Confining Engineered FeS Nanoparticles in Mesoporous Silica for Enhancing Mercury Sequestration and Methylation Suppression

Addressing mercury (Hg) contamination is an urgent priority due to its severe threats to human health. However, conventional approaches pose risks of generating highly toxic methylmercury (MeHg), highlighting the need for advanced strategies to reduce Hg bioavailability in remediation. To address this challenge, we developed a nanoconfinement strategy utilizing mesoporous silica nanoparticles (MSNs) as carriers to anchor highly dispersed mackinawite (FeS) nanoparticles within the pores for Hg(II) immobilization. Compared to FeS synthesized via homogeneous coprecipitation, the synthesized nanoconfined FeS (FeS@MSNs) exhibited enhanced adsorption kinetics with a pseudo-second-order adsorption rate constant of 5.50 × 10^-5 g FeS/(mg·min) and a maximum adsorption capacity of 1815.95 mg/g FeS, and improved resistance to environmental interference. Importantly, the size confinement effect of the pores prevented methylating bacteria from accessing immobilized Hg, thereby inhibiting MeHg generation by 97%. With a combination of spectroscopic and microscopic evidence, FeS@MSNs preferentially removed Hg(II) by forming mercury sulfide (HgS) precipitates within the pores rather than via surface adsorption or bulk precipitation. This study provides valuable insights into how nanoconfinement enhances nanomaterial performance and reduces the long-term bioavailability of heavy metals, demonstrating potential for diverse heavy metal remediation applications.