LAUSR

Abstract The binding properties of dissolved organic matter (DOM) to iron oxides and heavy metal are critical to track their dynamic biogeochemistry cycling in aqueous environment. In this study, the mechanism of DOM-Fe-Cu coupled interaction based on coprecipitation (CPT) and adsorption (SOR) was compared, and the characteristics of fulvic acid (FA) in binding process were investigated. Different sorption affinities for Cu in coprecipitation versus adsorption were confirmed according to the changes of zeta potential. Fulvic acid, characterized by FTIR, EEM-PARAFAC and 2D-COS indicated the form of functional groups and their subsequent Fe Cu binding process were influenced to a great extent via the surface charge, pH and reaction mode. Three components were confirmed in Fe FA Cu complexes and the adsorption was more dominated by the protein-like component. The C O bonds and O C O bonds of FA played significant roles during the Fe Cu binding process, and aromatic C C showed the highest sensitivity to pH in adsorption but lowest in coprecipitation due to more faction of FA with high aromaticity. With these promising results, an enhanced picture about structural changes of FA in the Fe Cu aqueous solutions was constructed and the role of reaction modes was compared, highlighting the potential of combined spectroscopic technology in studying complex interactions in aquatic systems.