Uranium immobilization on reactive material using RPB [articol]

Abstract

The paper present the researches on the characterization and probation reactive materials identified as optimal for permeable reactive barriers (RPB) accomplishment, which can be used in mine water decontamination. Experimental studies using mine waters from the Banat-Romania area, in discontinuous system, led to the selection of optimal reactive materials, depending on the distribution coefficient, Kd, namely: activated carbon type AC 20 G > apatite > activated carbon tip MN + P > zero-valent iron > indigenous natural zeolite from the Slanic Prahova area > indigenous natural zeolite from the Mirsid area. These materials were used for experiments in the continuously system for a multilayer column and the established process parameters - the flow rate of mine water through the column (0.5 BEV/h) and therefore the contact time between phases, grain of reactive material (<0.2 mm) and feeding uranium content (1.72 mg/L), lead to high immobilization of uranium (<0.048mg/L after 120 hours). Chemical mechanisms for uranium recovery on the selected materials are appropriate for low uranium content in mine waters. Laboratory tests performed on the column have followed besides uranium immobilization on reactive material, variation and concentration of carbonate ions, iron, calcium, magnesium and variation of pH, redox potential and electrical conductivity of mines water. These data provide information on the possibility of precipitates formation in the reactive material, which may affect the operating manner and maintenance requirements for systems to remove inorganic contaminants from permeable reactive barriers. Utilization of these types of materials for permeable reactive barriers, lead to high decontamination of mine water from uranium mining activities, according to environmental quality standards.