The biosorption of Pb2+ and Cd2+ in a fixed bed column by immobilised Chlorella sp. was characterised in a fixed bed column. Effect of initial concentration of Pb2+ and Cd2+, pH, and pellet size on the biosorption capacity was studied, at laboratory scale, using a factorial experiment design 2(3), in a 10 cm heightx1 cm of diameter continuous flow column packed with immobilised biomass. Equilibrium uptake of Pb2+ and Cd2+, increased with increasing initial metal ion concentration. It was favoured to pH 5, with a pellet of 5 mm of diameter. Langmuir model described the biosorption equilibrium of both metals.The biosorption of each single cation was studied too in a large column (50 cm heightx5 cm of diameter) at bench scale with a range of flow of 40 to 80 mL min(-1). The mass transfer coefficient was determined fitting the experimental data to continuity equations that were discretised in the radial terms with orthogonal collocation method.
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