Mechanistic insight into multiple effects of copper ion on the photoreactivity of dissolved organic matter

Zhansheng Li; Hongxia Zhao; Jitao Lv; Shafiul Azam

doi:10.1016/j.jhazmat.2025.137124

Mechanistic insight into multiple effects of copper ion on the photoreactivity of dissolved organic matter

J Hazard Mater. 2025 Jan 5:487:137124. doi: 10.1016/j.jhazmat.2025.137124. Online ahead of print.

Authors

Zhansheng Li¹, Hongxia Zhao², Jitao Lv³, Shafiul Azam¹

Affiliations

¹ Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
² Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China. Electronic address: hxzhao@dlut.edu.cn.
³ State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.

PMID: 39813924
DOI: 10.1016/j.jhazmat.2025.137124

Abstract

Sunlight irradiation of dissolved organic matter (DOM) in surface water results in the production of photochemically produced reactive intermediates (PPRIs). This process is inevitably influenced by co-existing metal ions in aquatic environments; However, the underlying mechanism remains unclear. In this study, the effect of co-existing copper ion (Cu^{2 +}) on PPRIs produced by irradiation of DOM was systematically investigated, because Cu²⁺ is a typical redox transient cation and has strong affinity to DOM. The findings demonstrated that Cu²⁺, acting as cation bridge, caused DOM to aggregate, and had impacts on the optical properties and conformation of DOM. The electron shuttle and catalyst effect of Cu²⁺ could accelerate the charge transfer processes for the increasing of quantum yield and steady concentrations of hydroxyl radical (·OH) with the increase of concentrations of e^-_aq, O₂^.-, hydrogen peroxide (H₂O₂) and charge separated states of DOM (DOM^·+ or DOM^·-); On the other hand, Cu²⁺, as excited state quencher, decrease of apparent quantum yield of triplet state of DOM (³DOM*) and singlet oxygen (¹O₂) through static quenching of singlet excited of DOM (¹DOM*) and dynamic quenching of ³DOM*, respectively. The results provide a deeper understanding of the effect mechanism of Cu²⁺ on the DOM photochemistry in real environment and will be useful for assessment the photodegradation of organic contaminants in the presence of both DOM and Cu²⁺.

Keywords: Copper ion; Dissolved organic matter; PPRIs; Photochemical.