Neodymium sorption by clay minerals and zeoliferous rocks

The sorption of neodymium from its aqueous solutions (concentration range approx. 10-450 mg l(-1)) by montmorillonite, kaolinite and a clinoptilolite-containing rock has been investigated, using Nd-147 as radioactive tracer and gamma-ray spectrometry. The neodymium uptake by montmorillonite was found to be much higher than of the other two materials in the whole investigated concentration range. However, in the case of montmorillonite and zeoliferous rock, the uptake ability is lower than that allowed by the measured CEC values and can be described by Langmuir-type equations. In the case of kaolinite, the observed higher than CEC- allowed uptake values could be attributed to sorption by mechanisms other than ion-exchange. The corresponding data obey a Freundlich-type sorption equation. Among the three geological materials investigated, montmorillonite exhibits the highest perspectives of application for the treatment and disposal of neodymium and trivalent actinides in nuclear industry.