Highly pure MgO 2 nanoparticles as robust solid oxidant for enhanced Fenton-like degradation of organic contaminants.

•The purity of as-prepared MgO2 nanoparticles reaches more than 94 wt%.•The degradation reaction can be conducted in a wide pH range at room temperature.•Hydroxyl radicals are detected in the MgO2/Fe3+ degradation system.•Highly pure MgO2 is an ideal substitute for H2O2 in Fenton/Fenton-like reactions.