Kinetics modelling of biosorption by algal biomass from binary metal solutions using batch contactors

The biosorption from four binary metal solutions, Pb2+/Cu2+, Pb2+/Cd2+, Pb2+/Zn2+ and Cd2+/Zn2+, onto algae Gelidium, algal waste and composite material, at pH 5.3 and 20 °C, were studied in batch adsorber. A mass transfer model based on a one-dimensional intraparticle diffusion rate, combined with a binary Langmuir isotherm, was applied to describe the overall biosorption rate of binary metal solutions mixture in flat seaweed biomass. A good correlation has been found between mass transfer model and experimental data for all systems. Model equations were solved numerically yielding the metal ions homogeneous diffusion coefficients. The biosorbents showed a preference for sorbing Pb over Cd, Zn and Cu even for low lead initial concentrations. Cu and Pb show a similar competition for the binding sites, although a higher uptake was found for copper ions, due to the higher initial copper concentration.