Efficient adsorption of tetracycline hydrochloride by Willow Catkins based biochar: Performance, governing factors and mechanisms.

This work prepared a novel biochar from willow catkins (WC) by a two-step pyrolysis and KOH activate to adsorb tetracycline hydrochloride (TCH) in water. The effects of pyrolysis temperature and activator amount on adsorption capacity were investigated. The results showed that the adsorbent with the largest adsorption capacity, which was named as KWCBC, was obtained when the pyrolysis temperature of the first and second stage was 600 °C and 800 °C, and the dry mass ratio of KOH and WC biochar was 4. After KOH activation and two-step pyrolysis, the pore structure and adsorption capacity of biochar were greatly improved. KWCBC possessed developed pore structure and large specific surface area (2402.31 m²/g), which was conducive to the adsorption process. KWCBC had superior stability against the changes of initial pH and foreign ions. Moreover, KWCBC showed favorable application potential in actual water and excellent regeneration performance. The adsorption behavior was well explained by Freundlich isotherm model and pseudo-second order kinetic model. The maximum adsorption capacity of TCH on KWCBC determined by the Langmuir model was up to 1242.31 mg/g at 45 °C. The major mechanisms including pore filling, hydrogen bonding, electrostatic effects and π-π interactions were involved in the adsorption process. The findings obtained in this study can provide valuable insights into the adsorption properties and mechanisms of KWCBC, which may assist in developing effective adsorbents for TCH removal from water. [ABSTRACT FROM AUTHOR]