Biosorption study on Ni(II) and Cd(II) removal in a packed bed column using brewery sludge pellets

The study covers the results of investigations on performance of packed bed column as a continuous contactor for nickel [Ni(II)] and cadmium [Cd(II)] biosorption on pellets of brewery sludge. Experiments were conducted to assess influence of design variables such as bed height (2.5 to 10 cm) and flow rate (2.5 to 10 mL/min). By fitting the column data into the model equations, the parameters of the Thomas and bed depth service time (BDST) models, which are utilized in the design of packed column adsorbers, were determined. For Ni(II) biosorption, the computed values of N-0 and K-A obtained using the BDST model were 1833 mg/L and 0.022 L/mg.h, respectively, whereas for Cd(II) biosorption, the values were 5424 mg/L and 0.005 L/mg.h, respectively. Predicted Ni(II) and Cd(II) uptake using the Thomas model were 7.33 mg/g and 14.79 mg/g at 2.5 mL/min flow rate. Optimal biosorption conditions for Ni(II) and Cd(II) were observed at 2.5 mL/min flow rate and 10 cm bed height. Critical design factors such as length of the unused bed (LUB), stoichiometric time (t*), and mass transfer zone (delta t) needed for scaling up the biosorption process were also determined. The present study has demonstrated that the biosorption of Ni(II) and Cd(II) onto pellets of brewery sludge in packed bed column is intraparticle mass transfer controlled process.