Enhanced removal of doxycycline by iron modified sludge derived hydrothermal biochar: adsorption properties and the effect of Cu(II) coexisting

Recently, the use of biochar for wastewater treatment has become a central focus in environmental remediation studies. In this research, a simple and economical one-pot hydrothermal strategy was developed for the synthesis of iron-modified sludge-derived hydrothermal biochar (ISHB). The obtained optimum ISHB possesses abundant hydroxy, carboxyl and aromatic ring surface functional groups as well as relative high surface area and small particle size which contribute to the adsorption of the enhanced contaminants. The structure-activity relationship and the adsorption behavior between the ISHB and doxycycline (DOX) were explored. The loaded iron improved the adsorption capacity of ISHB from 51.65 to 78.93 mg g –1 at 20°C with an initial DOX concentration of 60 mg L –1 . As Cu(II) exists in the DOX solution, the adsorption of DOX is inhibited to 50.06 mg g –1 due to the site competition between DOX and Cu(II). Nevertheless, the adsorption of Cu(II) is promoted, which can be explained by the complexation between DOX and Cu(II).