Preparation of cerium oxide nanoparticles from monazite ore with microemulsion method

Abstract

Monazite ore in the South of Thailand was found to contain about 20% of cerium in the form of
phosphate compound. This cerium has been chemically separated from the ore and purified by ion exchange
columns at Rare Earth Research and Development Center, Thailand Institute of Nuclear Technology. Cerium
in EDTA solution from the ion exchange columns was precipitated with NaOH and then dissolved with HNO3
or HCl for the preparation of Ce(NO3)3⋅6H2O or CeCl3⋅7H2O precursors by crystallization. Microemulsion of
these cerium precursors was prepared in the mixture of n-hexane and butanol with cetyl trimethylammonium
bromide (CTAB) surfactant and mixed with microemulsion of NH4OH. Each mixture was dried at 250°C for
2 hr and calcined at 600°C for 1 hr to form nano-sized CeO2 powder. The powder was characterized by
XRD, TEM and BET. The average particle sizes of the prepared cerium oxide powders were found to be in the
range of 9 – 12 nm and their surface areas were in the range of 44 – 57 m2/g.