Adsorption of hexavalent uranium on dunite

Abstract

Pollution of the environment with uranium and associated health effects to human have
 recently become of major concern, particularly due to the use of depleted uranium in armourbreaking
 bullets. Indeed, uranium in environmentally significant concentrations is found near to
 uranium mining and processing facilities and usually involves large volumes of wastewater.
 Removal of uranium from such large volumes of wastewaters will require a cost effective
 remediation technology. Conventional wastewater treatment technologies usually rely on
 mineral adsorbents and chemical flocculating agents. On the other hand chemical behaviour
 and migration of uranium species in the geosphere is strongly governed by
 adsorption/desorption phenomena on the underlying rock formations. Hence, studies
 regarding uranium adsorption on natural minerals and the evaluation of the corresponding
 thermodynamic data is of fundamental importance with respect to the treatment of
 contaminated waters and uranium migration in the geosphere.
 The present paper reports about the adsorption of hexavalent uranium on dunite at various
 experimental conditions (e.g. uranium concentration, amount of adsorbent, ionic strength, pH,
 temperature and contact time) and discusses the effect of these parameters on uranium
 adsorption. Evaluation of the experimental data shows that the optimum pH regarding uranium
 adsorption on dunite is about 6.5. The experimental adsorption data are well fitted by the
 langmuir isotherm and there is a linear correlation between adsorbent mass and amount of
 uranium, indicating on the formation of inner-sphere complexes. Moreover, adsorption
 experiments at various temperatures indicate on a spontaneous, entropy-driven processes
 and kinetic measurements show that the adsorption process follows a first order rate
 expression.