Removal of methylene blue using MnO2@rGO nanocomposite from textile wastewater: Isotherms, kinetics and thermodynamics studies

Tshimangadzo S. Munonde, Azile Nqombolo, Siphosethu Hobongwana, Anele Mpupa, Philiswa Nosizo Nomngongo

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)


In this study, the adsorptive removal of methylene blue dye, which is commonly used in textile industries, was investigated using the MnO2@reduced graphene oxide (rGO) adsorbent. The sonication-assisted synthesis from rGO nanosheets and MnO2 nanoparticles resulted to the MnO2@rGO nanocomposite with improved physicochemical properties. The characterization results showed the improved surface area, porous structure and adsorption sites from the nitrogen adsorption-desorption studies, improved morphology from the Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) and the improved crystal structure from X-ray powder diffraction (XRD). The improved physicochemical properties on the MnO2@rGO nanocomposite played a significant role in enhancing the dye removal in textile wastewater. The equilibrium experimental data was best described by the Langmuir isotherm model with a maximum adsorption capacity of 156 mg g−1, suggesting a monolayer adsorption. The kinetic data best fitted the pseudo-second order kinetic model, suggesting a chemisorption adsorption process. The thermodynamic data (ΔG°, ΔH° and ΔS°) confirmed the feasibility, randomness and spontaneous nature of the adsorption process. The mechanism of adsorption involved the hydrogen bonding, π-π interactions and electrostatic interactions. The removal of methylene blue using MnO2@rGO nanocomposite in spiked textile wastewater yielded a 98–99% removal. The method demonstrated competitiveness when compared with literature reported results, paving way for further investigations towards industrial scale applications.

Original languageEnglish
Article numbere15502
Issue number4
Publication statusPublished - Apr 2023


  • Chemisorption
  • Isotherms
  • Kinetics
  • Methylene blue
  • MnO@rGO nanocomposite
  • Textile wastewater

ASJC Scopus subject areas

  • Multidisciplinary


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