Freundlich Adsorption Equation Research Articles

Determination of gas phase adsorption isotherms—a simple constant volume method

Single and ternary solute gas phase adsorption isotherms were conducted in this study to evaluate the effectiveness of a simple constant volume method, which was utilized by using Tedlar gas sampling bags as a constant volume batch reactor. For this purpose, gas phase adsorption of toluene, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK) on two types of activated carbons, BPL—bituminous base and OVC—coconut base, were investigated. For the single solute adsorption, the experimental adsorption data were found to be well correlated with Freundlich and Myers adsorption equations. The pore size distribution of adsorbents was found to affect their adsorption capacities; its effect was dependant on the solute concentration. The ternary adsorption experimental isotherms were accurately predicted by using the well-known model, i.e., ideal adsorbed solution theory (IAST).

Influence of the filtration modes on colloid adsorption on the membrane in submerged membrane bioreactor

The influence of three different filtration modes on the colloid adsorption in a submerged membrane bioreactor (SMBR) was evaluated and the feasibility for the characterization of the colloid adsorption on the membrane using a modified Freundlich isothermal adsorption equation q e = X / A = a C e 1 / n was also explored in this study. Under the same operating conditions, the adsorption equations determined in this study were 0.519 C e 1.1623 , 7.416 C e 0.7305 and 2.590 C e 1.0449 for modes of vacuum pump dragging with air back washing, vacuum and suction pumps dragging without air back washing, respectively. Compared with the filtration mode of suction pump or vacuum pump dragging without air back washing, the mode of 10 min vacuum pump dragging with 5 min air back washing could reduce the colloid adsorption. The results also demonstrated the modified Freundlich isothermal adsorption equation, q e = X / A = a C e 1/ n , was applicable to characterize the colloid adsorption on the membrane in the SMBR. Except the characterization of colloid adsorption, this approach also could be used for the optimization of operational conditions, the selection of membrane materials and the evaluation of module configuration, consequently alleviating the membrane fouling in a SMBR.

粘土鉱物へのフッ素吸着挙動に関するＦｒｅｕｎｄｌｉｃｈ吸着式による解析

For the purpose of examining the adsorption behavior of fluorine on clay minerals, the adsorption equilibrium experiments on fluorine were carried out using several clay minerals. Then various analysis and considerations, as listed in the followings, were done on the basis of the experimental results.1) The adsorbed amount of fluorine per unit mass of clay mineral was ranged as Kaolinite >Saponite >Pyrophyllite, Dickite >Montmorillonite.2) When the mass ratio of clay mineral to liquid was constant, the ratio of adsorption equilibrium concentration of fluorine to initial one became small, as the initial concentration of fluorine was lower.3) It was clear that there was less correlation between the BET specific surface area of the clay minerals and the adsorbed amount of fluorine, because the BET specific surface area was ranged as Saponite > Montmorillonite(Mikawa) > Kaolinite > Montmorillonite(Tsukinuno)> Dickite > Pyrophyllite. 4) The cations such as the alkali metal (Na, K), alkaline earth metal (Ca, Mg), iron, silicon and aluminum, which are contained in the clay minerals, are major chemical components which may be bonded with fluorine. However the quantitative correlation between those each content in the clay minerals and the absorbed amount fluorine could not be recognized. 5) For each clay mineral, the fluorine adsorption data can be arranged clearly in every conditions for the mass ratio of clay mineral to liquid. It was clarified the adsorption isotherm of fluorine on the clay minerals were represented using Freundlich's adsorption equation. 6) The correlation equations which took the mass ratio of clay mineral to liquid into consideration were proposed on the adsorption coefficient and index in Freundlich's adsorption equation. Using both those equations and the values of adsorption parameters obtained in this study, it becomes possible to estimate the adsorbed amount of fluorine on the clay minerals and fluorine concentration in liquid phase.

고정층 활성탄 흡착반응기에서 기상 톨루엔의 흡착특성

Adsorption characteristics of toluene vapor, which is one of important source of volatile organic compounds (VOCs), by activated carbon were investigated using a fixed bed adsorption column. The operating parameters such as breakthrough curve, adsorption capacity, mass transfer zone (MTZ), and length of unused bed (LUB) were studied. The experimental results showed that the breakthrough time decreased with increasing inlet toluene concentration and gas flow rate. MTZ and LUB increased with the increase of inlet concentration, gas flow rate, and particle size of activated carbon. The adsorption capacity increased with the increase of inlet toluene concentration, while it decreased with increasing particle size. However, it was kept at constant value regardless of the increase of gas flow rate. Adsorption isotherm of toluene vapor could be represented by the Freundlich adsorption equation fairly well. From the adsorption experiments using some VOC gases such as toluene, xylene, butyl acetate. butanol and acetone, it was also found that the adsorption capacity was higher in the case of gas with higher boiling point and lower vapor pressure.

Removal of 2,4-dichlorophenoxyacetic acid from aqueous solutions by partially characterized organophilic sepiolite: thermodynamic and kinetic calculations

The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on organophilic sepiolite (dodecylammonium sepiolite, DAS) was studied as a function of solution concentration and temperature. The observed adsorption rates were found to be equal to the first-order kinetics. The rate constants were calculated for temperatures ranging between 25 and 40 degrees C at constant concentration. The adsorption energies, E, and adsorption capacity, q(m), for 2,4-D adsorption on organophilic sepiolite was estimated using the Dubinin-Radushkevic equation. Thermodynamic parameters (Deltag(a), Deltah(a), Deltas(a)) were determined by a new approximation from the isotherm of 2,4-D adsorption on DAS. Also, DeltaS(0) and DeltaH(0) values were calculated from the van't Hoff equation. These isotherms were modeled according to the Freundlich and Dubinin-Radushkevic adsorption equations. The amount of adsorption of this herbicide on organophilic sepiolite was found to be dependent on the relative energies of adsorbent-adsorbate, adsorbate-solvent, and adsorbate-adsorbate interaction.

The effects of acid and alkali modification on the adsorption performance of fuller's earth for basic dye

The objective of this work was to prepare modified adsorbents from fuller's earth (FE) by acid and alkali treatment for enhancement cationic dye adsorption. Toluidine blue (TB) was selected as adsorbate for evaluating the adsorption performance of fuller's earth samples, which was affected significantly by acid and alkali modification. The adsorption of TB was studied by visible spectra. The absorption band of the monomer at low loading of TB in FE suspension with respect to its maximum in aqueous solution is red-shifted, which is related to accessibility of dye interlamellar space in the presence of positively charged surface sites. Since all surfaces are negatively charged under experimental conditions, this effect has not been observed in acid- and alkali-treated FE suspensions. It was seen that the adsorption capacity of alkali-treated surface (FEAl) for TB was higher than these of acid-treated adsorbent (FEAc) and FE. Scanning electron micrographs (SEM) and X-ray diffraction (XRD) and fluorescence (XRF) spectra were applied to analyze the structure of the raw and modified FE samples. Absence of any identifiable amount of a crystalline compound in the solid reaction products after acid treatment was confirmed by XRD and SEM, whereas the crystalline form of FEAl was preserved. Experimental data for high-concentration regions were well described by Freundlich and Langmuir adsorption equations. The thermodynamic parameters were estimated for FE, FEAc, and FEAl by using temperature dependence of adsorption equilibrium constants.

Adsorption of nitrosamines in acidic solution by zeolites

Adsorption of N-nitrosopyrrolidine (NPYR) by zeolite NaZSM-5, Hβ and NaZSM-11 in acidic solution with pH of 1 was investigated. The NPYR uptake process obeyed the first-rate Lagegren kinetic equation describing adsorption, and the equilibrium data were fitted to the Langmuir or Freundlich adsorption equation. Zeolite ZSM-5, Hβ and NaZSM-11 possessed a higher adsorption capacity than amorphous silica or ordered mesoporous siliceous SBA-15, implying their potential application for adsorption of nitrosamines in gastric juice to anti-cancer.

Rate Equation of Antisynergic Extraction of Cadmium with D2EHDTPA-TOA

The kinetics of antisynergic extraction of cadmium with D2EHDTPA (di-(2-ethylhexyl)-dithiophosphoric acid)-TOA(trioctylamine) under the condition of interfacial reaction controlling model was investigated by using an improved constant interfacial area stirred cell. The extraction course was composed of several interphase transfer processes (transfer between bulk phase and interfacial phase (or boundary phase)) and several chemical reactions. The extraction rate equation was: r = 1.42 x 10(-7)[Cd2+](0.42)[BHA](O)(0.47)/[B](O)(0.85)[H+](0.21) (mol . m(-2) . s(-1)) The interfacial concentration was associated with the bulk concentration by using Freundlich adsorption equation. The concentration exponents in the extraction rate equation were decided by the two factors of the interfacial chemical reactions and the interphase transfer processes. The physical meaning of the fractional reaction order in the rate equation was analyzed. The bigger the Freundlich power n of a reactant, the more the repulsion exerted by the interfacial layer. The apparent extraction activation energy E = 44.2 kJ . mol(-1), the extraction enthalpy DeltaH = 72.9 kJ . mol(-1). The inconsistency in extraction mechanism due to different interface models was also discussed.

Sorption of241Am by Aspergillus niger spore and hyphae

Abstract Biosorption of 241Am by a fungus A. niger, including the spore and hyphae, was investigated. The preliminary results showed that the adsorption of 241Am by the microorganism was efficient. More than 96% of the total 241Am could be removed from 241Am solutions of 5.6-111 MBq/l (C o) by spore and hyphaeof A. niger, with adsorbed 241Am metal (Q) of 7.2-142.4 MBq/g biomass, and 5.2-106.5 MBq/g, respectively. The biosorption equilibrium was achieved within 1 hour and the optimum pH range was pH 1-3. No obvious effects on 241Am adsorption by the fungus were observed at 10-45 °C, or in solutions containing Au3+ or Ag+, even 2000 times above the 241Am concentration. The 241Am biosorption by the fungus obeys the Freundlich adsorption equation. There was no significant difference between the adsorption behavior of A. nigerspore and hyphae.

Study of the desorption of linuron from soils to water enhanced by the addition of an anionic surfactant to soil–water system

The influence of the addition of the anionic surfactant sodium dodecyl sulphate (SDS) to the soil–water–linuron system in the herbicide desorption from soils with different organic matter (OM) content to water have been studied. SDS was used at critical micelle concentrations (cmc) of 0.75, 1.50, 5 and 10. The adsorption–desorption isotherms of linuron in aqueous medium and in SDS solutions at concentration of 0.75 cmc fitted the Freundlich adsorption equation for all the soils studied. When the SDS concentration was 1.50 cmc only the desorption isotherms for the soils with OM content ⩽5.40% fit this equation and was not fulfilled by any of the soils when the SDS concentration was 5 or 10 cmc. All the desorption isotherms displayed hysteresis, the hysteresis coefficients of the desorption isotherms in SDS solutions always being lower than those of the desorption isotherms in water. The efficiency coefficients, defined as the relationship between the percentages of linuron desorbed in SDS solution and the percentages of linuron desorbed in water, range from 1.02 to 2.41 in the soil with the lowest OM content, and from 1.91 to 17.1 in the soil with the highest OM content. The results obtained indicate the enhancement of linuron desorption by the addition of SDS surfactant to soil–water system. The efficiency of SDS is seen as from surfactant concentrations below the cmc and varies with the surfactant concentration and with the soil OM content.

The Adsorption Properties and Kinetics of Uranium(VI) with a Novel Fibrous and Polymeric Adsorbent Containing Amidoxime Chelating Functional Group from Seawater

The adsorption properties of U(VI) with a new type of fibrous and polymeric adsorbent containing amidoxime chelating functional group (FPAO) from seawater was studied by the method of the static state adsorption at 25 °C. The optimum conditions of the adsorption were determined by investigating the influence of the concentrations of FPAO, U(VI), feed acidity, temperature, and the shape and size of FPAO on the adsorption equilibrium. The maximum adsorption capacity of U(VI) in theory was deduced to be 384.6 mg/g dry FPAO by Langmuir isothermic adsorption equation. Freundlich isothermic adsorption equation, expressed asQ=4.116[U(VI)]0.4293, shows that this process can taken place easily because the adsorption factor 1/n equals to 0.4293, which is in the region of 0.1–0.5. Meanwhile, the adsorption kinetics of U(VI) with FPAO was also studied. The rate equation of the adsorption reaction was determined as −d[U(VI)]/dt=k[U(V)]FPAO]1.70/[H+] and the rate constant of the adsorption reaction k was calculated to be 0.5912 min−1 for pH 6.0 and ionic strength 0.1 mol/l. The activation energy of the adsorption reaction was calculated to be 28.54 kJ/mol. On the basis of the kinetics results, the adsorption mechanism of FPAO on U(VI) was discussed. The diffusion of uranium ion in internal of the adsorbent was thought to be the rate-controlling step.

Assessment of the process of cottonseed oil bleaching in hexane

This work has been initiated to assess the feasibility of bleaching cottonseed oil in miscella as a processing step next to alkali refining in miscella. Alkali refining of cottonseed oil in miscella has several advantages over conventional refining technologies with respect to oil quality, oil losses and process cost. Therefore, the process efficiency of the bleaching of cottonseed oil in presence of hexane (at a volumetric ratio of 1:1), has been studied and compared to that without solvent. The process efficiency has been evaluated according to the decolourization capacity, the oil losses on spent earth, the filtration rate of the oil from the clay and the acidity of the bleached oil as well as its peroxide content. The bleaching in presence of hexane was carried out at 25oC whereas that by conventional bleaching at 110oC. Different clay loads were used in each of the two bleaching techniques and the colour indices of the oils before and after bleaching determined in each case. The results were used to predict Freundlich adsorption equations for the oil pigments in both cases. These equations were then used to predict the colour of the oils obtained by bleaching of refined oils of different grades. The results have shown that oil decolourization is more efficient in presence of solvent when the starting oil is of an acceptable grade and the reverse is true for low grade oils. Also, the possibility of oil oxidation during bleaching is less in presence of solvent. Moreover, the bleaching in miscella has proved two other additional advantages over conventional bleaching. The filtration of oil from clay is much faster in miscella bleaching and the oil losses on spent earth is lower. This will be reflected on the overall process economy.

ADSORPTION OF SULFATE AND NITRATE ON NANO-BALL ALLOPHANE

The adsorption of sulfate and nitrate on two allophane samples, with high and low Si/Al ratio, was found to decrease with increasing pH. The highest adsorption of sulfate and nitrate was obtained at initial pH 3 for both the allophane samples. No adsorption of nitrate was observed at equilibrium pH above 7, however, sulfate was still adsorbed. The strong adsorption of sulfate at pH about below 7 could be attributed to ligand exchange reaction, whereas nitrate was non-specifically adsorbed throughout the pH examined. Allophane sample with low Si/Al ratio or KyP adsorbed more sulfate and nitrate than with the high Si/Al ratio sample or KnP. This is because KyP has high aluminol groups (Al-OH, Al-OH 2 ) per unit mass than KnP. The aluminol groups are believed to be responsible for the adsorption of sulfate and nitrate on nano-ball allophane. Both sulfate and nitrate adsorption results showed a better fitness with the Freundlich adsorption equation with sulfate having a higher k and n values as compared to nitrate which implies that sulfate was strongly adsorbed on nano-ball allophane as compared to nitrate.

Biosorption of 241Am by Rhizopus arrihizus: preliminary investigation and evaluation

The biosorption of 241Am from solution by a fungus— Rhizopus Arrihizus ( R. arrihizus), and the effect of experimental conditions on the adsorption were investigated. The preliminary results showed that the biosorption of 241Am by R. arrihizus is very efficient. An average of more than 99% of the total 241Am was removed by R. arrihizus of 1.3 g/l (dry weight) from 241Am solutions of 5.6–111 MBq/l (44.3–877.2 μg/l) ( C 0), with adsorption capacities ( W) of 4.2–79.4 MBq/g biomass (dry weight) (33.2–627.5 μg/g). The biosorption equilibrium was achieved within 1 h and the optimum pH ranged from 1 to 3. No significant differences in 241Am biosorption were observed at 10–45°C, or in solutions containing Au 3+ or Ag +, even 2000 times above 241Am concentration. The relationship between concentrations and adsorption capacities of 241Am indicated that the 241Am biosorption by R. arrihizus obeys the Freundlich adsorption equation.

SOIL PROPERTIES INFLUENCING THE ADSORPTION AND MOBILITY OF PENCONAZOLE IN VINEYARD SOILS

A study was made of the adsorption and mobility of the fungicide penconazole (1-[2-(2,4-dichlorophenyl)pentyl]-1H-1,2,4-triazole) in 19 vineyard soils with low organic matter contents (0.31-1.98%) and in seven uncropped soils from oak and beech forests or grasslands with higher organic matter contents (3.30-8.24%). Adsorption isotherms were obtained using the batch equilibrium technique, and mobility was studied using soil thin layer chromatography. The aim of this study was to evaluate the adsorption and mobility behavior of this relatively new fungicide in vineyard soils. The adsorption isotherms fit the Freundlich adsorption equation, the Kf values ranged between 10.3 and 151, and the nf values were always lower than unity. The Kf constants were correlated positively with the soil organic matter content. According to the r2 determination coefficients, the organic matter content accounted for 85% of the variance in adsorption when all soils were considered together and for 76% and 36%, respectively, when considering the natural and vineyard soils. In no case was any influence of clay or silt contents on adsorption observed. According to the Rf values obtained, penconazole is immobile in 8% of soils and slightly mobile in 92% of soils. Adsorption of the fungicide by individual soil components, clay minerals and humic acid, confirms the importance of the organic matter fraction as the only soil parameter that affects adsorption. The results obtained indicate that vertical leaching of penconazole is low. The fungicide may, however, cause surface pollution of the soil because of its accumulation. If its degradation rate is low, this accumulation may lead to the pollution of surface water through runoff of the sorbed pesticide.

Adsorption and mobility of linuron in soils as influenced by soil properties, organic amendments, and surfactants.

Adsorption and mobility of the herbicide linuron (3-3, 4-dichlorophenyl-1-methoxy-1-methylurea) in 35 irrigated soils with organic matter (OM) contents in the 0.43-2.59% range and in four natural soils with OM contents in the 4.16-11.69% range were studied using the batch equilibration technique. The adsorption isotherms were found to conform to the Freundlich adsorption equation. The Freundlich constant, K, and the distribution coefficient, K(d), were seen to be highly significantly correlated (p < 0.001) with the OM content when all soils or only those with an OM content above 2% were considered. There was also a significant correlation of K and K(d) with the OM content (p < 0.05) and of K(d) with the clay and silt plus clay contents (p < 0.1) when the soils with a OM content below 2% were considered. On the basis of the R(f)() values obtained by soil TLC, the pesticide was found to be slightly mobile in 77% and moderately mobile in 23% of the soils studied. The results of the leaching of linuron in soil columns unmodified and modified with two organic agricultural amendments, a city refuse compost, and two surfactants (one of them cationic and the other anionic) revealed that the leaching rate and the mass transfer of the herbicide to water were affected, increasing or decreasing according to the characteristics of the amendments and the doses added. These results also point to the usefulness of selected organic materials and surfactants in the development of physicochemical methods for preventing the pollution of soils, sediments and aquifers by hydrophobic pesticides.

Sodium dodecyl sulphate-enhanced desorption of atrazine: Effect of surfactant concentration and of organic matter content of soils

A study was made of the adsorption–desorption of atrazine in aqueous medium in five soils with organic matter (OM) contents in the range 1.4–10.3% and also of the desorption of the herbicide in aqueous solutions of the anionic surfactant sodium dodecyl sulphate (SDS) at critical micelle concentrations (cmc) of 0.75, 1.50, 5 and 10. The adsorption and desorption isotherms in water together with the desorption isotherms in SDS solutions with concentrations of 0.75 and 1.50 cmc fit the Freundlich adsorption equation. All the desorption isotherms displayed hysteresis. The increase or reduction in hysteresis of the desorption isotherms in SDS solutions with respect to those of desorption in water depend on the SDS concentration and on the OM content of the soils. Below the cmc, SDS only increases the desorption of atrazine in the soil with the highest OM content (10.3%). However, above the cmc (5 and 10 cmc) the desorption of atrazine increases in all soils, the efficiency of desorption increasing with the OM content of the soils.

Removal of 2, 4‐D from aqueous solution by the adsorbents from spent bleaching earth

The removal of 2, 4‐D (2, 4‐ dichlorophenoxyacetic acid) from aqueous solutions by activated spent bleaching earths (SBE) was studied at 20 °C. Experiments were performed as a function of time, initial concentration, dose and particle size of the adsorbent. The Langmuir and Freundlich adsorption equations were fitted by the adsorption data obtained. The values of Langmuir and Freundlich constants were determined. The adsorption kinetic was found to follow Lagergren equation. Both the boundary layer and intraparticle diffusion played important roles in the adsorption rate of 2, 4‐D. As the size of the adsorbent increased, the time to reach equilibrium increased but adsorption capacity decreased.

Sorption Studies of 2,4-D on Selected Soils

Adsorption/desorption characteristics of the herbicide 2,4-D on various types of soils were investigated. Batch equilibrium techniques were used in the laboratory experiments. Data were fitted to the linear and Freundlich sorption equations. K and Kf values ranged between 0.32–1.89 L- 1 mg and 2.6 × 10-3 – 7.4 mg kg- 1, respectively. Results showed that both for linear and Freundlich adsorption equations, for all soils, K and Kf were correlated to the organic matter content (r = 0.87 and r = 0.66, respectively). Adsorption was also positively correlated with silt and clay content of soils (r = 0.53) and negatively correlated with sand content.

Effect of flow rate on the adsorption and desorption of glyphosate, simazine and atrazine in columns of sandy soils

SummaryAdsorption and desorption of the herbicides glyphosate [N‐phosphonomethyl‐aminoaceticacid], simazine [6‐chloro‐N,N′‐diethyl‐1,3,5‐triazine‐2,4‐diamine] and atrazine [6‐chloro‐N2‐ethyl‐N4‐isopropyl‐1,3,5‐triazine‐2,4‐diamine] were studied in four sandy soils from Western Australia. Distribution coefficients (Kds) were calculated from breakthrough curves (BTCs) resulting from leaching step changes in concentrations through small saturated columns of soil at flow rates ranging from 0.3 to 30 m day–1. A comparison was made with Kds obtained after batch equilibrating solutions of the herbicides with the same soils. The Kds of herbicides in soils decreased with increasing flow rate and most strongly for glyphosate in soils rich in clay content. Resulting increases in mobility of about 40–50% were estimated for simazine and atrazine and &gt; 50% for glyphosate at flow rates of 3 m day–1. Adsorption and desorption rates were estimated by fitting numerically simulated BTCs to experimental BTCs. Best fits were obtained with a time‐dependent Freundlich adsorption equation. The resulting coefficient for time dependency in the equation suggests that the rates of adsorption and desorption are controlled mainly by diffusion in an adsorbing layer on or in soil particles.