Effects of added Fe°, Fe₃O₄, and Fe ₂O₃ on sorption of cephalosporin antibiotic in quartz-rich sands

Batch experiments were performed to evaluate sorption of zwitterionic and anionic cephapirin (CHP and CHP-, respectively), a cephalosporin antibiotic, in two quartz-rich sands spiked with iron (0.5-5% by weight). Sand A was approximately 65% quartz and 29% feldspar, with a grain diameter of 0.11 mm. Sand B was approximately 97% quartz and approximately 2% feldspar with a grain diameter of 0.39 mm. Bulk CHP sorption was evaluated relative to four added iron phases, namely, Fe [zero-valent iron (ZVI)], Fe3O4 (magnetite), and two forms of Fe2O3 (dull and specular hematite). Iron-particle sizes matched the respective sands to which they were added. Experiments were performed at two temperatures (21 and 39 C) and the results were compared with CHP sorption in unspiked sands. Maximum sorption occurred in Sand B and was approximately 225 mg/kg of spiked sand for initial aqueous CHP concentrations of 5-50 ppm, at 39 C and pH 5. Addition of ZVI caused the largest increase in CHP sorption with distribution coefficients (Kd′s) nearly 12 times those of ZVI-free sands. The study results imply the potential use of microscale ZVI, and to a lesser extent iron oxides, in the remediation of cephalosporin-contaminated groundwater and soil.