Study on the cadmium adsorption performance of Sepia ink melanin from Mussel cooking juice

The performance of Cd adsorption of Sepia ink melanin from Mussel cooking juice was investigated in the present study. The effect of melanin content,pH,contact time and initial concentration of Cd on Sepia ink melanin from Mussel cooking juice was investigated. These parameters were fitted by using of the kinetic and thermodynamic model. The physical and chemical properties of melanin were characterized by using of scanning electron microscope and Fourier transform-infrared spectroscopy. Finally,the regeneration of Sepia ink melanin to cadmium adsorption was conducted. The results showed that the adsorption equilibrium of Cd was reached after reaction for 45 min at 25℃ when 0.10 g Sepia ink melanin was added into 100 mL pH3~6 of Mussel cooking juice at an concentration of 50 mg/L Cd. The maximum cadmium adsorption capacity of was(46.47±0.12) mg/g and the removal rate of cadmium was 93.1%±0.1% under the optimum conditions. The equilibrium data were well explained by pseudo-second-order kinetic model(R²=0.998)and fitted Langmuir isotherm. SEM and FT-IR confirmed that the adsorption reaction mainly existed on the surface of the melanin and the major functional groups involved in adsorption reaction was-OH,-NH,-COOH. The cadmium adsorption capacity did not significantly changed after regeneration three times. The present study suggested that Sepia ink melanin is good adsorbed material of cadmium and have good biological regeneration.