Mariela A. Fernández

Removal of Humic Acid by Organo-Montmorillonites: Influence of Surfactant Loading and Chain Length of Alkylammonium Cations

In this study, the characterization and adsorption properties of montmorillonite (MMT) and organomontmorillonites with different surfactant/cationic exchange capacity (CEC) ratios (1 and 2) of tetradecyl trimethylammonium (TDTMA+) and hexadecyl trimethylammonium (HDTMA+) cations were evaluated. The particle apparent diameter, determined by laser and scanning electron microscopy showed aggregate formation, which varied with loading and cation length of the surfactant used. X-ray diffraction analysis revealed the formation of a pseudotrilayer arrangement of both surfactants in the interlayer space, FTIR showed the characteristic bands of the surfactants and micelle formations, and zeta potential determinations indicated neutral or negative surface charge values, except for sample obtained with one CEC concentration exchanged with HDTMA+ (HDTMA1-MMT) where a charge reversal to positive was found. Higher adsorption amounts of humic acid (HA) were found for HDTMA1-MMT and TDTMA1-MMT samples than for MMT sample, while the increase in the loading of both surfactants decreased the amounts of HA adsorbed could be assigned to a higher micelle formation and different packing density of alkyl chain, in the external surface. The correlation found between the total surface area and negative zeta potential values and the HA adsorption rate, within each surfactant, indicated the strong influence that these properties have on HA adsorption.

Water decontamination by silver and copper montmorillonite

Several bactericide inorganic materials have been used for the purification of water with varying success. The characterisation of the incorporation of Ag or Cu cations in montmorillonite (MMT) clay, to obtain a bactericide material against E. coli, indicated that both outer and interlayer surfaces act as adsorption sites of AgO and Ag2O or CuO, respectively. The Ag-exchanged clays retain their bactericide ability even after being stirred in aqueous suspension, whereas samples with the highest concentration of Cu do not inhibit bacterial growth. Experiences from supernatants of Cu-exchanged clays indicated that bactericide capacity was present at high clay concentration.