Adsorption of ciprofloxacin and Cu2+ onto biochars in the presence of dissolved organic matter derived from animal manure

Biochar are widely used as adsorbents/amendments for immobilizing pollutants in contaminated soils. In this study, the effects of dissolved organic matter derived from chicken manure (CMDOM) on the adsorption of ciprofloxacin (CIP) and Cu2+ onto biochars were investigated. The FTIR spectra indicated that π-π donor-acceptor interactions between the hydroxyl groups on the biochar surface and the fluorine group connected to the benzene ring of CIP molecule was the main adsorption mechanism for CIP. CMDOM molecules interacted with the aromatic components in biochars and thus modified the surface chemical properties of biochar. The effect of CMDOM on the adsorption of CIP onto biochars showed great dependence on the distribution of solid adsorbed CMDOM and CMDOM in aqueous solutions. The solid adsorbed CMDOM facilitated CIP adsorption owing to increase the content of –OH on biochar surface, which could provide more π-electron donors and thus strengthened π-π EDA interactions between CIP and biochars. The EDS spectra showed that the ion exchange with K+ was the main adsorption mechanism for Cu2+ onto biochars, and the presence of CMDOM enhanced complexation of Cu2+ with adsorbed CMDOM, thus increasing Cu2+ adsorption onto biochars. These results are useful for the application of biochars to immobilize antibiotic and heavy metals in contaminated farmland soils when animal manure fertilizers is presented in soil environment.