Bentonite was modified by two novel bis-quaternary ammonium salts: hexamethyl propyl diammonium methylsulfate (PDAS) and hexamethyl butyl diammonium methylsulfate (BDAS). The microstructures of the organobentonites were characterized in terms of Infrared spectral (FT-IR), X-ray diffraction (XRD), differential thermogravimetry (DTG) and electron microscopy (SEM and TEM). The results show that basal spacings of organobentonites modified by PDAS and BDAS are 1.380 nm and 1.413 nm respectively, both of bis-quaternary ammonium salts are arranged in monolayers only among the interlayers of bentonite. Compared with one-step decomposition of BDAS, PDAS was decomposed by two steps within the bentonite galleries, and their onset decomposition temperatures and temperatures corresponds to the maximum mass loss rate (tpeak) is higher than their solid bis-quaternary ammonium salts by 15, 30 ℃ and 30, 80 ℃. Particle sizes and aggregation of organobentonites modified by PDAS are quietly different from those modified by BDAS.

Bentonite was modified by hexamethyl hexyl diammonium methylsulfate (HDAS), hexamethyl decyl diammonium methylsulfate (DDAS), hexamethonium bromide (HMB) and decamethonium bromide (DMB), respectively. The microstructures of the organobentonites were characterized using N ₂ adsorption technique, infrared spectral (IR), X-ray diffraction (XRD) and thermogravimetric analysis (TG). The results show that the specific surface area of the organobentonites is increased, while the pore volumes of two organobentonites are increase and other two are decrease. The bis-quaternary ammonium salts are intercalated into bentonite interlayer and arranged in monolayer, without changing the layer skeleton structure of silicate. The alkyl chain length and the matching anion of the quaternary ammonium salts have some impact on the microstructure of organobentonite.

Na-montmorillonite(Na-MMT) was modified by gemini quaternary ammonium salts (MD, DMB) and mono-quaternary ammonium salt (HTMAB) through the intercalation. Changes in the surfaces and microstructure were characterized using N ₂ adsorption isotherms, X-ray diffraction(XRD), and fourier transform infared spectrometer(FT-IR). The results show that the BET surface area and the basal spacings of MMT are reduced when modified by MD, DMB or HTMAB, which is contrast to the MMT when modified by the monovalent quaternary ammonium salts with long chain. The quaternary ammonium salts have intercalate into the interlamellar space of montmorillonite and the microstructure has changed. The surface properties change from hydrophilic to hydrophobic. In addition, the fractal dimension(D) of organo-MMT is decreased, that is to say, the porosity distribution is more uniformity. 

The flocculability of composite system of molecular deposition filming flooding agent(MDFFA) and fluorine-containing cationic surfactant (FC-4), decamethonium bromide (DMB), hexadecyl trimethyl ammonium (CTAB) was investigated, and the preliminary flocculation mechanism of these composite flocculants was discussed by analyzing Zeta potential on bentonite suspension. The results show that DMB and MDFFA have better flocculation capability on bentonite suspension. FC-4/MDFFA composite system has synergistic effect. 10%FC-4, 90%DMB and 10%CTAB appear best flocculability on bentonite suspension. Several tests on treating oil emulsion contenting bentonite reveal that the floccculability follows the order CTAB> DMB>MDFFA>FC-4. 90%FC-4, 70%DMB and 90%CTAB have best flocculability. Flocculating mechanism of FC-4, CTAB and their mixed systems with MDFFA is mainly charge neutralization, while MDFFA,DMB and DMB/MDFFA composite system is mainly compress electricity double layer.

 

Critical micelle concentration (cmc) of molecular deposition filming flooding agent (MDFFA) and sodium dodecyl sulfate (SDS) mixed systems were determined by conductivity method, and the effect of MDFFA on the precipitating behavior of anionic surfactant and multivalent cation was studied by means of light transmission measurement. The results show that MDFFA can decrease the cmc of SDS, the cmc decreases with the increasing of the concentration of MDFFA. With the increasing of temperature from 25 ℃ to 50 ℃, the cmc of  2 mmol/L MDFFA/SDS mixed system decreased. The cmcof 2 mmol/L MDFFA/SDS decreased with the increasing of concentration of NaCl. The precipitating behavior did not happen when MDFFA and SDS were mixed. MDFFA can restrain the precipitating behavior of anionic surfactant and Ca ²⁺. The capability of MDFFA restrain the precipitating behavior is better than NaCl, NaOH and NaHCO ₃.