Synthesis and characterization of ferrocene-based Schiff base and ferrocenecarboxaldehyde oxime and their adsorptive removal of methyl blue from aqueous solution

The ferrocene-based Schiff base 3 was synthetized by reaction of ferrocenecarboxaldehyde 1 with 4-aminoantipyrine 2. However, the reaction of 1 with hydroxylamine affords ferrocenecarboxaldehyde oxime 4. Compounds 3 and 4 were fully characterized by IR, 1H, 13C and DEPT-135 NMR spectroscopy, elemental analyses and also by single crystal X-ray diffraction. Compounds 3 and 4 were used to remove anionic methyl blue dye from wastewater. The results established that both compounds have high adsorption capacity towards methyl blue. Langmuir adsorption capacity of compound 4 (464 mmol/g) is much higher than that of compound 3 (193 mmol/g) at 25 °C. The kinetics data was fitted well pseudo-second-order model. Thermodynamic studies show that the adsorption of methyl blue onto compound 3 was endothermic, while its exothermic in case of adsorption onto compound 4. The process was spontaneous for both compounds.