Removal of trichloroethene by glucose oxidase immobilized on magnetite nanoparticles

To overcome the safety risks and low utilization efficiency of H₂O₂ in traditional Fenton processes, in situ production of H₂O₂ by enzymatic reactions has attracted increasing attention recently. In this study, magnetite-immobilized glucose oxidase (MIG) was prepared to catalyze the heterogeneous Fenton reaction for the removal of trichloroethene from water. The successful immobilization of glucose oxidase on magnetite was achieved with a loading efficiency of 70.54%. When combined with substrate glucose, MIG could efficiently remove 5-50 mg L^-1 trichloroethene from water with a final removal efficiency of 76.2% to 94.1% by 192 h. This system remained effective in the temperature range of 15-45 °C and pH range of 3.6-9.0. The removal was slightly inhibited by different cations and anions (influencing degree Ca²⁺ > Mg²⁺ > Cu²⁺ and H₂PO₄ ^- > Cl^- > SO₄ ^2-) and humic acid. Meanwhile, the MIG could be recycled for 4 cycles and was applicable to other chlorinated hydrocarbons. The results of reactive oxidative species generation monitoring and quenching experiments indicated that H₂O₂ generated by the enzymatic reaction was almost completely decomposed by magnetite to produce ·OH with a final cumulative concentration of 129 μM, which played a predominant role in trichloroethene degradation. Trichloroethene was almost completely dechlorinated into Cl^-, CO₂ and H₂O without production of any detectable organic chlorinated intermediates. This work reveals the potential of immobilized enzymes for in situ generation of ROS and remediation of organic chlorinated contaminants.