Co-adsorption of tetracycline and Cu(ii) onto a novel amino-functionalized biochar: adsorption behavior and mechanism

Abstract

In this work, a novel amino-functionalized biochar (NS-700) was prepared successfully by pretreating biomass with (NH₄)₂S₂O₈, and could be used for the simultaneous and efficient removal of tetracycline (TC) and Cu(II). NS-700 was analyzed by Fourier-transform infrared spectroscopy (FTIR), elemental analysis, X-ray photoelectron spectroscopy (XPS) and other characterization techniques. Results showed that NS-700 contained a variety of oxygen-containing and nitrogen-containing functional groups, as well as a more developed pore structure. The specific surface area of NS-700 was up to 739.9 m² g⁻¹. Through the effects of changing the solution pH, adsorption kinetics and isotherm model arguments, the adsorption behavior and performance of NS-700 for TC and Cu(II) in different systems were investigated. The maximum adsorption capacity of NS-700 for Cu(II) and TC was 49.07 mg g⁻¹ and 323.26 mg g⁻¹, respectively. The existence of TC could slightly reduce the adsorption capacity for Cu(II). A low concentration of Cu(II) could increase the adsorption of TC, but a high Cu(II) concentration inhibited the TC adsorption on NS-700. Combined with theoretical calculations, the adsorption mechanism of NS-700 in different systems was explored. The results demonstrated that the amide groups on NS-700 were combined with TC through complexation, and the protonated amino groups could be ion-exchanged with Cu(II). Cu(II) could interact with O22–O26 or O22–N25 on TC to form a complex, and the complexation caused by the interaction of O22–N25 on TC and Cu(II) played an important role in the adsorption of Cu(II) and TC by NS-700. This study puts forward a guideline and practical method for the application of biochar in the pollution control of heavy metals and antibiotics.