Efficient porous adsorbent for removal of cesium from contaminated water

An adsorbent for Cs removal from contaminated water based on phosphotungstic acid (PTA) embedded in SiO2 network was synthesized and granulated with γ-Al2O3. PTA/SiO2 had a high adsorption capacity towards Cs while the binder provided excellent mechanical characteristics of the material. It was shown that small particles of PTA/SiO2 with the sizes of 0.1–1 µm occupied space between larger particles of the binder (up to 5 µm). Chemical interaction between PTA and γ-Al2O3 during the adsorbent preparation also took place. The obtained porous material with the specific surface area of 286.9 m2/g contained 4.73% of PTA. Presence of Keggin units in the structure was confirmed by solid state NMR spectroscopy. Study of the adsorbent in Cs+ adsorption from solutions demonstrated its high adsorption capacity. The concentrations of Cs+ in the solutions after the column tests decreased by 3.3–5.2 times. The presence of Na+ and K+ as competing ions did not affect the adsorption. The material was tested in clean-up of radioactive water from the shelter of Chernobyl nuclear power plant (Ukraine). A significant decrease of 137Cs radioactivity was detected in all samples of radioactive water, especially in acidic solutions. Thus the adsorbent can be used for water treatment after incidents resulting in release of radioactive isotopes 134Cs and 137Cs.