Exploring the synergistic sorption capacities of magnetic-chitosan-Arthrospira platensis biocomposite for simultaneous removal of tetracycline and heavy metals

The frequent co-occurrence of antibiotics and heavy metals in aquatic environments significantly affects their adsorption properties and removal efficiency. This study investigated the co-adsorption behavior of tetracycline (TC) and heavy metals (Pb, Cr, and Ni) using a magnetic chitosan/A. platensis (MCA) biocomposite as a biosorbent. Experiments were conducted on both single and binary systems to compare the biocomposite’s efficiency in adsorbing these pollutants. Results revealed that lead (Pb) enhanced TC adsorption through a synergistic effect, whereas chromium (Cr) and nickel (Ni) exhibited competitive interactions, reducing TC removal. TC removal reached 54% in the single system but increased to as much as 91.2% in the presence of 10 mg/L Pb. Adsorption equilibrium data were well described by the Langmuir model, implying monolayer coverage. The highest adsorption capacities were 505.91 and 421.40 mg/g for TC, and 518.39 and 495.26 mg/g for Pb in the binary and single systems, respectively. Kinetic experiments demonstrated that adsorption conformed to a pseudo-second-order model, suggesting chemisorption as the rate-controlling step, while thermodynamic parameters confirmed that the process was endothermic and spontaneous. These outcomes suggest that the MCA biocomposite is a promising solution for removing antibiotics and heavy metals from contaminated water.