Fe ₂ O ₃ /g-C ₃ N ₄ /CdS photocatalysts for complete sunlight-active detoxification of the tetracycline antibiotic and Congo red dye in water

A ternary heterojunction based on Fe₂O₃/g-C₃N₄/CdS was synthesized <i>via</i> an ultrasonic technique. The synthesized heterostructure was utilized for complete detoxification of the tetracycline (TC) antibiotic and Congo red (CR) dye in water. The three-component photocatalyst displayed the XRD patterns of Fe₂O₃, CdS, and g-C₃N₄, with band gaps of 2.62 eV, 2.47 eV, and 2.60 eV, respectively. The 0.10 weight% Fe₂O₃/g-C₃N₄/CdS heterostructure (denoted as 0.10Fe₂O₃/g-C₃N₄/CdS) provided the smallest photoluminescence intensity, indicating the slowest recombination speed of electron-hole pairs, compared to all the fabricated catalysts. This agrees perfectly with the greatest photoactivity detected in the 0.10Fe₂O₃/g-C₃N₄/CdS heterostructure. A photocatalytic performance of 84% was observed after 4 h of UV-visible light exposure. In addition, 97% removal of TC under natural sunlight was reported. This is assigned to the lowest carrier recombination rate of the ternary photocatalyst, compared to the bare components and the binary photocatalysts. The photodegradation of the pollutant follows the first-order kinetics. A maximum rate constant of 0.0432 min^-1 was detected. The ternary heterojunction displayed excellent photocatalytic activity even after five cycles. The trapping test indicated that the photo-created holes played a main role in TC detoxification. This research provides a novel route to generate ternary heterojunctions for complete detoxification of the harmful TC drug and CR dye in natural water.