Experimental Studies Concerning the Semipermeable Membrane Separation Efficiency for 134Cs, 137Cs, 57Co, 58Co, 60Co, 54Mn in Liquid Radioactive Waste I. Treatment of secondary waste from POD decontamination procedure

Abstract

The paper presents the experimental tests concerning the treatment by membrane techniques of radioactive aqueous waste. Solutions, which have been treated by using the bench-scale installation, were radioactive simulated secondary wastes from the decontamination process with modified POD. Generally, an increasing of the retention is observed for most of the contaminants in the reverse osmosis experiments with pre-treatment steps. The main reason for taking a chemical treatment approach was to selectively remove soluble contaminants from the waste. In the optimization part of the precipitation step, several precipitation processes were compared. Based on this comparison, mixed [Fe(CN)6]4-/Al3+/Fe2+ was selected as a precipitation process applicable for precipitation of radionuclides and flocculation of suspended solid. Increased efficiencies for cesium radionuclides removal were obtained in natural zeolite adsorption pre-treatment stages and this was due to the fact that volcanic tuff used has a special affinity for this element. Usually, the addition of powdered active charcoal serves as an advanced purifying method used to remove organic compounds and residual radionuclides; thus by analyzing the experimental data (for POD wastes) one can observe a decreasing of about 50% for cobalt isotopes subsequently to the active charcoal adsorption.. The semipermeable membranes were used, which were prepared by the researchers from the Research Center for Macromolecular Materials and Membranes, Bucharest. The process efficiency was monitored by gamma spectrometry.

The application of polyethylenimine grafting reverse osmosis membrane in treating boron‐containing low‐level radioactive wastewaters

“…Lost salt rejection to a small extent 28 Surface adsorption Polyethyleneimine (PEI) Significantly improved antifouling properties to cationic foulants Less stable modification 29 Graft polymerization Polyethyleneimine (PEI) The zeta potential is positive under neutral conditions Salt rejection is to be improved 30 RO process. 10 Usually, the rejection of cesium(I) is only about 83-95% by using commercial membranes, and even lower in practical applications. 5 In order to achieve high rejection level of nuclides, the multiple-stage RO system has to be considered in many cases.…”

“…From previous studies, RO has a lower rejection of monovalent nuclides such as cesium(I) than bivalent nuclides such as cobalt(II) and strontium(II) . Considering the low concentration of nuclides in LRWs, it is difficult to remove cesium(I) in the RO process . Usually, the rejection of cesium(I) is only about 83–95% by using commercial membranes, and even lower in practical applications .…”