Preparation of a cobalt mono-substituted silicotungstic acid doped with aniline for the selective adsorption of ovalbumin

Abstract

A Keggin-type cobalt mono-substituted silicotungstic acid doped with aniline (SiW₁₁Co–PANI composite, where PANI denotes polyaniline) is prepared by a liquid phase method at room temperature. The obtained SiW₁₁Co–PANI composite possesses a porous framework structure and has proven to be a promising adsorbent for the retention of proteins, which exhibits favorable selectivity toward the adsorption of ovalbumin from egg whites. 5.0 mg of SiW₁₁Co–PANI composite gives rise to an adsorption efficiency of >70% for 100 mg L⁻¹ ovalbumin in 1.0 mL of sample solution within a wide pH range of 3–9, and a maximum adsorption efficiency of 92% is achieved at pH 9. The adsorption behavior of ovalbumin onto the SiW₁₁Co–PANI composite fits the Langmuir adsorption model, corresponding to a sorption capacity of 200.0 mg g⁻¹. The retained ovalbumin could be readily recovered by using a 0.1 mol L⁻¹ phosphate buffer at pH 5.6 as a stripping reagent, providing a recovery of 84.4%. Circular dichroism (CD) spectra illustrate virtually no change in the conformation of ovalbumin after the process of adsorption–desorption. The SiW₁₁Co–PANI composite has been applied for the selective adsorption of ovalbumin from the chicken egg white, and SDS-PAGE assay demonstrates that high purity of ovalbumin is obtained.