Removal of lincomycin from aqueous solution by birnessite: kinetics, mechanism, and effect of common ions

The removal of lincomycin (LIN) from aqueous solution by birnessite was investigated by batch experiments. When the dosage of birnessite is 500 mg L^-1 and the initial concentration of LIN is 15.5 μmol L^-1, more than 90% of LIN was removed within 240 min at pH 4.90. Under different conditions, the reactions were well fitted with the second-order model (R² > 0.95). The removal kinetics and the reaction mechanism were described. The presence of cations (e.g., K⁺, Ca²⁺, Mg²⁺, Fe²⁺, and Mn²⁺) inhibited the removal of LIN by birnessite, following the order: Mn²⁺ > Fe²⁺ > Ca²⁺ > Mg²⁺ > K⁺ ≈ Na⁺, due to the sorption of cations on birnessite, companying with the electron transfer and precipitation of oxides (for Mn²⁺ and Fe²⁺). The addition of Cu²⁺, SO₄^2-, or NO₃^- improved the reactions. The presence of Cu²⁺ could oxidize antibiotics, and the repulsion between SO₄^2-or NO₃^- and birnessite might disperse the birnessite suspensions during the reactions. Mn(IV) and Mn(III) were the core Mn species that play an important role in LIN removal. These findings will help to understand the removal process of LIN and illustrate the influence of cations and anions on the removal of similar pollutants by birnessite.