We report that simple adsorption of iron ions to graphene oxide (GO) can enhance a persulfate (PS) activation to degrade organic pollutants. The GO-Fe(II) and GO-Fe(III) were synthesized by directly adsorbing iron salts (Fe(II) and Fe(III), respectively) to GO. It is the first report to improve the PS activation by GO with simple Fe(III) addition without using toxic chemicals or high temperature/pressure conditions. Compared to GO and GO-Fe(II), the GO-Fe(III) exhibited highest phenol degradation (97.3%, 600 min) by activating PS, which was an encouraging result considering a competitive price of Fe(III). A comprehensive study utilizing particle characterization and iron leaching test revealed that PS reacted with the generated Fe(II) ions and oxygen-containing functional groups on the surface of GO-Fe(III). For the first time, the generation of 1O2 accompanied by radicals (%OH, SO4%? and %O2?) was discovered in the PS activation by iron heteroatom doping on GO. Lastly, the PS/GO-Fe(III) was applied to remediate a phenol spiked groundwater, river water and wastewater for possible practical applications. The findings can be used for the cost-efficient and scalable synthesis of GO catalysts for various heterogeneous catalytic processes.