Removal of tetracycline by Fe/Ni bimetallic nanoparticles in aqueous solution

This study investigated the degradation of tetracycline (TC) by Fe/Ni bimetallic nanoparticles (Fe/Ni BNPs) and nanoscale zero-valent iron (NZVI) in aqueous solution. Results revealed that Fe/Ni BNPs showed much better performance than NZVI. The effects of pH (5, 7 and 9), initial TC concentration and competitive anions (NO₃^-, H₂PO₄^-, SO₄^2- and HCO₃^-) on the removal of TC by Fe/Ni BNPs were investigated. The results indicated that the removal of TC was higher under acidic conditions and the reaction reached equilibrium more quickly at lower initial TC concentrations. The presence of NO₃^- greatly hindered the removal of TC, while the other anions (i.e., H₂PO₄^-, SO₄^2- and HCO₃^-) exhibited less inhibition. The significant impact of NO₃^- was due to the fact that Fe/Ni BNPs could be consumed via redox reaction with NO₃^-. Total organic carbon (TOC) and liquid chromatography-mass spectrometry (LC-MS) analysis shed light on the removal mechanisms of TC by Fe/Ni BNPs. The decrease of TOC in solution and the appearance of intermediate products on the surface of Fe/Ni BNPs indicated that both adsorption and degradation were involved in the reaction process. Based on the results of LC-MS, the detailed pathway of TC degradation by Fe/Ni BNPs was proposed.