Efficient removal of tetracycline by a novel bimetallic nickel/copper-loaded biochar: The crucial roles of π-π interaction and complexation

The development of a novel type of high-efficient biochar (BC) is important for the removal of tetracycline (TC). In this study, a bimetallic nickel/copper-loaded BC (Ni/Cu-BC) was synthesized, which had not been used for TC removal and lacked research on its safety and stability. The adsorption process was more likely to be monolayer chemical adsorption from the experiment. The density functional theory (DFT) calculation revealed that the interaction energy (E-ads), energy gap (E-g) and dipole moment (P(D)) confirmed that the bimetallic loading improved the adsorption strength of the BC to TC. Moreover, the distribution of Ni/Cu-BC surface charge was considerably different from BC after bimetallic loading, and local polarization occurred according to the analysis of molecular surface electrostatic potential (ESP). It was demonstrated that the pi-pi interaction and complexation played a crucial role in the removal of TC. Finally, the functional groups of Ni/Cu-BC in removal were in the following order: C=O > C=C > -NH2 > M-O > C-O. This study proves that Ni/Cu-BC is a novel, highefficient, safe and reusable adsorbent. Overall, this study provides a new perspective on the design of BC and develops its environmental applications.