Wettability of compound organobentonites with ultra-low swelling modified by a series of bis-quaternary ammonium salts

Abstract A series of compound organobentonites were prepared by using three kinds of bis-quaternary ammonium salts (BQAS), hexamethyl ethyl diammonium methylsulfate (EDAS), hexamethyl hexyl diammonium methylsulfate (HDAS) and hexamethyl decyl diammonium methylsulfate (DDAS), with different alkyl chain lengths. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the structure of organobentonites. The results suggested that these organic cations lie flatly as a monolayer between the siloxane layers, the swelling of organobentonites was obviously decreased and the morphology of bentonite was largely changed after modification. In addition, the wettability of organobentonites for deionized water and n -heptane were measured by Washburn's pressure method simultaneous with height method. The simplified lipophilic-to-hydrophilic ratio ( SLHR ) and relative wettability index ( RWI ) were introduced to evaluate the relative lipophilic and hydrophilic properties of different organobentonites. The hydrophilic increased in an order of E–B, H–B and D–B for the unitary organobentonites; ED–B, EH–B and HD–B for the binary organobentonites; and 2.0CEC, 1.5CEC, 1.0CEC and 0.5CEC for the ternary organobentonites. It should be noted that, from the presence of ultra-low swelling and wettability of compound organobentonites, we can see a synergistic effect, the compounding of different chain-length of BQAS had, on the wettability of organobentonites.