Persulfate (PS)-activated, iron-based heterogeneous catalysts have attracted significant attention as a potential advanced and sustainable water purification system. Herein, a novel Fe 3 O 4 impregnated graphene oxide (Fe 3 O 4 @GO)-activated persulfate system (Fe 3 O 4 @GO+K 2 S 2 O 8 ) was synthesized by following a sustainable protocol and was tested on real wastewater containing dye pollutants. In the presence of the PS-activated system, the degradation efficiency of Rhodamine B (RhB) was significantly increased to a level of ≈95% compared with that of Fe 3 O 4 (≈25%). The influences of different operational parameters, including solution pH, persulfate dosage, and RhB concentration, were systemically evaluated. This system maintained its catalytic activity and durability with a negligible amount of iron leached during successive recirculation experiments. The degradation intermediates were further identified through reactive oxygen species (ROS) studies, where surface-bound SO 4 − was found to be dominant radical for RhB degradation. Moreover, the degradation mechanism of RhB in the Fe 3 O 4 @GO+K 2 S 2 O 8 system was discussed. Finally, the results indicate that the persulfate-activated Fe 3 O 4 @GO catalyst provided an effective pathway for the degradation of dye pollutants in real wastewater treatment.Water 2020, 12, 733 2 of 17 many advantages, such as a higher redox potential, wide pH range (2-11), longer life span, and more efficiency over •OH that enables excellent electron transfer of the oxidant toward higher contaminant degradation [6,7]. In general, the production of sulfate radicals can be obtained through PS activation by using several strategies, such as heat, ultraviolet, ultrasound, transition metal ions, carbonaceous-based materials, base, phenol, glucose, and ascorbic acid [8]. Consequently, transition-metal-based catalysts have been widely utilized as a PS activator due to their excellent catalytic efficiency [9]. However, the drawbacks of transition-metal-based catalysts for inhomogeneous systems include poor removal efficiency, precipitation of iron (III) as sludge, and less reusability, which has hindered their widespread use [10]. Hence, transition-metal-based heterogeneous catalyst systems have received tremendous attention for PS activation because of their environmentally friendly nature, high performance, simple operation stability, and high availability [11]. Iron (Fe)-based heterogeneous catalyst materials (e.g., Fe 3 O 4 ) have received much attention regarding frequently activating PS because of their high natural abundance, low price, and they could easily prevent secondary pollution through their recovery performance [12]. However, Fe 3 O 4 nanoparticles usually tend to aggregate in the solution, which can decrease their surface area and cause lower stability and catalytic efficiency [13]. Taking this into consideration, it is necessary to use a proper support that can enhance their overall performance. Graphene has been widely reported to be an emerging supporting material f...