Heterogeneous Fenton-like catalytic removal of p-nitrophenol in water using acid-activated fly ash

► A nitric-acid-activated fly ash (AFA) as heterogeneous Fenton-like catalyst. ► Catalyst for PNP wastewater treatment. ► Good p-NP removal efficiency can be achieved if only enough long-time under milder pHs. ► Better catalytic stability and reusability can be achieved under less reaction time and higher AFA load. ► AFA catalytic mechanisms are similar with that to decomposition of H2O2 by homogeneous Fe3+.