جستجوی مقالات مرتبط با کلیدواژه "kinetic study" در نشریات گروه "شیمی"

Recently, utilizing biomass for adsorption TEMPhas become a widely adopted approach to diminish contaminants in wastewater before its discharge into teh environment. Our objective is to scrutinize teh adsorption process of Basic Fuchsin (BF) on sugarcane bagasse (SCB). Teh investigation involves optimizing teh process by exploring parameters such as bio-adsorbent mass, contact time, temperature, and teh pH of teh BF solution; teh solutions studied were analyzed using UV-Vis spectrophotometry to assess teh concentration of teh BF dye. Teh basic fuchsin dye TEMPhas a limit of detection (LOD) of 0.06 mg L-1 by UV-Vis spectrophotometry, while teh limit of quantification (LOQ) is 0.1 mg L-1. Teh method's measurement range varies from 0.1 to 10 mg L-1, guaranteeing precise, reproducible measurements. Teh findings indicate dat BF adsorption on SCB is most TEMPeffective in a basic environment, attributed to electrostatic interactions between teh negatively charged SCB surface wifin dis pH range and teh organic cations of teh dye. Under optimal conditions, BF removal by SCB reaches 97%. Kinetic modeling of adsorption reveals dat teh pseudo-second-order model best describes BF adsorption on SCB. In contrast, isotherm modeling indicates dat Langmuir and Freundlich's models provide teh most accurate descriptions. Teh Langmuir separation coefficient RL and teh Freundlich parameter 1/n both fall below one, signifying teh favorability of BF adsorption on SCB. Thermodynamic assessments underscore teh spontaneity of teh BF adsorption process on SCB. Overall, teh study results emphasize teh capability of SCB as a bio-adsorbent for removing organic dyes from aqueous solutions.

This work investigates and compares the effectiveness of chemical advanced oxidation techniques to remediate real refinery wastewater generated from the Al-Samawa refinery plant which has not been treated before by using the present technologies. Real refinery wastewater underwent a batch photo-Fenton oxidation treatment (UV/H2O2/Fe2+) to reduce the oil content. The experiments were designed using a factorial experimental design containing the effects of 30-90 min irradiation time, 25–250 ppm hydrogen peroxide, and 2–8.5 pH. A statistical program was used to analyze the results. The optimum values of these variables were 90 min, 100 ppm H2O2, and pH 3. The effect of solution temperature on the removal efficiency was studied in the range of 20–400 °C. It was found that the temperature notably influences the treatment process, where the highest removal of the organic content of 95.15% was achieved at 30°C. Adsorption equilibrium investigation revealed that the Langmuir model was a more fitted model (R2 = 0.9999) for photo-Fenton elimination of oil content than other isotherm models. Consequently, a comparative study of the treatability of UV-photolysis, Fenton, and photo-Fenton processes has been conducted. The core findings of this comparison showed that the oil content removal by using the UV-photolysis process is (49.2%), the Fenton process (69.6%, while it shows that the photo-Fenton process is the most effective at getting rid of pollutants (92.75%). As observed the photo-Fenton methods are more effective than other studied methods to treat refinery wastewater.

Alkaline hydrolysis of phosphate diester compounds with a common leaving group (LG) and varying non-leaving groups (NLG) was investigated. The nitrophenyl group was employed as a leaving group due to its favorable leaving group properties, significant absorbance for reaction monitoring, and selective cleavage of the phosphorus-oxygen bond, which is relevant for DNA and RNA degradation. Reactions were conducted under pseudo first-order conditions in NaOH solutions 70 °C. In addition, the alkaline hydrolysis was studied using a 1M NaOH solution at different temperatures (50–80 °C), pH (12-14) levels, and viscosities (with 0% - 40% glycerol). Reaction progress was continuously monitored by measuring the absorbance increase of the 4-nitrophenolate ion at λ = 400 nm. The rate constant (kobs) was determined by fitting the data to a first-order equation. The results demonstrate kobs increased with higher NaOH concentration, temperature, pH, and solution viscosity, except for NppNPP. Investigation of the effect of the non-leaving group's pKa revealed slight sensitivity of the hydrolysis reaction with βNLG = -0.12. Thermodynamic parameters were determined and the values were as follows: ∆H = 48.8 kJ.mol-1, ∆S = -171.6 J.mol-1.K-1, ∆G = 99.9 kJ.mol-1 for BpNPP; ∆H = 64.9 kJ.mol-1, ∆S = -127.1 J.mol-1.K-1, ∆G = 102.8 kJ.mol-1 for PypNPP; ∆H = 86.3 kJ.mol-1, ∆S = -76.7 J.mol-1.K-1, ∆G = 109.2 kJ.mol-1 for MpNPP, and ∆H = 63.7 kJ.mol-1, ∆S = -152 J.mol-1.K-1, and ∆G = 109 k kJ.mol-1 for NppNPP. All four hydrolysis processes have positive ∆G values, which means they are non-spontaneous and require external energy to proceed.

Studies on the epoxidation of fatty acids have garnered much interest in recent years due to the rising demand for eco-friendly epoxides derived from vegetable oils. This study aims to optimize the process parameters of epoxidation of palm oleic acid via an in situ peracid mechanism with an applied homogenous catalyst. Oleic acid was epoxidized using performic acid-generated in situ through the reaction between hydrogen peroxide and formic acid when sulfuric acid was applied as a catalyst. The optimum reaction condition of epoxide was at the temperature of 45°C, the molar ratio of formic acid to oleic acid at 1.64:1 and the molar ratio of hydrogen peroxide to oleic acid at 2:1. Lastly, a mathematical model was developed using the numerical Runge Kutta-4th Order method. In the model, the method was applied with a genetic algorithm optimization to determine the process model that fit the experimental data using MATLAB software. After 100 iterations, the reaction rate constant for epoxidized oleic acid production was: k11 = 1.9305 L/mol. min, k12 =15.2284 L/mol. min, k21 = 0.0570 L/mol. min, k31 = 0.0106 L/mol. min. Overall, epoxidized oleic acid was successfully produced by in situ performic acid mechanism with 80% relative conversion to oxirane.

Acidic corrosions for oil and natural gas pipelines have been investigated by studying the effect of sulfuric acid (H2SO4) on carbon steel surface sample. Three different concentrations of sulfuric acid (0.1, 1, and 2 M) and two distinct kinds of carbon steel were used in this research. The results demonstrates that when the concentrations of acid medium (H2SO4 solutions) increased, the corrosion rates also increased due to the effect of high concentration of the acid. In addition, kinetic of corrosion rates were studied in which the corrosion rates followed the pseudo first order from the values of R2 for the samples. Furthermore, polymer electrolyte liquid of polymethyl methacrylate (PMMA) has been used to decrease the acidity strength. The PMMA was indicated that the medium acidity decreased leading to supply further protection from corrosion. These results can be applied to successfully manage pipelines and improve the pipeline protection in acidic corrosion condition. Likewise, polymer electrolyte liquid PMMA oligomer should be considered as a novel form in polymer electrolyte field that might be employed in electrochemical devices for corrosion control purposes in acid media.

Clays in the soils are a natural barrier against pollution. A representative sample of clay (illite) from Algeria is collected and analyzed by XRD. The results show that this sample is illite containing calcite and quartz as impurities. We also analyzed the clay by SEM, EDS, and BET, and modified it by chemical treatment with NaCl in order to increase its specific surface area with the insertion of Na+ cations into the inter-foliar space. The study of Cr(VI) ions adsorption onto Na-Clay was performed. The influence of Cr(VI) initial concentration, pH of the solution, temperature, and solid/liquid ratio was studied. Among the tested models, the equilibrium data are well-fitted by the Langmuir isotherm. The maximum Cr(VI) adsorption rate was 44% at 25°C with limited capacity adsorption of 10 mg/g. The adsorption kinetic is best described by the pseudo-second-order model. The Cr(VI) ions reduction onto Na-Clay/Fe2O3 and the effect of the same parameters were also performed. The maximum reduction (98%) was reached at pH = 2, T = 25°C, [Cr(VI)] = 50 mg/L, and S/L = 1 mg/mL. It was found that the reaction follows the pseudo-first-order rationalized well by the Langmuir-Hinshelwood (LH) model. The evaluation of the thermodynamic parameters (ΔG°, ΔH°, and ΔS°) revealed that chromium (VI) adsorption and reduction were endothermic and exothermic respectively.

This study used the cation exchange approach to carry out significant chemical modifications in Moroccan Rhassoul clay by inserting a cationic surfactant (N-Methyl-N,N,N-trioctylammonium chloride) through the void between the leaves. In order to investigate the chemical composition and surface characteristics of clay as it was being treated, Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were explored as physical approaches.. The treatment of a textile effluent (blue reagent 19 RB19) using this modified clay as an adsorbent has demonstrated a substantial removal efficiency of the pollutant load.The experiments were carried out under static conditions to optimize certain parameters such as the pH value, the adsorbent concentration, as well as the characteristic time of contact. The maximum adsorption capacity was 80% with a mass-volume ratio of 0.6 g / l at pH = 5. The kinetic study has revealed that the second-order model is better suited for a contact time of about 60 min. The study of adsorption isotherms shows that the Langmuir model correctly describes the adsorption process with an extreme adsorbed amount up to 204 mg/g at 25 ° C.

Dyes are utilized in several plants and factories. Contaminated wastewaters containing dyes cause many illnesses and have many adverse effects on humans, animals, and plants. This research aims to the usage of Populus alba tree’s sawdust as a costless pruned agricultural waste material for the removal of crystal violet from simulated wastewater in batch adsorption experiments. The dye removal process by the adsorbent was performed by varying various parameters such as the weight of the adsorbent, pH of the solution, adsorption time, and the initial dye concentration. Generally, increasing the weight of the adsorbent and decreasing the initial dye concentration led to increasing removal efficiency. The optimum solution pH was found to be 6.5. Also, the optimum weight of the adsorbent and the optimum initial dye concentration were found to be 0.15 g and 10 mg/L, respectively. Moreover, the adequate adsorption time for the accomplishment of the treatment procedure was 10 min. Adsorption data were fitted well by the Langmuir adsorption isotherm model and the maximum amount of the adsorbate on the adsorbent (qmax) was calculated to be 12.25 mg/g. The kinetic study data illustrated the adaption of the adsorption rate with the pseudo-second-order kinetic model. The results of the ANN model proved the fitness of theoretical and experimental data according to the obtained correlation coefficient values. Eventually, the dye removal efficiency reached 97% in the optimum conditions of the experiments. So the sawdust of Populus alba tree’s pruned hardwood is introduced as a costless and highly capable adsorbent for the adsorption of crystal violet from contaminated wastewaters in order to perform a successful wastewater treatment beside the accomplishment of a waste management procedure.

The pseudo-first order rate constants and activation parameters have been determined using two methods, constant-temperature kinetic (CTK) and variable temperature kinetic (VTK), for the oxidative addition reactions of [Pt2Me2(C^N)2(µ-dppf)], (1a, C^N = deprotonated 2-phenylpyridine (ppy); 1b, C^N = deprotonated benzo[h]quinoline (bhq)) with MeI. The results obtained from VTK method are in agreement with those obtained at CTK method, but there are significant advantages to determine the kinetic reaction parameters under VTK method including time and chemicals saving.

Biosorption of Cu(II) ions from aqueous solutions onto waste Tea and Coffee powder (WTCP) has been investigated in a batch biosorption process. The biosorption process was found to be dependent on pH of solution, initial metal ion concentration, biosorbent dose, and contact time. The experimental equilibrium biosorption data were analyzed by Langmuir, Freundlich, Temkin and Dubinin ̶ Radushkevic isotherms models. The Langmuir model gave a better fit than the other three models by higher correlation coefficient, R2. The maximum biosorption capacities calculated from the Langmuir isotherm model were 526 and 417 mg/g, for coffee and tea, respectively at optimum conditions. The kinetic studies indicated that the biosorption process of the metal ions followed well pseudo-second-order model. According to the biosorption capacity, waste coffee and tea powder considered as an effective, low cost, and environmentally friendly biosorbent for the removal of Cu (II) ions from aqueous solutions.

A new multi-site phase-transfer catalyst viz., N,N’-dihexyl-4,4’-bipyridinium dibromide (DSPTC) was synthesized from the low cost starting materials. The structures of the synthesized DSPTC and 1-(prop-2-ynyl)-1H-indole were evidenced by 1HNMR and 13C NMR. The potentiality of the new multi-site phase transfer catalyst was demonstrated by following the kinetics propargylation of the indole under pseudo-first order conditions by using the aqueous sodium hydroxide and indole in excess, and the reaction was monitored by gas chromatography. Moreover, the catalytic efficiency of the DSPTC was compared with the single-site phase-transfers catalysts.

Herein, the removal of methyl orange (MO), a monoazo dye, from aqueous solutions was investigated using bimetallic ferromagnetic Fe/Ni nanoparticles (NPs) with the average particle size of 12-16 nm. The effect of contact time, pH, temperature, and Fe/Ni dosage on dye removal process was investigated. The results showed that 60 mg of Fe/Ni NPs at 25 oC and pH= 1 can remove 99.5% of 50 mg/L dye solution within 15 min. The MO removal follows the pseudo-second-order kinetics with the rate constant of 0.4114 g mg-1 min-1. The chromophore structure of the dye was broken down in the presence of Fe/Ni NPs. The Fe/Ni NPs were prepared by simple co-reduction method and characterized by several techniques including X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, scanning tunneling microscopy, and vibrating sample magnetometer.NPs.

An Nd doped ZnO (1-5%) photocatalyst was successfully synthesized via chemical co-precipitation method. The optical property, nature, and morphology of the synthesized nanoparticles were analyzed by UV-Visible, XRD, and FESEM respectively. XRD study reveals that Nd has been effectively incorporated in the ZnO lattice in the lower level dosage; however, the crystalline nature has been distorted towards the increase in the Nd. The selected brilliant green dye was degraded photo-catalytically with the help of the synthesized nanoparticles and the study has been extended with catalyst dosage and dye concentration. The 2% Nd-doped ZnO showed a remarkable result of 98.26% degradation of brilliant green dye compared to the other 1,3,4 & 5 % Nd-doped ZnO nanoparticles which clearly indicates the optimization of depletion region corresponding to the maximum degradation. The increased content (3-5%) of Nd-doped ZnO exhibited moderate photocatalytic degradation of the dye due to the decreased crystalline nature which was further evidenced from XRD studies.

In this study, two Carbon Molecular Sieves using Pistachio shell (CMS P) and Walnut shell (CMS W) were prepared by a chemical vapor deposition method and used for pressure swing adsorption and separation of CO/H2 and CO/CH4. Adsorption isotherms of gases obtained for both CMS’s. The Dubinin-Radushkevich isotherm model was used for comparing pore volume of CMS’s. The obtained isotherms for both CMS were compared with Langmuir and Freundlich isotherms. It was observed that Freundlich equation can better correlate the experimental data. The adsorption capacity of each CMS and selectivity of them for separation of CO/H2 and CO/CH4 were obtained with the aid of kinetic studies. In comparison with CMS W, CMS P showed higher adsorption capacity values for gases, but lower selectivity for separation of them. Finally by fitting experimental data to a pseudo second-order equation, adsorption capacities at equilibrium were obtained for abovementioned gases on both CMS’s.

An agricultural waste and eco-friendly biosorbent i.e. rice husk has been used as a cheap adsorbent for the removal of methylene blue dye from aqueous solutions. The physical properties of the developed adsorbent were characterized using FTIR. The study was realized using batch experiments. The effects of contact time, pH, initial dye concentration, biosorbent dose and temperature were investigated. The adsorption data were evaluated by Freundlich and Langmuir isotherm models. The adsorption isotherm is best fitted by the Freundlich model, while the adsorption kinetics is well described by the pseudo-secondorder model. Different thermodynamic parameters i.e., changes in standard free energy, enthalpy and entropy have also been evaluated and it has been found that the dye adsorption onto rice was a spontaneous, endothermic and physical reaction.

In the present study, a new carbon paste electrode chemically modified with copper sulfide nanostructures is constructed and used for the catalytic oxidation of cisapride. The voltammetric behavior and electrochemical reaction mechanism of cisapride have been investigated at modified electrode using cyclic voltammetry (CV), steady state polarization and differential pulse voltammetry. In CV studies, no oxidation response of cisapride can be seen at the unmodified electrode, but at the copper sulfide nanostructures modified carbon paste electrode (CSN-MCPE), a large anodic peak appears, indicating that the anodic oxidation of cisapride could be catalyzed at CSN-MCPE. This proves that the copper sulfide nanostructures bear the main role in electrocatalytic oxidation of cisapride. The kinetic parameter such as the electron transfer coefficient (α) and exchange current density (j0) for the modified electrode were calculated. The differential pulse peak current varied linearly with the concentration of cisapride in range of 9×10−8 to 15×10−6 mol L-1. The modified electrode can be prepared very easy and renewed in its surface by simple polishing. The reproducibility of the electrode response, based on six measurements during two month, was 3.23% for the slope of the calibration curve.

Hydrolysis of paracetamol in acidic media was studied using electrochemical technique in different reaction temperatures. Based on the fact that both paracetamol (PAR) and its hydrolyzed product, p-aminophenol (PAP) are both electroactive and their voltammetric peaks do not overlap, differential pulse voltammetry was used for the determination of the remained PAR concentration in the reaction vessel as well as produced PAP concentration. Then, the kinetic parameters of PAR hydrolysis including reaction rates and half-lives in various temperatures and the activation energy of the reaction were calculated using proposed accurate method. PAR is hydrolyzed to PAP in the presence ofhydronium ion via first-order kinetic reaction with the reaction rates of 8.9×10-4, 2.16×10-3, 4.21×10-3, 6.26×10-3 and 1.46×10-2 min-1 at the reaction temperatures of 50, 60, 70, 80 and 90 °C, respectively. The activation energy of the hydrolysis reaction was calculated to be 63.61 kJ mol-1.

An agricultural waste and eco-friendly biosorbent i.e. rice husk has been used as a cheap adsorbent for the removal of methylene blue dye from aqueous solutions. The physical properties of the developed adsorbent were characterized using FTIR. The study was realized using batch experiments. The effects of contact time, pH, initial dye concentration, biosorbent dose and temperature were investigated. The adsorption data were evaluated by Freundlich and Langmuir isotherm models. The adsorption isotherm is best fitted by the Freundlich model, while the adsorption kinetics is well described by the pseudo-secondorder model. Different thermodynamic parameters i.e., changes in standard free energy, enthalpy and entropy have also been evaluated and it has been found that the dye adsorption onto rice was a spontaneous, endothermic and physical reaction.

Mercaptans are commonly present in petroleum products. Their foul odor and highly corrosive nature make them the most undesirable sulfur compounds so they should be removed because of environmental issues. Merox process is used for oxidation of mercaptans to disulfide using air in the presence of alkaline solution and Merox catalyst. In this paper، due to lack of information about the kinetic of mercaptan oxidation، the kinetic of conversion of ethyl mercaptan in gasoline and kerosene is studied in order to be able to model and simulate this process. The experiments were carried out in a semi-batch bubble column reactor and it was proved that increasing the temperature، improves the rate of the reaction. The obtained results were analyzed and a correlation for the rate of reaction is suggested. The suggested equation is first-order with respect to mercaptan concentration.