Synthesis of Eskolaite (α-Cr₂O₃) Nanostructures by Thermal Processing of Cr₂O₃-Loaded Activated Carbon

Abstract

A porous-nanostructured material made of short-chain eskolaite (α-Cr₂O₃) nanoparticles has been synthesized from Cr₂O₃-loaded activated carbon. The size of the nanoparticles in the chain ranges from 2 to 100 nm. The Cr₂O₃-loaded activated carbon was prepared by adsorption of dichromate () ions from aqueous solutions on ultrafine activated carbon (less than 12 µm in size) in a batch-glass-stirred reactor at 28°C. After a filtration step, the Cr₂O₃-loaded activated carbon was processed at high temperature under an oxidizing atmosphere to remove the carbon as CO₂(g) and obtain a product high in Cr₂O₃. This thermal process was carried out in a tube furnace using air as the oxidant. At 1100°C, a product with 98% Cr₂O₃ was produced. The synthesized material is highly porous and is composed by agglomerates of short chains of eskolaite nanoparticles. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area (electron) diffraction (SAED) microscopy were used to determine the chemical composition, texture, crystal structure, and size of the product components.

Keywords:

• Activated carbon
• chromium oxide
• dichromate adsorption
• eskolaite
• nanoparticle synthesis

Acknowledgments

The authors thank A. Robledo Cabrera for her support to carry out the MEB characterization and surface area measurement.

Notes

Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/upst.