Linear Adsorption Model Research Articles

Evaluating the Adsorption Potential of Alachlor and Its Subsequent Removal from Soils via Activated Carbon

ABSTRACTAlachlor, a globally used aniline herbicide, has great agronomic interest for controlling the development of broadleaved weeds and grasses. This research aspires to evaluate the sorption attributes of Alachlor through batch equilibrium method and its successive removal through biomass based activated carbon prepared from Sawdust (Cedrus deodara). Six soil samples were collected from selected regions of Pakistan to assess the adsorption and removal phenomena. Adsorption capacity for Alachlor varied in soils depending upon their physicochemical properties. Adsorption coefficient (Kd) values ranged from 12 to 31 µg ml−1 with the highest Kd value observed in soil sample with highest organic content (1.4%) and least pH (5.62). The Gibbs free energy values ranged from −17 to −20 kJ mol−1 proposing physio-sorption and exothermic interaction with soils. Values of R2 (0.96–0.99) exhibited the best fit to linear adsorption model. Adsorption coefficient displayed a negative correlation (r = −0.97) with soil pH and positive correlation with organic matter (r = 0.87). The effect of contact time and pesticide concentration on the removal efficiency by activated carbon was investigated. The highest removal percentages observed through activated carbon were 66% and 64% at concentrations of 5 and 7.5 ppm respectively. Activated carbon from sawdust (Cedrus deodara) was investigated as a suitable adsorbent for the removal of Alachor from selected soils. Biomass based activated carbon can prove to be an effective and a sustainable mean to remove pesticides from soil.

Evaluation of the Foamability Potential of a Novel Biosurfactant Using the Solution to Advective-Diffusive Transport Model in Porous Media With a Linear Adsorption Trend

While geological sequestration of anthropogenic carbon dioxide is a technically and economically viable option for reducing emissions to the level required to avoid the predicted 2 degrees Celsius increase of atmospheric temperature by the end of this century, efficient sequestration planning is vital for the achievement of this goal.The petroleum industry has used conventional surfactants in enhance oil recovery projects aimed at prolonging the life span of a field, thereby increasing ultimate reserves. Notable among these is the use of surfactants for injected gas relative mobility control. Therefore, the potential for carbon dioxide mobility control in saline aquifers using surfactant alternating gas injection is huge, given the rich experience that can be tapped from the petroleum industry practice.Considering the expected surfactant loses in surfactant-enhanced geological sequestration similar to that encountered in the petroleum industry, this paper has used the analytical solution to advective diffusive equation that exists in the literature with a linear adsorption model where, adsorption has been used to predict trends in minimum pressure drop required for foam generation. The greatest utility of this work lies in the fact that the analytical solution is related a linear adsorption model related to a novel surfactant found from biological and hydrocarbon sources of geologic origin. This paper, therefore, extends the work of linear adsorption models for this novel surfactant aimed at exploring improved oil recovery potentials; in addition to exploring its potential for efficient geological carbon storage in saline aquifers.

Nonlinear Impedance Spectra Analysis of CO Poisoning on PEM Fuel Cell Performance

In polymer electrolyte membrane (PEM) fuel cells, hydrogen is the preferred fuel with air or oxygen as oxidant. However, many a time, the presence of carbon monoxide (CO), even at low ppm levels, inhibits the hydrogen oxidation reaction [1, 2]. In this work, we describe nonlinear impedance spectra analysis (NLEIS) of CO poisoning in PEM fuel cells. In NLEIS method, large amplitude perturbations are employed and the resulting signal have significant higher harmonic components, which, if acquired, can provide additional information about the system under investigation. Here we illustrate a NLEIS methodology in which governing equations were solved without linearization, using numerical method. The response signal was subjected to fast Fourier transform (FFT) to extract magnitude and phase at fundamental and higher harmonics. In this study, linear adsorption model, in which a CO molecule occupies one adsorption site was employed to generate NLEIS data [3]. Figure 1 shows the concentration effect on NLEIS results, simulated under galvanostatic mode employing large (Iac = 200 mA) amplitude perturbation at Idc =200 mA.cm-2 . The results show that the CO poisoning effects are more easily distinguishable at higher harmonics, when compared to the response at fundamental frequency. Key words: Nonlinear EIS, PEM fuel cell, CO poisoning, linear adsorption model

Nonlinear Impedance Spectra Analysis of CO Poisoning on PEM Fuel Cell Performance

CO poisoning in PEM fuel cells was analyzed using nonlinear electrochemical impedance spectroscopy (NLEIS). In this methodology, the governing equations were solved without linearization, using numerical simulations. The response signal was subjected to fast Fourier transform to extract the magnitude and the phase at fundamental and higher harmonics. Linear adsorption model (Springer et. al. (8)) approach was employed to model CO adsorption. The effect of CO concentration in the feed stream, the input signal amplitude and dc bias on NLEIS response was examined. The results show that, compared to the response at fundamental frequency, higher harmonic response enable easier identification of CO poisoning effects.

Functionalized MgO, CeO2 and ZnO nanoparticles with humic acid for the study of nitrate adsorption efficiency from water

In this study, the removal of nitrate using ZnO, MgO, and CeO2 nanoparticles (NPs) modified by humic acid from water was tested. Nanoparticles were modified by humic acid using the microwave-assisted technique and then modified ZnO (Zn–H), modified MgO (Mg–H), and modified CeO2 (Ce–H) were characterized through SEM, EDX, FTIR, and XRD analysis. Several important parameters influencing the removal of nitrate such as contact time, pH, adsorbent dosage and temperature were explored systematically by batch experiments. Isotherm studies were set up with the following optimum conditions: pH = 5, adsorbent concentration of 1 g L−1, 180 min and 25 °C. The results revealed that the adsorption were best fitted to pseudo-second order and simple Elovich kinetics models. Langmuir, Freundlich and linear adsorption models were fitted to describe adsorption isotherms and constants. The isotherm analysis indicated that the adsorption data can be represented by both Freundlich and linear isotherm models. The maximum adsorption capacity (qm) was obtained at 55.1, 74.2 and 75.8 mg g−1 for Zn–H, Ce–H, and Mg–H, respectively. The thermodynamic parameters such as free energy, enthalpy and entropy of adsorption were obtained. From the thermodynamic parameters, it is suggested that the adsorption of nitrate on modified NPs (MNPs) followed the exothermic and spontaneous processes. The obtained results showed that the MNPs were efficient adsorbents for removing nitrate from aqueous media.

A fast and easy approach to the simulation of binary mixtures sorption kinetics

Diffusivity of a component in a binary mixture is affected by the presence of a second component. The knowledge of the influence on each other component diffusivity is very useful for the prediction of sorption kinetics of binary mixtures. In this work kinetic studies of Cr(VI) and Cu(II) binary mixtures sorption onto exhausted coffee encapsulated in calcium alginate beads were carried out in both bench and pilot scale experiments. The spectroscopic analysis evidenced the complexity of the process since different mechanisms such as adsorption, redox reaction and ion exchange are involved. Experimental data were fitted to the Linear Adsorption Model (LAM). An empirical quadratic model was developed to estimate LAM parameters (De) and α=Cf/(Ci−Cf) as a function of the initial concentration of metals in the mixture. The empirical model developed enables to estimate the LAM parameters (De and α) of metal ions binary mixtures provided that the initial concentration of the metal ions is included in the range of concentrations studied. The estimated parameters introduced in LAM equation allow simulating the corresponding binary mixtures sorption kinetics. This study constitutes a fast and easy approach to the modelling of sorption kinetics of complex systems in which different processes take place simultaneously.

Vancomycin sorption on activated sludge Gram+ bacteria rather than on EPS; 3D Confocal Laser Scanning Microscopy time-lapse imaging

Antibiotics-bacteria interactions depend on antibiotic concentration at the scale of bacteria. This study investigates how vancomycin penetrates into activated sludge flocs and can be sorbed on the bacteria and extracellular polymeric substances (EPS). The 3D structure of flocs was imaged using EPS autofluorescence. The green fluorescent BODIPY® FL vancomycin was introduced in a microscopic chamber containing activated sludge and penetration of vancomycin into the flocs by diffusion was observed using time-lapse microscopy. The penetration depended on the floc structure, as long and large pores could go through the whole flocs making preferential path. The antibiotic concentration into the flocs was also found to depend on the sorption rate. BODIPY® FL vancomycin was found to bind preferentially into Gram+ bacteria than on EPS. The vancomycin adsorption constant on bacteria according to the linear adsorption model, Kdbacteria was estimated to be 5 times higher (SD 2.6) than the adsorption constant on EPS KdEPS. These results suggest that antibiotic removal by sorption into wastewater treatment plants could change according to the amount of bacteria in the sludge. Moreover, antibiotic concentration at the scale of bacteria could be significantly higher than the concentration in the bulk solution and this should be taken into account when studying antibiotic activity or biodegradation.

Biosorption of Cd(II) and Cs(I) from aqueous solution by live and dead cells of Saccharomyces carlsbergensis PTCC 5051

ABSTRACTThe biosorption characteristics of Cd(II) and Cs(I) using live and dead cells of Saccharomyces carlsbergensis PTCC 5051 as biosorbents have been investigated in the present research. The influence of different experimental parameters such as initial pH (pHi), shaking rate, sorption time and initial metal concentration was evaluated. The optimum pH was obtained as 4 for Cd(II) and 7 for Cs(I). The experimental adsorption data were fitted to the Langmuir linear equation adsorption model. The highest metal uptake values of 0.593 and 0.473 mmol g−1 were calculated for Cd(II) and Cs(I), respectively. The results of Fourier transform infrared analysis suggested the involvement of amine, carboxyl and hydroxyl groups during the biosorption process and also indicated that more functional groups were involved in the biosorption process of live adsorbents, compared with those linked to dead biomass. The results showed that the biomass of S. carlsbergensis PTCC 5051 is a suitable biosorbent for the removal of Cd(II) and Cs(I) from the aqueous solutions.

Polyphenols and β-glucan interactions through linear adsorption models

The aim of this work was to obtain information about interactions between polyphenols and β- glucan through linear adsorption equilibrium models. Polyphenolic compounds can interact with various food ingredients such as carbohydrates, proteins and lipids and this interactions can affect polyphenol bioactivities. Interactions can be studied through adsorption process at constant temperature and adsorption isotherms can be obtained. In this work the interactions between polyphenols like gallic acid, cyanidin-3- galactoside and cyanidin-3-glucoside and β- glucan as natural dietary fiber were studied through Freundlich's, Langmuir's, Dubinin- Radushkevich's, Tempkin's and Hill's models. Adsorption was carried out through model solutions of different concentrations of polyphenols and β-glucan in 16 hours at 25°C. After the adsorption, unadsorbed polyphenols were separated from adsorbed polyphenols by ultrafiltration. Concentration of unadsorbed polyphenols were determined by spectrophotometric Folin-Ciocalteu method for gallic acid and pH differential method for cyanidin-3-galactoside and cyanidin-3- glucoside. The results of adsorption isotherm parameters showed that adsorption between all polyphenols and β-glucan were physical and all interactions were favorized. Gallic acid showed the highest maximum adsorption capacity onto β- glucan. This study showed that information about interactions between polyphenols and dietary fibers can be obtained through the linear adsorption equilibrium isotherms.

A natural dye in water-based drilling fluids: Swelling inhibitive characteristic and side effects

The development of eco-friendly shale inhibitors is still an area which has attracted a lot of attention in the drilling industry. Henna extract is a natural dye which has recently shown considerable inhibition and weak deflocculation properties in clay-water system. This study aims to investigate swelling inhibitive feature and side effects of Henna extract in water-based drilling fluids (WBDFs). It was carried out through extensive experiments including adsorption measurements on shale by batch equilibrium, inhibition evaluation by dynamic linear swelling and cuttings dispersion, wettability alteration via contact angle measurements, compatibility by rheological properties determinations and fluid loss measurements, and lubricity. Both in natural pH and adjusted pH to 9, Linear adsorption model was more suitable for anticipating the adsorption behavior of Henna extract on the given shale sample. The results of the linear swelling and cuttings dispersion tests demonstrated that Henna extract in drilling fluid formulations diminished the swelling and dispersion characteristics of the addressed shale sample. Moreover, contact angle measurements showed that Henna extract expanded the hydrophobicity of shale formations, preventing and promoting water adsorption and shale stability respectively. This issue definitely introduces wettability alteration as a mechanism for shale stability by Henna extract. Compatibility determinations additionally uncovered that Henna extract is compatible with common WBDFs additives. As indicated by the lubricity tests, Henna extract enhanced the lubricity of WBDFs, a finding which can be of an incredible significance in directional drilling. Among others, advantages such as environmental friendliness, low cost, accessibility, and the counter corrosion property make the applicability of Henna extract in WBDFs profoundly suitable.

A second-order nonlinear model of monolayer adsorption in refractometric chemical sensors and biosensors case of equilibrium fluctuations

In adsorption-based chemical and biological refractometric sensors the dependence of the refractive index of the sensing area on the number of adsorbed particles is used for detection and quantification of analytes. We perform stochastic analysis of equilibrium fluctuations of the adsorbed particles number for monolayer adsorption using a nonlinear second-order model. We derive an analytical expression for the power spectral density (PSD) of the refractive index change fluctuations. Our theory is applicable to sensors operating in closed volume systems with spatially uniform analyte concentration. Our analysis of fluctuations in a benzene sensor shows a significant difference between the PSD according to the derived expression and the PSD obtained by the linear adsorption model, especially for very low amounts of analyte. The developed theory is valid in a wider range of pressures and temperatures. Since signal fluctuations determine the detection limit, the presented theoretical model is applicable as a tool for the design, optimization and characterization of practical adsorption-based refractometric sensors.

Influence of pH and ionic strength on Cd, Cu and Pb removal from water by adsorption in Na-bentonite

This article presents a study on cadmium, copper and lead removal by means of adsorption in a natural Na-bentonite. Influence of pH and ionic strength on clay fabric and its role on cation removal are analyzed by means of Zeta potential and sedimentation tests. Batch adsorption and kinetics tests were carried out to quantify the adsorption capacity of the bentonite at monospecies and multispecies conditions, where ion competition was analyzed. Experimental results show that ionic strength strongly affects clay structure and cadmium removal, but has little influence on lead and copper removal. Adsorption kinetics was fast in all cases, which was mostly related to reaction kinetics than to diffusion kinetics. Cadmium adsorption can be explained by linear adsorption models, while copper, lead and the multispecies tests showed good agreement with both the linear and Freundlich models within the tested concentration range. The results confirm that tested Na-bentonite possesses a high capacity for the removal of Cd, Cu and Pb.

Effect of CO Poisoning of PEM Fuel Cell Anode on Impedance Spectra- Simulations

In low temperature hydrogen based fuel cells such as proton exchange membrane (PEM) fuel cells, CO poisoning of the anode catalyst is a critical issue. The effects of poisoning on the performance of the cell are commonly investigated using electrochemical impedance spectroscopy (EIS) and other techniques. In the galvanostatic mode of operation, Wagner and Schulze experimentally measured the anode potential and reported that it increases during progressive anode CO poisoning [1]. Wagner and Gulzow measured the impedance of the complete fuel cell during CO poisoning and showed that the magnitude of the impedance, particularly at low frequencies, increased with the CO concentration [2]. On the other hand, reaction mechanisms have been proposed by Springer et al to model the PEM fuel cell anode, with and without poisoning. However, there are no reports which show EIS data of anode with CO poisoning using the proposed reaction mechanism models. A comparison of the simulated spectra with experimental results would facilitate validating the mechanism. In this work, we simulate chrono-potentiometric data and EIS spectra of the hydrogen oxidation reaction occurring in the half cell, under galvanostatic mode. Two anode kinetic models were chosen from literature [3, 4]. The two models differ in the adsorption mechanism of CO on the anode (linear and bridge). Using the kinetic model proposed by Springer and his coworkers, the steady state polarization curves, transient potential curves and galvanostatic EIS at different concentrations of CO in the feed gas are generated by simulations. The linear adsorption model was employed in the first set of results. The steady state polarization curves predict that the poisoning effect is prominent only for CO concentrations of greater than 10 ppm in the feed gas. At 200 mA/cm2current density, the anode potential increases due to CO poisoning and at 100 ppm CO concentration it reaches a steady state value of 50 mV. At higher CO concentrations the steady state anode potentials are higher. The transient potentials (normalized) at 0, 30, 50 and 100 ppm concentration of CO in the inlet stream are shown in Fig. a, and the results compare well with experimental results in literature. It is seen that the potential stabilizes faster at higher concentration of CO. The EIS obtained after stabilization of the potential corresponds to that when the poisoning of the electrode is under steady state conditions. The spectra simulated on the anode fed with pure hydrogen gas (0 ppm CO) and under steady state poisoned condition, for 50 and 100ppm concentration of CO is shown in Fig. b. These are obtained under galvanostatic conditions with 200 mA/cm2current density. The inset shows the complete spectrum at 100 ppm CO. The value of impedance increases from a few mΩ to the order of Ω due to the CO poisoning of the anode. The patterns observed are at variance with the experimental results reported. This indicates that either the kinetic parameters are not representative or the model itself may have to be changed. Normally, EIS data is analyzed with electrical equivalent circuits, implicitly assuming that the system has been linear, causal and stable. However, during the transient state of poisoning, when most of the data is acquired experimentally, the stability assumption is violated. Using numerical methods, we simulate the spectra duringthe progression of the poisoning process, i.e. under transient conditions, for various CO concentrations and current densities. The change in dc potential with time results in instabilities in the spectra, which are accounted for in numerically simulations. The spectra obtained using the two anode kinetic models in literature are also compared. REFERENCES: [1] N. Wagner, M. Schulze, Electrochimica Acta 48, 3899-3907 (2003) [2] N. Wagner, E. Gulzow, Journal of Power Sources 127, 341-347 (2004) [3] T.E Springer, T. Rockward, T.A. Zawodzinski, S. Gottesfeld, Journal of the Electrochemical Society, 148, A11-A23 (2001) [4] G. A.Camara, E.A Ticianelli, S Mukherjee, S. J. Lee, J.McBreen, Jounal of the Electrochemical Society, 149, A748-A753 (2002) Figure 1

Effect of nonlinear sorption on multispecies radionuclide transport in a coupled fracture-matrix system with variable fracture aperture: a numerical study

A one-dimensional numerical analysis on multispecies radionuclide transport in a single-horizontal coupled fracture-matrix system has been performed. Analysis considering linear and nonlinear adsorption cases with linear, Langmuir, and Freundlich adsorption models has been carried out. The results indicate that there is a significant change in the spatial distribution of radionuclides in a coupled fracture-matrix system when a nonlinear adsorption isotherm is considered as compared to the simplified linear sorption isotherm. Sensitivity analysis of Langmuir constant and Freundlich exponent has been performed, and the numerical results indicate that the behavior of radionuclide transport is strongly influenced by these nonlinear sorption isotherm parameters. In addition, an attempt has been made to consider the variation of fracture aperture thickness along its flow direction by introducing logarithmic distribution. A clear distinction in the spatial distribution of radionuclide concentration was observed when variable fracture aperture is considered as opposed to the conventional parallel plate model with a constant fracture aperture thickness. Further, the results suggest that there is an enhanced retardation of radionuclides within the high permeable fracture with varying fracture aperture.

Thermodynamics of Cadmium Sorption on Different Soils of West Bengal, India

A sorption study was conducted on different soils collected from five agroecological zones of West Bengal, India, to understand the soil environmental behavior and fate of cadmium. For this purpose batch adsorption experiments were carried out at the native soil pH and at three different temperatures (25°C, 35°C, and 45°C). The adsorption data fitted by a linear least squares technique to the different sorption isotherms. Most data obtained give the good fit to both Freundlich and modified Langmuir isotherms, but they are not consistent with the linear Langmuir adsorption model. Thermodynamic parameters, namely, thermodynamics equilibrium constant at a particular temperature T (K T 0), Gibbs free energy at a particular temperature T (ΔG T 0), and change of enthalpy (ΔH 0) and change of entropy at temperature T (ΔS T 0), were also determined by applying sorption value and concentrations of Cd in equilibrium solution within the temperature range. The thermodynamic parameters revealed that Cd sorption increases as the values of K T 0, ΔG T 0, ΔH 0, and ΔS T 0 were increased on reaction temperatures. The spontaneous sorption reaction can be concluded due to high values of ΔG T 0. The positive values of ΔH 0 indicated that the Cd sorption is an endothermic one. Under these present conditions, the soil and its components possibly supply a number of sites having different adsorption energies for cadmium sorption.

Study on the Competitive Adsorption of Dimethoate with Multiple Pesticides and Heavy Metals Based on Fractional Factorial Design

In order to reveal the composite contaminations characteristic of dimethoate adsorption onto the surficial sediments, the competitive adsorption of dimethoate in pesticide (dimethoate, metalaxyl, atrazine, malathion, and prometryn)/heavy metals (copper, zinc, lead, cadmium and nickel) system is investigated. A 210-5 fractional factorial design method at resolution IV and a multiple linear regression adsorption model are used to identify the main effects and interactions of above ten pollutions. The adsorption amount of dimethoate surficial sediments is set as the dependent variable, and the main effects and second-order interactions of ten pollutions are set as independent variables. Thus, a multiple linear regression model of dimethoate adsorption is screened and established. The results of model show that the main effects of Cd, malathion and prometryn performed a significant antagonistic effect (α=0.05) on the adsorption of dimethoate onto the sediment (competitive adsorption effects), and the order is: prometryn (-0.0925) > Cd (-0.0878) > malathion (-0.0827); while heavy metal Zn performed a significant synergy effect on the adsorption of dimethoate. The second-order interaction effects of Zn*prometryne, Pb*atrazine and Pb*atrazine has a significant antagonistic impact on the adsorption of dimethoate in sediments, which is in a sequence of Zn*prometryne (-0.0967) > Pb*atrazine (-0.0945) > Cd*atrazine (-0.0922). Moreover, according to the rate of contributions of main effects and second-order interaction effects in composite contaminations system, we can also estimate and definite the pollution levels of target pollutant.

Separation of epigallocatechin gallate from tea polyphenol by simulated moving bed chromatography

(−)-Epigallocatechin gallate (EGCG) was purified from tea polyphenol by a two-step simulated moving bed (SMB) chromatographic process with C18-bonded silica gel as stationary phase and a mixture of methanol and water as mobile phase, removing the more retained components firstly and the less retained components secondly. An open-loop 3-zone SMB approach was used, a gradient of solvent strength in zones I and II was formed by different methanol dosage in purge and desorbent solutions and pre-equilibration was reached by the elution at the end of zone III. Under the approximation including linear adsorption and ideal chromatographic model, the operating parameters of the simulated moving bed were selected according to the “triangle theory”. In the first SMB separation, a solution of tea polyphenol with 55.5% purity of EGCG was used for feeding and a raffinate solution with 92.2% purity and 99.7% recovery of EGCG was obtained. The raffinate solution was concentrated for feeding in the second SMB separation and an extract solution with 97.8% purity and 99.8% recovery of EGCG was obtained.

Removal of methyl orange from aqueous solution by uncalcined and calcined MgNiAl layered double hydroxides (LDHs)

In this study, both uncalcined (MgNiAl–CO3) and calcined (MgNiAl–C) hydrotalcites were used in the adsorption of methyl orange (MO) from aqueous solution as an anionic dye in a batch system. Various conditions such as initial dye concentration, adsorbent dosage, contact time, solution pH, and temperature were investigated. The adsorption kinetics was studied using classic equations of pseudo-first-order, -second-order and intraparticle diffusion models. The dynamical data fit well with the pseudo-second-order kinetic model. The positive value of the changes in enthalpy (ΔH°), the negative value of Gibbs free energy (ΔG°), showed that the adsorption is endothermic and spontaneous for all the studied temperatures. The equilibrium adsorption data were analyzed using three non linear adsorption models: Langmuir, Freundlich and Redlich–Peterson. The results showed that Langmuir and Redlich–Peterson isotherms fit the experimental results very well with high correlation coefficients. The Langmuir isotherm model exhibited a maximum adsorption capacity qmax of 375mg/g for the calcined MgNiAl–C. This result is of practical interest, with respect to the selection of sorbents, to optimize aquatic environment remediation technologies.

Sorption of a branched nonylphenol and perfluorooctanoic acid on Yangtze River sediments and their model components

Many metabolites of organic surfactants such as nonylphenol (NP) and perfluorooctanoic acid (PFOA) are ubiquitously found in the environment and are toxic if not sorbed on soils and sediments. In this study, we quantified the sorption of the NP isomer with the highest endocrine activity, [4-(1-ethyl-1,3-dimethylpentyl) phenol] (NP111), and that of PFOA on Yangtze River sediments and its model components illite, goethite and natural organic matter. The sorption experiments were performed with (14)C-labeled NP111 and PFOA by batch or dialysis techniques. The results showed that the sorption isotherms of NP111 and PFOA on the sediments were fitted well by the linear adsorption model. The sorption of NP111 depended largely on the organic carbon content of the sediments. The K(OC) values of NP111 ranged from 6 × 10(3) to 1.1 × 10(4) L kg(-1) indicating that hydrophobic interaction between NP and organic carbon is the main mechanism of sorption. The sorption of NP111 on illite was poor. The sorption of PFOA on the sediments was significantly lower than that of NP111. The affinity of PFOA to adsorb on goethite was slightly higher than on the sediments, but was moderate on illite and negligible on a reference natural organic matter. Principal axis component analysis confirmed that various sediment parameters control the binding of PFOA. This analysis grouped the respective K(d) values to the contents of black carbon, iron oxides and clay, and, hence, to the specific surface area of the sediments.

Alginate encapsulated pillared clays: removal of a neutral/anionic biocide (pentachlorophenol) and a cationic dye (safranine) from aqueous solutions

As a result of the cross-linking process between sodium alginate, Aluminium pillared clay (Al-Mont-PILC) or surfactant-modified pillared clay (CTAB-Al-Mont-PILC) and divalent cation (Ca 2+), gel-like beads were obtained under different ratios of PILCs vs. alginate. Experimental ratios (pillared clay/alginate; w/w) increased to a maximum of 3.5 to 4. The results of SEM analysis revealed that surface morphology changes by introducing Al-Mont-PILC and CTAB-Al-Mont-PILC. Structural modifications were evaluated using FTIR and thermal analysis. In agreement with previous works the pseudo-second order model equation fit well with the kinetics data. Diffusion coefficients were calculated using the Linear Adsorption Model; the D eff obtained in this study (3-7 10 −6 cm 2/s) are within the ranges reported in other works on inorganic pollutants or phenol diffusion in biopolymers. Adsorption isotherms of pentachlorophenol and safranine were analyzed using non-linear regression technique. Langmuir isotherms fit well with the results obtained for the sorption of safranine whereas the Freundlich isotherms was more in accordance with the pentachlorophenol sorption. A decrease of 35 to 40% in sorption capacity was observed for pentachlorophenol when the initial pH increased from 5.3 to 8. Modification of the biopolymers by introduction of pillared clays resulted in an enhancement of the adsorption capacity.