l‐cysteine‐modified Fe₃O₄ nanoparticles as a novel heterogeneous catalyst for persulfate activation on BTEX removal

Abstract

l‐cysteine‐modified Fe3O4 nanoparticles (l‐cys@nFe3O4) were synthesized successfully and used as catalyst to activate persulfate (PS) for benzene, toluene, ethylbenzene, and xylenes (BTEX) degradation. The composite was fully characterized, and the l‐cys@nFe3O4 had more protrusions and l‐cys was combined on the surface of nFe3O4. The removals of BTEX were 78.2%, 85.1%, 85.3%, 81.2%, respectively, in PS/l‐cys@nFe3O4 system, while only 52.7% 57.8%, 60.8%, and 56.3% of BTEX removals reached under the same condition for nFe3O4 chelated with l‐cys in 48 h. Four successive cycles of BTEX degradation were completed in PS/l‐cys@nFe3O4 system. The synergistic mechanisms of BTEX degradation in PS/l‐cys@nFe3O4 system were investigated by electron paramagnetic resonance (EPR), benzoic acid (BA) probe and X‐ray photoelectron spectroscopy (XPS) tests. SFe bond in l‐cys‐Fe complexes promoted the electron transfer between nFe3O4 core and the solution, iron and iron at the interface, thereby promoting the Fe3+/Fe2+ cycle and the catalytic capacity of nFe3O4. The optimal pH of PS/l‐cys@nFe3O4 system was 3, while HCO3− and Cl− exhibited negative influences on BTEX degradation. Only 14.2%, 15.5%, 15.9%, and 15.6% BTEX had been removed in the presence of 0.12‐M PS and 8.0 g/L l‐cys@nFe3O4 under the actual groundwater condition. However, expanding the dosage of PS and l‐cys@nFe3O4 was an effective strategy to overcome the adverse effect. Practitioner Points L‐cys@nFe3O4 were synthesized successfully and used as catalyst to activate PS for BTEX degradation. Four successive cycles of BTEX degradation were completed in PS/L‐cys@nFe3O4 system. lS―Fe bond in L‐cys@nFe3O4 promoted the electron transfer between PS and nFe3O4 core.