Carbonized eggshell membranes as highly active co-catalyst with Fe3+/ persulfate for boosting degradation of carbamazepine by accelerating Fe3+/ Fe2+ cycle

The sluggish Fe3+/Fe2+ cycle greatly limits the effectiveness of the Fe3+-induced persulfate (Fe3+/PS) system for degrading refractory organic pollutants. Coupling Fe3+/PS system with a co-catalyst is a promising strategy to solve this issue. Herein, we report a carbonized eggshell membrane (CESM) as a potential co-catalyst to efficiently drive Fe3+/PS oxidation. The promotion effect of the CESM on the Fe3+/Fe2+ cycle resulted in the improvement in the activity of the Fe3+/PS system to degrade carbamazepine (CBZ), with similar to 100 % CBZ removal achieved with low doses of Fe3+ (1.0 mg/L) and PS (100 mg/L). Crucially, a pseudo-first-order rate constant of CESM/Fe3+/PS system was 18- and 28-times that of the Fe3+/PS and CESM/PS systems. Experimental and theoretical findings reveal that the phenolic -OH groups and carbon--center persistent free radicals in CESM are electron donors, while the nitrogen sites function as favorable Fe3+-adsorption sites. The electron transfer in CESM/Fe3+/PS system occurred between a CESM and an attached Fe3+, facilitating the generation of Fe2+ and thus contributing to the continuous activation of PS. The quenching and electron paramagnetic resonance results indicate that active oxygen radicals (O-2(center dot-),(OH)-O-center dot and SO4 center dot-) and Fe(IV) acted together to realize the efficient CBZ degradation. Moreover, this system exhibited good reusability and environmental adaptability in various real water matrices. The co-catalyst effect of CESM is expected to inspire the exploration of utilization of different waste-biomass-derived organic materials as co-catalysts in the Fe3+/PS system for water purification.