Energy efficient photocatalytic activation of peroxymonosulfate by g-C3N4 under 400 nm LED irradiation for degradation of Acid Orange 7

Photocatalytic activation of peroxymonosulfate (PMS) by graphitic carbon nitride (g-C3N4) is emerging as a sulfate radical anion based advanced oxidation process (S-AOP) for degradation of organic pollutants. Importantly, photocatalytic activation of PMS by g-C3N4 is energy intensive as light irradiation requires high electrical energy. Here, we studied activation of PMS by g-C3N4 under 400 nm light emitting diode (LED) irradiation (g-C3N4/PMS/400-LED system) for degradation of Acid Orange 7 (AO7). LED array having optical emission maximum around 400 nm (FWHM = 16 nm), with electrical input power of 1.54 W (14 V and 110 mA) was used for irradiation. Pseudo-first order rate constant (k(obs)) value for degradation of AO7 by g-C3N4/PMS/400-LED system was determined to be 0.094 min(-1). O-2(center dot-), SO4 center dot- were revealed by radical scavenging and ESR investigations. k(obs) value in simulated ground and real tap water were determined to be 0.068 min(-1) and 0.063 min(-1), respectively. g-C3N4 was stable, and reused four times without any significant loss in its photocatalytic activity. Importantly, electrical energy per order (EEO) for degradation of AO7 by g-C3N4/PMS/400-LED system was determined to be 24.51 kWh m(-3) order(-1). In contrast, the EEO value for the degradation of AO7 by g-C3N4 activated PMS under visible light irradiation (>400 nm), using conventional xenon lamp, (g-C3N4/PMS/Vis-Xe system) was found to be very high as 2702 kWh m(-3) order(-1). Thus, the study highlights, LED irradiation source is promising for the development of energy efficient g-C3N4 photocatalytic activation of PMS for removal of organic pollutants.