Cobalt phthalocyanine-supported reduced graphene oxide: A highly efficient catalyst for heterogeneous activation of peroxymonosulfate for rhodamine B and pentachlorophenol degradation

In the present work, a cobalt phthalocyanine-supported reduced graphene oxide material (rGO-CoPc) was used as a catalyst for the degradation of rhodamine B (RhB) and pentachorophenol (PCP) in the presence of peroxymonosulfate (PMS). Inductively coupled plasma (ICP-OES), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were employed to characterize the properties of the composite and Co loading in the material. The catalytic activity of the rGO1-CoPc1 catalyst (rGO:CoPc = 1:1) was evaluated by UV–vis absorption spectroscopy at varying PMS concentrations and catalyst dosages. The complete dye removal was achieved in 9 min by rGO1-CoPc1/PMS system with a high initiation rate constant of 1.019 min−1 using RhB (25 µM), PMS (0.1 mM) and rGO1-CoPc1 (0.5 mg/mL). The removal efficiency was found to be as high as 100% after 11 cycles, suggesting a long-lasting catalytic activity of the of rGO1-CoPc1/PMS system. Quenching experiments suggested that sulfate (SO4−) radicals are the dominant species in the degradation process although hydroxyl (OH) radicals are also involved in the reaction mechanism. Furthermore, the catalyst was successfully applied for the efficient degradation of pentachlorophenol (PCP). A full degradation of PCP (25 µM) was achieved within 20 min using rGO1-CoPc1 (0.5 mg/mL) and PMS (0.6 mM). This study demonstrated that the use of rGO-CoPc as a heterogeneous catalyst for PMS activation is useful for the advanced oxidation processes (AOP) for practical wastewater treatment.