrium data, the Langmuir, Freundlich, Temkin, and Dubining Radushkevich (D-R) models were utilized. Pseudo-first-order, pseudo-second-order, Elovich, and Intraparticle diffusion models were used to calculate the adsorption kinetics. Using the Van't Hoff plot, the thermodynamic parameters affecting the adsorption process were calculated. The data were presented most effectively by a pseudo-second-order model with a maximum adsorption capacity of 46.511 mg/g, and Freundlich's interpretation of the adsorption isotherm was significantly more favorable than that of the other models examined. According to the thermodynamic characteristics, the process was viable and spontaneous, with adsorption values of ΔG (-6.737 to -8.271 kJ/mol), ΔH (16.616 kJ/mol), and ΔS (16.616 J/molK, respectively. The findings of this investigation demonstrate that RAW-TG is an efficient, reasonably priced, and environmentally friendly adsorbent for the removal of ARS dye from aqueous solutions.

SBA (Santa Barbara Amorphous)-15 nano mesoporous molecular sieve was successfully synthesized by hydrothermal method and after its adsorption of Pb2+ the prepared material was used to adsorb S2- from aqueous solution. The surface and pore structure of SBA-15, the (SBA-15)-Pb(II), and the composite material of S2- adsorbed by the (SBA-15)-Pb(II) were characterized by powder X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and low-temperature nitrogen adsorption-desorption isotherm. The effects of solution acidity, S2- concentration, contact time, and temperature on the adsorption of S2- by the (SBA-15)-Pb(II) were investigated. The optimized adsorption conditions were obtained. The adsorption rate for S2- by the (SBA-15)-Pb(II) reached 96.33 %. The change of Gibbs free energy in the adsorption process, DG°<0, can judge that the adsorption process is spontaneous. The enthalpy change in the adsorption process is less than zero, showing that the adsorption process is an exothermic reaction. The negative value of entropy change indicates that the adsorption process is a process of entropy reduction. The adsorption of S2- by the (SBA-15)-Pb(II) belongs to the pseudo-second-order kinetics. Freundlich isothermal adsorption equation can better describe the adsorption process. A novel method has been developed to adsorb S2- from wastewater.

This study uses the UV-Vis technique to describe the elimination of methylene blue dye from an aqueous solution by adsorption on an Iraqi bentonite clay surface. The batch approach was used to conduct adsorption studies carried out to evaluate the influence of factors of experimental like contact time (0–90 min), clay dose (0.1–0.35 g), and initial dye concentration (10–125 mg L-1) at the range of temperatures (25-40oC). The Langmuir and the Freundlich isotherms were used to analyze the data; the Langmuir isotherm (R2 = 0.998) proved more appropriate for the equilibrium data. The thermodynamic properties of the adsorption process, including Gibbs free energy (ΔGO), entropy(ΔSO), and enthalpy (ΔHO), were also studied. Since the (ΔGO) and (ΔHO) values were negative, it was clear that the adsorption process constituted an exothermic, spontaneous reaction. This investigation revealed that Iraqi bentonite clay effectively removed the dye methylene blue because of its high surface area. Methylene blue may be removed with an adsorption efficiency of up to 99.39 % at 25oC. By employing bentonite clay as an adsorbent surface, this research offers practical adsorption technology that is affordable and effective for treating wastewater.

This s tudy focused on the adsorption behavior of the cationic Crys tal Violet (CV) dye from aqueous solutions using a Co+2‒hectorite composite as an adsorbent surface. The initial and equilibrium CV dye concentrations were determined using a UV-Vis spectrophotometer. The results were discussed and presented for the impacts of pH, primary CV dye concentration, composite dosage, and temperature. The optimum conditions were found for eliminating Crys tal Violet dye from the aqueous solution at a pH 4, ideal temperature 293 K, and 0.5 g L-1 of composite dose. The pseudo-second-order kinetic, intraparticle diffusion analyzed the tes ts’ data and film diffusion models. Each model’s defining features have been identified, and these models were in good agreement and in charge of regulating the adsorption reaction. The adsorption operation was also thermodynamically examined to determine thermodynamic variables such as Gibbs free energy (ΔGo), entropy (ΔSo), activation energy (Ea), and enthalpy (ΔHo). The negative value of Gibbs free energy (ΔGo) and enthalpy (ΔHo) indicated that the adsorption process was a spontaneous and exothermic reaction. While the activation energy (Ea) data which fell within the normal range for physisorption, was discovered to be 22.434 kJ mol-1. This result proved that physical adsorption occurs between the CV dye and the adsorbent surface (Co+2‒hectorite composite).

Malachite Green (MG) dye belongs to the triphenylmethane class and exhibits a noxious impact on the living being. Thus, it’s being immensely important to remove it from the environment matrix. Herein, the sonochemical synthesized adsorbent material -pyrophanite-MnTiO3/TiO2 NanoParticles (NPs) was utilized to expel the commercial Malachite Green (MG) dye from the solution. The adsorption efficacy data indicate the maximum removal of MG (90.2%) is obtained for the NPs calcinated at 1000 °C (MT1). The optimized adsorption material (MT1) is characterized by using different techniques including XRD, FE-SEM, EDX, FTIR, BJH, and BET. The XRD analysis indicates the formation of divergent phases viz. rutile TiO2 and MnTiO3. The FE-SEM indicates the formation of a nano-rod-like structure. The average size and percentage of void space of MT1 NPs are evaluated by using IMAGE J software. The hysteric loops obtain from BET and BJH plots reveal the existence of type H3 hysteresis indicating the MT1 NPs exhibit mesoporous structure. The surface area, pore volume, and pore size are 61.245 m2/g, 0.139 cm3/g, and 2.0178 nm respectively. The pH, dye concentration, and temperature of the solution are optimized for the removal of MG by using MT1 NPs. Further, the adsorption isotherms, kinetics studies, and intra-particle studies indicate that monolayered second-order diffusion occurs onto the surface of MT1 NPs. The adsorption process is endothermic, thermodynamically driven, and accompanied by an increase in entropy.

The applicability of the synthesized NiO-SiO2NPs as a novel adsorbent for eliminating Methylene Blue (MB) dye from aqueous media was investigated. Various techniques including BET, FT-IR, XRD, SEM, and EDS were used to characterize this novel adsorbent. The investigation showed the applicability of NiO-SiO2NPs as an available, suitable, and low-cost adsorbent for the proper removal of MB dye from aqueous media. The effect of pH, adsorbent dosage (dose), initial MB dye concentration (C0) contact time (tc), and temperature (T) on the removal percentage (Ad%) of MB dye onto NiO-SiO2NPs was studied and the optimum value of each factor was determined (pH=7, dose=0.1g, C0=30 mg/L, tc=15 min, and T=298.0 K). The experimental equilibrium data were fitted to the conventional isotherm models and accordingly, Langmuir isotherm has good applicability for the explanation of experimental data with maximum adsorption capacity of the MB dye for SiO2 and NiO-SiO2NPs were roughly 117.0 and 140.0 mg/g respectively. Kinetics experiments were performed to investigate the adsorption kinetics, the pseudo-second-order kinetics coincided quite with the kinetic results. The thermodynamic behavior of the adsorption process was studied by considering the effect of temperature on the adsorption capacity, where the results showed that the process is spontaneous (DG0ad < 0) at the used temperature range and exothermic (DHad0 < 0) with DS0ad < 0. Based on the magnitude of DH0ad < 0, it was concluded that the studied adsorption process is a physisorption one.

Lanthanum-Modified commercial Activated Carbon (LMAC) adsorbent was synthesized, characterized, and then applied for reducing nitrate from aqueous solutions under various conditions. The extent of nitrate removal depended on four factors: temperature, the aqueous solution pH, initial nitrate concentration, and contact time. The Taguchi approach was used as the method of design for the experiments. Under optimal conditions ( T= 300°C, pH=3, C0=10 ppm, and t= 210 min), the removal percentages and capacity of nitrate adsorption were found to be 71.31%, and 1.43 for activated carbon (AC) and 93.31%, and 1.87 LMAC, respectively. Thermodynamic parameters, including enthalpy, Gibbs free energy, and entropy, indicated the spontaneous and exothermic nature of the adsorption process. Various isotherms and first and second-order kinetic models were applied to investigate the adsorption process. The pseudo-second-order kinetic model and Langmuir isotherm could well describe the adsorption process.

The purpose of the present study was investigating kinetic and thermodynamic analysis using eudragit (EUD) polymer as controller to drug release mebendazole. nanofibers containing various proportions of EUD polymer, that were prepared with electrospinning technique.  In this study, the amount of drug mebendazole release was investigated using nanofibers containing EUD at concentrations 50, 250, 500 ppm as controller at 0 -312 time by a Spectrophotometry (UV) method Measured.    For every Nanofiber at 25 °C, 31 °C, 37 °C, and 43 °C, drug release studies were performed for 72 h. The nanofibers of EUD 500ppm, EUD 250 ppm and EUD 50ppm had the highest resistance to drug release, respectively. The results showed that EUD plays a very good role in controlling drug release at the nanofiber. Experimental data were done fitted better with the Sahlin-Peppas model. Kinetic studies have shown that due to the hydrophilic nature of EUD, both diffusion and swelling mechanisms contribute to the drug release process. Thermodynamic analysis showed that drug release leading to increased disorder (ΔS<0) is also an endothermic process (ΔH>0) and at all controlling concentrations is not spontaneous (ΔG>0). As the amount of the controller increases, activation energy increases.

In order to understand the mechanism of the extraction process of polysaccharides from foxtail millet by hot water, the extraction was carried out for studying the kinetics and thermodynamics of the extraction process. After the appropriate stirring rate and liquid material ratio were selected through the preliminary experiment, the changes in polysaccharides mass concentration in the extract liquor extraction temperature and extraction time were measured. The experimental data were fitted by the first-order model. The kinetics and thermodynamics parameters were calculated. The results showed that the appropriate stirring rate and the liquid material ratio were 150 r/min, 20.0 mL/g respectively. A greater extraction rate and higher equilibrium mass concentration could be obtained under higher extraction temperatures. The extraction process accorded with the first-order dynamics model. The apparent activation energy of the process was 12.03 kJ/mol under study conditions. The internal diffusion coefficient was increased with increasing temperature in the range of 7.84×10-10 - 1.29×10-9 m2/min. The half-life was decreased from 25.2 min to 3.9 min as the temperature increased. The Gibbs free energies were all less than zero, the enthalpy change was 31.96 kJ/mol and the entropy change was 120.3 J/(mol·K) in process. The polysaccharides extraction process was a spontaneous, endothermic, and entropy increases process.

In this present study, raw water lily leaves (RWL) powder was prepared and used as low cost, efficient and environmental friendly adsorbent for the removal of malachite green (MG) from aqueous solution. The adsorbent’s surface functional group, net neutral charge and morphology were analysed by FT-IR, Point of Zero charge and Scanning Electron (SEM) spectroscopic techniques which confirmed the effective adsorption of MG dyes onto the RWL adsorbent surface. Batch adsorption technique was employed under various optimized conditions including contact time, adsorbent dosage, adsorbate concentration, pH and temperature respectively with an adsorption capacity of 216.66mg/g and percentage adsorption of 99.5. The physical properties: moisture content (13.49%), ash content (9.81%), organic matter (90.19%), bulk density (0.263g/cm3), pore volume (1.66cm3), pH (5.74) of the adsorbent were obtained using standard methods. The kinetic data were best fitted by pseudo-second order in all the models tested under different operating temperatures. The adsorption isotherms were estimated, established and found to fit into Freundlich isotherm as compared to other models tested. Thermodynamics of the adsorption was found to be spontaneous and feasible with values of Gibb’s free energy (∆G) ranging between -9.481 to -9.880kJ/mol, exothermic with enthalpy (∆H) of -11.75kJ/mol and a decrease in randomness of the adsorption process during the transfer of molecules between the adsorbent and adsorbates with entropy (∆S) of -6.33kJ/mol. This study confirmed that RWL could be employed as a low cost and environmental friendly adsorbent for the removal of toxic dyes such as Malachite Green from aqueous solution

Currently the use of agricultural waste as a low-cost adsorbent have attracted much attention of researchers. The removal of cadmium (II), copper (II) and lead (II) ions from aqueous solution using peels of Chrysophyllum albidum (African Star Apple) was studied. The sorption studies were carried out by varying adsorbent dose, contact time and temperature. The experimental results showed that the adsorption removal efficiency of Chrysophyllum albidum peels on cadmium (II), copper (II) and lead (II) ions had a direct relationship with adsorbent dose and contact time while the Temperature study showed an inverse relationship. The maximum adsorption efficiencies of the adsorbent were 95.30, 93.22 and 92.78 % for Cd2+, Cu2+ and Pb2+ respectively. Sorption kinetic data fitted well with the pseudo second order kinetic model. The experimental data were analyzed using Freundlich, Langmuir and Temkin isotherm equations. The best fit was obtained by Temkin isotherm for Cd2+ and Freundlich isotherm for Cu2+ and Pb2+ ions. The Arrhenius and Eyring activation energy showed that rate of Cd2+ adsorption is more rapid than rate of Cu2+ and Pb2+ adsorption. The thermodynamic data revealed that the Cd(II) and Pb(II) ion uptake was exothermic while Cu(II) ion was endothermic and they were all spontaneous in nature. From these results, Chrysophyllum albidum peel could be recommended as an adsorbent for metal ion removal from aqueous solution.

In the current study, carpobrotus edulis were used to prepare three adsorbent surfaces; (dry adsorbent material, DAM), (hot activated carbon, HAC), and (acid activated carbon, AAC), and applied for safranin dye removal as a function of pH, contact time, adsorbent dose, initial dye concentration, and temperature. The ideal pH for DAM, HAC, and AAC efficient adsorption were 7-11, 7-9, and 5-11, respectively, employing an adsorbent dosage of 0.10 g and contact time of 30, 40, and 90 min, respectively. Furthermore, the adsorption processes were better explained by the pseudo-second-order-kinetic model. It was also noticed that the safranin adsorption process demonstrated a favorable agreement with Freundlich isotherm for the three adsorbents with maximum calculated adsorption capacities of 47.49, 44.18, and 46.72 mg/g for DAM, HAC, and AAC, respectively. The results of the thermodynamic study revealed the exothermic nature of dye adsorption onto DAM and AAC and the endothermic nature onto HAC. Finally, results demonstrated that the studied surfaces are efficient adsorbents and could likely be utilized for dyes adsorption.