Manganese Dioxide Nanoparticles Show Promise for Janus Green Dye Removal

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Researchers from the College of Education for Pure Sciences have synthesized manganese dioxide (MnO2) nanoparticles and used them to remove Janus green dye from aqueous solutions. The study analyzed the kinetics and thermodynamics of the adsorption process and found that the manganese dioxide surface exhibited faster adsorption kinetics during the film diffusion step compared to intraparticle diffusion. The research also showed that the adsorption process is energy-intensive, requiring higher energy to form chemical bonds between the dye and the nanoparticles.

Key Takeaways:

  • The researchers synthesized manganese dioxide nanoparticles using the hydrothermal method and characterized them using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), and Fourier-transform infrared spectroscopy (FT-IR).
  • The adsorption kinetics were investigated using three models: pseudo-first-order (PFO), pseudo-second-order (PSO), and the intraparticle diffusion model. The PSO model provided the best fit (R2 = 0.999), indicating that the adsorption process is chemical in nature.
  • The study found that the manganese dioxide surface exhibited faster adsorption kinetics during the film diffusion step (rate constant 0.2776) compared to intraparticle diffusion (0.0042) at 298.15 K.
  • The thermodynamic parameters, including enthalpy change (ΔH*), entropy change (ΔS*), and Gibbs free energy change (ΔG*) of activation, were calculated from the Eyring equation to be 37.48 kJ/mol and -144.69 J/mol, respectively.
  • The positive ΔG* value (80.62 kJ/mol) suggests that the adsorption process is energy-intensive, requiring higher energy to form chemical bonds between the dye and the manganese dioxide nanoparticles.

Statistics:

  • Room temperature (298.15 K)
  • Rate constant for film diffusion step: 0.2776
  • Rate constant for intraparticle diffusion step: 0.0042
  • Enthalpy change (ΔH*): 37.48 kJ/mol
  • Entropy change (ΔS*): -144.69 J/mol
  • Gibbs free energy change (ΔG*) of activation: 80.62 kJ/mol

Sources:

  • Bulletin of the Chemical Society of Ethiopia: "Preparation, Kinetics, and Thermodynamic Investigation of Janus Green Dye Removal From Aqueous Solutions Using Mno 2 Nanoparticles As an Adsorbent" (2025;39(8):1509-1523)
  • College of Education for Pure Sciences, Ibn Al Haitham University of Baghdad, Iraq
  • NewsRx LLC, Nanotechnology Weekly, July 14, 2025