In Situ Preparation of Stabilized Iron Sulfide Nanoparticle-Impregnated Alginate Composite for Selenite Remediation.

Iron sulfide (FeS) nanoparticles have been applied for selenite (Se(IV)) remediation in recent decades. However, the easy aggregation and oxidization of FeS hamper their reactivity. In this study, in situ immobilization technology was applied to prepare FeS nanoparticle-impregnated alginate composite (FeS-SA) for Se(IV) remediation. FeS-SA removed 100% of the Se(IV) (0.13 mM), whereas pure nonstabilized FeS and sodium alginate (SA) beads eliminated only 27 and 20% of the Se(IV), respectively. The removal efficiency increased to 73% when pure stabilized FeS was used. Therefore, FeS-SA showed superior removal efficiency that was comparable with the joint effect of pure stabilized FeS and SA beads due to the homogeneous distribution of FeS in SA matrix. Furthermore, minor differences were established in the oxidation retardation effect of FeS exerted by SA beads under anoxic and oxic conditions. The biogenic regenerated FeS-SA still showed 40% removal efficiency for Se(IV) after five cycles due to the Fe leaching. XPS technique combined with the reference compounds and electron balance revealed that FeSe and metal selenium were the main selenium species after treatment. This in situ preparation of stabilized FeS-SA exhibited an excellent application prospect in the remediation of Se(IV).