Modification of Bentonite with Cationic and Nonionic Surfactants: Structural and Textural Features.

Magdalena Andrunik,Tomasz Bajda

doi:10.3390/ma12223772

Abstract

Surfactant-modified clay minerals are known for their good sorption properties of both organic and inorganic compounds from aqueous solutions. However, the current knowledge regarding the effect of both cationic and nonionic surfactants on the properties of bentonite is still insufficient. Bentonite, with montmorillonite as the base clay, was modified with hexadecethyltrimethylammonium bromide (a cationic surfactant) in the amount of 1.0 cation exchange capacity (CEC) of bentonite and varying concentrations of t-octylphenoxypolyethoxyethanol (Triton X-100, a nonionic surfactant). We aimed to improve the understanding of the effect of nonionic and cationic surfactants on clay minerals. The modified bentonites were characterized by X-ray diffraction (XRD), thermogravimetric analysis/differential thermal analysis (TG/DTA), Fourier transform infrared spectrometry (FTIR), field emission scanning electron microscopy (SEM) and specific surface area and pore volume (BET). According to our results, the presence of a cationic surfactant significantly increased the amount of the adsorbed nonionic surfactant. Moreover, an increase in the concentration of nonionic surfactants is also associated with an increase in the effectiveness of the modification process. Our results indicate that the amount of nonionic surfactant used has a significant effect on the properties of the obtained hybrid material. Modification of bentonite with a nonionic surfactant did not cause an expansion of the interlayer space of smectite, regardless of the presence of a cationic surfactant. The modification process was found to significantly decrease the specific surface area of bentonite. Improvement of hydrophobic properties and thermal stability was also observed.

Highlights

Bentonite is an aluminum phyllosilicate clay consisting primarily of montmorillonite
The results of the experiment performed to determine the effect of the concentration of the surfactant on the modification of natural bentonite and HDTMA–bentonite clearly show that an increase in the concentration of nonionic surfactant in the solution is associated with an increase in the effectiveness of the modification process
This study investigates the structural characterization of bentonite modified with cationic and nonionic surfactants

Summary

Introduction

Bentonite is an aluminum phyllosilicate clay consisting primarily of montmorillonite. Bentonite has found various applications, especially in pollution control [1,2,3,4] It is the most extensively used clay due to its abundance, low cost, and ease of availability [5,6]. Montmorillonite—the clay mineral—belongs to the smectite group of minerals and is the most common member of the clay minerals It has a 2:1-type layer silicate structure, which has excellent sorption capacity for many heavy metals [7,8,9]. The minerals belonging to this group have an overall negative surface charge; cations can be adsorbed onto their surface [10] This characteristic property is due to the presence of isomorphic substitutions in their structure

Objectives

Methods

Results

Conclusion