Equilibrium arsenic adsorption onto metallic oxides : Isotherm models, error analysis and removal mechanism

Abstract

Arsenic adsorption properties of mono-(Fe or Al) and binary (Fe-Al) metal oxides supported on natural zeolite were investigated at three levels of temperature (298, 318 and 338 K). All data obtained from equilibrium experiments were analyzed by Freundlich, Langmuir, Dubinin-Radushkevich, Sips, Toth and Redlich-Peterson isotherms, and error functions were used to predict the best fitting model. The error analysis demonstrated that the As(V) adsorption processes were best described by the Dubinin-Raduskevich model with the lowest sum of normalized error values. According to results, the presence of iron and aluminum oxides in the zeolite network improved the As(V) adsorption capacity of the raw zeolite (ZNa). The X-ray photoelectron spectroscopy (XPS) analyses of ZNa-Fe and ZNa-AlFe samples suggested that the redox reactions are the postulated mechanisms for the adsorption onto them while the adsorption process is followed by surface complexation reactions for ZNa-Al.

A critical review on arsenic removal from water using iron-based adsorbents

“…As(V) adsorption on mono-(Fe or Al) and Fe-Al-LDHs supported zeolite agreed with the Redlich-Peterson model with the correlation coefficient above 0.99. 94 Similarly, As(III) and As(V) adsorption on magnetic nanoscale Fe-Mn-LDHs loaded zeolite (MFM) could be well described by Redlich-Peterson model with the correlation coefficient above 0.98. 91 When the atomic ratio of Mn/Fe was 2 : 9, the specic surface area of the Fe-Mn-LDHs nanoparticles reached 340 m 2 g À1 , which is higher than most of the reported absorbents and showed high As removal efficiency of 99.0% at pH 7.0.…”

Novel composite sorbents based on carbon fibers decorated with ferric hydroxides—Arsenic removal

“…In order to examine adsorption characteristics, Langmuir, Freundlich, and Dubinin–Radushkevish (D‐R) isotherm models were applied to the experimental data (Supporting Information). The Langmuir isotherm is based on the concept of homogeneous adsorption, in which each molecule exhibits equal enthalpy and sorption activation energy, whereas Freundlich model is based on the multilayer adsorption, with nonuniform distribution of sorption heat, and the D‐R model is often used to distinguish physical and chemical adsorption mechanism. The Langmuir maximum adsorption capacity ( q m ) was calculated as 134.8 μg/g for CF, whereas that of was observed as 1,565.7 μg/g for CF–Fe (20%) sample (Table S1).…”

“…The determination of adsorption rate offers deeper insight in the understanding of adsorption mechanism. 17 The kinetic profiles of adsorption are represented in Figure 6 (a). As (V) adsorption rate increased with increasing amount of iron loading.…”

Circular economy approach for rice husk modification: equilibrium, kinetic, thermodynamic aspects and mechanism of Congo red adsorption

“…Isosteric heat of adsorption (ΔHX, KJ/mol), presented as the heat of adsorption at a constant amount of adsorbed adsorbate, is of great importance for obtaining an optimized adsorption process. The Clausius-Clapeyron equation is used to estimate this thermodynamic quantity (Simsek and Beker 2014).…”