CAPABILITY OF LEMNA GIBBA TO BIOSORB CESIUM-137 AND COBALT-60 FROM SIMULATED HAZARDOUS RADIOACTIVE WASTE SOLUTIONS

摘要

Low and intermediate level radioactive wastes are generated from daily applications of radioisotopes in various medical, industrial, agricultural and research fields. The release of these wastes to the surrounding environment represents a major complicated ecological crisis. Treatment of that radwastes is the most essential process in the radioactive waste management scheme. For simplicity and low running costs, phytoremediation technique has been candidate for processing some selected hazardous liquid waste streams. The submitted work aims at evaluating the capability of one of the aquatic plant, namely Lemna gibba, to biosorb Cs-137 and Co-60 from aqueous radioactive waste simulate. The study discusses, in batchwise laboratory scale experiments, the parameters that may affect the efficiency of Lemna gibba to bioremove and bioaccumulate the two radionuclides (e.g: contact time, pH value and the initial activity content of the waste simulate, light effect, biomass used, . . .). The uptake values, biosorption efficiency percentages, rate constant and isotherm factors were evaluated for the process. The uptakes values for Co-60 and Cs-137 respectively recorded 1213 Bq/gm and 872 Bq/gm from the waste simulate solution containing 6100 Bq and at pH=6.9 after 24 hours contact time. The results obtained exhibit the potential of the wide aquatic plant Lemna gibba to be used as a biological sorber for cesium-137 and cobalt-60 from their low and intermediate level aqueous radioactive waste stream successfully and efficiently.