Preparation Of Layered Nanocomposite Materials Containing Rare Earths, Titanium Dioxide And Clay

Recently, pillared interlayered clay being studied is a new nanocomposite material holding the layered structure of clay and achieving some new characteristics. In this paper, nanocomposite materials containing rare earths, titanium dioxide and clay were prepared by ion exchange technique using ethanol absolute as dispersant of clay, titanium tetrachloride as precursor to prepare sol of titanium dioxide, and cerium nitrate as precursor to prepare solution of rare earth ions.The preparation mechanism of composite materials was studied. Titanium ions were firstly exchanged by layered ions and introduced into the interlayers of clay, and rare earth ions began ion exchange when the interspace was big enough for them to enter into. The optimum preparation conditions of nanocomposite materials were found by studying the influence of titanium element content, rare earth elements content, concentration of glycerin aqueous solution, glycerin aqueous solution addition and concentration of suspension containing clay and ethanol absolute on pillared results. The nanocomposite materials with large interplanar distances were prepared as follows: the ratio of titanium elements to clay was 20.0~30.0 millmole titanium elements per 1.0g clay, the molar ratio of titanium elements to cerium elements was 0.1, the concentration of glycerin aqueous solution wasn't less than 33.0%, the ratio of titanium elements to glycerin aqueous solution was 2.0 millmole titanium elements per l.Og glycerin aqueous solution, the suspension concentration of clay wasn't higher than 5.0%. The mechanism of rare earth elements in the process of preparation of nanocomposite materials was studied. The results showed that rare earth ions in suspension not only had no block for titanium ions to transfer but also promoted their movement when doping appropriate rare earth elements, resulting in promotion of ion exchange and larger interplanar distances;big rare earth ions obstructed the access to the interlayers of clay when doping excessive rare earth elements, resulting in blocking the transfer of titanium ions and smaller interplanar distances.Photocatalytic properties of nanocomposite materials containing various rare earth elementsand titanium dioxide were studied. The results showed that nanocomposite materials prepared by doping appropriate rare earth elements had better photocatalytic properties than that prepared by doping excessive rare earth elements. The photocatalytic mechanism of composite materials was studied by integrating the theory of photocatalysis with experiment results. Because the site of photocatalytic reaction was limited in the interspace of clay, photocatalytic reaction occurred by two steps: firstly, organic molecules dispersed into the interlayers of clay;secondly, organic molecules and photocatalyst of RE/TiO2 occurred photocatalytic reaction, resulting in forming carbon dioxide.