Mechanistic revelation into the degradation of organic pollutants by calcium peroxide nanoparticles@polydopamine in Fe(III)-based catalytic systems

Fenton (or Fenton-like) reaction is widely used to degrade organic pollutants in water. However, instability and insecurity of liquid H2O2, narrow pH range and the low circulation rate between Fe2+/Fe3+ have become the most critical limiting factors of this technology. To break this technical barrier, calcium peroxide nanoparticles @polydopamine composites (nCaO2@PDA) with core–shell structures were prepared, which showed desirable hydrogen peroxide (H2O2) release performance as well as excellent activity for RhB degradation in a wide pH range of 2.0 ∼ 11.0 in the presence of Fe3+. By careful analysis the surface properties of PDA, the Fe2+ concentrations during reaction and the results of rational-designed control experiments, it is proved that PDA can reduce Fe3+ through the phenol-quinone transformation. More importantly, thanks to the unique core–shell structure, abundance of H2O2 and Fe2+ are both available in the vicinity of nCaO2@PDA, ensuring the superior catalytic performance than that of nCaO2. In addition, the HO• in solution rather than those adsorbed on PDA surface contribute most in the RhB degradation.