Peroxymonosulfate-enhanced visible light photocatalytic degradation of bisphenol A by perylene imide-modified g-C3N4

In this study, a metal-free photocatalyst (PI-g-C 3 N 4 ) was synthesized through an amidation reaction between perylene tetracarboxylic dianhydride (PTCDA) and graphitic carbon nitride (g-C 3 N 4 ). In order to enhance the photocatalytic degradation efficiency of bisphenol A (BPA) by 5 wt% PI-g-C 3 N 4 , peroxymonosulfate (PMS) was introduced into this system. When 5 mM PMS was added, 96% of BPA with an initial concentration of 10 mg/L was degraded within 60 min; the pseudo-first-order degradation kinetics constant of BPA was increased from 0.0057 to 0.0501 min −1 . Based on the photoelectrochemical analysis, it was proposed that PI-g-C 3 N 4 achieved a more effective separation of photogenerated electron–hole pairs and displayed higher conductivity than PTCDA and g-C 3 N 4 individually, thus promoting the PMS activation into active radicals by the photogenerated electrons. The BPA degradation was favored at high PMS concentrations under alkaline conditions. The slight inhibition effect of co-existing anions on the degradation of BPA followed the order: H 2 PO 4 − > NO 3 − ≈ HCO 3 − ; Cl − had a remarkable positive effect on the degradation of BPA. The radical quenching tests and electron spin resonance results indicated that O 2 − , 1 O 2 , and h + were the major species for the degradation of BPA. Combined with intermediates analysis, the degradation mechanism and pathway of BPA was proposed. The high stability of the 5 wt% PI-g-C 3 N 4 was finally demonstrated.