Biosorptive behaviour of casein for Zn2+, Hg2+ and Cr3+:: Effects of physico-chemical treatments

The uptake behaviour of milk protein (casein) for some heavy metal toxic ions [Zn2+, Hg2+ and Cr3+] was investigated by employing the 'radiotracer technique'. The effects of various physico-chemical treatments were investigated in order to explain the sequestering behaviour of this biomass. In a single batch equilibrium experiment a decrease in adsorptive concentration (10(-2)-10(-8) mol L-1) and increase in temperature (293-323 K) and pH (ca 3-10) specifically increased the uptake of the metal ions. The uptake followed a first-order rate law and obeyed the Freundlich isotherm. Changes in standard enthalpy and activation energy involved during the biosorption were deduced for these systems. Also, desorption experiments showed that no significant desorption took place. (C) 1998 Elsevier Science Ltd.