Preprint Review Version 1 Preserved in Portico This version is not peer-reviewed

Spectroscopic Studies of Synthetic and Natural Saponites: A Review

Version 1 : Received: 7 November 2020 / Approved: 10 November 2020 / Online: 10 November 2020 (13:00:59 CET)

A peer-reviewed article of this Preprint also exists.

Kloprogge, J.T.; Ponce, C.P. Spectroscopic Studies of Synthetic and Natural Saponites: A Review. Minerals 2021, 11, 112. Kloprogge, J.T.; Ponce, C.P. Spectroscopic Studies of Synthetic and Natural Saponites: A Review. Minerals 2021, 11, 112.


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.


Infrared spectroscopy; Magic-Angle-Spinning Nuclear Magnetic Resonance Spectroscopy; Raman spectroscopy; saponite, synthesis; X-ray Photoelectron Spectroscopy


Environmental and Earth Sciences, Atmospheric Science and Meteorology

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