Egg shell biochar-based green catalysts for the removal of organic pollutants by activating persulfate

The sulfate radical based advanced oxidation processes (SR-AOPs) has shown great potential in environmental remediation. In recent years, metal-free catalysts have attracted great attention due to their properties of low environmental risk and high catalytic activity. Among them, biochar-based catalysts are widely studied for their low cost by using substance existing in nature as raw material. In this work, egg shell derived biochar (ES-biochar), which was prepared by a simple one-pot pyrolysis method, has been proven to be an effective and innovative catalyst to activate persulfate for aqueous organic pollutant degradation. In addition, ES-biochar showed superior performance in the degradation reaction with removal efficiency of more than 90% in 120 min for 2,4-dichlorophenol (2,4-DCP), which was selected as a representative organic pollutant. Further quenching tests and electron spin resonance spectroscopy demonstrated that both free-radicals and non-radicals pathways were involved in this process, and OH dominated in free-radicals process. More importantly, this work not only proposed a novel biochar material as an efficient persulfate activator, but also provided a value-added reuse approach for egg shell in line with the concept of resource recycling and environmental sustainability.