Visible light promoted the removal of tetrabromobisphenol A from water by humic acid-FeS colloid

Abstract

Ferrous sulfide (FeS) and humic acid (HA) are typical black substances in black bloom water. Based on the strong reduction ability of FeS and the photosensitivity of HA, the transformation of toxic organic pollutants by the combination of FeS and HA (HA-FeS) is not clear. In order to explore this issue, the stability of HA-FeS was analyzed by measuring the hydrodynamic diameter and zeta potential of HA-FeS, and then the removal mechanism and possible degradation pathway of tetrabromobisphenol A (TBBPA) by HA-FeS under continuous illumination were discussed. The results showed that the hydrodynamic diameter of FeS was reduced and the stability of FeS was improved, and it was easily suspended after FeS combined with the HA in the water. The combination of HA and FeS promoted the removal of TBBPA in water, no matter it was in the presence or absence of light. Besides, compared with the absence of light, the removal efficiency of TBBPA was improved by HA-FeS with continuous light. There were two reasons for the increase in the removal efficiency of TBBPA by HA-FeS. On the one hand, Fe2+ and S2− of HA-FeS had more stable chemical valence and obtained better reducibility under continuous light than that in the dark. On the other hand, light induced the release of active species (O2−, 1O2, and OH) in the HA-FeS composite colloid and further promoted the degradation of organic pollutants. Therefore, the black substances (FeS) of black blooms may play a beneficial role in the removal of pollutants under sunlight.