Montmorillonite In Presence Research Articles

Synthesis and characterization of Al-pillared montmorillonite in presence of Mn(II)

The possibility of substituting aluminum in the Keggin tridecamer [Al 13O 4(OH) 24(H 2O) 12] 7+ by Mn(II) has been investigated and then the obtained polycation has been used as pillars for smectite. Pillaring solutions are prepared by a slow and partial hydrolysis of Al(III)–Mn(II) aqueous solutions with different Mn/(Al + Mn) molar ratio ( r = Mn/(Al + Mn) = 0, 1/13, 2/13 and 3/13) and examined by 27Al NMR spectroscopy. Powder X-ray diffraction (XRD), physisorption of N 2, chemical analysis and scanning electron microscope analyses (SEM) are used to study the precipitated sulfate salts and/or pillared clay minerals. This study reveals the absence of MnAl 12 species in the pillaring solution. The crystal system of the obtained Al 13–SO 4 salt is cubic (tetrahedral particles) in absence of Mn(II) and monoclinic (plate particles) in presence of Mn(II). When r is equal to 3/13, in addition to the monoclinic phase, an amorphous phase takes place. The intercalation process of montmorillonite is only disturbed, when r is equal to 3/13, because of the presence of a high polymeric aluminum phase.

Nickel Sorption to Goethite and Montmorillonite in Presence of Citrate

Mobility and bioavailability of nickel (Ni) in soil strongly depends on the interaction between Ni(II), ligands, and sorbents like organic matter and minerals. Sorption of Ni(II) and Ni(II)-citrate complexes to goethite and montmorillonite was examined in batch experiments with and without citrate as ligand in the pH range pH 4-7.5. Without citrate, montmorillonite shows higher Ni sorption than goethite. Citrate strongly decreases Ni sorption to montmorillonite; in presence of 100 microM citrate goethite becomes a stronger Ni sorbent than montmorillonite. Ni and citrate sorption was modeled successfully using the diffuse double layer model with the following reactions: Goethite: 3 [triple bond]FeOH + Citrate(3-) + 3H+ <=> [triple bond] Fe3Citrate + 3H2O, [triple bond]FeOH + Ni2+ <=> [triple bond] FeONi + H+ and 2 [triple bond] FeOH + Citrate(3)- + Ni2+ <=> [triple bond] FeONiCitrate(2-) + H+. Montmorillonite: 2X- + Ni2+ <=> X2Ni and [triple bond] AIOH + Ni2+ <=> AIONi+ + H+. Sorption of Ni to a mixture of goethite and montmorillonite could be calculated by use of reactions and constants for the monomineral systems. Without citrate, the sorbed amount of Ni per mass unit in the mixture can be found as a simple average of sorption to the two single sorbents, while in presence of citrate Ni sorption to montmorillonite is strongly influenced by citrate sorption to goethite.

Sorption and desorption of Co(II) on montmorillonite in presence and absence of fulvic acid

Sorption and desorption of Co(II) on montmorillonite under ambient conditions as a function of pH, ionic strength and fulvic acid are studied by batch technique. The results indicate that the sorption of Co(II) is dependent on pH, and ionic strength. The sorption-desorption hysteresis is found in the desorption tests. Surface complexation is considered as the main sorption mechanism of Co(II) on montmorillonite. The presence of fulvic acid (FA) enhances the sorption of Co(II) on montmorillonite. Montmorillonite is considered as a promising candidate for the solidification and pre-concentration of Co(II) from large volume of solutions.

Effect of microwave irradiation time on the synthesis of zirconia-pillared clays

In this work, we present the synthesis, at different zirconia/clay ratios, of zirconia-pillared montmorillonite in presence of microwave irradiation. The effect of irradiation time (5, 10, 20 and 30 min) on the structure and properties of the solids was also studied. The samples were characterized by X-ray diffraction, nitrogen adsorption (BET surface area) and thermo-programmed desorption of ammonia. It is shown that the irradiation time is critical between 5 and 10 min. For times longer than 10 min, no effect on the pillared clay features is observed.