Acid activation and bleaching capacity of bentonites from the islands of Milos and Chios, Aegean, Greece

Characterization of Unye bentonite after treatment with sulfuric acid

“…(Figure 1a). 18,22 The intensity of the d 001 peak of montmorillonite at 15.33 Å in RB drastically decreased in the diffraction patterns of 0.2-AAB and 0.4-AAB (Figure 1b-c). Meanwhile, the d 060 peak at 1.50 Å, which is typical of dioctahedral smectites, 14,23 reached a maximum in the 0.4-AAB pattern.…”

“…The initial exchange of H + for Na and Ca in the interlayer of the bentonite and other minerals and the relative resistance of the feldspar, cristabolite, and tridymite impurities to acid treatment (Table 1) are consistent with previously reported results for non-swelling phyllosilicate layers. [18][19][20] XRPD patterns of raw and acid-activated bentonites Figure 1 shows the XRPD patterns of the RB and AAB samples. (Figure 1a).…”

“…The intensities of the OH-stretching bands at 3624 and 3614 cm -1 and the hydroxyl bending vibrations at 915 cm -1 (Al 2 OH), 885 cm -1 (AlFeOH), and 840 cm -1 (AlMgOH) of RB (Figure 2a) 17,18 partially decrease due to the release of Al, Fe, and Mg atoms from 0.2-AAB (Figure 2b). The OH-bending band of AlFeOH disappears completely while the AlMgOH and Al 2 OH bending bands are barely distinguishable in 0.4-AAB.…”

“…However, only a part of the clay surface is effectively utilized, and most of the surface does not contribute to the catalytic capacity of the clay. [17][18][19] Furthermore, the composition of the smectite layers substantially affects their stability against acid treatment; trioctahedral clays dissolve much faster than their dioctahedral counterparts, and the extent of dissolution of the central atoms from the tetrahedral and octahedral sheets depends on both the clay mineral type and the reaction conditions, such as the acid concentration, time, and temperature of the treatment. 20,21 The uses of the bentonite deposits in Turkey vary depending on the types and amounts of constituents found, such as smectites, other clay minerals, and non-clay minerals, including quartz, calcite, dolomite, and feldspar.…”

Response surface modeling of acid activation of raw diatomite using in sunflower oil bleaching by: Box–Behnken experimental design

“…It seemed that quartz still remained even when it was treated with hot acid. However, the XRD pattern of the activated diatomite shows reflections characteristic for amorphous silica, as shown by the increase of the broad characteristic band of this compound situated between 15 and 30°2θ this due to the deposition of amorphous silica gel caused after the attack on the octahedral layer and the exposure of the tetrahedral layer (Christidis et al 1997) (Fig. 2).…”