Immobilization of aqueous and sediment-sorbed ciprofloxacin by stabilized Fe-Mn binary oxide nanoparticles: Influencing factors and reaction mechanisms

Fe-Mn binary oxide nanoparticles were reported to be effective for removal of aqueous pharmaceutical chemicals. However, little is known about its potential application in removing the sediment-sorbed contaminants. To bridge this knowledge gap, we synthesized stabilized Fe-Mn binary oxide nanoparticles using water-soluble carboxymethyl celluloses (CMC) as a stabilizer and tested their effectiveness for removal of aqueous and sediment-sorbed ciprofloxacin (CIP). Fully stabilized Fe-Mn binary oxide nanoparticles (0.05 g/L as Fe) were obtained in the presence of 0.5 g/L of CMC. When compared with non-stabilized Fe-Mn nanoparticles (FMBO), CMC-stabilized Fe-Mn nanoparticles (CMC-FMBO) showed relatively more favorable removal performance and particles stabilization facilitated delivering nanoparticles into sediment for in situ removal of CIP. The CIP removal by CMC-FMBO was highly pH dependent and the optimum pH was 6.0. A pseudo-second-order kinetic model was able to interpret the removal kinetics. When CIP-spiked sediment was treated with the CMC-FMBO, CMC-FMBO exhibited more excellent resistance to the sediment inhibitive effects and higher removal efficiency of CIP, compared to FMBO. This primary research suggests that CMC-FMBO hold the potential for facilitating removal of emerging contaminants in wastewater and sediment.