SORPTION OF RADIOACTIVE STRONTIUM ON A SILICA-TITANIA MIXED HYDROUS OXIDE GEL

A silica-titania (Si-Ti) mixed hydroxide gel with Ti to Si mole ratio of 1 : 1 was prepared Studies on the sorption of radiostrontium from a lkaline solutions having various concentrations of sodium were carried out with Si-Ti. The distribution coefficient (K-d) of strontium decre ased with increasing concentrations of sodium from 0.1 to 4.0 mol.dm(- 3). The plot of log K-d versus log [Na+] gave a slope of -0.55 as agai nst the theoretical value of -2.0. This suggests that some other paths in addition to the simple stoichiometric ion exchange is also existin g for sorption. From pH titrations the pH(pzc) of Si-Ti was found to b e 4.22 coinciding nearly with the pH sorption edge. An attempt was mad e to correlate the sorption results with the surface characteristics o f the sort,ent. It was found that sorption is favored when the surface of the sorbent transforms into an anionic form. Sharp increase in the sorption of strontium was observed when the equilibrium pH was betwee n 7 and 10. This behavior could be attributed to the abrupt increase i n net negative charge on the surface of the sorbent.