Separation of heavy metals from aqueous solutions using biosorbents: development of contacting devices for uranium removal

Abstract

The specific objective of the work described herein was to evaluate the utility of a mixed culture of denitrifying bacteria for the separation of uranium from process wastewaters. The selection of this culture was based upon the knowledge that wastewaters generated in a number of nuclear-materials processing operations require treatment to remove both nitrate and uranium. It was anticipated that microbial cells, resulting as a by-product in the conversion of nitrate to gaseous molecular nitrogen, might serve as an effective biosorbent for the separation of uranium from the wastewaters. The culture was evaluated with respect to the rate of uranium accumulation and the equilibrium distribution of uranium between the cell and solvent phases. The effects of process variables on the rate of uranium accumulation and equilibrium distribution were studied. Several methods for contacting the biosorbent with aqueous uranium solutions were examined. These included suspended cells or flocs in stirred-tank reactors and films of cells or inert particles in columnar reactors.