Effect of biochar-derived dissolved organic matter on adsorption of sulfamethoxazole and chloramphenicol

Biochar-derived dissolved organic matter (DOM) plays a crucial role in controlling the interactions between pollutants and biochars. Here, we determined the compositions of DOM5 extracting from biochars (BCs) and acid-modified-biochars (MBCs) at different pH using UV, 3D-fluorescence and ultra-high-resolution mass spectroscopy (ESI-FTICR MS), which allowed us, for the first time, to distinguish the effect of DOM from biochars on sulfamethoxazole (SMX) and chloramphenicol (CAP) adsorbed onto biochars. The detailed results showed DOM shortened SMX and CAP adsorption equilibrium time, and more DOM increased SMX adsorbed, while inhibit CAP adsorbed onto biochar. Low-temperature biochar with a high extracting solution pH could release more DOM, and the polarity index of DOM was opposite with corresponding biochar. The correlation between the polarity of biochar and adsorption capacity was opposite to the correlation between the DOM released from corresponding biochars and adsorption capacity. Moreover, we found the fulvic and humic acid-like of DOM5 inhibited biochar adsorption for SMX, however, the more compounds fulvic and humic acid-like of DOM5 and CcHhOoNnSs molecular structure would promote biochar adsorption of CAP. This study demonstrates the potential of DOM as a new mechanism in adsorption and remediation studies but also reveals challenges for the future application of biochar.