TEM, XRD, and thermal stability of adsorbed paranitrophenol on DDOAB organoclay

Abstract

Water purification is of extreme importance to modern society. Organoclays through adsorption of recalcitrant organics provides one mechanism for the removal of these molecules. The organoclay was synthesised through ion exchange with dimethyldioctadecylammonium bromide labeled as DDOAB of formula (CH3(CH2)17)2NBr(CH3)2. Paranitrophenol (pnp) was adsorbed on the organoclay at a range of concentrations according to the cation exchange capacity (CEC) of the host montmorillonite. The paranitrophenol in solution was analysed by a UV-260 spectrophotometer at 317 nm, with detection limits being 0.05 mg/L. The expansion of the montmorillonite was studied by a combination of X-ray diffraction and transmission electron microscopy. Upon adsorption of the paranitrophenol the basal spacing decreased. The thermal stability of the organoclay was determined by a combination of thermogravimetry and infrared emission spectroscopy. The surfactant molecule DDOAB combusts at 166, 244, and 304 degrees C and upon intercalation into Na-montmorillonite is retained up to 389 degrees C thus showing the organoclay is stable to significantly high temperatures well above the combustion/decomposition temperature of the organoclay.

Preparation and characterization of zwitterionic surfactant-modified montmorillonites

“…The temperatures correspond to the DTG peaks of the three pure surfactants (332, 326, and 334°C). This correspondence indicates that, at 0.8 CEC, the surfactant molecules are not only intercalated within the montmorillonite layers but also are adsorbed on the external surfaces of montmorillonite [40]. When the concentration of surfactant was increased further, the intensity of the first peak (349°C) increased, whereas the intensity of the second peak (382°C) decreased.…”

A thermal, sorptive and spectral study of HDTMA-bentonite loaded with uranyl phosphate

“…8c) shows a very complicated pattern with many peaks. The most interesting one is the endothermic peak in the region of 80-150°C, probably resulting from a phase change of solid HDTMA-Br, i.e., the formation of a gauche disordered conformation of surfactant cations [36][37][38].…”

Organic xenobiotics removal in constructed wetlands, with emphasis on the importance of the support matrix

“…This modification commonly consists of a simple ion exchange of the natural inorganic interlayer cations with certain organic cations such as quaternary ammonium cations of long hydrocarbon chains. By introducing cationic surfactant molecules into the interlamellar space through ion exchange, the properties of clay minerals are enhanced to those of organoclays [179][180][181]. The intercalation of a cationic surfactant between the clay layers changes the surface properties from highly hydrophilic to increasingly hydrophobic.…”