<![CDATA[Red mud is alumina industry waste that poses environmental concerns. It has a high silica content, which offers potential for use as an adsorbent. This study aims to investigate the effect of varying KOH concentrations (2.5, 3.0, and 3.5 M) on the particle size of extracted silica and its ability to adsorb Fe2+ ions. Silica was synthesized using the sol-gel method followed by calcination at 500 °C for 2 hours. The Particle Size Analyzer (PSA) revealed that the smallest particle size was observed at 2.5 M KOH, measuring 450.8 nm with a PDI of 2.488. The optimum silica sample was further characterized using X-ray fluorescence (XRF), Gas Sorption Analyzer (GSA), Fourier Transform Infrared (FT-IR), and X-ray diffraction (XRD). XRF analysis showed an increase in SiO2 content from 37.218% to 60.132%. GSA analysis indicated a surface area of 105.772 m2/g, pore volume of 0.367 cc/g, and pore diameter of 6.73 nm, classifying it as a mesoporous material. FT-IR spectra confirmed the presence of silanol and siloxane groups, while XRD diffractogram demonstrated a crystalline silica structure, quartz phase. Adsorption tests on Fe2+ ions showed an average removal efficiency of 75.53% and a distribution coefficient of 0.62 L/g.]]>
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