Effective sequestration of toxic hexavalent chromium ions from aqueous solution using L-methionine-supported Zr-MOF...

Rapid industrialization in recent times has resulted in a detrimental impact on the water medium, posing a significant risk to human health. For instance, several health hazards are encountered with heavy metal pollution, particularly chromium contamination, which is a recognized issue. In this study, zirconium MOF and L-methionine-conjugated chitosan (Zr-MOF/L-met@CS) were prepared and applied for chromium ion removal. From the experimental studies, it is evident that the prepared nanocomposite exhibits a maximum adsorption capacity of 218.32 mg g^-1 at pH 3, initial concentration of 300 mg L^-1 and dosage 10 mg. The prepared material was characterized using FE-SEM, FTIR, XRD, BET, TGA, and XPS analysis, which confirmed the successful formation of the composite. During the co-ion study, it was demonstrated that the inhibition of chromium adsorption was in the order carbonate > phosphate > fluoride. The surface charge of the material was determined using pH_zpc studies as 6.21. By these analytical techniques, the adsorption mechanism was also determined to be electrostatic attraction by protonated -NH₃⁺ groups, Surface complexation via ZrO bonds, and reduction through the oxidisable sulfur groups. The aforementioned experiment was fitted with the Langmuir isotherm model and the pseudo-second order kinetics model, confirming the chemisorption mechanism.