Iron-mineral-induced visible-light-catalytic degradation of BDE-47 enhanced by low-dose persulfate: Kinetics, mechanisms, and intervention of environmental factors.

Iron minerals and visible light are ubiquitous in the environment, which have crucial effects on the fate and migration of organic pollutants during in-situ remediation. In this work, the role of iron minerals in visible light-activated persulfate for BDE-47 degradation was systematically investigated. Under visible light irradiation, low-dose persulfate (PS) (10 μM) is capable of achieving the rapid elimination of BDE-47 in the presence of iron minerals, and goethite exhibited the best performance among selected iron minerals. In Goe/PS/vis system, the reactive species involved in the degradation of BDE-47 included ·OH, SO4·-, O2·-, h+ (photo-generated hole), and e-. The existence of O2 and S2O82- led to the synergy of ROS generation derived from h+/e-. Four oxidized intermediates of BDE-47 with lower estimated toxicity were identified by high-resolution mass spectrometry (HRMS), suggesting that PS-based in-situ remediation driven by goethite and visible light can achieve deep mineralization and detoxification of BDE-47. In addition, the Goe/PS/vis system adapts to various co-existing anions and NOMs. Co-existing heavy metals facilitated BDE-47 removal. Heavy metal ions adsorbed on goethite are reduced to zero valent metal by photoelectron during irradiation, which further promotes electron transfer. While heavy metals entering the goethite lattice in the form of isomorphous substitution introduce oxygen vacancy, further promoting BDE-47 degradation. These findings reveal the critical role of natural iron minerals in PS-based in-situ remediation for polluted water and soils under solar irradiation and provide new ideas for developing efficient strategies for the combined contamination of PBDEs and heavy metals.