Creation of accessible adsorption sites in Albizia lebbeck -modified zinc oxide to boost tetracycline removal from aqueous environments

The excessive use and improper disposal of pharmaceutical contaminants, such as tetracycline (TC), has led to their persistent accumulation in the environment, thereby posing a significant threat to both human health and aquatic life. Thus, its effective removal from aqueous environments is essential to ensure availability of clean and safer water for all. To address this issue, we incorporated zinc oxide (ZnO) at different concentrations on Albizia lebbeck pod surface (0.05M-ZnO@ALB and 0.1M-ZnO@ALB) through an in-situ co-precipitation, promoting uniform dispersion, enhanced interaction, reduced nanoparticle agglomeration, and increased accessibility of adsorption active sites. Characterization of the adsorbent materials using FTIR, XRD, SEM/EDX revealed their surface chemistry, morphological, elemental composition, crystallinity, and structural properties. The effect of contact time, initial TC concentration, pH, adsorbent dosage, and temperature were investigated on TC adsorption in a batch component system. Among the designed materials, 0.1M-ZnO@ALB demonstrated superior TC removal, achieving an adsorption capacity of 37.77 mg/g, thereby outperforming other adsorbents reported in previous studies. The adsorption processes were better explained by Langmuir isotherm and pseudo-second-order kinetics models, suggesting the predominance of chemisorption on heterogenous (multilayer) surfaces. The cyclic experiments with 3 cycles demonstrated that 0.05M-ZnO@ALB and 0.1M-ZnO@ALB had a superior reusability after 3 adsorption-desorption cycles, retaining at least >80% of the initial removal efficiency. Finally, this study demonstrates the potential use of zinc oxide nanoparticles -modified Albizia lebbeck as a sustainable, effective, and recyclable materials for removing TC from aqueous water.