Adsorption behaviors and mechanisms of florfenicol by magnetic functionalized biochar and reed biochar

A magnetic reed biochar (MRBC) was synthesized through chemical co-precipitation firstly and subsequently pyrolysis. The MRBC and reed biochar (RBC) were characterized by SEM, XRD, FTIR and VSM and were used for the adsorption of florfenicol (FF). Batch experiment results showed that the FF adsorption on MRBC exhibited a pronounced pH-dependent pattern and presented a bell curve. However, the FF adsorption on RBC decreased gradually with the increasing pH values. Ionic strength initially inhibited and then promoted the FF adsorption and the multivalent co-existing anions significantly increased the FF adsorption on MRBC. The FF adsorption was non-spontaneous, exothermic and entropy-decreasing on MRBC and was of a non-spontaneous, endothermic and entropy-increasing nature on RBC. The pseudo second-order model presented better fittings for the FF adsorption kinetic data. Langmuir and Freundlich models can well describe FF adsorption on MRBC and RBC, respectively. The FF adsorption on RBC may be controlled by pore-filling effect and π–π EDA interaction, while hydrogen bonding, pore-filling effect and π–π EDA interaction contributed to the FF adsorption on MRBC. The adsorption–regeneration cycles confirmed that the MRBC was a highly efficient and reusable adsorbent for the removal of FF from aqueous solution.