MAS NMR and EPR study of structural changes in talc and montmorillonite induced by grinding

Abstract

The milling process in the solid-state 2:1 clay minerals, montmorillonite and talc, which have different cation exchange capacities, is reported here. Several instrumental techniques were used to monitor systematically the products formed. The dehydroxylation/amorphization of the montmorillonite and talc structures occurs within 3 and 6 h of milling, respectively. Electron paramagnetic resonance spectra indicated that structural Mn2+ was oxidized more quickly in the montmorillonite structure than in talc, while the paramagnetic defects increased during milling. Nuclear magnetic resonance was also used to monitor the environmental changes for Si and Al during milling.

Nanoclay montmorillonite as an adsorbent for CO2 capture: Experimental and modeling

“…The most intense peak at 1,031 cm −1 is related to the Si‐O stretch in the plane and the shoulder at 1,114 cm −1 shows the stretching vibration of the Si‐O outside the plane . The peaks at 912 and 881 cm −1 are related to Al‐Al‐OH and Al‐Fe‐OH stretching, respectively . The peaks at 790 and 694 cm −1 indicate the presence of impurities in the form of amorphous tridymite and quartz in the structure .…”

“…The FTIR analysis in Figure shows that the range smaller than 1,250 cm −1 is related to the internal and external bonds of the MMT nanoclay. Existing peaks of 536 and 464 cm −1 , respectively, represent the reactions of Al‐O‐Si and Si‐O‐Si decomposition and the peak in 418 cm −1 is due to the bending vibration of Si‐O . The most intense peak at 1,031 cm −1 is related to the Si‐O stretch in the plane and the shoulder at 1,114 cm −1 shows the stretching vibration of the Si‐O outside the plane .…”

“…Existing peaks of 536 and 464 cm −1 , respectively, represent the reactions of Al-O-Si and Si-O-Si decomposition and the peak in 418 cm −1 is due to the bending vibration of Si-O. [20] The most intense peak at 1,031 cm −1 is related to the Si-O stretch in the plane and the shoulder at 1,114 cm −1 shows the stretching vibration of the Si-O outside the plane. [19] The peaks at 912 and 881 cm −1 are related to Al-Al-OH and Al-Fe-OH stretching, respectively.…”

“…[19] The peaks at 912 and 881 cm −1 are related to Al-Al-OH and Al-Fe-OH stretching, respectively. [20,21] The peaks at 790 and 694 cm −1 indicate the presence of impurities in the form of amorphous tridymite and quartz in the structure. [21] In the sample without calcining, the peaks at 3,411 and 3,388 cm −1 demonstrate the hydration stretching -OH and is related to the presence of H 2 O in the structure and the peak available at 3,627 cm −1 is related to the stretching -OH in the structure.…”

“…[21] In the sample without calcining, the peaks at 3,411 and 3,388 cm −1 demonstrate the hydration stretching -OH and is related to the presence of H 2 O in the structure and the peak available at 3,627 cm −1 is related to the stretching -OH in the structure. [20][21][22] To identify the structural characteristics of MMT, Brunauer-Emmett-Teller (BET) analysis was used for nitrogen adsorption and desorption in particles. The volume and distribution of pore size were calculated using the Barrett-Joyner-Halenda (BJH) method.…”