This study explores the activation of peroxydisulfate (PDS) using transition metal-doped granular activated carbon (GAC) as a heterogeneous catalyst for degrading recalcitrant organic micropollutants, namely phenol and 4-chlorophenol (4-CP). PDS is a potent oxidant widely employed in advanced oxidation processes (AOPs) due to its ability to produce sulfate radicals (SO₄˙⁻) when activated, which can effectively degrade various organic pollutants. However, the efficiency of PDS activation depends significantly on the catalyst used. Since transition metals such as Fe, Mn, Co, Ni, and Cu are known to catalyze the activation of PDS, this study evaluates the advantage of incorporating these metals into a cheap and readily available catalyst support GAC to enhance the catalytic activity and stability of GAC for PDS activation. The expected benefits of multi-metal doping were rigorously investigated through a series of advanced characterization techniques, including X-ray diffraction (XRD) to analyze the crystalline structure of the catalysts, electron paramagnetic resonance (EPR) to detect reactive oxygen species, and inhibition tests to identify the oxidation mechanisms. The impact of various ions and pH conditions on the catalytic process was also evaluated to provide a comprehensive understanding of the system’s behavior. Multi-metal doping (i.e. combining different metals) is hypothesized to mitigate metal leaching and accelerate catalytic activation of PDS owing to the potential synergistic effects of different metal species. Each multi-metal-doped GAC catalyst was synthesized and tested under identical conditions to assess its efficiency in removing phenol and 4-CP from aqueous solutions. The findings from this study offer novel insights into the design of multi-metal doped GAC catalysts, providing an understanding of the synergetic effects of various metal species for the synthesis of effective and stable catalysts for micropollutants removal.

Keyword: Advanced oxidation processes(AOPs), Granular activated carbon(GAC), Heterogeneous catalysts, Multi-metal GAC catalysts, Oxidizing radicals, Peroxydisulfate(PDS)