Enhancing adsorption capacity of Egyptian diatomaceous earth by thermo-chemical purification: Methylene blue uptake

Essam A. Mohamed, Ali Q. Selim, Ahmed M. Zayed, Sridhar Komarneni, Mohamed Mobarak, Moaaz K. Seliem

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

In the current study, calcination and thermo-chemical methods were applied in treatment of the processed diatomite fraction (<45 μm), which containing nearly 82.6 wt.% of the raw Egyptian diatomaceous earth. The untreated and modified diatomite fractions were characterized by optical microscopy (OM), X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Thermo-chemical purification produced the highest concentration of diatom frustules (>92% SiO2) without blocking impurities and created –Si–O–Si– active sites. These fractions were tested for Methylene blue (MB) adsorption at different pH solutions (2.0–10.0). The purified diatomite via thermo-chemical treatment (PD) gave the greatest adsorption capacity for MB compared to the untreated (UD) and calcinated (CUD) diatomite fractions. Effects of experimental parameters such as MB concentration (60–200 mg L−1), contact time (5–480 min), adsorbent mass (50–250 mg) and temperature (30–55 °C) on MB uptake were investigated. Linear and non-linear forms of Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models indicated that Langmuir model with a maximum adsorption capacity (qmax=105.03mgg-1) fitted well the adsorption data. The chemical nature of MB uptake was revealed by the values of mean free energy E=8.655kJ/moland correlation coefficient of the pseudo-second-order model (R2=0.9997). The calculated thermodynamic parameters (ΔH0, ΔG0 and ΔS0) indicated that the removal of MB is spontaneous and endothermic.

Original languageEnglish (US)
Pages (from-to)408-419
Number of pages12
JournalJournal of Colloid And Interface Science
Volume534
DOIs
StatePublished - Jan 15 2019

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Surfaces, Coatings and Films
  • Colloid and Surface Chemistry

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