Enhanced sequestration of tetracycline by Mn(II) encapsulated mesoporous silica nanoparticles: Synergistic sorption and mechanism

A novel Mn(II) encapsulated mesoporous silica nanoparticles (Mn-MSNs) was developed for efficiently removing antibiotic tetracycline from aqueous solutions. The material has a well-ordered, hexagonal mesopore structure with a large specific surface area (720 m(2)/g) and maximum sorption capacity (229 mg/g) that is about an order of magnitude higher than that of mesoporous silica nanoparticles without Mn-encapsulated, or encapsulated with other transition metal cations Fe3+ and Cu2+. Sorption results showed that the materials can sequestrate tetracycline within a large concentration range (5 jig/L-450 mg/L). Batch sorption experiment, spectroscopic analysis and density functional theory calculation collectively indicated that Mn-O complexation was the dominant mechanism for the tetracycline sorption. Electrostatic attraction and cation-pi interaction also contributed to tetracycline sorption with their contribution levels varying with pH in a synergetic way with the Mn-O complexation. The Mn(II) encapsulated MSNs exhibited a good regeneration property over five repeated sorption-desorption cycles, demonstrating its promising potential in the cost-effective applications of sequestrating tetracycline from wastewater, drinking water, and contaminated solutions.