In order to provide a theoretical foundation for the utilization of tailings as supplementary cementitious materials, the pozzolanic activity of muscovite—a typical mineral phase in tailings—before and after mechanical activation was investigated. In this study, significant pozzolanic activity of muscovite was obtained as a result of the structural and morphological changes that were induced by mechanical activation. The activated muscovite that was obtained after mechanical activation for 160 min satisfies the requirements for use as an active supplementary cementitious material, and the main characteristics of the pozzolana were as follows: median particle size (D50) of 11.7 μm, BET specific surface area of 28.82 m2 g−1, relative crystallinity of 14.99%, and pozzolanic activity index of 94.36%. Continuous grinding led to a gradual reduction in the relative crystallinity and an increase in the pozzolanic activity index due to the dehydroxylation reaction induced by mechanical activation, which occurred despite the fact that the specific surface area showed a decreasing trend when the grinding time was prolonged. Mechanically activated muscovite exhibited the capacity to react with calcium hydroxide to form calcium silicate hydrate, which is a typical characteristic of pozzolana. This experimental study provided a theoretical basis for evaluating the pozzolanic activity of muscovite using mechanical activation.

The harm caused by mine tailings has become increasingly problematic in recent years, so efforts are needed to dispose of or reutilize them in environmentally friendly ways. The objective of the present study was to find out if the hydration properties of muscovite contained in mine tailings are suitable for it to be used as a pozzolan in cement, after undergoing mechanical activation. Aqueous suspensions of mechanically activated muscovite were blended with 10, 20, or 30 wt.% calcium oxide and then allowed to harden. The hardened paste samples were analyzed by X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS) techniques. The results revealed that the mechanically activated muscovite exhibited pozzolanic reaction activity in the alkaline environment provided by calcium oxide, and the activated muscovite possessed a capacity to react with calcium hydroxide to form hydration products. The calcium oxide content affected significantly the quantities and kinds of hydration products, non-evaporable water content, and the compressive strength development of the paste samples. The hydration products of the 10% calcium oxide-activated, mechanically activated muscovite pastes were Al-containing hydrated calcium silicate (C-A-S-H) gel, stratlingite, and, upon addition of 20% and 30% calcium oxide, Ca-Al hydrotalcite-like (Ht) phases. The present study was helpful in evaluating the hydration properties of the mechanically activated muscovite and also provided a research basis for evaluating the hydration properties of mine tailings containing muscovite after mechanical activation. The results provided a theoretical basis for muscovite-containing mine tailings to be used as a cement additive, and was conducive to the large-scale utilization of mine tailings.

The effect of mechanical activation on the ion-exchange selectivity of natural zeolites from Russia, namely clinoptilolite-bearing tuffs and chabazites, was studied. The structural modifications and thermal properties were investigated, and the specific surface area and porosity of mechanically activated zeolites were determined. At activation doses of up to 1.0 kJ g–1 the main processes are the breakdown of the zeolite particles and pore structure changes. At greater activation doses amorphization takes place. It was shown that during the initial stage of activation in most cases the clinoptilolite selectivity for Sr2+ increased slightly and then decreased; the selectivity for Cu2+ increased 100 times; and the selectivity of chabazite-1 for Sr2+ increased 300 times.

A layered composite of Fe2O3-pillared bentonite (Fe-P-Bet), used as a catalyst in a Fenton-like process, was prepared and then its mechanical activation was studied in detail. The optimum conditions for preparation of Fe-P-Bet and the effects of mechanical activation on the catalytic activity of Fe-P-Bet were investigated systematically. The impact of the mechanical activation on the catalytic activity was affected by the filling ratio of the grinding medium, by the combination of different sized milling balls, by the rotation speed of the planet carrier, by the milling time and by the powder-to-ball ratio. Compared with the removal ratio of orange II of 14.5%, catalysed by Fe-P-Bet, the removal ratio catalysed by activated Fe2O3-pillared bentonite (A-Fe-P-Bet) was as high as 93.6%, and A-Fe-P-Bet had the merit of good stability and only a small amount of Fe leaching during the Fenton-like process. The catalysts prepared were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and by the BET method; A-Fe-P-Bet has a small particle size and a rough surface. The lattice distortion and decrease in the crystal size of α-Fe2O3, as well as damage to the layer structure of smectite in the bentonite, were the main reasons for the increase in the catalytic activity of A-Fe-P-Bet. The results indicated that mechanical activation was an easy and effective method for improving the catalytic activity of this bentonite-based layered composite and that A-Fe-P-Bet was a safe, ‘green’, catalyst material for use in Fenton-like oxidation during treatment of wastewater.