One-pot synthesis of bimetallic Pt/nZVI nanocomposites for enhanced removal of oxytetracycline: Roles of morphology changes and Pt catalysis

The bimetallic platinum-nanoscale zero-valent iron (Pt/nZVI) composites were synthesized by a liquid-phase reduction method. The as-prepared nanomaterials were first characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) surface area analysis, and zeta potential measurements. Results revealed that the introduction of Pt into bimetallic particles strongly affected their morphologies, which caused the improvement in the adsorption ability for organics. With 0.5 wt.% of Pt in Pt/nZVI composite (denoted as Pt0.5/nZVI), it exhibited the highest removal of antibiotic oxytetracycline (OTC). Nearly 100% of OTC (initially, 100 mg/L) was removed only after 20-min treatment under an optimal pH of 5.0 and a dose of 0.5 g/L. This study also confirmed that the removal of OTC by Pt/nZVI composite was contributed by adsorption (major), Fenton reactions, and reduction, although the fractional contribution changed during the reaction process. The intermediates formed during OTC degradation by nZVI and Pt/nZVI composite were finally detected and compared by UPLC®-QTof/MS analysis, which confirmed that the presence of Pt metal in bimetallic Pt/nZVI composites generated extra reactive hydrogen atoms for enhanced degradation of OTC.