Hydrous oxides of polyvalent metals:

The hydrous oxides are of particular interest because most of them can function both as cation and anion exchangers above and below a certain pH value. These substances are mostly amphoteric in nature and their behaviour mainly depends upon the basicity of the central atom and the strength of the M - O and O - H bonds. A hydrous oxides of tetravalent elements e.g., Zr (IV), Ti (IV), Mn(IV), Sn(IV) and Ce(IV)  are the most studied compounds of this class. Mixed hydrous oxides of di- and tetravalent metals, tri- and tetra-valent have also been investigated. A hydrous oxides of quinquevalent and sexivalent metals generally show cation exchange properties and are stable towards most of the commonly used reagents. A hydrous oxide is useful for column operations and can be easily regenerated for use. Apart from enabling routine separations of various cations and anions, hydrous oxides have been used for the purification and isolation of transuranium elements from highly radioactive fission products. The titanium oxides columns have been used for the recovery of uranium and plutonium from the spent nuclear fuels.