Equilibrium Characteristics Of Adsorption Research Articles

Methylene blue removal using modified poly(glycidyl methacrylate) as a low-cost sorbent in batch mode: kinetic and equilibrium studies.

Industrial textile wastewater contains large amounts of cationic dye material. Therefore, a new adsorbent was synthesized as modified poly(glycidyl methacrylate) (mPGMA) with a fluorine group-containing compound 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). mPGMA was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR). The proposed adsorbent has been used to remove methylene blue (MB) from aqueous solutions by the adsorption process. In further experiments, the removal efficiency of adsorbent in both powder (˂600 μm) and granular form was compared from aqueous solutions by adsorption process. Furthermore, the effects of changing parameters such as adsorbent dosage, contact time, pH, temperature, and initial dye concentration on methylene blue adsorption were investigated. Also, Langmuir, Freundlich, and Temkin isotherms have been used to describe the equilibrium characteristics of adsorption. Finally, the experimental data fitted well by Langmuir isotherm with a maximum adsorption capacity of 17.5 mg g-1. The experimental data were applied to pseudo-first- and second-order models. The experimental results were better fitted for the pseudo-second-order model than the other model. Consequently, the experimental results showed that mPGMA is a suitable low-cost adsorbent with great potential benefit in removing methylene blue from aqueous solutions.

In Situ Ring-Opening Polymerization of L-lactide on the Surface of Pristine and Aminated Silica: Synthesis and Metal Ions Extraction.

The development of functional materials from food waste sources and minerals is currently of high importance. In the present work, polylactic acid (PLA)/silica composites were prepared by in situ ring-opening polymerizations of L-lactide onto the surface of pristine (Silochrom) and amine-functionalized (Silochrom-NH2) silica. The characteristics of the ring-opening polymerization onto the surface of modified and unmodified silica were identified and discussed. Fourier transform infrared spectroscopy was used to confirm the polymerization of lactide onto the silica surface, and thermogravimetric analysis determined that PLA constituted 5.9% and 7.5% of the composite mass for Silochrom/PLA and Silochrom-NH2/PLA, respectively. The sorption properties of the composites with respect to Pb(II), Co(II), and Cu(II) ions were investigated, and the effect of contact time, initial metal ion concentration, and initial pH were evaluated. Silochrom-NH2/PLA composites were found to have a higher adsorption capacity than Silochrom/PLA for all chosen ions, with the highest adsorption value occurring for Pb2+ at 1.5 mmol/g (90% removal efficiency). The composites showed the highest performance in the neutral or near-neutral pH (created by distilled water or buffer pH 6.86) during the first 15 min of phase contact. The equilibrium characteristics of adsorption were found to follow the Langmuir isotherm model rather than the Freundlich and Temkin models. Perspective applications for these PLA/silicas include remediation of industrial wastewater or leaching solutions from spent lead-acid and Li-ion batteries.

Cluster Adsorption of L-Histidine on Carbon Nanotubes in Aqueous Solutions at Different Temperatures

Adsorption isotherms are obtained for L-histidine on carbon nanotubes using aqueous solutions at temperatures of 25, 35, 45, 55, 65, and 80°C. The isotherms are interpreted by using the cluster adsorption model and analyzing the dependence of the strength of the bond nanotube–amino acid on temperature. Equations of the adsorption isotherms are obtained for all temperatures. The calculated results indicate that L-histidine is fixed on a nanotube’s surface in the form of monomers and different clusters. The equilibrium characteristics of adsorption are found to change as the temperature rises. Values obtained for the coefficients of equilibrium are used to calculate apparent enthalpy ΔH* of L-histidine adsorption by nanotubes, according to the van’t Hoff equation.

Methylene blue removal using Salix babylonica (Weeping willow) leaves powder as a low-cost biosorbent in batch mode: Kinetic, equilibrium, and thermodynamic studies

In this article, Salix babylonica leaves powder (SBLP) has been used for the removal methylene blue (MB) from aqueous solutions by adsorption process. The surface of SBLP analyzed by scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR). The effects of changing parameters such as adsorbent dosage, contact time, pH, temperature, and initial dye concentration on methylene blue adsorption were investigated. Three isotherm equations, Langmuir, Freundlich, and Temkin, have been tested in order to describe the equilibrium characteristics of adsorption. The experimental data fitted well by Langmuir isotherm, with maximum adsorption capacity 60.97mg/g. The experimental data were fitted using pseudo-first-order and pseudo- second-order and intraparticle diffusion models. The experimental results were fitted better with pseudo-second-order model compared to the other two models. The amount of thermodynamic parameters such as Gibbs free energy (∆G°), change in enthalpy of adsorption (∆H°), and change in entropy (∆S°) were calculated and this parameter showed that MB adsorption on SBLP is spontaneous and exothermic in nature. The result of experimental shows that SBLP is suitable low-cost adsorbent for removal of methylene blue from aqueous solutions.

Optimal isotherm parameters for phenol adsorption from aqueous solutions onto coconut shell based activated carbon: Error analysis of linear and non-linear methods

Abstract Removal of phenolic pollutants from wastewaters has become mandatory due to stringent environmental regulations and adverse effects on aquatic marine environment. Adsorption process which is most effective process to remove pollutants, hinders its applications in diverse field due to high cost of adsorbents. In this study, a low cost and easily available agricultural waste of coconut shells based activated carbon were utilized as adsorbent to study its viability and efficiency for phenol removal from wastewater. The efficacy of the phenol removal by adsorption process in a batch reactor is evaluated with respect to contact time for effective adsorption and influence of initial phenol concentration on percentage phenol removal. The experimental adsorption data were examined with conventional isotherms models to describe the equilibrium characteristics of adsorption of phenol. The vigorousity and non-linearity inherent in the isotherm models were validated using various traditional linear and non-linear estimation methods namely gradient method, non-linear least square method and hybrid evolutionary optimization. A novel inverse modeling technique based on differential evolution (DE) optimization which is first of this kind for adsorption applications was implemented to estimate the isotherm parameters in their non-linear form. The model predictions from the DE based optimized parameters provided better predictions and closer to experimental values. The percentage removal of phenol from four different adsorbent dosages with constant initial feed concentrations of phenol found to be varying from 63% to 96% as increase in carbon loading at constant liquid flow rate. These experimental results also revealed that coconut shell based activated carbon is a viable cheaper adsorbent for phenols removal from effluent wastewater.

Evaluation of Fe3O4@MnO2 core-shell magnetic nanoparticles as an adsorbent for decolorization of methylene blue dye in contaminated water: Synthesis and characterization, kinetic, equilibrium, and thermodynamic studies

In this study, Fe3O4@MnO2 core-shell nanoparticles were synthesis by a simple one-pot method. These nanoparticles were applied for removal of methylene blue (MB) ions from aqueous solution by a batch technique and characterized by TEM, XRD, EDS, FTI), FE-SE, VSM and BET surface area measurement. The influence of different adsorption parameters, such as contact time, adsorbent dosage, initial concentration of MB ions, pH value of solution and temperature have been investigated. Three isotherm equations, Langmuir, Freundlich, and Tempkin, have been tested in order to describe the equilibrium characteristics of adsorption. The equilibrium data for adsorption of MB were fitted well by Freundlich isotherm and the maximum adsorption capacity of Langmuir was 434.78 mg/g at 298 K approximately. The experimental results were fitted better with pseudo-second-order model compared to the other two models. In addition, thermodynamic calculations revealed that the adsorption process was spontaneous, exothermic and feasible. The result of experimental shows that Fe3O4@MnO2 nanoparticles is suitable adsorbent for removal of MB from aqueous solutions.

Investigation of Natural Gas Storage through Activated Carbon

This paper presents an experimental investigation of adsorption equilibrium characteristics of natural gas onto granular activated carbon (GAC). Experiments have been conducted at adsorption temperatures ranging from 20 °C to 50 °C and pressures up to 10 bar. The measurements are based on measuring the adsorption uptake difference between two equilibrium adsorption states. Experimental data have been correlated using four adsorption isotherm models, namely, Langmuir, Toth, Dubinin–Astakhov (D–A), with and without volume correction. The proposed method reduces the time required to conduct the experiments significantly. It is found that 1 kg of GAC can adsorb about 77 g of natural gas at adsorption temperature of 20 °C and equilibrium pressure of 10 bar. Isosteric heat of adsorption of natural gas/GAC pair has been estimated using Clausius–Clapeyron equation. Comparison between storage capacities of adsorbed natural gas and compressed natural gas has also been discussed. Results extracted from the present s...

Review of fluoride removal from water by adsorption using soil adsorbents – an evaluation of the status

The fate of excessive fluoride in water is cause for serious public health concerns worldwide. Water defluoridation using various technologies therefore continues to attract disproportionate research interest from around the world. Defluoridation studies using soil adsorbents, in particular, have remained the focus of intense research efforts since the last few decades. So as to assess the research status in this area, soil adsorbents commonly reported for water defluoridation over the last few decades were reviewed. This paper presents a compilation of defluoridation capacities and a summary of requisite parameters for water defluoridation using soil adsorbents. Comparison of defluoridation efficiencies of soil adsorbents is also presented, and the fluoride adsorption kinetics and adsorption equilibrium characteristics of adsorbents discussed. The results indicate that the soil adsorbents that have attracted highest research interest in this regard include hydroxyapatites, montmorillonites, hydrotalcite, zeolites, pumice and kaolinites. On average, however, the minerals that have shown the highest capacities for water defluoridation are: ferrihydrites, hydrotalcite, palygorskites, boehmite/bauxite, and pumice. Fluoride adsorption for most soil adsorbents is fitted by the Langmuir and Freundlich isotherms. Most of the kinetic data, in contrast, were described by the pseudo-second-order kinetics model. Water pH and temperature were the dominant solution factors that controlled fluoride adsorption onto soil adsorbents.

Study of the processes of adsorption of amine-containing surface-active substance on the surface of Aluminum powder

Equilibrium characteristics of adsorption on a surface of a pigment depending on concentration factors and temperature of the dispersive environment are defined. Kinetic laws of superficial activity of binary, threefold homogeneous and heterogeneous modeling systems are studied. The estimation of mechanisms of process of adsorption is carried out.

Adsorption equilibrium of copper ion and phenol by powdered activated carbon, alginate bead and alginate-activated carbon bead

The adsorption equilibrium characteristics for single and binary components of copper ion and phenol onto powdered activated carbon, alginate bead and alginate-activated carbon (AAC) bead were studied. Adsorption equilibrium data of phenol and copper ion onto the adsorbents could be represented by Langmuir equation. The adsorption capacity of Cu 2+ onto different adsorbents was in the following order: alginate bead > AAC bead > powdered activated carbon (PAC). On the other hand, that of phenol was: PAC > AAC bead > alginate bead. Multi-component equilibrium data were correlated by three different models. Among them the ideal adsorbed solution theory (IAST) gave the best fit to our data. And the adsorption amount of Cu 2+ onto AAC bead was greater than that of phenol in the binary components.

Evaluation of Adsorption Parameters and Heats of Adsorption through Desorption Measurements

The construction of an apparatus for the rapid measurement of the adsorption equilibrium characteristics and evaluation of the isosteric heat of adsorption of activated carbons for gaseous adsorbates is described. The method is based on measuring the amount desorbed between two equilibrium adsorption states. The measurement system has been tested for methane adsorption over (5 to 75) °C and pressures from (2 to 24) bar on a Maxsorb−III specimen of activated carbon. The results are evaluated through regressions with various isotherm equations used in the literature for physisorption and are compared with results of other researchers for comparable adsorbent−adsorbate combinations. A method of accounting for the adsorbed phase volume is proposed.

Modeling Volatile Organic Compound Sorption in Activated Carbon. I: Dynamics and Single-Component Equilibrium

Design and development of new sorption technologies for control of volatile organic compound ~VOC! laden air discharges from industrial sources require characterization of proposed novel processes and systems. Extensive capital, labor, and time are needed to obtain multicomponent adsorption characteristic data through laboratory experiments. As a substitute for laboratory characterization experiments, this paper presents steps for computationally predicting VOC sorption equilibrium and nonequilibrium processes in activated carbon. The method of predicting sorption equilibrium has been described in detail, since it is critical for modeling even nonequilibrium sorption dynamic processes that are constructed as successions of equilibria steps. An accurate single-component ''thermal equation of equilibrium adsorption'' ~TEEA! is presented by modifying the Dubinin-Astakhov ~DA! adsorption isotherm. DA-TEEA is capable of accurately predicting thermodynamics of single-component vapor adsorption in ultra- and supernanoporous adsorbents. The adsorption affinity factor, determined from dispersion interaction theory, enables the DA-TEEA to predict adsorption equilibrium characteristics of VOCs from adsorption equilibrium data of only one similar reference adsorbate.

Adsorption equilibria characteristics of some chlorinated cleaning solvent vapors (CFC-113 and HCFC-141b)

Chlorinated cleaning solvents have been widely used industrially, but some chlorinated cleaning solvents are considered to be prime contributors to stratospheric ozone depletion. The use of activated carbons to adsorb specific solvent vapors has thus received great attention. The adsorption equilibrium characteristics of HCFC-141b (1,1- dichloro-1-fluoroethane) and CFC-113 (1,1,2-trichloro-1,2,2-trifluoroethane) vapors on an activated carbon pellet were studied at various temperatures. Adsorption isotherms were measured and fitted by Sips equations. Detail parameters and their values for the design of adsorption facilities are suggested. The heats of adsorption for two solvents were estimated from experimental data. CFC-11 CCl3F 47-80 0.9-1.0 1.0 CFC-12 CCl2F2 95-150 0.8-0.9 2.8-3.4 CFC-113 CClF2CClF2 96-117 0.6-0.8 1.3-1.4 HCFC-141b CH3CCl2F 9-11 0.07 0.083-0.097 a ODP, ozone depletion potential, based on 1 for CFC-11. a GWP, global warming potential, based on 1 for CFC-11.

Adsorption equilibrium characteristics of 2,4-Dichlorophenoxyacetic acid and 2,4-Dinitrophenol on granular activated carbons

Adsorption characteristics of 2,4-Dichlorophenoxyacetic acid (2,4-D) and 2,4-Dinitrophenol (2,4-DNP) onto granular activated carbon (GAC) were studied to obtain basic information on their removal from aqueous solution. Single component adsorption equilibria of 2,4-D and 2,4-DNP dissolved in water have been measured for three kinds of GACs (F400, SLS103, and WWL). In case of 2,4-D, the magnitude of adsorption capacity was in the order of F400> SLS103>WWL, and that for 2,4-DNP was SLS103> F400> WWL. The influence of temperature and initial pH of aqueous solution on adsorption has been discussed in detail by using the Sips equation.

Computer simulation studies of adsorption characteristics in supercritical fluids

Monte Carlo simulation methods are combined for studying the adsorption equilibrium characteristics in supercritical fluids (SCF): (i) the adsorption isotherms of adsorbate diluted in SCF and (ii) the distribution coefficient of adsorbate at infinite dilution. Carbon dioxide, benzene, and a slitpore of graphite plane walls are selected as a model system by use of the Lennard–Jones potential for representing interaction potentials. The calculated adsorption isotherms and the distribution coefficients have been interpreted by two factors: the solvent power of SCF and the competitive adsorptions in the adsorbed phase.

Adsorption of Benzene and Pyridine on Si Crystal Surface. Measurements of Adsorbed Layer Thickness by Ellipsometry.

Ellipsometry is used for measuring adsorption layer thicknesses of benzene and pyridine on silicon crystal surface (001). Variations of the thickness with specific pressures are shown to be correlated well by the BET multilayer adsorption isotherm equation, which allows us to estimate the thicknesses of saturated monomolecular layer and molecular occupied areas. It was found that the monomolecular layer thickness of pyridine is about 40 percent greater than that of benzene, while the occupied area of a pyridine molecule is about 60 percent less than that of a benzene molecule. These conclusions are coincident with spectroscopic results reported for adsorbate-surface interaction by means of UV photoemission and Raman spectroscopy. Ellipsometry has been proved to be an effective method for evaluating adsorption equilibrium characteristics.

Fundamentals for the thermal remediation of contaminated soils. Particle and bed desorption models

A major research effort has been initiated to characterize the rate-controlling processes associated with the evolution of hazardous materials from soils. A 3-fold experimental approach was used in conjunction with computer modeling to analyze thermal desorption of contaminants. Phenomena occurring both inside particles (intraparticle) and within a bed of particles (interparticle) were studied. The results obtained suggest that the most important process variables are local thermal environment and gas-phase contaminant concentration because the adsorption equilibrium characteristics of the contaminant/soil pair control the desorption of contaminant from a particle at a given temperature. A mass-transfer/desorption model, which assumes gas/solid equilibrium at all points and time, is proposed and the model was found to predict the measured temperature dependence.

A new method for calculation of the equilibrium adsorption of binary mixtures on microporous carbonaceous adsorbents

A new method has been proposed for calculating a priori the equilibrium characteristics of adsorption of binary mixtures as functions of the structure of carbonaceous microporous adsorbents, and the temperature and adsorbabilities of the mixture components from vapor or liquid. The method uses the results of the theory of volume filling of micropores and stoichiometric theory of adsorption. Besides, the approach has been based on the properties of temperature invariability and similarity of the characteristic curves of the mutual replacement of the adsorption solutions components characterized by the same type of intermolecular interaction recently found by the authors. The calculations for many mixtures have been based on the experimental results at one temperature for one of the mixture on one of the adsorbents being compared and standard vapor adsorption isotherms on all the adsorbents. The results are in good agreement with the experiment which enables a purposeoriented selection of highly specific adsorption systems.

Study of adsorption from solutions by column chromatography

A column chromatographic method is proposed for obtaining data on equilibrium characteristics of adsorption; the method makes it possible to obtain in a single chromatographic experiment the excess adsorption isotherm of binary solution over the whole range of concentrations. The potentials and limitations of the method with respect to equilibrium data and thermodynamic characteristics of adsorption systems are discussed. A comparison with static experimental data is made.