Adsorption behavior of bovine serum albumin on Zn–Al and Mg–Al layered double hydroxides

In this work, non-calcined Mg–Al and Zn–Al layered double hydroxides (LDHs) with molar ratio of 3:1 were investigated for the adsorption of bovine serum albumin (BSA). Both LDHs were synthesized using the co-precipitation method and were characterized by X-ray diffraction, N2 adsorption–desorption isotherm at −196 °C, elemental analysis and X-ray photoelectron spectroscopy. The adsorption of BSA was evaluated in a batch adsorption system to assess the influence of buffer solution and buffer pH, contact time and initial concentration. Fixed-bed adsorption experiments were also performed in order to evaluate the dynamic adsorption behavior of BSA on the LDH as well as the regenerability of this material. In the batch adsorption experiments, the maximum amount of BSA adsorbed was reached at its isoelectric point (pI = 4.8) with 50 mM acetate buffer for Mg–Al LDH and pH 6.7 with 50 mM 2-(N-morpholino)ethanesulfonic acid (MES) buffer for Zn–Al LDH. The Langmuir and Langmuir–Freundlich models provided maximum equilibrium adsorption capacity of 338.74 and 346.54 mg g−1for Zn-Al LDH, respectively, and 196.12 and 197.80, respectively, for Mg-Al LDH. Column experiments were carried out with a constant flow of 1 mL min−1, varying the feed concentration of BSA solutions from 1.0 to 2.0 mg mL−1. An average of 98 % of BSA injected into the column was retained, and a completely elution was reached using 50 mM sodium phosphate with pH 12.