A critical review of water contamination by polybrominated diphenyl ethers (PBDE) and main degradation techniques

The pollution of aquatic environments by polybrominated diphenyl ethers (PBDEs) has attracted considerable research interest in recent years. Photocatalysis, a well-established degradation technique, can be implemented to decompose PBDE congeners. Photocatalytic debromination is deemed to be the most applied method for the disintegration of PBDEs. However, the application of photocatalysis for less brominated congeners has not achieved the expected debromination efficiency due to the high chemical stability, lower electron affinity, and high electron density of benzene rings. This review paper provides an overview of the low brominated PBDEs debromination mechanisms and degradation pathways. Some of the most prevalent techniques applied for the decomposition of diphenyl ethers have been introduced and discussed. The capability of photocatalysis toward low brominated PBDEs congeners has been challenged. The photoreduction pathway of low brominated PBDEs has been explored in detail. The areas not investigated in previous research and the prospective of PBDEs photodecomposition in water media are proposed, and insightful suggestions have been made for future studies.