Removal of Methylene Blue From Contaminated Water Using Eco‐Friendly Cross‐Linked Chitosan/Organomodified Montmorillonite Nanohydrogels

ABSTRACT Cross‐linked chitosan/organomodified montmorillonite nanohydrogels (Cro‐Cs/Org‐Mt) were green synthesized using chitosan obtained by deacetylation of chitin from shrimp, organomodified montmorillonite with cetyltrimethylammonium bromide, and EDTA as a crosslinking agent. Three nanohydrogels were prepared with different chitosan: Org‐Mt ratios: Cro‐Cs ₁ /Org‐Mt ₃ (25:75), Cro‐Cs ₁ /Org‐Mt ₁ (50:50) and Cro‐Cs ₃ /Org‐Mt ₁ (75:25). Characterisation by FT‐IR confirmed the presence of all functional groups of cross‐linked chitosan and organomodified montmorillonite, while SEM and EDX verified successful intercalation. BET analysis showed that Cro‐Cs ₁ /Org‐Mt ₁ had a specific surface area of 5.5133 m ² /g, with pore sizes ranging from 3.1970 to 3.4256 nm. TGA and DSC indicated improved thermal stability of the nanohydrogels. Equilibrium water absorption at 25°C was 314.57% (Cro‐Cs ₁ /Org‐Mt ₁ ), 252.61% (Cro‐Cs ₃ /Org‐Mt ₁ ) and 116.61% (Cro‐Cs ₁ /Org‐Mt ₃ ); these values decreased to 210.50%, 161.42% and 71.61%, respectively, at 80°C. The adsorption of methylene blue (MB) was tested using 10 mg/L MB and 10–60 mg of Cro‐Cs ₁ /Org‐Mt ₁ at room temperature and in the dark, achieving 83% removal efficiency, demonstrating its potential as an effective adsorbent for dye removal.