Linear Langmuir Research Articles

Phosphorus Adsorption Characteristics of Natural Zeolite: A Laboratory Study

Zeolites are hydrated alumino-silicates of alkali and alkaline earth metals with high ion exchange capacity. If applied along with phosphate fertilizers, these reduces the P fixation time and increase the availability of phosphorus. Thus, the present study was carried to evaluate the potential of zeolite to adsorb phosphorus through batch experiments using graded concentrations of P (0 to 50 mg L−1). It was observed that with the increase in the initial concentration from 1 to 50 mg L−1, the equilibrium concentration increased from 0.55 to 38.8 mg L−1 in natural zeolite. Similarly, the amount of P adsorbed increased from 0.05 to 1.12 mg/g of natural zeolite. The adsorption was good and fitting well in linear Freundlich and Langmuir adsorption isotherm with r2 = 0.99 and 0.98, respectively. As zeolite is environment friendly and cost-effective, its application can enhance phosphorus use efficiency by reducing its fixation in soils.

Modeling studies for adsorption of phenol and co-pollutants onto granular activated carbon prepared from olive oil industrial waste

Granular activated carbon (OSAC) which was derived from olive oil industrial solid waste was chemically activated with different concentrations of phosphoric acid. OSAC-materials were evaluated for their ability to remove phenol from aqueous solution in a batch technique. Adsorption isotherms were determined and modeled with five linear Langmuir forms, namely the Freundlich, Elovich, Temkin, Kiselev and Hill-de Boer models. The experimental data for the adsorption of phenol onto OSAM-materials were fitted well with the Langmuir-1 and 2, Freundlich, Kiselev and Hill-de Boer models. Adsorption was carried out on energetically different sites as localized monolayer adsorption and was an exothermic process. The uptake of phenol onto OSAC increased in the following order: OSAC-80%> OSAC-70%> OSAC-60%; the maximum adsorption capacities of phenol were found to be 114.416, 125.628 and 262.467 mg/g onto OSAC-60%, OSAC-70% and OSAC-80%, respectively. On the other hand, OSAC-80% was used as a good adsorbent for the removal of phenol and Cd2+ as co-pollutants from waste aqueous solutions. 80.25% of phenol and 50.66% of Cd2+ can be simultaneously removed by OSAC-80%.

Thermodynamics and sorption characteristics of Zn(II) onto natural and chemically modified zeolites for agricultural and environmental using

Zeolites with high porous and cation exchange capacity have been widely used for agricultural and environmental purposes. This study was conducted to assess the thermodynamics and sorption characteristics of chemically modified zeolite (CMZ) from obtained natural zeolite (NZ), and to compare its properties. At first step of the sorption experiment, effects of pH, slurry concentration, stirring time, and heat on Zn removal were determined. Linear Langmuir isotherm was well fitted to data, and maximum sorption capacities (q max) were calculated as 20.87 and 33.44 mg/g for NZ and CMZ, respectively. Dubinin-Redushkevich (D-R) isotherm showed that the adsorption process was probably controlled by chemical ion-exchange mechanism. The solubility of zinc DTPA should be so directly related to the model of D-R model. Therefore, zeolites can be used as carrier Zn in soils with insufficient zinc arid and semiarid regions. Enthalpy (ΔH°) and entropy (ΔS°) values were positive. The change values of Gibbs free energy (ΔG°) illustrated that the sorption of Zn ions onto zeolites was feasible and spontaneous. From the obtained results, it could be concluded that chemical modification increased q max value of NZ, and the findings indicate clearly the possibility of using NZ and CMZ as Zn carrier in agricultural and also environmental treatments.

Sorption of uranium(VI) by La-Al-carboxymethyl konjac glucomannan microsphere sorbent

The microsphere of carboxymethyl konjac glucomannan immobilizing La3+ and Al3+ (CMKGM-La-Al) has been explored for sorption of U(VI). The maximum U(VI) sorption capacity of the microsphere is found to be 45.4 mg g−1 at pH 5. Experimental data are fitted well with the linear Langmuir and linear pseudo-first-order kinetic model. The sorption process is endothermic, spontaneous and favorable. The possible mechanism of CMKGM modification and sorption of U(VI) on CMKGM-La-Al involves ion exchange and coordination reaction. The comparison between CMKGM-La-Al and other sorbents suggests that CMKGM-La-Al can be considered as an effective sorbent for U(VI) sorption.

Removal of chromium (VI) from aqueous solutions using surface modified composite nanofibers

A novel material composite nanofibers (PAN-CNT/TiO2-NH2) based on adsorption of Cr(VI) ions, was applied. Polyacrylonitrile (PAN) and carbon nanotube (CNTs)/titanium dioxide nanoparticles (TiO2) functionalized with amine groups (TiO2-NH2) composite nanofibers have been fabricated by electrospinning. The nanostructures and the formation process mechanism of the obtained PAN-CNT/TiO2-NH2 composite nanofibers are investigated using FTIR, XRD, XPS, SEM, and TEM. The composite nanofibers were used as a novel adsorbent for removing toxic chromium Cr(VI) in aqueous solution. The kinetic study, adsorption isotherm, pH effect, initial concentration, and thermodynamic study were investigated in batch experiments. The composite nanofibers had a positive effect on the absorption of Cr(VI) ions under neutral and acidic conditions, and the saturated adsorption reached the highest when pH was 2. The adsorption equilibrium reached within 30 and 180min with an initial solution concentration increasing from 10 to 300mg/L, and the process can be better described using nonlinear pseudo first than nonlinear pseudo second order model and Intra-particle diffusion. Isotherm data fitted well using linear and nonlinear Langmuir, Freundlich, Redlich-Peterson, and Temkin isotherm adsorption model. Thermodynamic study showed that the adsorption process is exothermic. The adsorption capacity can remain up to 80% after 5 times usage, which show good durability performance. The adsorption mechanism was also studied by UV–vis and XPS.

Probing the essence of strong interaction in oily sludge with thermodynamic analysis

Abstract In this study, the oily sludge was extracted with toluene, naphthane, naphtha or petroleum ether as solvent to reveal the essential interaction in oily sludge through thermodynamic analysis method. The surface component activity (SCA) model was utilized to eliminate the particles accumulation effect (Cp-effect) in order to obtain evolutional Langmuir isotherm. The maximum adsorption capacity ( Γ o ) of oil and equilibrium constant (Keq) of desorption process was calculated from the slope and intercept of the linear fitted Langmuir isotherm. Hence, the thermodynamic functions, such as Gibbs free energy (△G), enthalpy change (△H) and entropy change (△S), were further determined from the results of Keq. The Fourier transform infrared spectroscopy (FT-IR) was applied to analyze the oily sludge. Strong interactions, such as O H⋯O hydrogen bond, between oil molecules and particles were eventually found to be the essential reason for preventing the oil desorption. The thermodynamic analysis method developed in this work also provided feasible guidance to improve the extraction efficiency for oily sludge.

Surface functionalized composite nanofibers for efficient removal of arsenic from aqueous solutions

A novel composites nanofiber was synthesized based on PAN-CNT/TiO2-NH2 nanofibers using electrospinning technique followed by chemical modification of TiO2 NPs. PAN-CNT/TiO2-NH2 nanofiber were characterized by XRD, FTIR, SEM, and TEM. The effects of various experimental parameters such as initial concentration, contact time, and solution pH on As removal were investigated. The maximum adsorption capacity at pH 2 for As(III) and As(V) is 251mg/g and 249mg/g, respectively, which is much higher than most of the reported adsorbents. The adsorption equilibrium reached within 20 and 60min as the initial solution concentration increased from 10 to 100mg/L, and the data fitted well using the linear and nonlinear pseudo first and second order model. Isotherm data fitted well to the linear and nonlinear Langmuir, Freundlich, and Redlich-Peterson isotherm adsorption model. Desorption results showed that the adsorption capacity can remain up to 70% after 5 times usage. This work provides a simple and an efficient method for removing arsenic from aqueous solution.

Langmuir wave filamentation in the kinetic regime. I. Filamentation instability of Bernstein-Greene-Kruskal modes in multidimensional Vlasov simulations

A nonlinear Langmuir wave in the kinetic regime kλD≳0.2 may have a filamentation instability, where k is the wavenumber and λD is the Debye length. The nonlinear stage of that instability develops into the filamentation of Langmuir waves which in turn leads to the saturation of the stimulated Raman scattering in laser-plasma interaction experiments. Here, we study the linear stage of the filamentation instability of the particular family (H. A. Rose and D. A. Russell, Phys. Plasmas 8, 4784 (2001)) of Bernstein-Greene-Kruskal (BGK) modes (I. B. Bernstein et al., Phys. Rev. 108, 546 (1957)) that is a bifurcation of the linear Langmuir wave. Performing direct 2 + 2D Vlasov–Poisson simulations of collisionless plasma, we find the growth rates of oblique modes of the electric field as a function of BGK's amplitude, wavenumber, and the angle of the oblique mode's wavevector relative to the BGK's wavevector. Simulation results are compared to theoretical predictions.

Rapid adsorptive removal of naphthalene from water using graphene nanoplatelet/MIL-101 (Cr) nanocomposite

The study of the adsorption equilibria of naphthalene onto graphene nanoplatelet supported MIL-101 composite material (GNP/MIL-101) has been conducted. In the experimental context of this study, firstly GNP/MIL-101 was synthesized by applying hydrothermal method and characterized via FTIR, XRD, SEM, TEM and surface area analyses. The effects of GNP/MIL-101 amount, temperature and initial naphthalene concentration on the adsorption process have been investigated. Results show that the maximum removal of naphthalene was obtained as about 93% by 0.075 g GNP/MIL-101 at 298 K. The isothermal data were fitted to linear and non-linear Langmuir, Freundlich, and Temkin adsorption isotherm models and the kinetic data were fitted to Elovich and other kinetic models. Adsorption depended on initial naphthalene concentration at investigated various temperatures (298, 308, 318 K) significantly. The temperature dependence of adsorption process is associated with the changes in several thermodynamic parameters such as standard free energy (ΔG°), enthalpy (ΔH°) and entropy (ΔS°).

Investigation of hexavalent chromium sorption in serpentine sediments

In this study the removal of hexavalent chromium (Cr6+) by serpentine sediments was investigated in order to delineate Cr6+ sorption behavior in aquifers with ultramafic geologic background. Batch experiments were conducted in order to determine the influence of several parameters on Cr6+ removal, including the pH of the sediment solution, mineralogy, sediment's particle size and Cr6+ initial concentration. The results showed that Cr6+ removal was due to both adsorption and reduction phenomena. Reduction was attributed to the presence of a magnetic fraction in the sediment, mostly related to magnetite, which contributed almost 50% of the total removal in the pH range 3–7. Adsorption behavior was dominated by the finer sediment fraction (d<0.075mm). The amount of Cr6+ adsorbed was constant in the pH range 3–7, while it decreased sharply in the range 7–8.5. Cr6+ adsorption was found to increase and decrease proportionally with increasing initial Cr6+ concentration of and particle size, respectively. The linear Langmuir and Freundlich adsorption isotherms were used to describe the experimental data, with Freundlich providing a better fit to determine distribution factors for transport modeling.

In vitro Bioequivalence Studies in Tablet Formulation Containing 625 mg of Colesevelam Hydrochlorides

Colesevelam hydrochloride is a second generation bile acid sequestrant that is used principally for treatment of elevated LDL cholesterol. Additionally, it is indicated to improve glycemic control in adults with type 2 diabetes mellitus. Colesevelam hydrochloride is an insoluble, non-absorbed polymer that binds bile acids in the intestine, impeding their reabsorption. Because the drug is not absorbed into the systemic circulation, pharmacokinetic information is not available. The present abstract focuses on the study of in vitro BE in tablet formulation containing 625 mg of Colesevelam hydrochloride. Bile acid salts of Glycocholic Acid (GC), Glycochenodeoxycholic Acid (GCDC) and Taurodeoxycholic Acid (TDC) were used in vitro BE studies. The binding capacity HPLC method was developed and validated for these bile acid salts. The equilibrium binding study that is the pivotal BE study and in vitro kinetic binding study that is the support the pivotal equilibrium binding study was repeated twelve times. In the in vitro equilibrium binding studies, the Langmuir binding constants k1 (affinity) and k2 (capacity) were calculated for the three salts, individually and combined (GC+GCDC+TDC) using both nonlinear Langmuir equation and linear Langmuir equation for the test and reference products. The calculated capacity constant (k2), the more important parameter, were obtained very similar between test and reference products in the 90% confidence interval and acceptance criteria of 80% to 120%. The test/reference ratio for capacity constant, k2, was obtained 0.918 and 0.922 using equation 1 and 2 for total bile acid salts from the without acid pre-treatment equilibrium binding study and 0.948, 0.953 using equation 1 and 2 for total bile acid salts from the with acid pre-treatment equilibrium binding study.

Adsorption of the mycotoxin zearalenone by clinoptilolite and phillipsite zeolites treated with cetylpyridinium surfactant

In this study, organozeolites were prepared by treatment of the natural zeolites (clinoptilolite and phillipsite) with cetylpyridinium chloride (CP) equivalent to 50 and 100% of their external cation exchange capacities (ECEC). Organoclinoptilolites (ZCPs) and organophillipsites (PCPs) were characterized by FTIR spectroscopy, thermal analysis, determination of the point of zero charge and zeta potential. Adsorption of zearalenone (ZEN) by ZCPs and PCPs at pH 3 and 7 was investigated. Results showed that adsorption of ZEN increases with increasing amounts of CP at the zeolitic surfaces for both ZCPs and PCPs but the adsorption mechanism was different. Adsorption of ZEN by ZCPs followed a linear type of isotherm at pH 3 and 7 while ZEN adsorption by PCPs showed non linear (Langmuir and Freundlich) type of isotherm at both pH values. Different interactions between the ZEN molecule (or ion) and ZCPs and PCPs occurred: partition (linear isotherms) and adsorption in addition to partition (non linear isotherms), respectively. For the highest level of organic phase at the zeolitic surfaces, the maximum adsorbed amount of ZEN was 5.73mg/g for organoclinoptilolite and 6.86mg/g for organophillipsite at pH 3. Slightly higher adsorption: 6.98mg/g for organoclinoptilolite and 7.54mg/g for organophillipsite was achieved at pH 7. The results confirmed that CP ions at both zeolitic surfaces are responsible for ZEN adsorption and that organophillipsites are as effective in ZEN adsorption as organoclinoptilolites.

Hexavalent Chromium Uptake from Aqueous Solutions using Raw Biomass of the Invasive Brown Seaweed Sargassum muticum from the Moroccan Shorelines: Kinetics and Isotherms

Raw biomass of the invasive Japanese brown seaweed Sargassum muticum, recently introduced to the Atlantic coast of Morocco, has been applied for the removal of hexavalent chromium Cr(VI) from aqueous solutions. Various parameters such as biomass dose, initial pH, contact time and initial Cr(VI) concentration were studied to reveal their effects on the biosorption process. At optimum values of the above mentioned parameters, total removal of Cr(VI) can be achieved within 10 min at pH 2, adsorbent dose of 0.5 g/100 mL for initial chromium ions concentration of 50 mg/L. Cr(VI) biosorption follows pseudo second-order kinetics. Adsorption isotherms were determined at room temperature and the experimental data were modelled with the Langmuir, Freundlich and Temkin isotherm equations. The isotherm data were found to be well fitted by linear Langmuir equation. The maximum sorption capacity calculated from Langmuir isotherm was estimated to be about 143 mg per gram of dry biosorbent. Thus, the biomass used in this study can be considered a promising and valuable natural adsorbent for the treatment of aqueous solution containing toxic hexavalent chromium ions.

Selective and competitive removal of dyes from binary and ternary systems in aqueous solutions by pretreated jujube shell (Zizyphus lotus)

ABSTRACTIn this work, the selective and competitive adsorption of organic dyes, such as methylene blue (MB), crystal violet (CV), and Congo red (CR), from binary and ternary mixtures in aqueous solutions on pretreated jujube shell (PJS) were evaluated. The characteristics of PJS were studied using FTIR analysis, this characterization suggests the grafting of sulfonate () groups on surface of PJS. The removal efficiency of MB, CV, and CR from a binary and ternary mixture of dyes solutions was examined and optimized toward various parameters: percentage of dye in the mixture, contact time, initial pH of the solution, temperature, and initial solution concentration. The results demonstrated that high effective PJS for adsorption of MB, CV and CR. The data were fitted to linear Langmuir, Freundlich, and Temkin isotherms models. It was found that the sorption of MB, CV, and CR from different mixtures agreed very well with the Langmuir model. The calculated thermodynamic parameters showed that the adsorption of these organic dyes from different mixtures on PJS was spontaneous, endothermic, and increased randomness in the solid/solution interface. The PJS could effectively treat industrial wastewater contaminated by organic dyes.

Encapsulation of a powdery spinel-type Li+ ion sieve derived from biogenic manganese oxide in alginate beads

A powdery lithium ion sieve (HMO) derived from biogenic birnessite was homogeneously integrated in sodium alginate (AL) beads. The composite beads were then characterized and their Li+ adsorption properties were investigated. Scanning electron microscopy–energy dispersive spectroscopy analysis showed that the HMO particles were homogeneously dispersed in the AL beads even after drying. The adsorption isotherm of Li+ adsorption to HMO encapsulated in AL beads (HMO–AL) was well fitted by the linear Langmuir model, and the beads showed a maximum adsorption capacity of 3.61mmol/g based on HMO, which is comparable with the value of the original powdery HMO. Kinetic studies revealed that adsorption of Li+ follows a pseudo-second-order model with rate constant k2=2.8–11.9×10−3g/(mmolmin) for the initial Li+ concentration range 2.56–4.23mM. Diffusion of Li+ from aqueous solution to the HMO particle through the Ca–AL network is the rate-limiting step for Li+ adsorption to HMO–AL beads. The HMO-AL beads enhanced the handling efficiency for Li+ adsorption and reused without significant reduction of Li+ adsorption efficacy.

Selective removal of Cr(VI) from aqueous solution by polypyrrole/2,5-diaminobenzene sulfonic acid composite

A polypyrrole/2,5-diaminobenzenesulfonic acid (PPy/DABSA) composite, synthesised by the in situ oxidative polymerization of pyrrole in the presence of DABSA, was studied as an adsorbent for the removal of Cr(VI) from aqueous solution. The structure and morphology of the composite were investigated by ATR-FTIR, FE-SEM, EDX, TGA, XRD and XPS studies. The adsorption of Cr(VI) by PPy/DABSA composite was highly pH dependent and optimum removal was achieved at pH 2. Adsorption of Cr(VI) was confirmed by EDX and XPS studies. The isotherm data fitted the linear Langmuir model well, with a maximum adsorption capacity of 303mg/g at 25°C. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) were calculated using isotherm data and confirmed that the adsorption process was spontaneous and endothermic. Adsorption kinetics was best described by the pseudo-second-order model. The activation energy of the adsorption process suggested that Cr(VI) was chemisorbed by PPy/DABSA composite. PPy/DABSA composite could be used for three consecutive adsorption-desorption cycles without loss of its original adsorption capacity. Highly selective removal of Cr(VI) was observed even when co-existing ions such as Cu2+, Zn2+, Ni2+, Cl−, SO42− and NO3− were present in the solution. In summary, the potential of PPy/DABSA composite for remediating industrial wastewater contaminated by Cr(VI) has been demonstrated.

Kinetic study of copper adsorption onto Moroccan Illitic and kaolinite clay

In order to optimize and reduce the rate of inorganic micropollutants rejected by various metal installations, according to wastewater treatment standards and environmental protection, we proceeded by studying the adsorption of heavy metals such as copper by using the Illitic and Kaolinite Clay from Moroccan (IKCM) of El Oulja-Sale region. We are interested in the analysis of the physicochemical parameters influencing the removal of heavy metals (time effect, mass effect absorbent, concentration of initial copper solutions effect, stirring rate effect and the solution’s pH). The results of this study was produced by the characterization technique of X-Ray Diffraction (XRD), the Atomic Adsorption Spectroscopy (AAS) and linear forms Langmuir isotherm and Frendlich models which show that the binding and removal copper by this clay is fast with increasing parameters mentioned previously.

Kinetics and isotherm study on adsorption of chromium on nano crystalline iron oxide/hydroxide: linear and nonlinear analysis of isotherm and kinetic parameters

Nano crystalline iron oxide was used as an adsorbent for removal of chromium from aqueous solutions. Linear and non-linear equations were applied to model the kinetic and isotherm data. Non-linear analysis included error analysis using the Solver addin of Microsoft Excel and Origin. Error analysis methods fitted the data better than Origin for determination of isotherm and kinetic parameters. Non-linear analysis suggests adsorption of chromium on nano crystalline iron oxide followed Langmuir isotherm. The maximum adsorption capacity of the adsorbent was found to be 11.18 mg/g. The system followed a pseudo second order model on the basis of linear and non-linear data. The Langmuir constant and partition coefficient methods were used to determine the thermodynamic parameters. Both methods suggested that the adsorption of chromium by nanocrystalline iron oxide is spontaneous and exothermic (−47.26 kJ/mol). The free energy values varied from −24.23 to −27.22 kJ/mol, and the process of removal progressed with a decrease in entropy (0.9256 kJ/mol). Thermodynamic parameters predicted by the linear Langmuir constant method suggested that the system is endothermic (9.65 kJ/mol), spontaneous, and occurs with an increase in entropy (0.1142 kJ/mol).

Equilibrium and kinetic studies on the removal of some metal ions using biogenic amorphous silica

ABSTRACTIn the present study agricultural waste (rice husks) was used for the production of biogenic silica. The resulting material was obtained by incineration of rice husks at a temperature of 800°С and was characterized by means of XRD, FTIR, SEM-EDS, Hg-porosimetry and N2-adsorption. The adsorption ability of the rice husks ash towards Fe(III), Pb(II), Cr(III) and Cu(II) ions in single- and multi-component aqueous solutions was studied in a batch system. The effects of contact time, acidity of initial solutions and metal ion concentrations were followed. Different models were used to determine the adsorption mechanism. Equilibrium experimental data were fitted to linear Langmuir and Freundlich models. The maximum adsorption capacities for single- and multi-component adsorption were calculated.

Adsorption of Acid Carmoisine B by Fly Ash/Chitosan Composite

With synthetic wastewater, the adsorption characteristics of acid carmoisine B (AC B) on fly ash/chitosan (FA/CTS) composite material prepared by FA loaded with CTS were investigated using a lab-scale batch experiment technique. The optimum preparation conditions for FA/CTS composite were obtained and the composite was further characterized by SEM. The adsorption rate of AC B onto FA/CTS is very fast and the adsorption can reach equilibrium in 60 minutes. Temperature may accelerate the adsorption rate. Equilibrium experimental data are well fitted to linear Langmuir model with the saturated adsorption capacity of 232.56 mg/g at 25°C and the nature of a monolayer adsorption. Dubinin-Radushkevich (D-R) isotherm model was applied to describe the nature of AC B sorption, and it has been found that AC B sorption mainly occurred chemically, but physisorption also exists at same time. The values of thermodynamic parameters, the change of free energy (ΔG◦), enthalpy (ΔH◦) and entropy (ΔS◦) of sorption calculated, show that the sorption process of AC B on FA/CTS is spontaneous and endothermic at 25~55°C. The results indicate that there is significant potential for FA/CTS as an effective adsorbent material for AC B removal from dye wastewater.