Adsorption of 17β-estradiol by a novel attapulgite/biochar nanocomposite : Characteristics and influencing factors

A novel attapulgite/biochar (ATP/BC) nanocomposite was synthesized via simultaneous activation and carbonization for 17 beta-estradiol (E2) removal in water. The one-step synthetic process significantly enlarged specific surface area and increased oxygen-contained functional groups. Compared to the pristine biochar (BC) and attapulgite (ATP), the ATP/BC nanocomposite exhibited higher adsorption capacity for E2 with the maximum adsorption capacity (q(max)) of 154.23 mg/g. The pseudo-second-order and Langmuir model were more suitable for E2 adsorption by ATP/BC. The adsorption capacity of ATP/BC for E2 was affected by initial solution pH and the low pH was favorable for the adsorption of E2. The presence of monovalent cations (Na+ and K+) improved the adsorption efficiency for E2, whereas the presence of divalent cations of (Ca2+ and Mg2+) inhibited the adsorption process of E2. Ionic strength had slight promoting effect at low concentration for the E2 adsorption. The presence of surfactant and humic acid inhibited the adsorption capacity of ATP/BC. Electrostatic attraction, pi-pi interactions and hydrogen bonds between ATP/BC and E2 molecules might be potential adsorption mechanisms. The results showed that the ATP/BC nanocomposite was a high efficiency and reusable adsorbent in the removal of E2 from water. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.