Magnetic powdery acrylic polymer with ultrahigh adsorption capacity for atenolol removal: Preparation, characterization, and microscopic adsorption mechanism

Contamination of pharmaceutically active ingredients (PhACs) in water has attracted the attention of the scientific community. Magnetic powdery acrylic polymer (MPAP) was prepared and used to adsorb atenolol (ATL) in aqueous solution for the first time. Adsorption kinetics results showed that the adsorption of ATL on MPAP reached equilibrium within 30 min, and the removal efficiency of ATL (100 mL, 500 mg·L⁻¹) with 0.05 g MPAP was 86.8%. Adsorption isotherms showed that the maximum adsorption capacity was 2.82 × 10³ mg·g⁻¹ at 323 K. The positive △H₀ (9.94 KJ·mol⁻¹) indicated that the increase of temperature was beneficial to the adsorption. The positive △S₀ (90.5 J·mol⁻¹·K⁻¹) indicated the increase of randomness of the adsorbent-solution interface. Cations in solution decreased the adsorption capacity of ATL by competing for the active sites on MPAP. The adsorption amount of ATL decreased with the decrease of solution pH. The hydrogen bonding adsorption mechanism was proposed and verified by the theoretical calculations. The adsorption of ATL on MPAP was more efficient under alkaline conditions, which could be explained by the loss of H from the carboxyl group being more favourable for the adsorption of protonated ATL. The degree of electron sharing between H-bond donors and H atoms decreased after the formation of H-bonds, which was reflected in the increase of bond length and the decrease of vibrational frequency. MPAP has high adsorption capacity and short adsorption equilibrium time, which is a promising adsorbent for removal of PhACs containing amide groups.