The mechanism of activity-controlled release of 2,2′,4,4′-tetrabromodiphenyl degradation by polystyrene microcapsulated nanoscale zero-valent iron

Nano zero-valent iron (nZVI) is widely used for polychlorinated biphenyl (PBDE) remediation due to its cost-effectiveness and strong reduction capacity. However, its practical application is limited by poor stability, mobility, and antioxidant performance, as well as high reactivity that leads to side reactions and activity loss. To overcome these challenges, a poly(styrene)-encapsulated nZVI (PS-nZVI) core-shell structure was developed using dispersion polymerization. The resulting 10–15 nm polystyrene coating improved antioxidation, stability, mobility, and pH resistance (pH 5–9) compared to conventional nZVI. Incorporating a controlled release agent (20% acetone) at the start and midpoint of the reaction enhanced BDE-47 removal efficiency by 2.64 and 2.02 times, respectively, achieving nearly 100% activity release. Mechanistic studies revealed that the release agent promotes microcapsule corrosion and improves nZVI-BDE-47 interaction, enhancing both removal and debromination efficiency. PS-nZVI thus mitigates activity loss during storage and transport while enabling controlled reactivity for effective remediation.