Synthesis and characterization of magnetic chitosan-polypyrrole composite for adsorption of tetracyclines from contaminated water

The extensive consumption of tetracyclines (TCs) has gained attention due to their toxic effect. The current study reports the synthesis and characterization of magnetic chitosan-polypyrrole (Cs-PPy-Fe₃O₄) composite, which was then used for the adsorption of TCs from aqueous solutions. The synthesized adsorbent had a surface area, pore volume, and pore size diameter of 129 m² g^-1, 0.32 cm³ g^-1, and 9.9 nm, respectively. Furthermore, the adsorbent had an elemental composition of C (53.6%), O (18.0%), N (12.4%), Fe (12.4%) and O (18.0%). Box-Behnken design (BBD) was used to investigate the effects of various parameters affecting the adsorption of TCs onto Cs-PPy-Fe₃O₄ composite. The results displayed that the sorption of the TCs onto Cs-PPy-Fe₃O₄ composite followed pseudo-first-order and best fitted the Langmuir isotherm model with adsorption capacities of 112, 95, 94, and 93 mg g^-1 for oxytetracycline, tetracycline, chlortetracycline, and doxycycline, respectively. Thermodynamic studies revealed that the adsorption of the analytes onto the Cs-PPy-Fe₃O₄ composite was physical with exothermic and increasing entropy. Furthermore, as the eluting solvent, the adsorbent could be regenerated using methanol and 0.01 oxalic acid (20:80 v/v). Therefore, the Cs-PPy-Fe₃O₄ composite could be a promising adsorbent for the simultaneous removal of TCs in water.