Activated hydrogen-promoted self-generation of H2O2 and reduction of Fe(III) mediated by Pd-based catalysts: A green Fenton-like process

The traditional Fenton process has two issues that hinder its further application and promotion. One is the generation of large amounts of iron sludge. The other is the safe storage and transport of explosive H₂O₂. The problems could be solved by accelerating to regenerate Fe(II) and realizing to self-generate H₂O₂. The key to the solution lies in the use of reducing active hydrogen [H] to supply electrons. The effect of different loading methods of Pd⁰ nanoparticles (NPs), active centres for [H] generation, on the catalytic performance is unknown. Herein, the Pd/UiO-66(Zr) (Pd⁰ NPs loaded on the surface of UiO-66(Zr)) and Pd@UiO-66(Zr) (Pd⁰ NPs confined into the pores of UiO-66(Zr)) were synthesized. It confirmed that the [H] could be used to promote to regenerate Fe(II) and self-generate H₂O₂. Using only a trace amount of ferrous (25 μM) and without H₂O₂, the trimethoprim (20 mg·L⁻¹) could be thoroughly removed within 90 min. Moreover, the stability of Pd@UiO-66(Zr) was slightly superior to that of Pd/UiO-66(Zr) because of the confinement effect of pore wall on Pd⁰ NPs, as well as the interception effect on the intermediate products that can be complexed with Pd⁰ NPs.