جستجوی مقالات مرتبط با کلیدواژه « جذب سطحی » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

In this work, the Monte-Carlo molecular simulation was applied to study the adsorption of H2S and CO2 from natural gas onto silica chabazite zeolite. The isothermal adsorption curves of pure CH4, CO2, and H2S on zeolite were simulated in a pressure range of 0-200 kPa at the temperature of 298, 323 and 348 K. The heat of adsorption analysis indicated that the physical adsorption has occurred. The simulation results showed a good agreement with experimental data and the average relative error of simulated results in 298 K for those gases were reported as 18.31%, 6.6%, and 9.8%, respectively. The isotherm of dual and triple combinations of these gases has been studied in the composition range of 70-90% of CH4. Results indicate that the tendency of chabazite for adsorption of H2S is much more than two other gases, because of its high polarity. In addition, results report that the selectivity of CO2 and H2S on chabazite in dual and triple gas mixtures are almost 2 and 4, respectively.

Nowadays, due to the reduction of fresh water resources and the increase in demand in the world, the removal of various pollutants, such as dyes, from industrial wastewaters to reuse them has received much attention. In this research, activated carbon (AC) was synthesized by the chemical activation of apricot kernel shell, and then, this adsorbent was modified by iron-containing functional groups (Fe-AC) and used as an adsorbent to remove reactive red dye 198 from the aqueous medium. The properties of these adsorbents were identified using BET, EDX-SEM, and FT-IR analyses. The results of equilibrium data showed that the adsorption process is single-layer and the maximum adsorption capacity of AC and Fe-AC absorbents is equal to 192.6 mg/g and 277 mg/g, respectively. The increase in adsorption capacity after modification is due to the positive adsorption sites of iron (O-Fe+) on the surface of the modified adsorbent, which adsorb the reactive dye red 198 by electrostatic mechanism. Also, the physical adsorption due to the porous structure of the adsorbent is effective in the adsorption of reactive red dye on the Fe-AC adsorbent. The analysis of kinetic data with different kinetic models showed that the pseudo-second-order kinetic model is consistent with the experimental result. The spontaneity and exothermic nature of the adsorption process were determined by determining the thermodynamic parameters. The successive cycles of adsorption and desorption indicate the ability to regenerate and reuse the synthesized adsorbent, which can be a suitable option for use in industrial dimensions.

One of the widely used methods to remove acid gas is surface adsorption using solid molecular sieves. The advantages of H2S adsorption with molecular sieves can be seen in reversibility of the process, chemical and thermal stability, no secondary product, and high selectivity of H2S in these adsorbents. Therefore, in this study, Aspen-Adsim software was used to investigate the effect of various parameters on adsorption of H2S on 4A molecular sieve adsorbent. The desired bed is considered vertical and one-dimensional. The results related to the breakthrough curves and saturation time showed that maximum amount of adsorption occurred in early times. As the adsorption time increases, the rate of H2S adsorption decreases. The results of investigating the effect of operating parameters showed that increasing the tower pressure from 90 to 104 bar reduces the output H2S content by 21 ppm. Also, reducing the feed temperature showed significant results on amount of H2S absorption and the reduction of the output H2S content, so that for every one degree of temperature reduction in the feed gas temperature, the dew point temperature of the output was reduced by 1.6°C. Due to high amount of absorbent and its heat capacity compared to the amount of H2S in the gas phase, a slight temperature increase occurs along the tower so that the difference between inlet and outlet temperatures does not exceed 1˚C. According to the breakthrough curve, it was also determined that after 7920 seconds, the entire bed of the tower is saturated with H2S molecules.

In this article, the removal of heavy metal ions from water environments with an environmentally friendly method is discussed. Industrial effluents contain toxic heavy metals such as mercury, lead, cadmium and chromium (VI); Copper, nickel, cobalt and zinc are not toxic, but increasing their amount in the environment is a serious concern. The adsorption capacity of different biosorbents is affected by several factors, including pH, temperature, contact time, biomass dose, and the initial concentration of heavy metals. Also, biosorption kinetics and isotherms are also investigated. Banana peel in agricultural residues and Chlorella minotissima in algae, fungi and bacteria showed a high adsorption capacity. The pseudo-second-order kinetic model showed a high correlation coefficient. Therefore, it is chemical adsorption in which metal ions stick to the adsorbent surface by forming a chemical bond. The Langmuir model has a better fit with the experimental data, which indicates the adsorption of a single layer.

This research aims to synthesize a novel adsorbent and reduce the contact time in removing methylene blue dye. Copper ferrite nanoparticles were prepared by solvothermal method and CuFe2O4/PVA/AG magnetic nanocomposite by freeze-thaw method and drying at room temperature. The structure and morphology of magnetic nanocomposite were investigated using FTIR, XRD, SEM, and EDX methods. CuFe2O4/PVA/AG adsorbent under optimal conditions of pH = 7, contact time 60 min, amount of adsorbent 40 mg, dye concentration 5ppm and temperature 25 ᵒC was investigated. The maximum absorption and absorption capacity were obtained as 81.1 % and 14.93 mg/g, respectively. In addition to investigating the recovery effect of the adsorbent for comparison, the PVA/AG adsorbent was investigated under the aforementioned optimal conditions, and the maximum removal efficiency was 63.5 %. Examining the isotherm of the equilibrium state of dye removal matches well with the Freundlich isotherm. The kinetics of surface adsorption were investigated, and observed that the adsorption process on the magnetic nanocomposite follows pseudo-second-order kinetic equations.

Removing sulfur and sulfur compounds from liquid fuel is one of the most important research topics. In this research, activated carbon was prepared by chemical activation from walnut shells, then modified by iron nanostructure and chitosan separately and together, and used to remove dibenzothiophene from isooctane fuel. BET, EDX-SEM, and FTIR analyses were used to investigate the adsorbent. Equilibrium experiments showed that the adsorption process is a single layer, and the maximum adsorption capacity is 285.71 and 178.57 mg of dibenzothiophene per gram of adsorbent modified by iron nanostructure and per gram of adsorbent modified by iron nanostructure and chitosan, respectively. The results of kinetic data showed that the pseudo-second-order kinetic model is consistent with the experimental result. To determine mass transfer parameters, the mathematical model of film-pore-surface diffusion model was used by MATLAB software and it was observed that external mass transfer and pore diffusion stages are more important.

The current research uses silica nanoparticles produced from rice husk through conventional and sonochemical precipitation to treat industrial tannery wastewater. The effects of NaOH concentration, precipitation pH, and ageing time on adsorption properties were studied via the central composite design (CCD) method. The obtained results indicated that rice husk ash, as a precursor used in the preparation of silica, should be dissolved in the dilute NaOH solution, 0.5 mol L-1, and precipitation pH should be controlled at the level of 9.0 to achieve an adsorbent with proper performance. Although the surface area of powder produced conventionally is larger than that obtained by the sonochemical method, the pore size distribution plays an effective role in the adsorption of Cr III compounds. The precipitation under sonication leads to large pores distributed in the 4-38 nm range, facilitating the diffusion of chromium compounds even in acidic environments.</em>

This study aims to synthesize a novel low-cost adsorbent in the form of film prepared by natural and available sources of elderberry kernel, with an easy preparation method and an efficiency higher than 90% in the adsorption of crystal violet dye. By investigating the effects of various parameters, including pH, adsorbent dose, temperature, contact time and dye initial concentration, the optimum conditions to reach the maximum adsorption were determined. Results showed that the maximum adsorption efficiency is 94.24 %, which is obtained under optimal conditions ofpH = 8, adsorbent dose 1 g/l, temperature 25 °C, contact time 90 min and dye initial concentration 10 mg/l. Isotherm and kinetic models reveal that the adsorption is physical and favourable, and equilibrium data are more compatible with Langmuir isotherm and pseudo-second-order kinetic models. The maximum adsorption capacity of adsorbent was calculated to be 30.30 mg/g. Thermodynamic investigation showed that the adsorption is spontaneous and exothermically. Desorption studies also stated that after several consecutive removal steps, the adsorption capacity is still favourable.

In this study, three composite adsorbents with different percentages zeolite ZSM-5 and silica aerogel, were synthesized. The adsorbents were characterized by FESEM, XRD, FTIR, BET-BJH, and zeta potential. By comparing the performance of the zeolite ZSM-5 (25)/silica aerogel (75) adsorbent as an optimal adsorbent and other inexpensive adsorbents, it was observed that the adsorbent studied in this experiment has good adsorption efficiency. The saturated adsorption capacity reached 476.2 mg/g for Pb+2. To obtain the best isotherm and kinetic model, error functions and regression coefficients, especially the Chi-square test (χ2) and sum square error (SSE), were used. The findings fit well with Temkin isotherm models, according to the adsorption isotherm investigations. The kinetic data for the pseudo-second-order kinetic model exhibited a high correlation coefficient and a low error function. The activation energies for lead were and 11.31 kJ/mol, respectively. These values indicate that physical adsorption has occurred. The Com3 absorbent was separated from the wastewater and reused after recovery. This feature caused the adsorbent to have a strong adsorption ability, so the adsorption process was performed in five cycles. FTIR and EDX analyses were performed to confirm the adsorption of heavy metals by the adsorbent. The results show that the zeolite ZSM-5/silica aerogel composite is a suitable adsorbent for the removal of various toxins(such as heavy metals) in aqueous systems that contain an adsorbate. As a result, the new zeolite ZSM-5/silica aerogel composite may be used on a larger scale as a material to absorb a variety of contaminants.

An accurate estimation of methane absolute adsorption in nanopores of shale gas is crucial for a good estimation of gas in place (GIP). However, experimental studies would only provide us with the excess adsorption isotherm directly. In this regard, knowing the adsorbed density is necessary to calculate the absolute adsorption. For this purpose, most researchers calculate the absolute adsorption isotherm via the Langmuir adsorption model with a constant value for the adsorbed density. In the present study, using hybrid grand canonical Monte Carlo/molecular dynamics simulations, we explained how to improve the calculation of the adsorbed density in calcite. For this purpose, methane inside calcite mineral with a pore size of 4 nm at temperatures of 30 and 90 °C and pressures up to 50 MPa is simulated, and the effects of temperature and pressure on the amount of adsorption and adsorbed density are investigated. This study showed that adsorbed density increases and decreases with increasing pressure and temperature, respectively. The results verify that the Langmuir adsorption model with constant adsorbed density will underestimate the absolute adsorption capacity, which is exacerbated with pressure. Finally, the adsorbed density obtained from molecular simulations to convert excess adsorption to absolute values can provide acceptable results that can be improved the GIP assessments.

In recent years, the textile industry has produced more than 50 % of the colored wastewater in the world. Clean water is essential in the lives of humans, aquatic organisms, and agricultural products. Due to their toxicity, dyestuff in water causes adverse quality, endangers their health, and causes environmental changes. There are different methods for wastewater treatment, which, based on the research, shows that today's surface absorption method is mainly used for wastewater treatment due to its cheapness, simplicity, and cost-effectiveness. In this article, the removal of dyestuff from wastewater was investigated using different nanocomposites, and the effect of adsorption with nanocomposites was investigated based on factors affecting adsorption, including contact time, initial concentration, the effect of temperature, and pH of the solution. Adsorbents significantly impact removing dyestuff and can perform wastewater treatment with good quality. This research used activated carbon nanocomposites, carbon nanotubes, silver nanoparticles, zinc ferrite, ZnO, TiO2</sub>, Fe3</sub>O4</sub> and zero-valent iron nanoparticles for wastewater decolorization. In this article, the results show that different nanocomposite adsorbents are promising. They are a promising future for the treatment of colored wastewater.  

In this research, the application of adsorption isotherm, kinetic and thermodynamic models in a rotating disk reactor covered with graphene nanoparticles designed to remove aromatic compounds from the wastewater of the refinery located in Sari oil facilities and as a result reducing the chemical oxygen demand (COD) of the wastewater was investigated. Langmuir-Freundlich thermocouple was used to investigate the removal process. Also, adsorption kinetics were investigated by pseudo-first-order, pseudo-second-order and intermolecular diffusion models. The thermodynamics of adsorption was studied by Vant Hoff relation and its results were analyzed. Also, the effect of change in effluent concentration (70,100,150 mg/L) and temperature (20, 30 and 40˚C) and the number of discs containing graphene on the COD removal rate of the effluent was investigated. The results of the experiments showed that the rate of absorption and reduction of effluent COD increased with the increase of initial concentration and the temperature of the process and under optimal conditions was equal to 66%. From the examination of the equations, the applicability of two isothermal equations in the form of Freundlich Langmuir and models Kinetics were determined as pseudo-second order > intermolecular diffusion > pseudo-first order. From the analysis of the data, it was found that increasing the concentration and efficiency of the adsorbent has a positive effect and improves COD removal. At high concentrations, the ratio of effluent to graphene active surfaces and concentration gradients were the leading factors of absorption. The COD reduction percentages for concentrations of 70, 100, and 150 mg/L were 48%, 62%, and 73%, respectively.

In this study, a mesoporous silica nanostructure was synthesized and magnetized (Magnetic-SBA-15) and then its ability to remove reactive red 198 dye (RR198) from aqueous solution was investigated. The structure of produced adsorbent were evaluated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). the effect of effective parameters on the adsorption process such as pH, adsorbent dose, contact time, temperature and dye concentration were investigated and optimized. The optimum conditions for removal of reactive red 198 dye was pH =2, adsorbent dosage of 0. 4 g/l ,contact time of 60 minutes and temperature 25 ⁰C in 60 ppm of dye concentration. UV-vis spectrophotometer was used to determine the amount of residual dye in the solution. To determine the type of adsorption isotherm, the Langmuir, Freundlich and dubinin-radushkevich equations of adsorption isotherms were used. The results showed a good fit for the Langmuir adsorption isotherm (R2 = 0.997 and RL = 0.275). According to the values obtained from thermodynamic parameters such as enthalpy (-15.346 kJ/mol) and Gibbs free energy, the removal of reactive red 198 dye by Magnetic-SBA-15 was exothermic and spontaneous.

Research subject: 

Poly (2-oxazoline) (PEOX) polymers are a family of synthetic macromolecules with biodegradable and biocompatible features. They resemble polypeptides in structure and therefore, have recently taken put to use in drug delivery. Nonetheless, these polymers suffer from relatively low thermal and mechanical performance and thus are reinforced with nanoparticles as nanocomposites. The molecular details of the reinforcement mechanism of PEOX have not yet been elucidated.

Research approach: 

This research work was done to reach an understanding on interaction of 2-oxazoline-based polymers with 2D nanoscale reinforcements and to shed light on the mechanism of reinforcing the respective nanocomposites. To this end, conformation and dynamics of poly (2-ethyl-2-oxazoline), as a known representative member of this family, near a functionalized graphene nanosheet were studied via classical molecular dynamics for a period of 10 ns. The effects of various temperatures and polymer chain lengths on polymer conformation and dynamics were assessed.

Molecular dynamics snapshots exhibited effective interaction of the polymer chain with the graphene nanosheet leading to adsorption, whereby conformation and dynamics of the chain underwent transition. The adsorbed polymer chain adopted a flat, folded arrangement parallel with the graphene plane. Also, the gyration radius was found to increase, when the polymer chain approached the graphene nanosheet. Pair correlation function curves revealed that the adsorption correlation length was on the order of the repeating unit end-to-end distance. Mean-square-displacement of the polymer chain decreased as it moved towards graphene. An increase in temperature led to a change in structure and dynamics of the adsorbed polymer chain.

This work compares two conventional methods of adsorption with zeolites and azeotropic distillation for dehydration of industrial ethanol (95%) to produce 99.8% ethanol. To this end, both processes were simulated by a similar feed flowrate of 136kg/h and the suitable alternative was selected using techno-economical study. The results revealed that the adsorption process is more economical than azeotropic distillation for ethanol dehydration, as it possesses lower total investment cost and total product price. The amount of production at break-even point and the investment-return period for the adsorption process were equal to 1223800L and 12 months, respectively, and those for the azeotropic distillation were 2004905L and 25 months, respectively. In addition, the net annual profit, net present value and internal rate-of-return for adsorption process were equal to 413456$, 1181279% and 276%, respectively, which are much higher than those for the azeotropic distillation, equal to 263925$, 979370$ and 87%, respectively.

In this research, it was tried to use a reactor containing plates covered with Graphene nanoparticles and placing it after the anaerobic biological treatment unit of dyeing treatment plant will reduce the pollution load for the next stages of treatment by absorbing aromatic substances resulting from the anaerobic biological destruction stage. The results of the field emission electron microscope (FE-SEM) analysis showed that the Graphene layers on the reactor plates were multi-layered. Then the effect of three parameters of effluent concentration (COD: 70, 100, 150 mg/L), pH (5, 7, 9) and temperature (20, 30 and 40 ˚C) on the amount of removal of aromatic compounds, COD and effluent turbidity were investigated. The results showed that high concentration of COD had faster and better absorption by Graphene than its low concentration. Among the three tested temperatures, a higher absorption rate was observed at the higher temperature. Also, with the increase of pH from 5 to 9, the amount of absorption increased. This system showed relatively good performance in absorbing aromatic substances and reducing COD. Optimum conditions of reactor performance were determined as COD: 150 mg/L, pH = 9 and temperature 40 ˚C.

Trace amounts of Cu (II) and Pb (II) in the wastewater sample were removed with a new nano biosorbent based on cross-linked chitosan magnetic beads modified with methionine-glutaraldehyde Schiff's base (MG-Chi/Fe3O4) in wastewater samples. Fourier transform infrared spectra (FTIR), X-ray diffraction (XRD) analysis, and scanning electron microscope (SEM) have been applied to characterize nano biosorbent. Various parameters affecting the uptake behavior of the metal ions were examined and optimized, including pH, adsorbent dose, contact time, and initial concentration. Freundlich and Langmuir isotherm models were applied to estimate adsorption mode. The equilibrium data were well fitted with the Langmuir isotherm model. The maximum adsorption capacities for Cu (II) and Pb (II) were 172.4 and 175.4 mg g-1, respectively. The adsorption kinetics are better consistent with the pseudo-second-order model. It was concluded that this method was successfully applied for the simultaneous removal of Cu (II) and Pb (II) in industrial wastewater samples.

Injection of nanoparticle-stabilized foam has been considered by the oil industry due to its high stability. In this study, the interaction between nanoparticles and surfactants as well as the hysteresis of the foam injection sequence is investigated. For this purpose, secondary and tertiary core injection experiments were performed on synthetic glass core to investigate the oil recovery behavior of foam stabilized with calcium carbonate nanoparticles and SDS surfactant in sandstone reservoirs. According to the results, the secondary oil recovery by foam stabilized with a mixture of 0.04 wt.% of surfactant and 0.1 wt.%  of nanoparticles is significantly higher than the foam stabilized with counterpart nanoparticle and surfactant. In all cases, tertiary oil recovery was significantly lower than the tertiary mode. This phenomenon was attributed to the diffusion regime governing tertiary recovery compared to the convective regime in the secondary injection. In order to prove this hypothesis, the aging process performed in the core injection experiments was repeated in the contact angle device. In the diffusion regime, the nano fluid could not change the wettability of the glass to more water-wetness. The surfactant solution reduced the glass oil-wetness by only 5 degrees. The mixture of surfactant and nanoparticles brought this change in wettability to 16. The Nano fluid, surfactant solution, and mixture of surfactant and nanoparticles brought the initial wettability of about 150˚ to 76˚, 45˚, and 23, respectively, which it confirms the higher rate of convective regime in the change of wettability. Based on surface tension experiments, the superior behavior of the surfactant and nanoparticle mixture was attributed to the adsorption of surfactant molecules on the nanoparticles and the surface activation of the nanoparticles.

Adsorption is an effective method for the treatment of dyed wastewater contaminants the aqueous environments. In this study, an alginate-based foam adsorbent was prepared via freeze-drying and post-cross-linking method and then used to remove methylene blue dye from aqueous solutions. Characterization using different analyzes, kinetics, isotherm, swelling, and regeneration experiments, and the parameters affecting the dye adsorption process such as dye concentration (2-10 mg/L), pH (3-11) were investigated. The findings obtained from the adsorption process indicated that the adsorption of methylene blue using synthetic adsorbents has good conformity with conventional kinetic and isotherm models and the kinetics and isotherm are adjusted with the pseudo-second-order and the Freundlich models, respectively. The adsorption capacity of methylene blue was 3.80 mg/g with 97% removal efficiency for alginate-based foam. With the increase in initial solution pH and dye concentration, better adsorption performance was observed. The prepared adsorbent presented remarkable chemical stability and was readily recyclable after three reuse cycles.

The loss of surfactants and polymers in the injection process in reservoirs is considered the most crucial issue in the chemical injection process›s Feasibility. Simultaneous injection of polymers and surfactants causes interaction between surfactant and polymer and a significant reduction in performance. The best solution for solving this problem is using a new material called polymeric surfactant that can be an exciting alternative for currently available methods. These new materials can have the effect of polymer and surfactant like increase of water viscosity, reduction of interfacial tension between water and oil, and change in reservoir rock wettability simultaneously; thus, these new materials will further increase oil production relative to traditional methods. One of the fundamental problems of chemical injection is the adsorption of these substances on the reservoir rock. Because of limited research regarding the analysis of the adsorption rate of polymeric surfactant on reservoir rocks and comparing them with the adsorption rate of conventional polymers, in this study, the adsorption rate of this substance has been studied in different temperatures. First, in this research, A HPAM and HMZPAM As a polymeric surfactant synthesized using a Zwitterion hydrophobic group, and the effect of these two polymers was measured in concentrations between 50 to 1000 mg/L at temperatures between 25 to 80 oC on adsorption of surface in carbonate rock. The results show that the adsorption of HPAM and HMZPAM on reservoir rock, which made of dolomite, increases with the increase in polymer›s concentration. Generally, the main factor in the adsorption of polymers are electrostatic forces which because HMZPAM compared to HPAM, in addition to COO- group also has SO3- group that these negative groups adsorbed more to the positive charge of the rock surface in which as a result increases the amount of adsorption of polymeric surfactant compared to HPAM.