Intervention timing of H* and •OH determines the catalytical degradation of tribromophenol by palladium(II) doped green rust in redox-alternating environments

Abstract

Atomic hydrogen (H*) and hydroxyl radicals (•OH) can synergistically realize efficient mineralization of halogenated organic pollutants, but it requires an electrocatalytic or photoelectrocatalytic system. In this work, we developed a simple synergetic reduction-oxidation system for the degradation of tribromophenol (TBP) using Pd(II) doped green rust (GR). GR reduced Pd(II) to Pd(0) which catalyzed H2O/H+ to produce H* . H* completely reduced TBP to phenol. Meanwhile, excess H* involved in the generation of •OH under oxic conditions. The synergistic involvement of H* and •OH realized the mineralization of TBP, which could not be achieved by H* or •OH alone. Furthermore, the diffusion rate of dioxygen into solution determined sequential or synchronous involvement of H* and •OH, which significantly affected the mineralization efficiency of TBP. We proposed that the most efficient way to mineralize TBP was initiating H*-involved nucleophilic hydrodebromination first and then initiating •OH-involved electrophilic oxidation.