Fenton’s reaction is often used to decompose stable substances in wastewater. In this study, experiments based on the effect of porous phosphate heterostructures as catalyst sorbent of Fe2+ synthesised by different procedures were planned. The examined PPH-Fe/H2O2 as oxidant in a heterogeneous process under mild conditions at pH 5 was found to be very efficient for discoloration of a simulated wastewater containing 50 mg L−1 of a commercial azo dye (Reactive Black 5) reaching 95% of decolourization. Under the described conditions total visual decolourization was achieved after 360 min. This study can provide a simple, effective, and economic system ideal for the treatment of toxic and nonbiodegradable azo dyes.