A Piezo-Fenton System with Rapid Iron Cycling and Hydrogen Peroxide Self-Supply Driven by Ultrasound.

The piezo-Fenton system has attracted attention not only because it can enhance the Fenton reaction activity by mechanical energy input, but also because it is expected to realize a class of stimuli-responsive advanced oxidation systems by regulating energy input and hydrogen peroxide self-supply, thus greatly enriching the application possibilities of Fenton chemistry. In this work, a series of Fe-doped g-C 3 N 4 (g-C 3 N 4 -Fe) as a piezo-Fenton system were synthesized where the iron stably immobilized through Fe-N interaction. The piezo-induced electrons generate on g-C 3 N 4 matrix support the conversion of Fe(III) to Fe(II) and promote rate-limiting step of Fenton reaction. With the optimal Fe loading, g-C 3 N 4 -0.5Fe can achieve methylene blue (MB) degradation under ultrasonic treatment with first-order kinetic rate constants of 75×10 -3  min -1 . Most importantly, the g-C 3 N 4 -Fe can maintain good catalytic activity in a wide pH range (pH=2.0∼9.0) and be cyclic used without iron leaching to solution (<0.001 μg ⋅ L -1 ), overcoming the disadvantage of traditional Fe-based Fenton catalysts that can only be applied under acidic conditions and prone to secondary pollution. In addition, g-C 3 N 4 -0.5Fe also exhibits antibacterial properties of Escherichia coli and Staphylococcus aureus under ultrasound. Hydroxyl radicals mainly contribute to the degradation of MB and the sterilization process. Our work is an attempt to clarify the role of g-C 3 N 4 -Fe in the conversion of mechanical energy to ROS and provide inspirations for the piezo-Fenton system design.