Piezo- and photo- responsive ZnO nanostructures for efficient tetracycline water remediation

Tetracycline (TC) is one of the most produced and consumpted antibiotics. TC pollution represents a serious environmental and health risk, since TC overaccumulates in water and food. Wastewater purification is of course an urgent need. In this frame, zinc oxide nanoflakes have been synthesized and used as catalyst for TC degradation in water. A double external trigger has been used to promote the TC degradation: luminous and mechanical stimuli were demonstrated to induce TC degradation, with kinetic constant values of 0.026 min-1 and 0.027 min-1, respectively. The two mechanisms clearly promote different degradation pathways and a synergic effect of the two stimuli is observed when combined. In fact, a kinetic parameter of 0.063 min-1 is recorded when the two stimuli are simultaneously applied. The photo- and piezo- degradation physical chemical mechanisms were rationalized starting from the experimental evidence recorded when ascorbic acid and isopropanol are used as superoxide radical and hydroxyl radical scavenger. Interestingly, TC degradation efficiency induced by the two separated stimuli, alternatively used in order to simulate a day-night alternance, was evaluated and demonstrated. Tap water spiked with TC was indeed used and again the proposed nanostructures allowed TC degradation with 66% of efficiency in 40 min