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(70-09) Modelling of metal sorption to a mixed microbial population. Samaranayake, Rajika1, Singhal, Naresh*,1, Lewis, Gillian2, Hyland, Margaret3, 1 Department of Civil and Environmental Engineering, Auckland, AK, New Zealand2 School of Biological Sciences, Auckland, AK, New Zealand3 Department of Chmical and Materials Engineering, Auckland, AK, New Zealand ABSTRACT- Mathematical models can be used to estimate the distribution of metal immobilization quantities due to surface complexation between metal-bacterial interactions. A mathematical model is developed to estimate metal adsorption onto surfaces of a mixed bacterial population. Results show that adsorption reactions are rapid and steady state attained within 2 h in all studies. The model is based on an assumption of thermodynamic equilibrium for reactions that occur at the water-bacterial interface. Experiments were carried-out to describe metal uptake by cell walls in multi metal system in variable cell concentrations with mixed population under different pH values. Experiments were performed for sorption of Cd, Cu, Fe, Zn, Pb, Mg, Ni, Ca and Mn to yield stability constants for the metal-bacteria reactions. Two empirical models based on the Langmuir and Freundlich isotherms are developed as: Mesorbed = (Qmax * CMe)* Bmax/(CH+KL + CMe) Mesorbed = KF * (CMe)1/n* Bmax/CH+ Parameter constants were determined for metal sorption to dead and live bacterial cells. Live cells show a reduced tendency to sorb metals than dead cells. Model predictions show excellent agreement with the sorption data.for both dead and live cells. Fe, Mn, Ni, Zn, and Cd show better agreement with the Freundlich model and the remaining metals showed good agreement with both models. Based on the apparent surface complex formation constants (KL), order of sorption is Pb>Cu>Ni>Zn>Ca>Mg>Fe>Cd. Organic ions have complexing ligands with metal ions, resulting relatively lower biosorption for some metals than the other. This indicates that metal sorption is non-selective and competitive. Key words: heavy metals, bio-sorption, adsorption isotherm model, mixed population |
