Abstract
In this study, a novel dual-cation organomontmorillonites (OMt) nanocomposite was synthesized by two kinds of modifiers cetyltrimethylammonium chloride and cysteamine hydrochloride, and the adsorption behavior of modifiers into montmorillonite (Mt) has been investigated. The OMt were characterized by techniques, such as X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and thermogravimetric and differential thermal (TG-DTA) analyses. The effects of temperature, contact time, the order of addition and the concentration of organic modifiers on the amounts of organics adsorbed were investigated. The adsorption amount of cetyltrimethylammonium chloride (CTAC) and cysteamine hydrochloride (CSH) increased with the increase of the added CTAC amount and contact time, while the addition order of modifiers and modification temperature had no significant effect on the actual adsorption amount of CTAC and CSH on Mt, as confirmed by the XRD patterns. The experimentally determined isotherms showed a good fit with the Langmuir adsorption models. The adsorption kinetics demonstrated that the adsorption of CTAC and CSH by Mt followed the pseudo-second-order model, and CTAC adsorption rate on Mt was faster than that of CSH. FTIR spectrum clearly revealed the incorporation of surfactant ions into the interlayer region. The TG-DTA analyses showed that the total mass losses of OMt strongly depended on the molecular volume of modifiers.
Highlights
Montmorillonite (Mt) is a 2:1 type of layered silicate mineral composed of two silica tetrahedral sheets (SiO4 ) sandwiching an aluminum octahedral sheet [Al2−x Mgx O4 (OH)4 ]
cetyltrimethylammonium chloride (CTAC)-cysteamine hydrochloride (CSH)-coMt (33.85%) > CSH modified montmorillonite (CSH-Mt) (16.38%), which indicated that the total mass losses of OMt strongly depended on the molecular volumes of organic modifiers
Cetyltrimethylammonium chloride and cysteamine hydrochloride were used to modify montmorillonite (Mt), and the effects of temperature, contact time, the addition order of modifiers and modification temperature were investigated by using a batch process-type of experiments
Summary
Montmorillonite (Mt) is a 2:1 type of layered silicate mineral composed of two silica tetrahedral sheets (SiO4 ) sandwiching an aluminum octahedral sheet [Al2−x Mgx O4 (OH)4 ]. The natural Mt can attract species with opposite charges, such as heavy metal ions and organic cations, and it shows high specific surface area, high cation exchange capacity (CEC), and micro and meso-porosity properties [5,6]. Based on these unique characteristics as well as their natural abundance and cost-effectiveness, Mt is usually used as a low cost adsorbent in wastewater treatment. The adsorption mechanism of modifiers on Mt was discussed from the aspects of adsorption kinetics and thermodynamics
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