Feifei Jia

Preparation of monolayer muscovite through exfoliation of natural muscovite

The exfoliation of layered materials to two-dimensional (2D) nanosheets has sparked much attention since the emergence of graphene. These starting layered materials have strong in-plane bonds and weak van der Waals forces between layers. However, the exfoliation of layered materials with stronger interlayer forces has rarely been reported. Among them, natural muscovite is challenging to split into nanosheets due to its extreme interlayer forces. Here, stable monolayer muscovite was successfully prepared for the first time through weakening its layer attractions by enlarging the basal spacing followed by micromechanical cleavage to nanosheets. The XRD and IR results demonstrated that the crystalline structure of muscovite did not change, and that OTA+ exhibited a less ordered arrangement after exfoliation. HRTEM observation of the muscovite treated by our method revealed that it lost the periodicity in stacking, had hexagonal lattice fringes and was transparent to visible light, indicating that it was a highly crystalline 2D material. The smallest thickness of these 2D nanosheets confirmed by AFM was around 1.2 nm, demonstrating the existence of monolayer muscovite.

Correlation of natural muscovite exfoliation with interlayer and solvation forces

The correlation of natural muscovite exfoliation with interlayer and solvation forces was investigated in this work, respectively. The former was studied through exfoliating seven muscovite samples with different interlayer forces in 40% tert-butanol/water solvent, while the latter was performed by exfoliating a muscovite in various alcohol/water solvents. This study was implemented by means of measurements using a UV-VIS spectrophotometer, surface tension measurements, XRD, IR spectroscopy, and ICP-OES. The results indicated that the exfoliation degree of natural muscovite was strongly related to the interlayer and solvation forces. Weak interlayer forces facilitated the exfoliation of muscovite, which might be due to the fact that the interlayer structure was easily broken down. Solvents with a larger molecular size and similar surface energy to the muscovite (around 54.8 mJ m−2) were better for the exfoliation. This observation was attributed to the fact that the molecules of the solvents had stronger solvation forces to muscovite layers, leading them to intercalate into the adjacent layers to overcome the interlayer interactions and thus the exfoliation.

Cr(VI) Removal from Water with Amorphous Graphite Concentrate Contaminated by Iron

ABSTRACT This work attempted to explore the feasibility of using iron-contaminated graphite concentrate as an effective adsorbent for Cr(VI) removal from polluted water. Adsorption isotherm and kinetics were conducted to investigate the Cr(VI) removal capacity by the iron-contaminated amorphous graphite concentrates. In addition, SEM-EDS, XPS were carried out to further examine the solid samples. The results showed that amorphous graphite concentrate had a 1.52 mg/g adsorption capacity of Cr(VI), with the adsorption being fitted well with the pseudo-second-order kinetics model. In addition, chemical adsorption of Cr(V) on iron-contaminated graphite concentrate due to the formation of ≡Fe-O4HCr and Fe2-(CrO4)3 complexes was proposed. This study revealed that iron-contaminated amorphous graphite concentrate would be a cheap and good adsorbent for the removal of Cr(VI) from contaminated water.