A recyclable biochar with ultrahigh absorption ability for efficient removal of tetracycline hydrochloride

In this study, a novel iron-doped biochar (Fe@C) with excellent adsorption capacity and strong magnetism was easily prepared by a simple one-step synthesis method to adsorb tetracycline hydrochloride (TCH) in water. The adsorption capacity of biochar prepared from different materials was investigated, and the results showed that the adsorption performance of cotton-based biochar for TCH was much higher than other materials. The effects of pyrolysis temperature, material ratio and pH on adsorption capacity were explored. The adsorption kinetics and isotherms of TCH removal were studied, from the fitted adsorption curves, it was shown that the prepared Fe@C had superior adsorption capacity, and the maximum adsorption amount could reach as high as 1492.4 mg/g at 45 °C. The strong magnetic property of Fe@C (94.65 emu/g) enabled it to be rapidly separated from the solution after adsorption. In addition, the obtained Fe@C exhibited good stability and reusability, it maintained a high adsorption capacity even after five times of reuse. The adsorption mechanism was investigated systematically, which was mainly collaborated by pore filling, electrostatic effect and π-π interaction. Overall, the Fe@C had ultrahigh adsorption capacity, easy separation and good reusability, showing great potential for the removal of THC from water.