Augmented photocatalytic degradation of Acetaminophen using hydrothermally treated g-C3N4 and persulfate under LED irradiation
S. Das Gupta, Jemi Gandhi, Santosh Kokate, Laxman G. Raikar, Vijayakumar Gupta Kopuri, Halan Prakash
Abstract
Photocatalytic degradation of organic pollutants in water using graphitic carbon nitride and persulfate under visible light (g-C 3 N 4 /PS system) has been studied. Here, we demonstrate augmentation of photocatalytic degradation of Acetaminophen (AAP) using hydrothermally treated g-C 3 N 4 and PS under 400 nm LED irradiation (HT-g-C 3 N 4 /PS system). A pseudo-first-order rate constant (k obs, 0.328 min −1 ) for degradation of AAP using HT-g-C 3 N 4 /PS system was determined to be 15 times higher compared to g-C 3 N 4 /PS system (k obs, 0.022 min −1 ). HT-g-C 3 N 4 showed a higher surface area (81 m 2 /g) than g-C 3 N 4 (21 m 2 /g). Photocurrent response for HT-g-C 3 N 4 was higher (1.5 times) than g-C 3 N 4 . Moreover, Nyquist plot semicircle for HT-g-C 3 N 4 was smaller compared to g-C 3 N 4 . These results confirm effective photoelectron-hole separation and charge-transfer in HT-g-C 3 N 4 compared to g-C 3 N 4 . AAP degradation using HT-g-C 3 N 4 /PS system was significantly inhibited with O 2 . − and h + scavengers compared to 1 O 2, S O 4 . − and H O . scavengers. ESR results revealed O 2 . − formation in HT-g-C 3 N 4 /PS system. Moreover, photocurrent measurements reveal AAP oxidation by h + of HT-g-C 3 N 4 was effective than g-C 3 N 4 . HT-g-C 3 N 4 was reused for five cycles in HT-g-C 3 N 4 /PS system. Augmented photocatalytic degradation of AAP by HT-g-C 3 N 4 /PS system compared to g-C 3 N 4 /PS is attributed to effective photoelectron hole separation of HT-g-C 3 N 4 that generates O 2 . − and h + for oxidation of pollutant. Importantly, electrical energy per order (E EO ) was 7.2 kWh m −3 order −1 . k obs for degradation of AAP in simulated groundwater and tap water were determined as 0.029 and 0.035 min −1 , respectively. Degradation intermediates of AAP were proposed. AAP ecotoxicity against marine bacteria Aliivibrio fischeri was completely removed after treatment by HT-g-C 3 N 4 /PS system.