Synthesis and adsorption performance of metakaolin clay derived photoactive geopolymer

This study presents a simple, cost-effective and eco-friendly method to develop adsorbents for environmental remediation by combining natural metakaolin clay and chemically synthesized α-Fe 2 O 3 forming geopolymer (GP) and iron oxide-modified composites (FeGP). Comprehensive characterization through XRD, SEM, EDX, FTIR, and compressive strength testing confirmed the successful and uniform mixing of α-Fe 2 O 3 within the geopolymer framework. The modified FeGP samples exhibited broader light absorption (250–540 nm) than unmodified GP (250–330 nm), indicating enhanced photocatalytic potential. Additionally, FeGP samples demonstrated enhanced mechanical strength and stability across a wide pH range. Adsorption studies revealed that while GP was more efficient in removing methylene blue (MB) dye, FeGP showed superior fluoride removal capability. Optimal dye adsorption was achieved at 0.6 g adsorbent dosage, 10 mg/L initial dye concentration, and pH 7. The adsorption mechanism for MB dye was further elucidated using kinetic modelling, thermodynamic analysis, and adsorption isotherms. These findings suggest that incorporating α-Fe 2 O 3 into geopolymers creates multifunctional adsorbents with strong mechanical strength and effective adsorption and photocatalytic abilities, offering a promising, sustainable option for water treatment.