Removal of 17β-estradiol from aqueous solution by graphene oxide supported activated magnetic biochar: Adsorption behavior and mechanism

A novel graphene oxide supported activated magnetic biochar (GO-AMBC) is fabricated for 17 beta-estradiol (E2) removal from aqueous solution by grafting graphene oxide (GO) and magnetite nanoparticles onto the activated biochar surface with a one-step activation, magnetization, and carbonization method. GO-AMBC is characterized using SEM, TEM, FTIR, VSM, XRD, XPS, BET surface area and zeta potential measurements. The characterization results show that GO-AMBC possesses a larger surface area and more oxygen-containing functional groups than the unmodified biochar. When the E2 initial concentration is 6 mg/L, its adsorption capacity by GO-AMBC (46.22 mg/g) is more than two times higher than that of pristine biochar (23.09 mg/g) at 298 K and pH = 7.0. Adsorption results show that E2 uptake follows by pseudo-second-order kinetic and Freundlich isothermal models. Thermodynamic analysis indicates that the adsorption process is spontaneous and exothermic. E2 removal by GO-AMBC is significantly affected by the actual water conditions, including solution pH, ionic strength, and organic acids. Among them, organic acids have obvious inhibition effect on E2 removal, and the inhibition effect by oxalate is stronger than that of benzoate. The adsorption mechanism of E2 on GO-AMBC is mainly controlled by hydrogen bonds, electrostatic and pi-pi interactions. The experimental results of this study and comparative analysis with other adsorbents suggest that GO-AMBC is an economical, efficient and recyclable adsorbent and has great potential for E2 removal from contaminated water. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.