Preparation and Characterization of Clay-Based Geopolymer for Adsorptive Dye Removal

Abstract

Clay based adsorbents offer a promising solution for the remediation of dye contamination in wastewater This study investigates metakaolin based geopolymer adsorbents for removing cationic dye from aqueous solutions Geopolymer adsorbents were synthesized by varying the Na₂SiO ₃/ NaOH content to achieve different SiO ₂/ Na₂O ratios 1 3 to 1 5 in the activator and by adjusting the metakaolin to alkali activator ratio to produce batches with distinct SiO ₂/ Al₂O ₃ compositions The impact of these variations on geopolymer phase formation and adsorption efficiency was studied The raw clay and the alkali activated reaction products were described using various techniques to determine their oxide composition, phase formation, surface area, and morphology Batch adsorption experiments and UV Visible spectroscopic study are carried out to evaluate the adsorbents’ performance in removing methylene blue dye The results revealed that the prepared adsorbents effectively treated the dye contaminated water, with optimized batches achieving removal efficiencies greater than 80 Electrostatic attraction facilitated the adsorption of cationic dye on the adsorbent surface, while chemisorption strengthened and stabilized the overall process the combined effect of these two mechanisms enhanced the adsorption efficiency The batch adsorption data followed the pseudo second order kinetic model and the Langmuir isotherm, indicating that dye uptake occurred via monolayer chemisorption This work demonstrates that metakaolin based geopolymers with a tailored alkali activator and precursor ratios, can be effective, sustainable adsorbents for removing cationic dyes from contaminated water.