Preparation of Fe-doped Silicalite-1 Using Geothermal Sludge as a Potential Adsorbent for Methylene Blue Removal
DOI:
https://doi.org/10.48048/tis.2026.12650Keywords:
Geothermal sludge, Hydrothermal synthesis, Fe-doped silicalite-1, Adsorption, Methylene blue, Sustainable silica sourceAbstract
Geothermal sludge contains a high concentration of silica (85% - 93%) that is typically waste in geothermal plant, offering a promising alternative silica precursor for synthesizing of silicalite-1. In this study, geothermal sludge was acid-leached to remove impurities and enrich reactive silica, then used for hydrothermal preparation of Fe-doped silicalite-1 with Fe addition of 0.002 - 0.014 mol. Low Fe loading preserved the MFI framework with only a slight reduction in relative crystallinity (Fe@S-2 = 95.81%), whereas excessive Fe loading largely suppressed MFI formation (Fe@S-14 = 1.77%) and produced a partially amorphous material. The as-prepared Fe@S-5 exhibited a spherical morphology with an average particle size of 2.89 µm and the external surface area increased with Fe loading, reaching 174.2 m2 g−1 for Fe@S-14. In methylene blue adsorption, Fe@S-14 showed the highest uptake of 46 mg g−1 compared with S-1 of 7.9 mg g−1. The adsorption kinetics followed the pseudo-second order model and equilibrium data were reasonably described by the Langmuir isotherm within the investigated concentration range. Overall, this work demonstrates a sustainable route to utilize geothermal sludge into functional adsorbents for dye-containing wastewater treatment with clear potential for industrial implementation.
HIGHLIGHTS
- Geothermal sludge used as a silica source
- HCl leaching increased SiO2 purity to 93 wt%
- Higher Fe loading enhanced methylene blue adsorption performance
- The adsorption followed pseudo-second order kinetics and Langmuir isotherm model
GRAPHICAL ABSTRACT
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