Adsorption and photocatalysis compiled toxic dyes mineralization using graphitic carbon nitride modified ZnFe2O4 and CoFe2O4 photocatalysts supported onto N-doped graphene

Abstract

The novel attributes of graphitic carbon nitride (GCN), such as non-toxic nature, less cost, simple fabrication, earth abundance, and great chemical resistance have popularized them as multifac-eted nanomaterials, as compared to the traditional semiconductors. In present work, GCN modified ZnFe2 O4 (ZF) and CoFe2 O4 (CF) were immobilized onto N-doped graphene (NG) via modified hydrothermal method. GCN/ZnFe2 O4 /NG and GCN/CoFe2 O4 /NG photocatalysts were characterized using advanced spectral techniques viz. High-resolution transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared, UV, and X-ray photoelec-tron spectroscopy. The photocatalytic performance of the fabricated photocatalysts was examined for effective photodegradation of malachite green (MG) and methyl orange (MO) under visible light radiation. The photodegradation of MG within 70 min followed the trend: GCN/CoFe2 O4 /NG (98%) > GCN/ZnFe2 O4 /NG (93%) > CoFe2 O4 (50%) > ZnFe2 O4 (48%) > GCN (46%) > NG (28%). For MO, removal efficiency followed the order after 140 min: GCN/CoFe2 O4 /NG (99%) > GCN/ZnFe2 O4 /NG (96%) > CoFe2 O4 (51%) > ZnFe2 O4 (49%) > GCN (48%) > NG (28%). The degradation rate constants (k) for MG degradation using GCN/ZnFe2 O4 /NG and GCN/CoFe2 O4 /NG were 0.032 and 0.034 min–1, respectively, meanwhile, for MO elimination the obtained rate constants were respectively 0.029 and 0.026 min–1. The adsorption experiments revealed that the MG maximum adsorption happened at pH 8–9, whereas MO maximum adsorption occurred at pH 4. The formation of intermediates during the photodegradation method was demonstrated by high-performance liquid chromatography and gas chromatography–mass spectrometry analysis. During the recycle experiments, GCN/ZnFe2 O4 /NG and GCN/CoFe2 O4 /NG displayed effectual photodegradation activity, respectively after 10 successive cycles. Due to significant recyclability, GCN/ZnFe2 O4 /NG and GCN/CoFe2 O4 /NG could be used as economical photocatalysts for the wastewater remediation.