Changes in the surfaces of adsorbed para-nitrophenol on HDTMA organoclay—The XRD and TG study

Surfactant modified montmorillonitic clays synthesized by ion exchange using the hydrothermal reaction method have been compared using XRD and thermal analysis. X-ray diffraction (XRD) shows the changes in the surface properties of organoclays through expansion with surfactant loading. A polynomial relationship exists between the basal spacing and the CEC loading described by the equation y=0.3232x2+0.2052x+1.2834y=0.3232x2+0.2052x+1.2834 with R2=0.9955R2=0.9955. Different arrangements of the surfactant molecules in the organoclays are inferred from the changes in basal spacings. para-Nitrophenol also causes the expansion of the montmorillonite clay and affects the arrangements of the surfactant molecules within the clay layers. Changes in the surfactant molecular arrangements were analyzed by thermogravimetry. Additional thermal decomposition steps were observed when para-nitrophenol is adsorbed on the organoclay.

Graphical abstractSurfaces of a sodium montmorillonite from Neimeng, China were modified through intercalation with the cationic surfactant hexadecyltrimethylammonium bromide labeled HDTMAB (CH3(CH2)15(CH3)3N+Br−). Different configurations of surfactants within montmorillonite interlayer are proposed based on d(001) basal spacings. Changes in these configurations are enforced when para-nitrophenol is adsorbed.Figure optionsDownload full-size imageDownload as PowerPoint slide