Surfactant-modified montmorillonite by benzyloctadecyldimethylammonium chloride for removal of perchlorate

A high adsorption capacity (0.90mmol/g) of perchlorate was achieved on organo-montmorillonites (organo-MMTs) through modification by benzyloctadecyldimethylammonium chloride (BODMA-Cl), which typically possesses a long alkyl chain and a benzene ring. With increase in the amount of BODMA-Cl added, the XRD and FTIR results showed that the BODMA⁺/BODMA-Cl achieved a lateral bilayer, pseudo-trilayer and tilted paraffin-like bilayer configurations in the MMT interlayer space with improvement of ordered arrangement, and the formation of bilayers and/or micelles on the external surface also was demonstrated by TG-DTA and zeta potential curves. The EDX spectra of resultant products and adsorption isotherms of perchlorate on organo-MMTs suggested that a larger content of BODMA-Cl resulted in synthesized adsorbent with a greater adsorption capacity, because neutral BODMA-Cl is predominantly responsible for ion exchange with perchlorate. The maximum adsorption capacity was attained not only by enhanced affinity between BODMA⁺ and metallic layer of MMT, but also by increasing density of intercalated BODMA-Cl which is caused by hydrophobic interactions through long alkyl chains and π-π interactions through benzene rings among BODMA⁺/BODMA-Cl. It was also emphasized that the high adsorption capacity of perchlorate on organo-MMTs was achieved with a rapid adsorption rate and stably maintained against variations in temperature, initial solution pH and co-existing competitive anion.