Adsorption of casein onto some oxide minerals and electrokinetic properties of these particles

Abstract

In this study, the adsorption properties of casein onto some oxide minerals such as sepiolite, kaolinite and expanded and unexpanded perlites samples were studied as a function of concentrations of casein, sodium phosphate and NaCl, temperature and pH of the aqueous solutions. According to the experimental results, the adsorption of casein increases with temperature from 15 to 45 degrees C and ionic strengths of the solutions over the range of 0.0 and 0.1 mol L-1. The adsorption decreased with increasing pH from 7.00 to 11.00 and the concentration of phosphate ions from 0.02 to 0.10 mol L-1. Maximum adsorption capacity values (q(m)) showed dependence on pH. It was observed that q(e)-pH curves reached a maximum at around neutral pH value. Furthermore, the electrokinetic properties of casein-covered oxide particles were also investigated at similar conditions to those of the adsorption process. The nature of the adsorption process was investigated using Langmuir and Freundlich isotherm models.