Fe3O4 and Fe3O4/Fe2+/Fe0 catalyzed Fenton-like process for advanced treatment of pharmaceutical wastewater

Batch experiments were conducted for advanced treatment of pharmaceutical wastewater (after biological treatment) in a series of Fenton-like systems. Fe3O4-H2O2 system had the highest reactivity for COD removal comparing to classic Fenton and Fe-0-H2O2 systems. Effects of crucial experimental factors were investigated, including H2O2 and Fe3O4 dosage, pH, and reaction time. To reach 20% COD removal, the optimal conditions were pH of 3.0, Fe3O4 dosage of 1.0 g/L, and H2O2 dosage of 10 mg/L. Comparing with the classical Fenton's reaction, the Fe3O4-H2O2 system saved 75% H2O2, reduced 47% excess sludge, and slightly improved the COD removal. Furthermore, in order to meet the upcoming new local standard, Fe2+ and Fe-0 were introduced into Fe3O4-H2O2 system to form a hybrid system, Fe3O4/Fe-0/Fe2+-H2O2 (pH of 3.0, Fe3O4 of 1.0 g/L, Fe-0 of 0.23 g/L, Fe2+ of 34 mg/L, and H2O2 of 40 mg/L). Fe-0 and Fe2+ not only improved the COD removal and decreased iron sludge, but also enhanced the reuse of catalysts. Compared to the classic Fenton process, 80% H2O2 dosage was saved and 94% iron sludge was decreased. Meanwhile, the cost decrease by 1.66 RMB/m(3)-wastewater.