One-Step Synthesis of a Mn-Doped Fe2O3/GO Core-Shell Nanocomposite and Its Application for the Adsorption of
Siyasanga Mpelane1,2,3, Nomvano Mketo4, Mbuso Mlambo5
1Department of Chemical Sciences, University of Johannesburg, Doornfontein Campus, P.O. Box 17011, Doornfontein 2028, South Africa.
Abstract:
This study describes for the first time the synthesis, characterization, and application of a MnFe2O3/GO core-shell nanocomposite as an adsorbent for the removal of levofloxacin (Lev) from real water samples. The formation of the proposed nanocomposite was confirmed using various characterization techniques. The structural techniques revealed a 20 nm average particle size of the MnFe2O3/GO core-shell nanocomposite, with a surface area of 70.7 m2 g-1, as shown by the BET results. The most influential parameters (adsorbent dosage, stirring rate, and Lev pH) that affected the adsorption process were optimized using the response surface methodology (RSM) based on a central composite design. The optimum conditions were 0.007 g, 2, and 7 for adsorbent dosage, stirring rate, and Lev pH, respectively. The adsorption behavior of Lev on the MnFe2O3/GO core-shell nanocomposite was examined using isotherm models, kinetics, and thermodynamics. The kinetic models demonstrated that the adsorption process was controlled by both intraparticle and outer diffusion. Furthermore, the results obtained revealed that the adsorption of Lev on MnFe2O3/GO was dominated by electrostatic interactions. Moreover, Dubinin-Radushkevich and Temkin isotherms confirmed that the sorption mechanism was dominated by electrostatic interactions, while Langmuir and Sips models confirmed a monolayer adsorption process. The maximum adsorption capacity of Lev onto the MnFe2O3/GO adsorbent was found to be 129.9 mg g-1. Furthermore, the thermodynamic data revealed that the adsorption system was spontaneous and exothermic. The synthesized MnFe2O3/GO core-shell nanocomposite showed significant recyclability and regenerability properties up to five adsorption-desorption cycles. As a proof of concept, the performance of the prepared adsorbent was evaluated for laboratory-scale purification of spiked real water samples. The prepared adsorbent significantly reduced the concentration of Lev in the real water samples and the removal efficiency ranged from 86 to 97%.
