Enhanced tetracycline removal from complex real wastewater using a sustainable hog plum-ZnO-Ag₂O composite

The increasing occurrence of pharmaceutical contaminants such as tetracycline (TC) in aquatic environments poses significant environmental and public health concerns due to their persistence and contribution to antibiotic resistance. In this study, a ZnO/Ag₂O-functionalized hog plum (Spondias mombin) composite (MHGP) was synthesized and evaluated for TC removal from aqueous systems. To the best of our knowledge, this represents the first report on the simultaneous ZnO and Ag₂O nanoparticle modification of Spondias mombin biomass for antibiotic adsorption and its application in a real wastewater matrix. The successful incorporation of the ZnO and Ag₂O nanoparticles onto the hog plum biomass (HGP) was confirmed using multiple physicochemical characterization techniques. Batch adsorption studies revealed that optimum TC removal occurred at pH 2, with an adsorbent dosage of 50 mg achieving maximum TC sequestration from a 25 mg L^-1 solution within 4 h. The maximum adsorption capacity (Q _max) in ultrapure water was 1.96 mg g^-1. Isotherm studies showed that the Brouers-Sotolongo model best described the adsorption in ultrapure water, whereas the Sips isotherms provided a superior fit for real wastewater, indicating heterogeneous adsorption in the presence of competing ions. Kinetic modelling showed that the adsorption followed the pseudo-second-order, suggesting that adsorption may be governed by interactions involving surface functional groups and metal active sites. Despite the chemical complexity of the real wastewater matrix, the MHGP composite maintained a TC removal efficiency of 55%. Overall, these results demonstrate the potential of MHGP as a practical and sustainable adsorbent for pharmaceutical wastewater remediation.