Spectroscopic Studies of Synthetic and Natural Saponites: A Review

Abstract

Saponite is a trioctahedral 2:1 smectite with the ideal composition MxMg3AlxSi4-xO10(OH,F)2.nH2O (M = interlayer cation). Both the success of the saponite synthesis and the determination of its applications depends on robust knowledge of the structure and composition of saponite. Among the routine characterization techniques spectroscopic methods are the most common. This review, thus, provides an overview of various spectroscopic methods to characterize natural and synthetic saponite with focus on the extensive work by one of the authors (JTK). The IR and Raman spectra of natural and synthetic saponites are discussed in detail including the assignment of the observed bands. The crystallization of saponite is discussed based on the changes in the IR and Raman spectra and a possible crystallization model is provided. Infrared emission spectroscopy has been used to study the thermal changes of saponite in-situ including the dehydration and (partial) dehydroxylation up to 750˚C. 27Al and 29Si Magic-Angle-Spinning Nuclear Magnetic Resonance Spectroscopy is discussed (as well as 11B and 71Ga for B- and Ga-Si substitution) with respect to, in particular, Al(IV)/Al(VI) and Si/Al(IV) ratios. X-ray Photoelectron Spectroscopy provides besides chemical information also some information related to the local environments of the different elements in the saponite structure as reflected by their binding energies.

Removal of iron, zinc, and nickel-ions using nano bentonite and its applications on power station wastewater

“…The peaks at 466-624 cm À1 are due to a (Si-O) bending vibration, and the peak at 796 cm À1 may correspond to the stretching vibration of Al-O-Si. The OH bending bands [11,12]. After the adsorbent (Nano Bentonite) was loaded with Fe 3þ , Zn 2þ and Ni 2þ ions, it was located that there is a difference in the intensity or the places of the absorbance peaks and major change within the FTIR spectra after adsorption of Fe 3þ , Zn 2þ and Ni 2þ ions had been quite similar, this indicated the mechanism for the adsorption of both were the same [13].…”