Effect of pH and temperature on the adsorption of bovine serum albumin onto titanium dioxide

The effects of pH and temperature on the equilibrium and the kinetics of bovine serum albumin (BSA) adsorption onto titanium dioxide (TiO2) were investigated. Adsorption rate and equilibrium experiments were carried out at pH conditions of 4, 5, 10 and in a temperature range of 20–40 °C. Adsorption rate was increased with decreasing pH and increasing temperature. The Langmuir isotherm constants corresponding to adsorption capacity, Q0, were 35.8, 40.0 and 42.6 mg/g for 20, 30 and 40 °C and pH 4; and 24.5, 29.1 and 33.4 mg/g for 20, 30, 40 °C and pH 5, respectively. The BSA adsorption capacities of TiO2 were higher for pH 4 at 40 °C. Adsorption of BSA on TiO2 at different pH and temperatures was found to be first order kinetics. At pH 4, k1 has values of 0.018 and 0.019 min−1 at 20 and 40 °C, respectively. For pH 5, k1 is 0.013 min−1 at 20 °C and 0.019 min−1 at 40 °C. The first order rate constants are higher at pH 4 than the values at pH 5. Higher values of the adsorption rate constants at pH 4, could be due to the change of pore structure of TiO2 or denaturation by conformational change of BSA with increasing pH.