Integrated forward osmosis-adsorption process for strontium-containing water treatment: Pre-concentration and solidification

Highlights: • An integrated forward osmosis-adsorption process was proposed for radioactive water treatment. • Radioactive Sr²⁺ could be effectively pre-concentrated and volume reduced by forward osmosis. • Forward osmosis fouling was more susceptible to Sr²⁺ concentration instead of draw solution concentration. • Further solidification of pre-concentrated Sr²⁺ was achievable through adsorption. • The proposed process could be modularized with the compact structure. The volume reduction and subsequent solidification of soluble radionuclides have been known as the major challenges in global radioactive water management, with the urgent needs for new technology development. Thus, a novel forward osmosis (FO)-adsorption process was developed for decontamination of strontium-containing radioactive water. The FO filtration driven by the osmotic pressure difference across FO membrane was more cost- and energy-effective for pre-concentration and volume reduction of low-concentration radioactive water prior to solidification, whereas subsequent adsorption with a novel adsorbent offered an effective mean for high-efficiency fixation of soluble radioactive on adsorbent. Results showed that the FO unit in the proposed integrated process could lead to a concentration factor of 10, with 90% of water volume reduction. The concentrated stream with a smaller volume from FO was further treated through adsorption of Sr²⁺ by nanostructured layered sodium vanadosilicate which had an excellent adsorption capacity of 174.3 mg Sr²⁺/g. It was found that 96.8–99.9% of soluble Sr²⁺ in FO concentrate could be removed by adsorption within several seconds. As the result, an excellent solidification of Sr²⁺ with an ultimate concentration factor of 1000 was achieved in the proposed novel integrated FO-adsorption process. These clearly demonstrated that this process would offer an environmentally sustainable and economically viable engineering solution for high-efficiency decontamination of Sr²⁺-containing radioactive water.