Abstract
In the present work, the modified bentonites were prepared by the modification of bentonite with cetyltrimethylammonium bromide (CTAB), both cetyltrimethylammonium bromide and hydroxy-Fe cations and both cetyltrimethylammonium bromide and hydroxy-Al cations. X-ray diffraction (XRD), thermal analysis (TG-DTA), infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and nitrogen adsorption/desorption isotherms were utilized to characterize the resultant modified bentonites. The modified bentonites were employed for the removal of phenol red dye from aqueous solution. Phenol red adsorption agreed well with the pseudo-second-order kinetic model. The equilibrium data were analyzed on the basis of various adsorption isotherm models, namely, Langmuir, Freundlich, and Dubinin‒Radushkevich models. The highest monolayer adsorption capacity of phenol red at 30°C derived from the Langmuir equation was 166.7 mg·g−1, 125.0 mg·g−1, and 100.0 mg·g−1 for CTAB‒bentonite, Al‒CTAB‒bentonite, and Fe‒CTAB‒bentonite, respectively. Different thermodynamic parameters were calculated, and it was concluded that the adsorption was spontaneous (∆G° < 0) and endothermic (∆H° > 0), with increased entropy (∆S° > 0) in all the investigated temperature ranges.
Highlights
In recent years, dyes are used widely in many industries such as textiles, paper, printing, and cosmetics
Iqbal et al [14] found that the phenol red adsorption process on activated carbon materials was spontaneous with increasing entropy. e kinetic and thermodynamic studies of the phenol red absorption on bottom ash and deoiled soya were investigated very by Mittal et al [12]. e highest monolayer adsorption capacity has been obtained for the phenol red-bottom ash system (2.6 × 10−5·mol·g−1) at 50°C
E purified bentonite (B) exhibits the characteristic peaks of the montmorillonite according to JCPDS No 00003-0014. e changes of basal spacing of the modified bentonite can reflect the intercalations of Cetyltrimethylammonium bromide (CTAB), hydroxy‒ Al, and hydroxy‒Fe cations into bentonite interlayer spaces
Summary
Dyes are used widely in many industries such as textiles, paper, printing, and cosmetics. These industries release a large amount of highly toxic dyes in wastewater every year, most of which have negative effects on human and animal health. Various techniques such as adsorption [1,2,3,4], catalysis [5, 6], electrochemical oxidation [7], ozonation [8], membrane filtration [9], biological treatment [10], and enzymes [11] have been used to remove the dye components from polluted wastewater. E kinetics, isotherms, thermodynamics, and the mechanism of phenol red adsorption process on modified bentonite materials are addressed The synthesis of CTAB‒bentonite, Al‒ CTAB‒bentonite, and Fe‒CTAB‒bentonite and phenol red adsorption are demonstrated. e kinetics, isotherms, thermodynamics, and the mechanism of phenol red adsorption process on modified bentonite materials are addressed
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