Sulfate radical based advanced oxidation processes are promising techniques for the removal of organic compounds in aqueous solutions. In this study, FeO_3−xH_3−2x/Fe⁰ catalyst was prepared and used to activate persulfate (S₂O₈²⁻) for the degradation of p-chloroaniline (PCA). The results showed that nearly complete degradation of PCA was observed within 1 h in the persulfate-FeO_3−xH_3−2x/Fe⁰ system under the following optimized reaction conditions: PCA concentration 0.05 mM, FeO_3−xH_3−2x/Fe⁰ 1 g L⁻¹, persulfate 2.5 mM and pH 7.0. The PCA degradation was higher under acidic conditions when compared to alkaline conditions. A complete removal of the added PCA (0.05 mM) was achieved within 5 min with the addition of 2.5 mM persulfate and 1 g L⁻¹ FeO_3−xH_3−2x/Fe⁰ at pH 3.0. FeO_3−xH_3−2x/Fe⁰ catalyst was prepared by the calcination of Fe⁰ at 200 °C. The morphology of the catalyst was investigated with X-ray diffraction patterns (XRD), Scanning electron microscopy (SEM) and Fourier transform infrared spectra (FTIR). The results demonstrated that the catalyst surface was mainly composed of hematite γ-Fe₂O₃ and goethite (α-FeOOH).