For the purpose of using zeolite together with polymer coagulant in the chemical treatment of low-level radioactive liquid wastes, the experiments were carried out on the removal of 137Cs by natural zeolite under different conditions.
Cation exchange capacities of natural zeolites produced in Japan were determined on powdered condition by means of batch method. Results obtained show that cation exchange capacities of natural zeolites, clinoptilolite and mordenite are 134-156meq Cs+/100g and 170-183meq Cs+/100g, respectively.
The removal of 137Cs by the zeolite which had the highest cation exchange capacity among them tested, was studied. The removal efficiency of both natural and Na-form zeolite was more than 95% under the following condition: concentration of 500ppm, pH of 2-11, Na+<250ppm, K+<50ppm, NH4+<25ppm, Ca2+<1, 000ppm and Cs<10-4M/l as a carrier. The removal efficiency from tap water was about 99% with 250ppm of zeolite. The combined use of 500ppm zeolite and 5ppm nonionic polymer coagulant was particularly effective for the removal of 137Cs.
