Sphere-like Mn2O3 nanoparticles: Facile hydrothermal synthesis and adsorption properties

• MnCO3 microspheres were synthesized using hydrothermal method at 80 °C for 0.5 h.
• Pure Mn2O3 nanoparticles were produced via thermal decomposition of the hydrothermally as-prepared MnCO3.
• Adsorption properties of the Mn2O3 adsorbent were investigated using Reactive Black 5 dye.
• The as-prepared Mn2O3 nanoparticles showed good adsorptivity.
• The adsorption data fitted the Langmuir isotherm model.

Thermal decomposition of the hydrothermally prepared MnCO3 produced pure Mn2O3 nanoparticles with 23 nm crystallite size. The products were characterized and the adsorption properties of Mn2O3 adsorbent were investigated using Reactive Black 5 dye. Thence, some factors affecting the adsorption process were studied and the results exhibited good adsorption capacity (qm = 14.6 mg/g) of the adsorbent and the percent dye removal reached 92% in 40 min. Additionally, the kinetics, thermodynamics, and isotherms of the adsorption were investigated. The Langmuir model fitted the adsorption data. The adsorption process followed pseudo-second-order kinetic model. The adsorption of the dye on Mn2O3 adsorbent is an endothermic (ΔHº= 44.52 kJ/mol) and spontaneous (ΔGº= –21.63 kJ/mol) process.

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