Fabrication of lignin-based biochar containing multi-metal ferrite and efficient removal for oxytetracycline hydrochloride

Efficient removal of oxytetracycline hydrochloride (OTC) from wastewater is of great significance but extremely challenging. Herein, a novel adsorbent lignin-based multi-metal ferrite biochar (FeNiZn-LBC) was synthesized through pyrolysis with controllable temperature and hydrothermal reaction using lignin of sinocalamus oldhami as raw material. The adsorption property of FeNiZn-LBC for OTC was systematically researched, and the results displayed that adsorption of FeNiZn-LBC to OTC accorded with the Langmuir model and the equilibrium adsorption capacity was 476 mg g−1. Notably, FeNiZn-LBC can be regenerated with 0.100 mol L−1 NaOH. Additionally, we raised rational explanations for the mechanisms of adsorption behavior based on the zeta potential and XPS spectra. The adsorption of FeNiZn-LBC for OTC was mainly controlled by the electrostatic interactions, hydrogen bonds and complexation involving FeNiZn-LBC and OTC, especially the metal-oxide bond (M-O) generated after loaded with multi-metal ferrite played a positive role in the removal of OTC from water. Our work highlighted the potential of FeNiZn-LBC for excellent adsorption of OTC in next generation.