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Summary background: Montmorillonite (Mt) as a low-cost and
high-efficient adsorbent for cationic dyes has a promising application in
dye wastewater treatment. However, proper disposal of the used Mt is
critical to its application. Objective: In this work, the used Mt after the
adsorption of crystal violet (CV) was calcined under the protection of N"2,
with the purpose of transforming the used Mt into carbon monolayer-Mt
nanocomposites. Methods: Mt, the used Mt after CV adsorption, and the
calcined Mt have been characterized by XRD, FTIR, Raman spectra, thermal
analysis and elemental analysis. Results: X-ray diffraction results showed
that calcination led to the decrease of basal spacing of the used Mt from
2.06nm to 1.34nm. As such, the interlayer spacing of the calcined Mt is
0.38nm, close to the thickness of a single graphene layer (0.34nm),
suggesting the formation of carbon monolayer within the interlayer space of
Mt. FTIR characterization results showed that the infrared absorption bands
of CV, which were clearly displayed on the infrared spectra of the used Mt,
disappeared after the calcination. On the other hand, Raman spectra clearly
showed the presence of D-band and G-band on the calcined Mt. These
spectroscopy characterization results further proved the formation of
carbon monolayer within the interlayer spaces of Mt. Elemental analysis
results showed that about 40% carbon and 22% nitrogen from CV were
transformed into the carbon monolayer at 600 ^oC calcination, and the
transformation ratios decreased to 37% and 12% respectively at 800 ^oC
calcination. Therefore, the obtained carbon monolayer was an N-doped
graphene-like material. Conclusions: As such, this work provided an easy
way to transform the used Mt after the adsorption of cationic dyes into
carbon monolayer-Mt nanocomposites.
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