Synthesis, characterization, and structural studies of biochar capped magnetic iron oxide and its potentials as adsorbents for organic dyes

Abstract

The preparation of biochar capped magnetic nanoparticles as adsorbents for the removal of methylene blue (MB), bromophenol blue (BPB) and rhodamine B (RhB) dyes is reported. Morphological studies of the untreated magnetic biochar nanoadsorbent showed monodispersed particles of about 20 nm. Brunauer, Emmett and Teller (BET) analysis revealed surface area of 138.28 m2/g while saturation magnetization was 12.61 emu/g. The energy bandgap of pure magnetite was reduced from 4.03 to 2.70 eV after capping with biochar. Maximum adsorption capacity (Qo) of the dyes onto the magnetic biochar are 14.39, 16.47 and 2.65 mg/g for MB, RhB and BPB respectively. The Langmuir equation best interpreted the sorption of methylene blue while Freundlich equation was more suitable for the sorption of bromophenol blue and Rhodamine B dyes. FTIR spectra of the magnetic biochar nanoadsorbent after adsorption indicated that uptake of the organic dyes occurred through physisorption. Competitive adsorption studies indicate the sorption of methylene blue, and bromophenol blue dyes occurred in acidic medium in comparison to neutral and alkaline media. The result from the study also shows that ethanol is the best eluent for the desorption of the organic dyes and eluted about 70% of adsorbed dyes in the first run.

Keywords

• Biochar
• Magnetic iron oxide
• Adsorption
• Organic dyes
• Invasive alien plants