Enhanced degradation of trichloroethylene in oxidative environment by nZVI/PDA functionalized rGO catalyst

Nano zero-valent iron (nZVI) particles with higher reactivity have been recognized as more efficient catalysts than Fe(II) for the groundwater remediation. The rapid emergence of novel catalyst supports efficiently prevent the rapid aggregation of nZVI and further improve catalytic reactivity. However, the lack of ability to avoid the potential oxidation of bare nZVI-support structure in air environment hinders its wider application in the actual contaminated sites. In this study, nZVI on reduced graphene oxide (rGO) functionalized by polydopamine (PDA) (nZVI-PDA@rGO) was synthesized successfully and applied into sodium persulfate (SPS), potassium monopersulfate (PMS) and H₂O₂ oxidative environments to remove trichloroethylene (TCE). For comparison, nZVI supported on solely rGO was prepared. The XRD test displayed the stronger stability of α-Fe(0) in nZVI-PDA@rGO catalyst against oxidation exposed to air. Compared with nZVI-rGO, a core shell structure of nZVI-PDA@rGO was observed in TEM image obviously. The dosage tests showed nZVI-PDA@rGO had a better catalytic reactivity than nZVI-rGO for TCE removal at lower catalyst and oxidant dosages, i.e. PMS dosage: 0.3 mM, catalyst dosage: 50 mg L^-1, TCE removal: 45.0% (nZVI-rGO) up to 99.6% (nZVI-PDA@rGO). TCE removal mechanisms were revealed through radical scavenger tests, demonstrating sulfate radicals played more important role in nZVI-PDA@rGO catalyzed-oxidant systems.