Synthesis and characterization of a NaA zeolite membrane and its applications for desalination of radioactive solutions

NaA zeolite membranes were prepared by hydrothermal synthesis on a porous α-alumina support with secondary growth crystallization. These membranes were characterized by XRD, SEM, AFM and permeation tests and were used for desalination of simulated radioactive wastes through pervaporation process. The influence of several operating parameters such as synthesis time, number of zeolite layers and seeding procedure was investigated. Based on our results the performance of NaA zeolite membranes can be improved by employing a multi-stage synthesis method. Results showed that membranes which were prepared in a four-stage process (each step 3 h) can yield best separation. At first the membranes were evaluated by dehydration of water/isopropanol solutions. Results showed that a separation factor equal to 5041 with 1.2 kg/m2.h total flux can be obtained. For ionic solutions including 0.001 M of Cs+, Sr2+ and MoO42– very high rejection factors were obtained (more than 99%). This work showed that zeolitic membranes can be used for treatment of low level radioactive wastes as well as desalination and volume reduction of these solutions especially through the pervaporation process.