Synthesis and characterization of montmorillonite-(Ce or Zr) phosphate crosslinked compounds

A series of montmorillonite-(Ce or Zr) phosphate crosslinked compounds has been synthesized by reaction of a cerium or zirconium cation exchanged montmorillonite (diameter ~2 pm) with phosphoric acid under appropriate conditions of concentration, addition rate and temperature. The materials thus obtained were characterized by chemical and thermal analyses, X-ray diffraction, IR spectroscopy and SEM-EDX. The results show that tetravalent metal phosphate acts as a cement among the clay particles, hindering material dispersion in aqueous media. At the same time, this framework limits the cerium or zirconium hydrolysis. The surface area of the metal(W) phosphate crosslinked montmorillonite obtained increases, relative to that reported for the individual precursors. On the other hand, micrographs and microanalyses of the samples show that a fraction of the Ce(IV) or Zr(IV) ions remain as exchange cations in the clay particles.