The piezoelectric catalysis effect of tourmalines in the degradation of organic pollutants

Abstract

The discovery of the piezoelectricity of tourmalines has been reported over three decades, but very few studies exploring the piezoelectric catalysis effect of tourmalines. Herein, the piezoelectric catalysis effect of iron-based and lithium-based tourmalines (Fe-TM and Li-TM) was studied through the degradation of Rhodamine B (RhB) and p-nitrophenol (PNP) in aqueous solution as model reaction in tourmaline/ultrasound system. In ultrasonic condition, the obvious degradation of RhB and PNP was observed and confirmed stemming from the piezoelectric catalysis effect of Fe-TM and Li-TM. Fe-TM was found to have higher surface voltage (560–590 mV) and a higher piezoelectric coefficient of 9.5 pC/N, compared to Li-TM (surface voltage: 410–450 mV; piezoelectric coefficient: 6.7 pC/N). Accordingly, high and stable piezoelectric catalysis activity was observed on Fe-TM in the degradation of RhB and PNP. Through annealing at 800 ℃ in air, Fe-TM can be converted from buergerite tourmaline into foitite tourmaline, and the piezoelectric catalysis activity was basically unchanged. In tourmaline/ultrasound system, the degradation of RhB and PNP was mainly initiated by •OH that be produced from the oxidation of water with the piezoelectric potential of tourmalines. The present work observes and confirms the piezoelectric catalysis effect of tourmalines, which could inspire the new applications and understanding of tourmalines.