Synergistic effect of light in piezocatalytic activation of peroxymonosulfate using graphtic carbon nitride nanosheets for degradation of organic pollutants

The objective of the study was to understand the photo-piezocatalytic response of graphitic carbon nitride nanosheets (CNNS) for the activation of peroxymonosulfate (PMS). Methylene blue (MB) dye was targeted by PMS activation using CNNS under ultrasonic-assisted piezocatalysis and photo-piezocatalysis in a batch reactor for 120 min. CNNS has shown 98.4% MB removal within 120 min in a batch study (PMS = 200 mg L-1, CNNS = 1 g L-1, ultrasonicator = 40 kHz, UV-A light = 250 W). CNNS (0.0157 min-1) showed 1.3 times higher photo-piezocatalytic activity compared to bulk graphitic carbon nitride (CNB) for PMS activation due to improvement in in-plane polarization. In the photo-piezocatalytic CNNS/PMS/MB system, a scavenging study revealed that the primary contributors for MB removal were hydroxyl radical (.OH) and sulfate radical (SO4.-). The piezoelectric effect combined with light at CNNS improved the excitation of charge carriers, followed by charge carrier separation due to band tilting. Finally, the effects of CNNS dose, PMS dose, and competitive anions were studied for MB removal using CNNS under photo-piezocatalysis. Overall, CNNS is a promising photo-piezocatalyst for the removal of emerging organic pollutants through PMS activation.