Values Of Thermodynamic Parameters Research Articles

Chromatographic Method for Evaluation of Polymeric GC Stationary Phases Ageing Using the Novel Non-Cross-Linked Poly(3-(Tributoxysilyl)Tricyclononene-7) as the Model Stationary Phase.

The chromatographic properties and thermal stability are investigated for the polymeric stationary phase based on the norbornene polymer. It was shown that without additional cross-linking, poly(3-(tributoxysilyl)tricyclononene-7) demonstrates properties similar to liquid chromatographic stationary phases. It was also found to be more thermally stable than previously studied trimethylsilyl- and trimethoxysilyl- derivatives. The long-term heating at 170 °C resulted in an increase of mass transfer rate between stationary and mobile phases which could be observed as a decrease of parameter C of Van Deemter equation. This effect is rather unusual, as the polymeric stationary phases tend in decrease of the layer volume and porosity while ageing. Additionally, the values of thermodynamic parameters of sorption are calculated for the polymeric stationary phase: enthalpy of sorption varied −28 to −37 kJ/mol, entropy change was −41 to −51 J/mol K. The compensation curves were plotted for the alkanes, arenes, and alcohols, and the parameters of compensation plot were calculated, demonstrating the different sorption mechanisms both for hydrocarbons and oxygen-containing compounds, and different classes of organic compounds.

Inhibition of acid corrosion in API 5L X52 steel with 1,2,3-triazole derivatized from benzyl alcohol: Experimental and theoretical studies

This work presents the synthesis of new triazoles derived from benzyl alcohol to be used as corrosion inhibitors for API 5L X52 steel in HCl 1M medium. The results showed that all derivatives displayed a better inhibitory capacity than benzyl alcohol. Electrochemical impedance spectroscopy in conjunction with polarization curves revealed that compound 6 showed the highest inhibitory capacity of all derivatives with 94.2% inhibition efficiency at a concentration of 50 ppm. Furthermore, it was determined that compounds 3, 6 and 7 were inhibitors with anodic behavior and compounds 4 and 5 acted as mixed inhibitors. Benzyl alcohol and all its synthesized derivatives fitted the Langmuir adsorption isotherm. The combined adsorption phenomenon was proposed according to the thermodynamic parameter values obtained. Dispersion-corrected DFT studies, assuming the cluster approach, obtained free binding energies that matched well with experimentally determined standard adsorption free energies. The mixed physisorption-chemisorption observed was explained in terms of the electrostatic interactions and chemical bonding between the metal surface and the corrosion inhibitor. Finally, compound 6 obtained the largest charge transference to the metal cluster.

Treatment of shale gas flowback water by adsorption on carbon- nanotube-nested diatomite adsorbent

A carbon-nanotube-nested diatomite adsorbent (CND-composite adsorbent) was successfully prepared and introduced to remove organic contaminants from shale gas flowback water. The CND-composite adsorbent was then characterized using Scanning Electron Microscopy, Brunauer Emmett Teller, Mercury Intrusion Porosimetry and X-ray Diffraction (XRD) analyses. The changes in the organic species present in the shale gas flowback water before and after adsorption were characterized via Gas Chromatography-Mass Spectrometer. The kinetics, isotherms and thermodynamics of the adsorption of organic matter in shale gas flowback water on the CND-composite adsorbent were investigated on the basis of static experiments. The CND-composite adsorbent had hierarchical mesoporous/ macroporous structures. The adsorption experiments indicated that the maximum removal efficiency for total organic carbon was 78.91 %. The adsorption mechanisms mainly involved intermolecular interactions, electrostatic interaction and hydrogen bonds. Results showed that the Freundlich isothermal model and pseudo-second-order model were suitable for the characterization of the adsorption process in this work. The changing values of thermodynamic parameters, including the Gibbs free energy, entropy, and enthalpy, indicated that the adsorption process was spontaneous and endothermic. In addition, the adsorption process was jointly controlled by physical and chemical mechanism. In summary, the CND-composite adsorbent has potential for utilization in the removal of organic pollutants in real wastewater.

Synergistic solvent extraction of neodymium form nitric acid medium using Cyanex 302 and D2EHPA

AbstractIn this research, a binary mixture of Cyanex 302 (bis‐2,4,4 trimethylpentyl monothiophosphinic acid) and D2EHPA (di‐2‐ethylhexyl phosphoric acid) in kerosene was used for extracting neodymium from nitric acid medium. The different variables affecting the extraction of Nd(III) such as contact time, solution acidity, extractant concentration, and temperature were investigated. Stripping of neodymium ions from the loaded organic phase using HCl, HNO3, and H2SO4 for the re‐extraction of neodymium was also carried out. Results indicated that the most efficient reagent for the stripping of neodymium was nitric acid. The extraction reaction of neodymium with the synergistic mixture was determined using graphical method to be NdH5A2B6. The organo‐metallic complex containing neodymium was examined by Fourier Transform Infrared Spectroscopy (FT‐IR). The values of stoichiometric coefficients and thermodynamic parameters were calculated for this mixture. The extraction was an endothermic process, and the thermodynamic functions, ΔH and ΔS were determined to be 10.532 kJ/mol and −123.681 j/mol °K, respectively for the system under study. The Cyanex 302+D2EHPA system not only increased the extraction efficiency of neodymium but also improved the selectivity significantly. The separation factor of neodymium and praseodymium suggested that this mixture would be of practical value in the separation of neodymium.

Formation of mixed micelles in an aqueous mixture of a biamphiphilic surface active ionic liquid and an anionic surfactant: Experimental and theoretical study

The micellization behaviour of biamphiphilic surface active ionic liquid (BAIL), 3-methyl-1-pentylimidazolium dodecylsulfate [C5mim][C12SO4] with anionic surfactant, sodium dioctylsulfosuccinate (AOT) was investigated using different techniques in an aqueous solution. The values of critical micelle concentration (cmc) and thermodynamic parameters have been ascertained by employing conductometric measurement at (298.15, 308.15 and 318.15) K. The interfacial parameters viz. surface pressure, maximum surface excess concentration, and minimum surface area per surfactant molecule evaluated by using the surface tension measurement at 298.15 K shows the less effectiveness of mixtures to reduce the surface tension. The size and turbidity of the mixed aggregates were investigated using dynamic light scattering (DLS) and turbidimetry. The turbidity results show the existence of micelles as well as mixed aggregates. Different proposed theoretical models like Clint, Rubingh and Motomura was employed for the evaluation of mixed micellar parameters (ideal values of cmc, activity coefficients of the components in the mixed micelle, and interaction parameters etc.) at different compositions. The existence of both the interactions (synergistic and antagonistic) has been inferred in the studied system. The mixed micelle formation was found dependent on micellar composition.

Experimental investigation of temperature effect on hydrodynamic characteristics of natural cavitation in rotational supercavitating evaporator for desalination

Increasing temperature is proposed to improve the performance of Rotational Supercavitating Evaporator (RSCE, a novel supercavitation-based desalination device). In order to investigate the temperature effect on the hydrodynamic characteristics of RSCE, visualization experiments are conducted on cavitating flows at different water temperatures (25–50 °C) in RSCE under different rotational speeds (up to 4000 r/min). Then the thermodynamic effect of cavitation in the water at different temperatures is evaluated to obtain the temperature range suitable for the operation of RSCE. Results show that the spatiotemporal evolutions of cavitation at different water temperatures are similar and the cavitation intensity increases with increasing temperature. Combining the present experimental results with revisits to the published results, four criteria are put forward to evaluate the thermodynamic effect of cavitation, including the variation of dimensionless supercavity length with cavitation number, the variation of incipient cavitation number with temperature, the appearance of cavitation, and the threshold value of thermodynamic parameter Σ of order hundred. It can be deduced by these criteria that the thermodynamic effect of cavitation in the water is insignificant within the temperature range considered in the present work. Hence, the desalination performance of RSCE can be improved by increasing temperature within above temperature range.

Modeling analysis on the effective elimination of toxic pollutant from aquatic environment using pyrolysis assisted palmyra palm male inflorescence

In this study adsorption of Cd(II) ions using the pyrolysis assisted Palmyra palm male inflorescence (PAPMI) was systematically examined. A batch adsorption study was carried out to determine the type of interactions and removal efficiency which is based on the surface property of PAPMI. The diverse parameters which affect the adsorption performance of PAPMI for Cd(II) ion removal were optimized: biosorbent dose – 1.25 g/L, pH – 6.0, temperature – 303 K, initial cadmium ions concentration – 50 mg/L and contact time – 40 min. Pseudo-first order kinetics and Langmuir isotherm models were more suitable to describe the adsorption kinetics and isotherm, respectively. Therefore, modeling studies portrayed the present Cd(II) ions adsorption on PAPMI as monolayer adsorption occurs on the homogeneous surface and follows the physisorption mechanism. The maximum adsorption capacity of the synthesized PAPMI was examined as 233.2 mg/g from the equilibrium isotherm investigation. Based on the calculated thermodynamic parameters (ΔGo, ΔHo and ΔSo) values, the present Cd(II) ions adsorption on PAPMI was explicated as feasible, and exothermic. The outcome proposed that Palmyra palm male inflorescence can be a suitable adsorbent for expulsion of Cd(II) ions from aqueous environment. In the interim, the utilization of pyrolysis assisted is a viable and fast uptake innovation for the removal of heavy metals from water environment.

A multi-laboratory benchmark study of isothermal titration calorimetry (ITC) using Ca2+ and Mg2+ binding to EDTA.

A small-scale ITC benchmarking study was performed involving 9 biophysics laboratories/facilities, to evaluate inter-laboratory and intra-laboratory basal levels of uncertainty. Our prime goal was to assess a number of important factors that can influence both the data gathered by this technique and the thermodynamic parameter values derived therefrom. In its first part, the study involved 5 laboratories and 13 different instruments, working with centrally prepared samples and the same experimental protocol. The second part involved 4 additional laboratories and 6 more instruments, where the users prepared their own samples according to provided instructions and did the experiments following the same protocol as in the first part. The study design comprised: (1) selecting a minimal set of laboratories; (2) providing very stable samples; (3) providing samples not requiring preparation or manipulation; and (4) providing a well-defined and detailed experimental protocol. Thus, we were able to assess: (i) the variability due to instrument and data analysis performed by each user on centrally prepared samples; (ii) the comparability of data retrieved when using 4 different software packages to analyze the same data, besides the data analysis carried out by the different users on their own experimental results; and (iii) the variability due to local sample preparation (second part of the study). Individual values, as well as averages and standard deviations for the binding parameters for EDTA-cation interaction, were used as metrics for comparing the equilibrium association constant (logK), enthalpy of interaction (ΔH), and the so-called "stoichiometry" (n), a concentration-correction factor.

Facile Synthesis and Characterization of Zn(II)-Impregnated Chitosan/Graphene Oxide: Evaluation of Its Efficiency for Removal of Ciprofloxacin from Aqueous Solution

Zn(II)-impregnated chitosan/graphene oxide composite (Zn(II)-CS/GO) was prepared and applied for adsorptive removal of ciprofloxacin (CFN) from aqueous solutions. The material was characterized by FTIR, XRD, SEM coupled with EDX, and TGA- DTA. The experimental variables were optimized by Box- Behnken design. Under optimized conditions, the adsorption capacity of Zn(II)-CS/GO for CFN was 210.96 mg/g at pH 6.5. The experimental adsorption data fitted well to Langmuir model with R2 $$\ge 0.9914$$ . The sorption kinetic data were well described by pseudo- second- order kinetic model (R2 $$\ge 0.9989)$$ . Elovich model with R2 ˃ 0.986 indicated towards the chemical nature of adsorption. The adsorption of CFN on the adsorbent occurs through electrostatic and π-π interactions. The values of thermodynamic parameters (ΔG°, ΔS°, and ΔH°) indicated that the sorption of CFN on the Zn(II)-CS/GO was an endothermic and spontaneous process. Adsorption- desorption studies suggested that the Zn(II)-CS/GO composite can be used effectively for CFN removal from water.

Superadsorbent Fe3O4-coated carbon black nanocomposite for separation of light rare earth elements from aqueous solution: GMDH-based Neural Network and sensitivity analysis

A series of nanocomposites adsorbents with different magnetite/carbon black ratios were synthesized by using the co-precipitation method and used for separation of LREEs (Ce, La, and Nd) from aqueous solution. The adsorption efficiency of nanocomposites is strongly dependent on both pH and the loading carbon on nanocomposite. The maximum adsorption capacity (370 mg/g) was reported by nanocomposite with 20% Fe3O4 and 80% carbon in pH 7 for LREE initial concentration of 250 ppm. Results revealed that the LREEs adsorption behavior of the optimal adsorbent fits well with Langmuir isotherm and pseudo-first-order kinetic model. Moreover, the average values of thermodynamic parameters suggest the endothermic and irreversible chemisorption mechanism. An empirical correlation was obtained by using GMDH (Group Method of Data Handling)-based Neural Network to predict the adsorption kinetics of LREEs as a function of ion’s electronegativity, molecular weight, and initial concentration. The results showed that the correlation can predict the experimental data mostly lower than 12.5% and it can predict the results of other researches with similar conditions with up to 25% from the experimental values. Finally, the results of sensitivity analysis revealed that the adsorption of LREEs is more sensitive to ions electronegativity and molecular weight at equilibrium conditions.

Thermal degradation characteristics, kinetics and thermodynamics of micron-sized PMMA in oxygenous atmosphere using thermogravimetry and deconvolution method based on Gauss function

Micron-sized poly (methyl methacrylate) (PMMA) with high flammability is widely applied in industries, constructions and transportations. Study on the thermal degradation behaviors of micron-sized PMMA in oxygenous atmosphere, which receives scarce attention to date, can provide valuable guidance for the prevention and mitigation of injuries and damages arising from the micron-sized PMMA dust explosions and fires. In the present study, the thermal degradation characteristics of micron-sized PMMA in air were investigated by thermogravimetry. Deconvolution method using Gauss function coupled with model-free and model-fitting methods was employed to conduct the kinetic modeling. The values of thermodynamic parameters (ΔH, ΔG and ΔS) were estimated. The results indicated that one peak and one shoulder occurred in the mass loss rate (MLR) variations of the micron-sized PMMA degradation in air. The values of MLR at peak and shoulder both decreased with heating rate. Besides, the average value of the MLR varied little with heating rate. The values of MLR at the peak and the average MLR of micron-sized PMMA degradation in air were both less than those of the traditional-sized PMMA degradation in air. The calculated kinetic parameters can be used to well predict the thermal degradation behaviors of micron-sized PMMA in air. Additionally, the micron-sized PMMA in air was easier to decompose than the traditional-sized PMMA in air. Non-spontaneous reactions were involved in the thermo-oxidative degradation of micron-sized PMMA. Besides, with the progressing of thermo-oxidative degradation, less energy was required and pyrolytic products with well-ordered structures may be generated.

A Spotter’s guide to dispersion in non-catalytic surface-confined voltammetry experiments

• Effects of thermodynamic and kinetic dispersion in surface confined voltammetry. • Distinguishing dispersed from non-dispersed cases by looking at voltammetry data. • Thermodynamic dispersion is usually resolvable for all experiments. • Kinetic dispersion is only resolvable for certain systems under defined conditions. Dispersion, or the distribution of kinetic and thermodynamic parameter values describing a redox reaction, has long been acknowledged as a complicating factor in the analysis of both solution and surface-confined voltammetry experiments. In this tutorial paper, we show how varying levels of dispersion can affect the appearance of the experimental current, mainly illustrating the concept with reference to surface-confined reversible one electron transfer. We focus on three voltammetric techniques, ramped Fourier Transform AC Voltammetry, Purely Sinusoidal Voltammetry and Direct Current Voltammetry, showing the effect the dispersion parameters have on the appearance of the resulting current. We have also implemented an interactive web-based simulation package for comparison of the effects of the various parameters, available here. As modelling dispersion significantly increases the computational burden of simulating voltammetry experiments, making well-informed choices about when to include this effect is essential. To facilitate this, we discuss the intuition for when to include dispersion when fitting experimental voltammetry data, again with reference to the three techniques described above.

Removal of methylene blue dye by adsorption onto Natural Muscovite Clay: experimental, theoretical and computational investigation

ABSTRACT The ability of Natural Muscovite Clay (NMC) to adsorb Methylene Blue (MB) as a dye widely used in the industrial sector was investigated, and the adsorption process was interpreted at the molecular scale through computational modelling. After the characterisation of NMC, the effect of adsorbent mass (5–40 mg), contact time (1–60 min), solution pH (3.7-11.78), stirring speed (100–900 rpm), initial MB concentration (15–80 mg.L-1), and temperature (293.15-333.15 K) on the adsorption efficiency were inspected in the batch mode. The results showed that the basic pH, high stirring speed, and low temperature were the favourable conditions for the MB adsorption onto NMC. The adsorbed quantity Qe,exp of MB dye was found to be 59.828 mg.g-1 for the initial concentration of 80 mg.L-1 at 293.15 K using an NMC mass of 20 mg. The obtained values of thermodynamic parameters suggested that the removal of the MB dye was exothermic, and physical in nature. The adsorption isotherm of the MB/NMC system was analysed according to the statistical physics approach using the Levenberg-Marquardt iterating algorithm and showed a best fitting with the monolayer model with one energy. The analysis of kinetic data showed that the external diffusion and intra-particle diffusion steps have occurred simultaneously and contributed to the control of the adsorption rate of the MB dye onto NMC. The computational modelling of interactions between the MB molecule and the muscovite, kaolinite, and quartz minerals were examined according to the Monte Carlo simulation (MCS) and showed an ability of the dye molecule to be adsorbed onto the surface of these minerals. The calculated adsorption energies ranged between -2.23×104 and -1.10×104 Kcal.mol-1 reflected the stability and the spontaneity of the adsorption process. So, the surface of clay minerals (i.e. muscovite and kaolinite) was more favourable to the adsorption of the MB molecule.

Experimental and theoretical study of adsorption of L-cysteine on the passivation and corrosion inhibition of aluminum alloy in alkaline environment

<p class="Default">L-Cysteine (L-Cyst) was tested as a corrosion inhibitor of 3003 aluminum alloy (AA3003) in Na<sub>2</sub>CO<sub>3</sub> 0.1M + NaCl 1M solution. The inhibition action of this inhibitor was studied by using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), and cyclic voltammetry (CV) techniques. The temperature effect on the inhibition efficiency was studied in the range from 298 to 328K, and the values of activation thermodynamic parameters were calculated and explained. Experiment results show that inhibition efficiency increases with the increase of L-Cysteine concentration, and its inhibition efficiency reaches 92% at 10<sup>−3</sup>M. The inhibition efficiency decreases slightly with the elevation of a corrosive medium temperature. Analysis of the polarization curves revealed that L-Cyst is considered a mixed inhibitor. The results from electrochemical measurements and theoretical calculations are in good agreement. The morphological changes of the surface during corrosion, in the presence and absence of the inhibitor, were studied by scanning electron microscopy (SEM).</p>

Interaction study of monoisoamyl dimercaptosuccinic acid with bovine serum albumin using biophysical and molecular docking approaches

Monoisoamyl 2,3-dimercaptosuccinic acid (MiADMSA), a lipophilic chelator has been evaluated for its potential use as an antidote in arsenic poisoning. The pharmacokinetics and pharmacodynamics properties of a drug could be understood via study its mechanism of interaction with bovine serum albumin protein (BSA). Therefore, the interaction between MiADMSA with BSA was investigated using various spectroscopic techniques and computational methods. Linear quenching of BSA intrinsic fluorescence intensity with the increasing concentration of MiADMSA was observed in the fluorescence study. Furthermore, synchronous results revealed that MiADMSA slightly changed the conformation of BSA. The binding constant value of the BSA-MiADMSA complex was found 1.60 × 104 M−1 at 298 K. The value of thermodynamic parameters ΔG, ΔH, and ΔS described that the process is spontaneous, endothermic, and hydrophobic forces are involved in the interaction of MiADMSA with BSA. Competitive site marker experiments showed that MiADMSA binds to site-II of BSA. Conformational changes of BSA with the interaction of MiADMSA were apparent by CD, UV–Visible, FT-IR, and 3D fluorescence spectroscopy. To strengthen the experimental findings we have also performed a theoretical study on the BSA-MiADMSA complex. Two sites were identified with docking score of − 6.642 kcal/mol at site IIa and − 3.80 kcal/mol for site IIb via molecular docking study. Molecular dynamics simulation study inferred the stability of the BSA-MiADMSA complex which was analyzed in a long simulation run. The experimental and computational studies have shown the effective binding of MiADMSA with BSA which is essential for the transportation and elimination of a drug from the body.

Thermodynamic analysis of micelles formation of anionic surfactant SDS in the presence of aqueous and aqueous solution of ionic liquid 1‐butyl‐3‐methylimidazolium chloride

AbstractIn this study, the experimental conductivity, fluorescence, and UV spectroscopy study have been done for aqueous solutions of sodium dodecyl sulfate (SDS) and in aqueous ionic liquid (IL) 1‐butyl‐3‐methylimidazolium chloride [C4mim][Cl] solutions at a temperature of 298.15 K. Experimental conductivity measurement has been done at different temperatures from 298.15 to 308.15 K. Moreover, the critical micelle concentrations (CMCs) of the mentioned systems were determined by different methods; furthermore, the CMC values have been utilized to originate the values of thermodynamical parameters of micellization like standard enthalpy of micellization ( ), the standard free energy of micellization ( ), and standard entropy of micellization ( ). Fourier transform‐infrared (FT‐IR) spectra have been recorded to investigate the interactions and structural changes that occurred in the mixed system. Work has been discussed in terms of the effect of the aqueous IL solution on the micellization process of the SDS.

Characterization of prepared eco-friendly biochar from almond (Terminalia catappa L) leaf for sequestration of bromophenol blue (BPB) from aqueous solution

Novel eco-friendly adsorbents were prepared through pyrolysis and acid activation of raw almond leaf (RAL) to form almond leaf biochar (ALB) and chemically activated almond leaf biochar (CAL), respectively. The prepared adsorbents were characterized using TGA, FTIR, SEM–EDX, BET and XRD techniques and their physicochemical properties investigated. RAL, ALB and CAL were utilized for adsorption of BPB dye from aqueous solution using batch technique under optimum conditions. The optimum dye adsorbed by RAL, ALB and CAL were 92.83, 93.21 and 94.89%, respectively at pH 3, dye initial conc. (100 mg/L), adsorbent dose (0.04 g/25 mL), 60 min contact time and 301 K adsorption temperature. Although, Langmuir maximum monolayer adsorption capacities were found to be 365.36, 535.62 and 730.46 mg/g for RAL, ALB and CAL, respectively, but isotherm conformed to Freundlich model. Kinetic study confirmed suitability of pseudo-second-order model with rate constant 9.33 × 10–4, 9.91 × 10–4 and 12.60 × 10−4 g mg−1 min−1 for RAL, ALB and CAL, respectively. Negative values of thermodynamic parameters (∆G and ∆H) established sequestration process to be spontaneous and exothermic. RAL, ALB and CAL were discovered to be highly efficient adsorbents that could be used in place of expensive commercial adsorbents.

Consecutive phase transition in the new polymorphic crystal 4F2PMP, a critical study of thermal stress in the crystal structure with DSC and VT- PXRD analysis

A Novel molecular Schiff based organic crystal, (E)-4-Fluoro-2(Phenylimino)methyl)phenol), was synthesized and characterized by Thermogravimetric, Differential Scanning Calorimetry, UV Spectroscopy, Vicker’s Hardness, Microstructure and Powder X-Ray Diffraction. The 4F2PMP crystal involves the binding of molecules via an inherent O-H•••N hydrogen bond, S(6) forms the ring. The crystalline structure features C-H•••O hydrogen bonds. The phase transition-I, transition-II, and phase transition-III were confirmed by variable-temperature powder XRD and DSC analysis and showed endothermic reaction. The thermodynamic and kinetics parameters values, including such enthalpy, entropy of fusion, melting point, and activation energy, have been determined by exploring DSC and TGA data respectively. The superior performance and highest hardness of this 4F2PMP crystal indicate that it’s a super hard material. The vicker’s elastic properties, such as young’s modulus, bulk modulus, shear modulus, and poisson’s ratio, have been determined by Vicker’s hardness (Hv). The morphology of the 4F2PMP crystal is tightly packed grain without any cracks, EDAX confirms the composition analysis.

Characterization of Ethyl Violet Adsorption on Used Black Tea Leaves from Aquatic Environment: Kinetic, Isotherm and Thermodynamic Studies

Ethyl violet (EV) is one of the common pollutants in industrial wastewaters. This study presents the kinetic, isotherm and thermodynamic characterization of the adsorptive removal of EV from aqueous solution by used black tea leaves (UBTL) as a low cost adsorbent. Batch adsorption experiments were performed to investigate the effects of initial dye concentration, solution pH and temperature on the adsorption kinetics. Experimental data were evaluated by inspecting the liner fitness of different kinetic model equations such as pseudo-first order, pseudo-second order, Elovich and Intra-particle diffusion models. The equilibrium amounts adsorbed at different equilibrium concentrations were determined from well fitted pseudo-second order kinetic plot to construct the adsorption isotherm. The maximum adsorption capacity, <i>q</i>_m=91.82 mg/g was determined from the well fitted Langmuir plot compared with Freundlich and Temkin plots. Thermodynamic parameters such as free energy change (∆<i>G</i>_ads), enthalpy change (∆<i>H</i>_ads) and entropy change (∆<i>S</i>_ads) of adsorption were determined from adsorption equilibrium constants at different temperatures. The values of thermodynamic parameters revealed that the adsorption of EV on UBTL was feasible, spontaneous and endothermic in nature leading to chemisorption. Again, the equilibrium amount adsorbed, calculated from pseudo-second order kinetic plots for different initial pH of solution was found to be minimum at neutral medium compared with acidic and basic media due to the amphoteric nature of Ethyl violet in aqueous solution and zero point charge of pH of UBTL.

РАЗРАБОТКА МАТЕМАТИЧЕСКОЙ МОДЕЛИ УПРАВЛЯЕМОГО ПРОЦЕССА ЛИТЬЯ С КРИСТАЛЛИЗАЦИЕЙ ПОД ДАВЛЕНИЕМ

Various types of impacts, which in terms of the process approach are aimed at creating value, at giving metal products a complex of higher consumer properties, change the value of thermodynamic parameters. These include temperature, pressure, enthalpy, entropy, Gibbs energy, etc. Processing processes are associated with energy costs, with movement, and therefore control problems can be represented as problems of dynamics, solved using differential equations. The paper proposes a mathematical model of the casting process with crystallization under pressure, where the pressure acts as a factor that can be varied widely at different stages of the process. The controlled process model is based on phase coordinates. The evolution of the state of the system under consideration is represented by differential equations. A block diagram of the control system has been developed.