Green synthesis of Mn3O4 nanoparticles using Costus woodsonii flowers extract for effective removal of malachite green dye

Abstract

The pollution of organic dyes such as malachite green is one of the globally critical issues, calling for efficient mitigation methods. Herein, we developed green Mn3O4 nanoparticles synthesized using natural compounds extracted from Costus woodsonii flowers under an ultrasound-assisted mode. The materials were characterized using several physicochemical techniques such as Fourier-transform infrared spectroscopy, X-ray diffraction, Energy-dispersive X-ray spectroscopy, scanning electron microscopy, Raman spectroscopy, and N2 adsorption desorption isotherm measurement. The X-ray diffraction and N2 isotherm plots confirmed the presence of tetragonal γ-Mn3O4 phase and mesoporous structure, respectively. Carbonyl groups derived from flavonoids or carboxylic compounds were found in the surface of green Mn3O4 nanoparticles. The effect of pH, contact time, dose, and concentration on the adsorption of malachite green over green Mn3O4 was carried out. The maximum malachite green adsorption capacity for green Mn3O4 nanoparticles was 101–162 mg g−1. Moreover, kinetic and isotherm adsorption of malachite green obeyed Langmuir (Radj.2 = 0.980–0.995) and pseudo first-order models (Radj.2 = 0.996–1.00), respectively. Adsorption of malachite green over green Mn3O4 was a thermodynamically spontaneous process due to negative Gibbs free energy values (ΔGο < 0). Green Mn3O4 nanoparticles offered a high stability through the FR-IR spectra analysis. With a good recyclability of 4 cycles, green Mn3O4 nanoparticles can be used as potential adsorbent for removing malachite green dye from water.