Synthesis and Structural Studies of Manganese Ferrite and Zinc Ferrite Nanocomposites and Their Use as Photoadsorbents for Indigo Carmine and Methylene Blue Dyes.

Solar-moderated adsorptions of indigo carmine and methylene blue dyes were investigated using manganese and zinc ferrite capped with biochar prepared from the root of . TEM micrograph of the as-prepared manganese ferrite nanocomposites (MnFeO@BC) revealed octagonally shaped particles with an average size of 42.64 nm while the zinc ferrite nanocomposite (ZnFeO@BC) micrograph revealed mixtures of rod- and cone-shaped particles with an average size of 43.82 nm. Biochar capping of MnFeO@BC reduced the band gap from 3.63 to 2.08 eV. The nanocomposite surface areas were 197.64 and 92.14 m/g for MnFeO@BC and ZnFeO@BC, respectively. Photoadsorption of the as-prepared nanocomposites showed that 10 mg of ZnFeO@BC effectively removed 69.07 and 98.60% of 70 mg/L indigo carmine and methylene blue dyes while MnFeO@BC removed 77.65 and 94.83% of indigo carmine and methylene blue dyes after 2 h of equilibration under visible light irradiation, respectively. The nonlinear form of the Langmuir isotherm had a better approximation to the experimental solid-phase concentration ( ) for the adsorption of indigo carmine dye using both nanocomposites. In contrast, the linear form gave a better goodness-of-fit for the adsorptions of methylene blue dye. The manganese ferrite (MnFeO@BC) and zinc ferrite (ZnFeO@BC) nanocomposites showed no inhibition of and , which indicates that they could be used for both biological and environmental applications.