Search results for "Freundlich equation"
showing 10 items of 32 documents
Kinetics of the intestinal uptake of zinc acexamate in normal and zinc-depleted rats.
1990
Abstract The uptake of zinc as acexamic acid salt in the small intestine of the anaesthetized rat was shown to be a two-phase process in normal animals. The first phase is rapid mucosal binding which satisfies the Freundlich isotherm equation and which involves about 30 per cent of the initially perfused zinc. The second phase was characterized as an apparent absorption step which obeys Michaelis-Menten and first-order combined kinetics, with the following parameters: Vm = 6.51 mg h−1; Km = 2.96 mg; ka = 0.306 h−1. In largely non-saturated conditions, an apparent global rate constant of about 2.50 h−1 was calculated. No significant interference due to endogenous zinc excretion into the smal…
Sorption characteristics of heavy metal ions by a natural zeolite
2005
Zeolites have been shown to be effective adsorbents for the removal of heavy metals from aqueous solutions. A natural material from Cuba, containing zeolite, has been used for the removal of several metal ions, namely Cu2+, Zn2+, and Ni2+, to evaluate its potential use as a low-cost adsorbent. Batch experiments have been conducted to evaluate the process kinetics and the removal equilibrium at different pH values, metal and zeolite concentrations. Pseudo-second order kinetics and Freundlich equilibrium parameters have been obtained. Results suggested that this natural zeolite has a high potential for heavy metal retention. The selectivity of the studied metals was determined as Cu2+ ≫ Zn2+ …
Modelling Cd(II) removal from aqueous solutions by adsorption on a highly mineralized peat. Batch and fixed-bed column experiments
2006
This paper evaluates the potential use of a locally available organic soil amendment as a low-cost adsorbent. The removal of cadmium from aqueous solutions was studied by means of kinetic, batch and fixed-bed experiments. Batch experiments were conducted to evaluate the process kinetics and the removal equilibrium over a broad pH range. Pseudo-second-order kinetics and Freundlich equilibrium parameters were obtained. Six column experiments were carried out at different flow-rates and feed concentrations. Breakthrough curves showed higher metal retention than expected from the batch adsorption isotherms. Column modelling assuming rate-controlled pore diffusion was successfully performed. The…
Effect of pH, cation concentration and sorbent concentration on cadmium and copper removal by a granular activated carbon
1999
The single adsorption of cadmium and copper from aqueous solutions has been investigated on Darco 12-20 mesh granular activated carbon for a wide range of experimental conditions: pH, metal concentration and carbon concentration. The results showed the efficiency of the activated carbon as sorbent for both metals. Metal removal increases on raising pH and carbon concentration, and decreases on raising the initial metal concentration. The adsorption processes have been modelled using the surface complex formation (SCF) Triple Layer Model (TLM) with a single surface bidentate species or with an overall surface species with fractional stoichiometry. Bidentate stoichiometry considering pH, meta…
Resin adsorption as a means to enrich rare stilbenes and coumarin from pigeon pea leaves extracts
2011
Abstract In this study, resin adsorption as a means to enrich rare stilbenes cajaninstilbene acid (CSA) and longistyline C (LLC), and coumarin cajanuslactone (CL) from pigeon pea leaves was investigated. Among widely used twenty macroporous adsorption resins, NKA-9 resin presented higher adsorption capacity and desorption ratio in static tests. The adsorption kinetic model fitted better depended on types of compounds and pH values. The experimental adsorption data were better fitted to Langmuir isotherm (R2 0.921–0.991) than Freundlich isotherm (R2 0.753–0.988). In order to optimize the operating parameters for separating CSA, LLC and CL, dynamic adsorption and desorption tests were carried…
Pb(II) adsorption by a novel activated carbon - alginate composite material. A kinetic and equilibrium study.
2016
The adsorption capacity of an activated carbon – calcium alginate composite material (ACAA-Ca) has been tested with the aim of developing a new and more efficient adsorbent material to remove Pb(II) ion from aqueous solution. The study was carried out at pH = 5, in NaCl medium and in the ionic strength range 0.1–0.75 mol L−1. Differential Pulse Anodic Stripping Voltammetry (DP-ASV) technique was used to check the amount of Pb(II) ion removed during kinetic and equilibrium experiments. Different kinetic (pseudo first order, pseudo second order and Vermuelen) and equilibrium (Langmuir and Freundlich) models were used to fit experimental data, and were statistically compared. Calcium alginate …
Predicting breakthrough of vanadium in fixed-bed absorbent columns with complex groundwater chemistries: A multi-component granular ferric hydroxide−…
2020
Granular ferric hydroxide (GFH) is often used for fixed bed adsorbent (FBA) columns in groundwater purification units around the world to remove arsenate contaminations. Groundwater can contain also other toxic (e.g., antimonite and vanadate) and non-toxic oxo-anions (phosphate and silicic acid) that are known to affect FBA lifetimes. Therefore, understanding the breakthrough of toxic compounds intended for removal by FBA is essential to their design, and is important to predict accurately breakthrough curves (BTCs) for FBAs in waterworks to plan future operating costs. Rapid small-scale column tests (RSCCT) and pilot-scale FBA were used to simulate vanadate BTCs for complex groundwater che…
Sorption of polycyclic aromatic hydrocarbons (PAHs) to carbonaceous materials in a river floodplain soil
2007
We report on sorption isotherm of phenanthrene (Phe) for river floodplain soil associated with carbonaceous materials, with particular attention being devoted to the natural loading of Phe. Our sorption experiments with original soil samples, size, and density sub-fractions showed that the light fraction had the highest sorption capacity comparable to low rank coals. In addition, the light fraction contributed most for the sorption of Phe in total soil samples. K(oc) values for all fractions were in the same range, thus indicating that coal and coal-derived particles in all samples are responsible for the enhanced sorption for Phe. Sorption was strongly nonlinear and the combined partitioni…
Experimental and theoretical study using DFT method for the competitive adsorption of two cationic dyes from wastewaters
2016
Abstract The adsorption of cationic dyes, Basic Yellow (BY28) and Methylene Blue (MB) on a new activated carbon from medlar species were studied in both single and binary system. Some experimental parameters, namely, pH, amount of adsorbent and contact time are studied. Quantum chemical results indicate that the adsorption efficiency was directly related to the dye electrophilicity power. Some theorical parameters were calculated and proved that MB is more electrophilic than BY28, than greatest interaction with surface sites. Kinetic study showed that the adsorption follows the pseudo-second-order model and Freundlich was the best model to describe the phenomenon in the single and binary sy…
Effects of pyrolysis conditions on the porous structure development of date pits activated carbon
2012
International audience; Activated carbons were prepared from biomass of Algerian date pits for developing efficient and cheap adsorbents in the aim to remove heavy metals from waste water. Carbon adsorbents were obtained following two successive treatments: pyrolysis under dry nitrogen flow and physical activation under wet nitrogen flow. Pyrolysis process was optimized by varying some operating parameters such as temperature, nitrogen flow, heating rate and pyrolysis hold time in order to determine their effects on the porous structure development of date pits activated carbon. Chars obtained from pyrolysis process were activated with the same operating conditions (activation temperature o…