Green synthesis of CoAl2O4@ZnO nanocomposite using Aamygdalus scoparia Spach gum and its photocatalytic activity for tetracycline degradation

A novel CoAl₂O₄@ZnO nanocomposite (NC) was synthesized via a green, low-cost, and simple sol-gel method using Amygdalus scoparia Spach gum. The photocatalytic efficacy of the produced CoAl₂O₄@ZnO NC was examined for the degradation of tetracycline (TC) under visible light (fluorescent lamp, 80 W, λ > 400 nm). The CoAl₂O₄@ZnO NC analyzed using XRD, BET, UV-Vis-DRS, FESEM, TEM and EDX. The XRD analysis confirmed the formation of CoAl₂O₄ with a cubic spinel structure and ZnO with a hexagonal wurtzite structure. BET analysis revealed a specific surface area of approximately 40 m²/g. The band gap energy was estimated to be around 3 eV using the Tauc equation. The CoAl₂O₄@ZnO NC demonstrated significant photocatalytic efficacy, achieving 92.93% degradation of tetracycline in 45 min under visible light irradiation. The addition of ethanol as a scavenger led to reduced photocatalytic activity which demonstrates that hydroxyl radicals (•OH) play a crucial role in the degradation process. LC-MS analysis identified multiple intermediate products (m/z = 358, 276, 260, 208, 192, 118, 104, 86) during the photodegradation of tetracycline, confirming the proposed degradation pathway. The nanocomposite maintained stability and photocatalytic efficiency throughout five repeated tests, showing only a minimal reduction of 3% in activity after the fifth cycle.