Energy efficient photocatalytic activation of peroxymonosulfate by g-C3N4 under 400 nm LED irradiation for degradation of Acid Orange 7
2022
Kokate, Santosh | Gupta, Smita | Kopuri, Vijayakumar Gupta | Prakash, Halan
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 (kₒbₛ) value for degradation of AO7 by g-C₃N₄/PMS/400-LED system was determined to be 0.094 min⁻¹. O₂·⁻, SO₄·⁻ were revealed by radical scavenging and ESR investigations. kₒbₛ 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.
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