The effects of gamma-irradiation on the electrokinetic and thermal behaviour of zirconium hydroxide

Zirconium hydroxide particles produced by rapid precipitation at pH 10.4, 7 or 2 were subjected to gamma-irradiation up to a final dose of 20 MGy. The effects of the gamma-irradiation were examined by X-ray powder diffraction , laser Raman spectroscopy, differential scanning calorimetry and microelec trophoretic measurements. It was found that gamma-irradiation had no influe nce on the behaviour of zirconium hydroxide during calcination and subseque nt cooling. The results of microelectrophoretic measurements showed that ga mma-irradiation influences the surface properties of zirconium hydroxide as a function of the precipitation pH. Zirconium hydroxide precipitated at pH 2 proved to be the most susceptible to gamma-irradiation, while the same g amma-irradiation had very little (if any) effect on the surface properties of zirconium hydroxide precipitated at pH 10.5. After gamma-irradiation, th e electrophoretic mobility of zirconium hydroxide precipitated at pH 2 was increased at both low and high pH, thereby indicating an increase in its ad sorption capacity. The analogy observed between the pH-dependence of the ef fects of gamma-irradiation on the electrokinetic behaviour of zirconium hyd roxide and the influence of ball-milling on the thermal behaviour of zircon ium hydroxide [8] suggested that the susceptibility of amorphous zirconium hydroxide increases with decrease of the precipitation pH.