Showing papers on "Freundlich equation published in 1996"
TL;DR: In this paper, the adsorption of dyes such as congo red, procion orange and rhodamine-B by waste orange peel was examined at different concentrations of dye, adsorbent dosage, agitation time and pH.
585 citations
TL;DR: In this paper, the Tian−Calvet type calorimeter is applied to the simultaneous determination of adsorption isotherms and the heats of adorption in zeolites.
Abstract: A Tian−Calvet type calorimeter is applied to the simultaneous determination of adsorption isotherms and heats of adsorption This is the first of a series of studies of the effect of adsorbate size and polarity on the energetics of adsorption in zeolites The adsorbate gases used in this study are quadrupolar (N2 and CO2) and nonpolar (Ar, O2, CH4, C2H6, and SF6) The heats of adsorption of both polar and nonpolar gases are either constant or increase with coverage, so silicalite may be classified as a relatively homogeneous adsorbent compared to X type zeolite Reversibility was established by comparing adsorption and desorption isotherms Reproducibility was studied by comparing runs for different samples of the same adsorbent The average experimental error in loading is ±06% The error in the isosteric heat of adsorption is ±2% for heats larger than 20 kJ/mol and ±5% for heats smaller than 20 kJ/mol
407 citations
TL;DR: In this paper, the authors investigated the maximum adsorption of antimony on the sand of Haro river (10 mg-1 g) with respect to the selection of an appropriate electrolyte, shaking time, and amount of sand.
236 citations
TL;DR: In this paper, the adsorption of vanadium (IV) by chitosan, a naturally occurring material, is studied according to equilibrium and kinetics, and single mechanisms of diffusion are studied.
235 citations
TL;DR: In this paper, the removal of Cu, Ni and Zn ions from water solution by ungranulated blast-furnace slag has been studied depending on contact time, initial ion concentration, pH and solution temperature.
181 citations
TL;DR: The dual-site Langmuir model as discussed by the authors provides a powerful framework to correlate multicomponent gas adsorption since it has a flexible mathematical form for pure-gas adaption, and it provides a flexible way to describe mixed-gas competition.
Abstract: The dual-site Langmuir model (bimodal two-site discrete distribution with the Langmuir isotherm) provides a powerful framework to correlate multicomponent gas adsorption since it has a flexible mathematical form for pure-gas adsorption, and it provides a flexible way to describe mixed-gas competition. The model meets the requirements imposed by thermodynamic consistency. The power of this model as a correlative tool is analyzed and demonstrated by applying it to a set of single- and multicomponent data for the adsorption of nitrogen and oxygen on 5A-zeolite.
144 citations
TL;DR: In this article, the liquid phase adsorption equilibria of eight phenolic compounds onto activated carbon fibers were measured in the concentration range 40−500 g·m-3 at 303 K. Several two-and three-parameter isotherm equations were tested.
Abstract: Liquid-phase adsorption equilibria of eight phenolic compounds onto activated carbon fibers were measured in the concentration range 40−500 g·m-3 at 303 K. High adsorption capacities were observed for the chlorinated phenols compared to the methyl-substituted phenols. Several two- and three-parameter isotherm equations were tested. Among the equations tried, the three-parameter equation of Jossens et al. based on a heterogeneous surface adsorption theory was found to be the most satisfactory over the entire range of concentration. The widely used two-parameter equations of Langmuir and Freundlich were not applicable to the present adsorption systems.
129 citations
TL;DR: In this article, a study of the Langmuir and Freundlich isotherms was carried out to evaluate the affinity and capacity of a feedstuff additive, a montmorillonite silicate, to adsorb the four major naturally occurring aflatoxins.
114 citations
TL;DR: In this article, the Freundlich isotherm was used to determine the adaption isotherms for phenol, 3-chlorophenol, and 2,4-dichlorophenol from water onto fly ash.
Abstract: Adsorption isotherms for adsorption of phenol, 3-chlorophenol, and 2,4-dichlorophenol from water onto fly ash were determined. These isotherms were modeled by the Freundlich isotherm. The fly ash adsorbed 67, 20, and 22 mg/g for phenol, chlorophenol, and 2,4-dichlorophenol, respectively, for the highest water phase concentrations used. The affinity of phenolic compounds for fly ash is above the expected amount corresponding to a monolayer coverage considering that the surface area of fly ash is only 1.87 m2/g. The isotherms for contaminants studied were unfavorable, indicating that adsorption becomes progressively easier as more solutes are taken up. Phenol displayed a much higher affinity for fly ash than 3-chlorophenol and 2,4-dichlorophenol.
113 citations
TL;DR: In this paper, an adorption model is proposed which assumes a different partial molar surface ω for adsorbed molecules depending on the degree of saturation of the adsorption layer.
Abstract: An adsorption model is proposed which assumes a different partial molar surface ω for adsorbed molecules depending on the degree of saturation of the adsorption layer. Equations for an adsorption isotherm and a surface tension isotherm are derived for the adsorption of one single surfactant or of a mixture of surfactants. The model assumes that the molecules may adsorb in two different states, i.e. a large ω at smaller surface pressures Π and a smaller ω at large surface pressures Π. Adsorption data of (N-n-hexadecyl-N,N-dimethylammonio)acetic acid bromide at the air/solution interface are used to demonstrate the application of the theory. The experimental results are in very good agreement with the model.
110 citations
TL;DR: The distribution of heavy metals in the aqueous phase of aquifers is strongly dependent on the kind of solid phase and on the presence of dissolved organic matter as mentioned in this paper, and NOM increased the dissolved fraction of Cu and Pb, and decreased that of Cd.
TL;DR: In this paper, the authors examined the intestinal absorption of zearalenone and evaluated several sorbent materials for the same purpose, and found that cholestyramine was the best adsorbent, followed by crospovidone, montmorillonite, bentonite, sepiolite and magnesium trisilicate.
TL;DR: A review of the use of the Freundlich isotherm in investigating adsorption processes of vegetable oils and its current value in adsoreption studies can be found in this paper.
Abstract: The objective of this review is to discuss the history of the use of the Freundlich isotherm in investigating adsorption processing of vegetable oils and to evaluate its current value in adsorption studies. The Freundlich isotherm was originally developed to explain the adsorption of a single solute from solution. However, a similar adsorption pattern has been observed when studying a more complex system of adsorption of vegetable oil pigments onto bleaching clay during commercial bleaching of vegetable oils. The Freundlich isotherm has been useful for decades in finding the commercial value of adsorbents as long as a narrow experimental interval of adsorbate is used. More recent studies have shown that a complex series of interactions controls the adsorption process. While the isotherm summarizes these interactions, investigating them is vital to understand the physicochemical factors involved during adsorption. Statistical modeling and spectroscopy are useful in understanding the vegetable oil bleaching/refining process as a multiple-component adsorption system.
TL;DR: In this article, the authors investigated the sorption of five pesticides (metsulfuron methyl, atrazine, 2,4D, phorate, and terbufos) in a range of allophanic and non-allophanic soils of New Zealand, using surface and subsoil horizons from 10 soil series.
Abstract: We investigated the sorption of five pesticides (metsulfuron methyl, atrazine, 2,4‐D, phorate, and terbufos) in a range of allophanic and non‐allophanic soils of New Zealand, using surface and subsoil horizons from 10 soil series. Sorption of pesticides was measured by a batch equilibrium technique using 14C‐labelled pesticides. The effect of soil properties on pesticide sorption was also examined. Sorption of pesticides was adequately described by the Freundlich equation with an R 2 value > 0.97. The value of the exponent in the fitted Freundlich equation for the pesticide sorption varied from 0.79 to 0.98. The pesticide sorption, as measured by the distribution coefficient (Kd, sorption per unit concentration), was as follows: terbufos > phorate > 2,4‐D > atrazine > metsulfuron methyl (Kd = 20.7, 18.1, 4.88, 3.74, and 0.54 L/kg, respectively). Sorption of pesticides was higher for allophanic than for non‐allophanic soils and in general decreased with depth. Multiple regression analysis between ...
TL;DR: In this paper, the results of investigations into alternative adsorption technologies which might be more effective at removal of NDMA than bituminous coal granular activated carbon (GAC) systems located at the boundaries of the RMA are evaluated.
TL;DR: In this article, the electrical double layer of mineral hydroxides is analyzed and a brief description of the solution side of the double layer based on the Gouy-Chapman and the GCHStern model is given together with some arguments against the triple layer model.
TL;DR: In this paper, the removal efficiency of chemical warfare (CW) agents from aqueous solutions was evaluated using coconut charcoals of different grades and the results enabled identification of an activated carbon suitable for use in reverse-osmosis water filtration systems.
TL;DR: In this paper, the adsorption-desorption behavior and the degradation of an ionic herbicide (2,4-D) were examined using 10 soils from New Zealand that differed in their organic matter and clay content.
Abstract: The adsorption-desorption behaviour and the degradation of an ionic herbicide (2,4-D) were examined using 10 soils from New Zealand that differed in their organic matter and clay content. Adsorption isotherms for 2,4-D were adequately described by the Freundlich isotherm and the values of the exponent N of the Freundlich isotherm were close to 1 (0.92-0.98), indicating that the adsorption isotherm tended to become linear. The extent of adsorption, as measured by the distribution coefficient (Kd), increased with an increase in soil organic carbon. The rate of desorption of 2,4-D followed first-order reaction kinetics with respect to surface concentration, and decreased with an increase in the organic carbon content of the soils. The rate of degradation of 2,4-D, as measured by the half-life (t1/2), decreased with an initial increase in soil organic carbon, which is attributed to the increase in adsorption. With increasing adsorption, the rate of desorption decreased, resulting in a low concentration of 2,4-D in the soil solution that is available for microbial degradation. When the organic carbon content was more than 12%, however, both the adsorption and rate of degradation increased. The enhanced degradation of 2,4-D at these levels of organic carbon may be related to the increased biological activity of the soil, as measured by substrate-induced respiration, and the decreased 2,4-D-induced inhibitory effect on microbial activity.
TL;DR: In this article, a new Jovanovic-Freundlich isotherm model is derived for describing single-component adsorption equilibria on heterogeneous surfaces, which is obtained by assuming that the rate of decrease of the fraction of the surface unoccupied by the adsorbate molecules is proportional to a certain power of the partial pressure.
TL;DR: In this paper, the adsorption of chromium(VI) to C. crispata was investigated in a two-staged batch reactor, where the Freundlich adaption isotherm was used for the calculation of the equilibrium value of the residual or adsorbed chromium concentration(Ceq or Cxeq).
Abstract: In this study, the adsorption of chromium(VI) to C. crispata was investigated in a two-staged batch reactor. The sorption phenomenon was expressed by the Freundlich adsorption isotherm and this expression was used for the calculation of the equilibrium value of the residual or adsorbed chromium(VI) concentration(Ceq or Cxeq) at each stage for a given “quantity of alga/volume of waste water containing chromium(VI)” or (Xo/Vo) ratio in a two-staged batch reactor. Experimental Ceq values were compared to calculated ones at each stage. Applications in waste water treatment for chromium(VI) removal have been suggested.
TL;DR: In this paper, the degradation of two herbicides (metolachlor and pendimethalin) and a nematicide (cadusafos) were evaluated under laboratory conditions with six soils selected in a tropical zone (Martinique, French West Indies) and in the Mediterranean area (Languedoc, South of France).
Abstract: Adsorption, desorption, and degradation of two herbicides (metolachlor and pendimethalin) and a nematicide (cadusafos) were evaluated under laboratory conditions with six soils (ferralsol, regosol, andosol, fluvisol, and two vertisols), selected in a tropical zone (Martinique, French West Indies) and in the Mediterranean area (Languedoc, South of France). Adsorption parameters were calculated using the Freundlich equation, and desorption parameters were evaluated using a 2-compartment model corresponding to two different energy levels. Degradation rate was calculated with a first order equation. Combining values of Koc and half-life in soil, an estimation of the mobility of these pesticides in the soil was made using GUS (ground water ubiquity score). Consideration of pesticide adsorption and resistance to desorption allowed classification of these three compounds according to their mobility: pendimethalin ferralsol > regosol > andosol > fluvisol. Clay or sand content (and cation exchange capacity) of the soils clearly affected adsorption-desorption parameters. The degradation study in the six soils did not show significant differences, but revealed the influence of temperature. GUS values indicated that pendimethalin could be considered as a non-leacher compound, and that cadusafos and metolachlor exhibit a moderate tendency to leaching.
TL;DR: In this article, the first order rate law and obeys the Freundlich isotherm over the entire range for the bulk concentration of Hg(II) was investigated.
TL;DR: In this article, root tissues of two common weeds, Amaranthus spinosus and Solanum nigrum, were found to adsorb dissolved Cu2+ in aqueous solutions.
TL;DR: In this paper, changes in the adsorption of four 14C-labelled pesticides -diazinon, acephate, atrazine and ethofumesate- on a sandy loam soil, induced by application of anionic, cationic and nonionic surfactants - tetradecyltrimethylammonium bromide (TDTMA), sodium dodecyl sulphate (SDS), polyoxyethylene sorbitanmonooleate (Tween 80), were determined using a batch equilibrium method.
TL;DR: In this paper, liquid phase adsorption of two dyes on activated carbon was measured in the 283-323 K temperature range and the best-fit model for basic dye changed from the Langmuir to the Freundlich equations when the temperature was raised.
Abstract: Liquid-phase adsorption of two dyes on activated carbon was measured in the 283–323 K temperature range. Higher capacity and faster kinetics of adsorption were obtained for a basic dye than for an acidic dye under comparable conditions, probably due to the different ionic natures of the dyes. The equilibrium data for acidic dye could be well described by the Freundlich equation, but the best-fit model for basic dye changed from the Langmuir to the Freundlich equations when the temperature was raised. In addition, the thermodynamic functions were determined. A plot of the fraction of adsorption against (time)1/2 was adopted to describe the adsorption process. It was shown that for an acidic dye the amount of adsorbent used played an important role in the adsorption mechanism.
TL;DR: In this article, the effectiveness of vermiculite extract solutions (VES) as a coagulant and of VES as an adsorbent for removal of color from dye wastewater was investigated.
Abstract: The purpose of this laboratory study was to investigate the effectiveness of vermiculite extract solutions (VES) as a coagulant and of vermiculite as an adsorbent for removal of color from dye wastewater. In coagulation experiments, it was found that VES could be applied to the treatment of dye wastewater with its contents of various cations (e.g. Mg, Fe, Al, Ca, Si etc.) useful for coagulation. Coagulation with VES produced less sludge at a lower coagulant dosage in comparison with to conventional inorganic coagulants. For evaluation of adsorption characteristics of vermiculite on basic dye wastewater, adsorption parameters for Langmuir and Freundlich isotherms were determined. The adsorption of the basic blue dye on vermiculite was found to conform with both isotherms. The adsorption capacity of vermiculite was found to increase with the decreasing particle size and with the increase of temperature and of intensity of agitation. The results indicate that vermiculite is an excellent adsorbent for basic b...
TL;DR: In this article, the impacts of total metal concentration, ionic strength and pH on adsorption capacity are quantified in terms of the Freundlich isotherm equation for isotherms conducted at a single initial pH value.
Journal Article•
TL;DR: In this paper, the results showed that although the pH for maximum efficiency varied slightly with the concentration of Cr(VI) being applied, the most effective pH was in the range 2.5 to 3.0.
Abstract: Batch adsorption trials were used to assess the effectiveness of using activated carbon as a sorbent for the removal of hexavalent chromium from solution. The results show that, although the pH for maximum efficiency varied slightly with the concentration of Cr(VI) being applied, the most effective pH was in the range 2.5 to 3.0. Based on linear regression analysis, the data obtained from the batch studies showed a good compliance with both the Langmuir and the Freundlich equations. The values obtained for the isotherm constants showed that the maximum adsorption capacity, X m , was 145 mg/g. An examination of the adsorption kinetics was also made and an analysis of the data shows that pore diffusion is not the only factor governing the sorption rate.
TL;DR: Perchloroethene (PCE) was determined over a wide concentration range (∼ 1-90,000 μg L−1, or ∼ 0.0007-60% of solubility) for four diverse natural clay-rich aquitards using a batch method as mentioned in this paper.
TL;DR: In this paper, a comparison between the suggested method and precipitation, the most common method used for metals removal, was conducted in parallel, where the main parameters examined in single component systems include initial metal concentration, temperature, and inhibition of the removal process by the existence of soluble constituents.
Abstract: Toxic metals, such as zinc, nickel, and cadmium, can be removed from dilute aqueous solutions by sorption onto nonliving sewage sludge applied as finely dispersed biosorbent particles after sterilization and drying. A comparison between the suggested method and precipitation, the most common method used for metals removal, was conducted in parallel. The main parameters examined in single component systems include initial metal concentration, temperature, and inhibition of the removal process by the existence of soluble constituents. Adsorption isotherms were employed to describe the metals uptake; the Langmuir types were found to fit the experimental data better than the Freundlich ones. Moreover, the desorption of metals from metal-loaded biomass was investigated. The possible selective separation of metals from binary and ternary mixtures by biosorption, which could lead to the recovery and recycling of the removed metals, was also examined by introducing an illustrative selectivity factor. ∗ P...