Surfactant-assisted intercalation of crystal violet in layered γ-zirconium phosphate. Dye uptake from aqueous solutions

Batch intercalation experiments have carried out using gamma-zirconium phosphate (gamma-ZrP) and one of its cationic surfactant forms (gamma-ZrP/SUR+) for removing crystal violet from aqueous solutions. The intercalation reactions have conducted along two different intervals of time (24 and 48 h). The intercalation process has followed up by X-ray diffractometry (XRD), UV-Visible and FT-IR spectrophotometries. Regarding gamma-ZrP, XRD patterns show that obtained phases are impure, even after 48 h of the reaction time at a maximum dye loading of 18%. On the other side, gamma-ZrP/SUR+ gives an impure phase after 24 h while a pure one (2.47 nm) is obtained after 48 h at a maximum dye loading of 19%. In both cases, the observed dye loading values are approximately equal to the one calculated by molecular modeling (ca. 20%). The used analysis approaches prove that dye uptake capacity is a function of the reaction time and inclination angle of the dye molecules inside the solid matrices, where the highest dye uptakes are observed with gamma-ZrP and gamma-ZrP/SUR+ after 48 h of the reaction time. This time (48 h) is long enough for the dye molecules to be sufficiently accumulated inside the interlayer regions, in such situation dye molecules are forced to stand up perpendicular to the inorganic layers. With respect to intercalation properties, the difference between gamma-ZrP and gamma-ZrP/SUR+ could be referred to the difference between their gallery heights (1.22 and 3.00 nm, respectively). The pre-intercalation of gamma-ZrP with the surfactant molecules assists the inclusion and intercalation of the huge dye molecules into the interlayer region.