Preparation of mesoporous silica/sodium alginate composites and its removal performance of radioactive Sr2+

The extensive use of nuclear energy has brought new challenges to nuclear wastewater treatment, and it is urgent to develop absorptive materials with promising applications. The mesoporous silica(HMSS, MCM-41, SBA-15)/sodium alginate(SA) composites were constructed by embedding method, and the effects of raw material ratio, pH, adsorption time, initial concentration, adsorbent dosage, and competing ions on the Sr2+ adsorption performance of composite materials were explored. The composite materials before and after adsorption were characterized by fourier transform spectroscopy(FT-IR), scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). The results showed that under the conditions of T=298 K, pH=7.0, t=240 min, the saturated adsorption capacities of HMSS/SA(1∶3), MCM-41/SA(1∶3) and SBA-15/SA(1∶3) for Sr2+ could reach 49.67, 40.54 mg/g and 34.90 mg/g, respectively. The adsorption process was consistent with the Langmuir isotherm model and the pseudo-second-order reaction kinetics model, indicating that chemical adsorption characterized by monolayer adsorption was primarily involved. In the presence of competing ions Na+, K+, Ca2+ and Mg2+, the inhibitory strength followed Na+≈K+<Mg2+<Ca2+, and still a high selectivity for Sr2+ in Cs+ and Sr2+ systems. In addition, HMSS/SA(1∶3), MCM-41/SA(1∶3) and SBA-15/SA(1∶3) had good recycling performance.