Efficient removal of Cs+ and Sr2+ from aqueous solution using hierarchically structured hexagonal tungsten trioxide coated Fe3O4

Efficient, irreversible capture of radioactive strontium and cesium from aqueous media remains a serious task for nuclear waste disposal and environmental protection. To address this task, an effective sorbent based on magnetic composites coated with the synthetic porous exchanger WO3 was prepared by a facile method and characterized in detail. XRD analysis indicated that the WO3 coating did not change the phase of the Fe3O4 core, and TEM imaging further showed that Fe3O4@WO3 particles were successfully obtained with nearly uniform size. A batch of experiments was carried out to investigate the efficiency of Fe3O4@WO3 in removing Sr2+ and Cs+ under various environmental conditions. Experimental results showed that Fe3O4@WO3 has higher adsorption capacity for Sr2+ and Cs+ in acidic aqueous solution in comparison to the previous literature. The theoretical maximum adsorption capacities of Fe3O4@WO3 for Sr2+ and Cs+ are 44.178 and 53.175 mg g−1, respectively, as modeled by Langmuir isotherms. The adsorption process is fast and reaches equilibrium within 3 h, which is attributed to the good dispersion of WO3 on the surface of Fe3O4 and provided much more adsorption sites. Other than Ca2+ and K+, coexisting electrolyte ions had no significant competition effects on the removal of Sr2+ and Cs+ by Fe3O4@WO3. In addition, the Fe3O4@WO3 adsorbent remains stable in acidic solutions and may be repeatedly used 5 times without any noticeable loss in adsorption capacity; the used adsorbents can be easily separated from the aqueous solution using a magnetic method. The advantages of being nontoxic, highly stable, and resistant to acid, as well as having high adsorption capacity for Sr2+ and Cs+, indicate that Fe3O4@WO3 has significant potential for real radioactive wastewater treatment.