Wettability alteration of organo-vermiculites induced by layer charge and tailored bis-N-heterocyclic quaternary ammonium salts

Wettability is an important surface property that deserves to further explore the factors on its alteration. Series of bis -N-heterocyclic quaternary ammonium salts with different spacer length and N-heterocyclic headgroups (morpholinium (BMMB, BMMD and BMMH), piperidinium (BPMH) and piperazinium (BMPMH)) have been synthesized and employed for altering the wettability of vermiculite and its derivates (Vts) treated by Li + -saturated heating method. The results of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM) and N 2 adsorption/desorption isotherms indicate that all of the bis -N-heterocyclic quaternary ammonium salts have been successfully inserted into the vermiculite layers, leading to the organic monolayer. The results of capillary rise tests combined with Lipophilic to Hydrophilic Ratio ( LHR ) values unveil the wettability alteration of the organo-Vts. As the layer charge decreases, the hydrophilicity of the organo-Vts gradually increases, which is probably caused by the decline in binding sites. As the result of the change in spacer length of modifier, the wetting properties of morpholinium-based organo-Vts change in order of BMMD-Vts > BMMH-Vts > BMMB-Vts, and difference in N-heterocyclic headgroups leads to the sequence of wettability: BMPMH-Vts > BPMH-Vts > BMMH-Vts. Layer charge of Vt, spacer length and the type of the N-heterocyclic headgroup of modifier have the synergistic effect on the regulation of the wettability.