Background: Although pristine and modified manganese oxides were used as adsorbent
for dyes removal from aqueous solutions, their applications were limited to the removal of single dye
components. From the practical viewpoint, it is necessary to investigate the adsorption behavior of
dyes on manganese oxide adsorbents in multi-component systems. Herein, the present work investigated
the performance of core-shell magnetic manganese dioxide (Fe3O4/C/MnO2) nanocomposites
as an adsorbent to remove methylene blue (MB) and rhodamine B (RhB) in single and binary dye
Method: Fe3O4/C/MnO2 microspheres were prepared using the redox reaction of KMnO4 to MnO2 in
alkaline solution on the surface of carbon-coated magnetite (Fe3O4/C). The effect of pH and adsorbent
amount on adsorption was examined, and the adsorption isotherms and kinetics of MB and RhB
in single and binary dye solutions were studied.
Results: In single dye solutions, the adsorption isotherms of both MB and RhB fitted well with the
Langmuir model. In binary dye solution, the adsorption amount of MB increased because of the
synergetic effect, while the adsorption amount of RhB decreased due to competitive effect. The adsorption
isotherms of MB and RhB in binary dye solution followed the Sheindorf-Rehbun-Sheintuch
(SRS) and extended Langmuir model, respectively. Both MB and RhB adsorption could be expressed
by the pseudo-second-order kinetic model in single or binary dye solutions.
Conclusion: Fe3O4/C/MnO2 nanocomposites exhibited an excellent adsorption property to MB and
RhB and high magnetic separability.