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<p>In this study, manganese dioxide nanoparticle-modified thermochemically treated diatomite (MnO<sub>2</sub>-DE), was synthesized and assessed for removing methyl orange (MO) dye from aqueous solutions. The raw diatomite was treated with 5 M HCl and calcined at 600 °C, followed by modification with MnO<sub>2</sub> nanoparticles. Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR), Brunauer-Emmett-Teller, and UV-vis spectroscopy were used to characterize the adsorbent. The functional groups were determined by FTIR, BET was used to assess the surface area, Using SEM, the morphology was determined, crystallinity was evaluated by XRD, the size was determined by DLS, whereas UV–Vis spectrophotometry was used to measure the absorbance. Adsorption efficiencies for raw diatomite, treated diatomite (TDE), and MnO<sub>2</sub>-DE were found to be 45%, 71%, and 84%, respectively. Response surface methodology based on the Box-Behnken design was used to optimize adsorption parameters such as pH, adsorbent dosage, dye concentration, contact time, and temperature. This resulted in a maximum MO removal of 93.03% at pH 2.1, 2.85 g of adsorbent dosage, and 71 °C. Isotherm models (Langmuir EXT, Freundlich EXT, and Sips) indicated a strong correlation with experimental data (R<sup>2</sup> values of 0.9953, 0.9952, and 0.9953, respectively), suggesting multilayer adsorption on heterogeneous surfaces. The adsorption process was best described by the pseudo-first-order model, according to kinetic studies, suggesting that physical adsorption is the rate-controlling phase. The spontaneity of the adsorption was validated by thermodynamic analyses. The equilibrium adsorption capacity, or qe, was found to be 1.66 mg/g. These results suggest that MnO<sub>2</sub>-DE is an effective adsorbent for removing MO dye from water.</p>

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Optimization of Methyl Orange Adsorption onto MnO2-Modified Diatomite Using Response Surface Methodology

  • 期刊论文

  • 发表日期：

    2025年7月9日

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  • Girma Gonfa,
  • Yonas Kifle,
  • Belete Tessema,
  • Sintayehu Shewatatek,
  • Ali Eltayeb Ibrahim Elkhalifah

摘要

In this study, manganese dioxide nanoparticle-modified thermochemically treated diatomite (MnO2-DE), was synthesized and assessed for removing methyl orange (MO) dye from aqueous solutions. The raw diatomite was treated with 5 M HCl and calcined at 600 °C, followed by modification with MnO2 nanoparticles. Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier-Transform Infrared (FTIR), Brunauer-Emmett-Teller, and UV-vis spectroscopy were used to characterize the adsorbent. The functional groups were determined by FTIR, BET was used to assess the surface area, Using SEM, the morphology was determined, crystallinity was evaluated by XRD, the size was determined by DLS, whereas UV–Vis spectrophotometry was used to measure the absorbance. Adsorption efficiencies for raw diatomite, treated diatomite (TDE), and MnO2-DE were found to be 45%, 71%, and 84%, respectively. Response surface methodology based on the Box-Behnken design was used to optimize adsorption parameters such as pH, adsorbent dosage, dye concentration, contact time, and temperature. This resulted in a maximum MO removal of 93.03% at pH 2.1, 2.85 g of adsorbent dosage, and 71 °C. Isotherm models (Langmuir EXT, Freundlich EXT, and Sips) indicated a strong correlation with experimental data (R2 values of 0.9953, 0.9952, and 0.9953, respectively), suggesting multilayer adsorption on heterogeneous surfaces. The adsorption process was best described by the pseudo-first-order model, according to kinetic studies, suggesting that physical adsorption is the rate-controlling phase. The spontaneity of the adsorption was validated by thermodynamic analyses. The equilibrium adsorption capacity, or qe, was found to be 1.66 mg/g. These results suggest that MnO2-DE is an effective adsorbent for removing MO dye from water.