Separation Science and Technology, Vol.31, No.4, 533-544, 1996
Performance Evaluation of Reverse-Osmosis (Ro) and Nanofiltration (NF) Membranes for the Decontamination of Ammonium Diuranate Effluents
Our earlier studies using cellulose acetate membrane for the removal of radioactive species from ammonium diuranate filtrate effluents (ADUF) indicated promising performance in terms of very good decontamination factors (DF) and volume reduction factors (VRF). In view of the inherently short membrane life of cellulose acetate membrane, studies were carried out to assess the potential of polyamide (PA) based reverse osmosis (RO), nanofiltration (NF), and ultrafiltration (UF) membranes. Experiments based on real effluents corresponding to specific activity levels of microcuries/liter containing about 4% ammonium nitrate yielded decontaminated streams containing nanocuries/liter levels of radiocontaminants both for RO and NF membranes. UF membrane failed to give reasonable decontamination factors and hence was found unsuitable for the purpose. Due to very high ammonium nitrate solute rejection of PA membranes under RO condition, it was not possible to get high volume reduction factors. However, NF membranes have shown the potential to achieve very high VRF with good decontamination factors owing to their poor ammonium nitrate rejection characteristics and the consequent maintenance of permeate fluxes. The studies indicate the viability of the NF process for the treatment of ammonium diuranate filtrate effluents in large scale.