جستجوی مقالات مرتبط با کلیدواژه « isotherms » در نشریات گروه « پزشکی »

This study initiates an experimental and theoretical investigation to evaluate the selective and competitive adsorption of two dyes, sulforhodamine B and Brilliant Green, on coal from pomegranate seeds. For this purpose, the effects of numerous parameters like initial dye concentration, initial pH, adsorbent dose and solution temperature were examined and studied in batch mode. The experimental results indicate that the adsorption is fast and fits better with the quasi-second order kinetic model than the quasi-first order kinetics. Adsorption data were studied using Langmuir and Freundlich isotherms. The obtained results showed that the Freundlich model provided a better correlation of the experimental data. The geometries of sulforodamine B and Brilliant Green were optimized using Gaussian 09W software through the density functional theory (DFT) at the theoretical level B3LYP / LanL2DZ, and the calculations (link length and connection angle) were well matched with experimental data at both levels.

In the present study, natural and synthetic adsorbents were used to remove nickel ions through the adsorption process. First, TiO2 nanoparticles (NPs) were prepared through the sol-gel method. The synthesized samples were then characterized using X-ray diffraction spectroscopy (XRD), Fourier transform-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N2 adsorption/desorption isotherms (BET). The influences of different operational parameters including adsorbate content, pH, adsorbent concentration, contact time, ionic strength, and stirring speed were also explored. According to the results, the pseudo-second-order kinetic model showed the best performance in evaluating the experimental data when using both adsorbents. The adsorption of nickel cations by the thin film membrane on the surface of TiO2 NPs is a rate-determining step of the removal reaction. The removal rate constants of nickel ions from aqueous solutions by TiO2 NPs and pomegranate peel were evaluated to be 0.013 and 0.018 g mg-1 min-1, respectively. The thermodynamic parameters such as Gibbs free energy, enthalpy, and entropy were also determined. Nickel removal processes in all cases were endothermic and spontaneous. The removal mechanism also followed physical adsorption. Equilibrium data were fitted with Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich models. The results showed that the adsorption of Ni2+ on TiO2 NPs and pomegranate peel followed Freundlich and Temkin isothermal models, respectively. Based on the calculated removal percentage, TiO2 is a better adsorbent for removing Ni2+ from the aqueous medium as compared to pomegranate peel.

This research work aims to investigate the sorption characteristic of synthesized Poly (vinyl alcohol)/Chitosan nanofiber mats modified with aluminum-cerium spinel oxide (CeAlO3) nanoparticles for methylene blue (MB) removal from aqueous solutions. The sorption is carried out by a batch technique. The structural characterization of this nanocomposite was performed by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD). Scanning electron microscopy (SEM) results showed uniform net and improved nanofibers with diameters ranging about 420 and 450 nm, respectively. The optimum conditions of MB removal onto modified PVA/CS nanofibers were found to be: pH 10, contact time 45 min, and 0.01 g of adsorbent in 400 ml in aqueous solution. Furthermore, the experimental adsorption data were in excellent agreement with the pseudo-second-order kinetics. The experimental results showed that there is a good correlation between the obtained data and the adsorption isotherm in the concentration range studied (400-600 mg/l). The results revealed that the maximum adsorption capacity of MB was 817.81 and 714.61 mg/g onto improved and net nanofibers, respectively.

A surface area of 1085.92 m2/g and a monolayer adsorption capacity of 497.66 mg/g were obtained from the optimum activated carbon derived using Prosopis africana seed hulls (PASH-AC) at the activation temperature of 795°C, activation time of 62 minutes, and impregnation ratio of 2.45. Five different forms of the linearized Langmuir equations along with two other models (Freundlich and Temkin) were tested on the adsorption data. The best adsorption model was selected using correlation coefficient (R2) and chi-square (χ2) was used for assessing the validity of each isotherm model. Langmuir-2 along and pseudo-second-order models were found to be the most suitable model for describing the equilibrium and kinetic processes, respectively.

The textile industry discharges large quantities of highly colored wastewater from industrial processes using chemical components. Many dyes are designed to be chemically stable so that they are difficult to decolorize due to their complex structure and synthetic origin. The dye waste is subsequently released directly to water bodies during the textile finishing process. This improper released has adverse effects on the environment and may reduce photosynthesis in aquatic plants. Even though adsorption techniques have been widely used to remove textile dye from waters, the kinetic models used to describe the adsorption of textile dye onto a porous material is still not yet fully understood. This study investigated different applications of absorbent from sugarcane bagasse (SB) and rice husks (RH) in removing color from aqueous solution and the application of kinetic model for adsorption of color from aqueous solutions onto SB and RH. A batch study was carried out under various mass of adsorptions and contact time with constant with the initial concentration of aqueous solution was 400ADMI. The data obtained from batch experiments showed that the removal of RH (93%) was more efficient than SB (49%). This study also advanced the understanding on the kinetic adsorption study of RH and SB to prove that the adsorbents have potential to reduce dye from synthetic solution. The contribution of this study in the removal of significant dye pollutants from industrial wastewater will require future assessment in a prospective wastewater treatment facility setting.

Today, due to the industrialization of societies, the existence of heavy metals has created many problems for humans, other organisms, and the environment. Lead (Pb) is highly toxic and the second most commonly used metal. The aim of this study was to evaluate the efficiency of melaminemodified nanographene oxide in the removal of Pb from aqueous media. To increase the efficiency of graphene oxide, it was mechanically converted to nano graphene oxide and melamine (4, 2 and 6-triazine, 3, 1 and 5 triamine). Experiments were performed at pH value of 3-8, temperature of 15-50°C, Pb concentration of 5-200 mg/g, adsorbent dose of 0.01-0.06 g, and contact time of 15- 150 minutes. The mechanism of the adsorption process was investigated using two Langmuir and Freundlich isotherm models, pseudo-first order and pseudo-second order kinetic equations, and thermodynamic equations. The results showed that the adsorption rate corresponds to the Freundlich isotherm model and pseudo-second order kinetic equation. Thermodynamic studies also showed that the adsorption process is associated with increasing irregularities and it is endothermic. In constant conditions (pH of 6, contact time of 60 minutes, ambient temperature of 22°C, Pb concentration of 20 mg/L, and adsorbent dose of 0.01 g), the adsorption capacity was 191.65 mg/g. The highest adsorption occurs at the concentration of 5 mg/L and the highest adsorption capacity and removal percentage was observed at a concentration of 200 mg/L, which were 1896.3 mg/g and 98.8%, respectively. Due to the high adsorption capacity, the adsorbent was able to remove lead from the contaminated environment.

The derivatives of phenols are among the most widely used chemicals in day-to-day life, which lead to water contamination by chlorophenols (CPs). These compounds belong to a class of those widely used chemicals that increase global concern about environmental protection due to their recalcitrant nature. Adsorption process has been employed for the removal of CPs from contaminated water out of many methods of wastewater treatment. This is due to its insensitivity to toxic substances, effectiveness, universal nature, fast kinetics, as well as the ease of operation and its simplicity in the design and applicability. Thus, this study compared the adsorption isotherm models such as linear and nonlinear and well discussed the fundamental characteristics, modelling, and mathematical derivations. Finally, the study highlighted and addressed the role of different isotherm models that were used in describing the adsorptive removal of CPs using various adsorbents.

Dyes are among the most hazardous chemical compounds, which are found in industrial effluents. The removal of dyes before the discharge of wastewater to the environment could reduce these environmental hazards. The present study aimed to evaluate the efficiency of cetyltrimethylammonium bromide-modified bentonite (CTAB-MB) surfactant in the adsorption of acid blue 80 (AB80) dye. This experimental study was conducted using a shaker (100 rpm) at room temperature and fixed pH of 7 using conical flasks (200 ml) containing the dye solution (100 ml) to assess the adsorption conditions. In addition, five concentrations of the reactive blue dye were prepared to evaluate the effects of the initial dye concentration on adsorption. The experimental data indicated that the AB80 removal procedure was fitted with the Langmuir isotherm. The Langmuir adsorption capacities (qe) were 38.15 and 21.76 mg/g for 1 and 2 g/l of the adsorbent, respectively. Moreover, three kinetic models were selected to fit the kinetic data, including the pseudo-first-order and pseudo-second-order models and intra-particle diffusion. AB80 was fitted with the pseudo-second-order model at all the concentrations. According to the results, CTAB-MB was an affordable alternative to the removal of dyes from industrial wastewater

Surfactants are one of the main groups of pollutants released into aqueous solutions due to human activities and their harmful effects have been proven on human. In this study, first, magnetic multi-walled carbon nanotubes (MMWCNTs) were synthesized and then, the effects of operating parameters such as surfactant concentration, adsorbent dosage, and pH values were analyzed on the adsorption process. MMWCNTs were characterized by means of X-ray diffraction (XRD) analysis and fourier transform infrared spectroscopy (FTIR). The optimal adsorption conditions were achieved at initial pH = 4.6, adsorbent concentration = 0.5 g/L, and initial SDS concentration = 15 mg/L. In addition, the equilibrium of sorption reached after 120 min and the maximum capacity of SDS for monolayer coverage was found to be 61 mg/g at 25°C. Kinetic studies were performed under optimal conditions and the sorption kinetics was described using the pseudo-second-order kinetic model. The experimental data were studied using Freundlich, Langmuir, and Sips models. Finally, the experimental data were fitted reasonably by Langmuir isotherm. The results demonstrated that MMWCNTs with respect to their high adsorption capacity, relatively low equilibrium time, and capability to be separated from aqueous solutions (after adsorption) could be applied to wastewater treatment.

Surfactants are one of the main groups of pollutants released into aqueous solutions due to human activities and their harmful effects have been proven on human. In this study, first, magnetic multi-walled carbon nanotubes (MMWCNTs) were synthesized and then, the effects of operating parameters such as surfactant concentration, adsorbent dosage, and pH values were analyzed on the adsorption process. MMWCNTs were characterized by means of X-ray diffraction (XRD) analysis and fourier transform infrared spectroscopy (FTIR). The optimal adsorption conditions were achieved at initial pH = 4.6, adsorbent concentration = 0.5 g/L, and initial SDS concentration = 15 mg/L. In addition, the equilibrium of sorption reached after 120 min and the maximum capacity of SDS for monolayer coverage was found to be 61 mg/g at 25°C. Kinetic studies were performed under optimal conditions and the sorption kinetics was described using the pseudo-second-order kinetic model. The experimental data were studied using Freundlich, Langmuir, and Sips models. Finally, the experimental data were fitted reasonably by Langmuir isotherm. The results demonstrated that MMWCNTs with respect to their high adsorption capacity, relatively low equilibrium time, and capability to be separated from aqueous solutions (after adsorption) could be applied to wastewater treatment.

Adsorption isotherms describe the relationship between the equilibrium concentration of the adsorbed matter in the solution and the amount of adsorbed matter on the surface of the adsorbent.
The main objective of the present research was to investigate different adsorption isotherms for describing adsorption of humic acid by nanoclay.
In this study, Langmuir, Freundlich, BET, Temkin and Dubinin Radushkevich isotherms, for describing the behavior of humic acid adsorption by bentonite and montmorillonite nanoparticles, were examined.
The results showed that due to the regression coefficient (R2), humic acid adsorption on bentonite and montmorillonite nanoparticles has greater compliance with Dubinin Radushkevich isotherms. The value of E or average energy of adsorption for humic acid by bentonite and montmorillonite nanoparticles was 0.17 and 0.15 kJ mol-1, respectively, which specifies that the type of adsorption of humic acid on both nanoparticles was physisorption. The qmax value obtained from the Dubinin-Radushkevich isotherms, for bentonite and montmorillonite nanoparticles were 27.78 and 28.70 mg/g, respectively.
According to the results of this study, bentonite and montmorillonite nanoparticles have a great potential for the removal of humic acid from aqueous solutions.

Background & Aims of the Study: water pollution by synthetic organic dyes is mainly regarded as environmental and ecological critical issues worldwide. In this research, magnetite iron oxide/silica gel nanocomposite (termed as Fe3O4/SG) was synthesized chemically and then used as an effective adsorbent for removal of sulfur dyes from aqueous solution.
The various parameters such as pH, sorbent dosage, initial dye concentration, contact time and dye solution temperature were investigated in a batch system. The equilibrium data were analyzed by Langmuir and Freundlich isotherm models.
The experimental data fit well with pseudo-second-order kinetic model (R2≥0.998) and conformed better to Langmuir isotherm model (R2≥0.997). The maximum adsorption capacity for Fe3O4/SG obtained from the Langmuir model was 11.1mg/g. Evaluation of thermodynamic parameters proved that the adsorption process was normally feasible, spontaneous and exothermic.
It can be concluded that the Fe3O4/SG can be considered as a cost-effective and an environmental friendly adsorbent for efficient removal of sulfur dyes from aqueous solutions.