The adsorption of cesium by sulfonic acid functionalized hollow mesoporous silica microspheres

With the development of nuclear industry, radioactive elements such as ¹³⁷Cs put a threat on the water environment. It is a challenging task to remove the Cs⁺ in the nuclear wastewater. In the current study, we prepared a new Cs⁺-adsorbing material by introducing sulfhydryl group onto the surface of hollow mesoporous silica microspheres, then oxidizing the sulfhydryl group to sulfonic acid group. The obtained HMSS-SO₃H material had an excellent adsorption capacity for Cs⁺ in the aqueous solution, with an adsorption capacity of 51.53 mg g⁻¹ in 30 min. Characterization approaches, such as FT-IR and EDS, were used to confirm the result of modification. Adsorption experiments were carried out under. The influence of various parameters on the adsorption process was investigated under the conditions of changing pH, temperature, and time. The effect of competitive ions was also explored. The results indicated that the adsorption process followed the pseudo-second-order model and the main adsorption mechanisms are electrostatic interaction and coordination. The material had a best adsorption performance at a neutral pH. The adsorption process could well-fit the Langmuir's model, with a theoretical maximum adsorption capacity of 81.31 mg g⁻¹. And the adsorption capacity was slightly affected by competing ions such as Mg²⁺ and Ca²⁺. The results indicate that the HMSS-SO₃H prepared in this study is a promising adsorbent for Cs⁺, with the advantages of high adsorption capacity, fast adsorption rate and high selectivity.