Study of Physical, Chemical and Morphological Alterations of Smectite Clay upon Activation and Functionalization via the Acid Treatment

Abstract

The present study was carried out on the effect of acid leaching on the modification and structure alteration of montmorillonite. A nanostructured, activated material was prepared by selective leaching of pure smectite clay with different concentrations of sulfuric acid (1-10 N/L) at 85˚C for 120 min using a solid/liquid ratio of 1:20 and a reflux system. The Fourier transform infrared (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-Ray diffraction (XRD) techniques were used for the characterization and study of the acid-treated montmorillonite clay. Chemical structure of specimens was distinguished by FTIR. The results showed that the formation of Si-OH bonds and leaching of Al 3+ ions increased progressively with severity of the acid treatment. As the FTIR studies indicated, acid treatment led to the removal of the octahedral Al 3+ cations and an increase in the Si-OH bonds. The morphological alteration of the untreated and treated montmorillonite was investigated by using TEM and SEM. X-ray fluorescence (XRF) analysis revealed a considerable decrease in the relative content of Al by increasing the acid strength. Moreover, the XRD results showed that the treatment using highly concentrated acid resulted in the formation of an amorphous silica phase.

Adsorption of Anionic Dye on the Acid-Functionalized Bentonite

“…The lower fraction of particles with a small diameter than 2 µm of RF2 can be related to this charge characteristic [70,71]. related to this charge characteristic [70,71]. Table 2 summarizes the granulometric compositions and average size of particles.…”

Ethylene vinyl acetate nanocomposites with hybrid silicate nanofillers of destabilized natural and commercial bentonites and organomontmorillonites

“…The changes in intensity of a peak also indicate the alteration of the bentonite structure. Reduction in peak intensities of AlAlOH and MgAlOH is due to the dissolution of Al and Mg cations during the destabilization process . CB_s shows an increasing peak intensity of AlAlOH and MgAlOH, and these peaks shifted toward a lower frequency when compared to its pristine bentonite.…”

“…, the IR band around ∼3,623 cm −1 represents the stretching vibration of the OH group, which coordinated to octahedral Al 3+ cation . The peaks that appear around ∼3,430 cm −1 and ∼1,640 cm −1 represent OH‐stretching vibration that attribute to adsorption of water molecules on the clay surface . Another peak appears at ∼1,039 cm −1 , which indicates SiO stretching .…”

Pirólise catalítica do PEBD usando como catalisador a vermiculita modificada

“…Na Tabela 1 observa-se que a lixiviação é acompanhada pelo o aumento da área específica (S BET ) até o sólido V3, entretanto, no tratamento a 4 mol.L -1 (V4), houve um decréscimo da valor de S BET , que é atribuído a fusão dos microporos formando mesoporos, diminuindo assim a área específica; tem-se também uma diminuição nos valores de acidez média com o tratamento ácido, o que é esperado pela retirada dos sítios de Al 3+ e Fe 3+ , acidez de Lewis [22] , e o aumento nos valores de acidez fraca é concordante com o aumento percentual de SiO 2 dos materiais, e conseqüente aumento dos grupos silanóis (SiOH), principais responsáveis pela acidez fraca [23] ; outra fonte de sítios de Brönsted são os prótons (H + ), que substituem os cátions interlamelares das argilas, devido a lixiviação [24] .…”