Efficient piezo-catalytic oxidation of aqueous As(III) over crystalline carbon nitride poly(heptazine imide)

Abstract

Piezo-catalysis is an emerging approach for green chemistry and water decontamination, which however is absent in aqueous arsenic remediation. Polymeric carbon nitride (PCN), a new piezoelectric material, was recently up-graded into crystalline carbon nitride, potassium poly(heptazine imide) (K-PHI). But the piezo-catalytic property of K-PHI is still blank in literature. This work first realized the oxidation of As(III) by piezo-catalysis and revealed the advanced piezo-catalytic property of K-PHI in comparison with PCN. A much superior (6.7 times faster) piezo-catalytic oxidation of As(III) was achieved on K-PHI, which benefits from its enhanced piezoelectric response deriving from the extended in-plane conjugation of heptazine units. Apart from the crystallinity of carbon nitride, the solution pH, sonication power and catalyst dosage were also found to be positively correlated with the piezo-catalytic As(III) oxidation. Additionally, h+ and ·O2− rather than OH· were proved to be the active species. These findings not only supply a novel approach for As(III) pollution regulation in water bodies, but also point out the direction to improve the piezo-catalytic performance of carbon nitride.