Comparison of 2-compartment, 3-compartment and stack designs for electrodialytic removal of heavy metals from harbour sediments

• Multivariate design and analysis were used to compare 3 electrodialytic designs.
• Multivariate modelling revealed that the 3 set-ups were different.
• The highest efficiency was found for the 2-compartment cell.
• The type of sediment and experimental set-up were the most significant variables.

Comparisons of cell and stack designs for the electrodialytic removal of heavy metals from two harbour sediments, were made. Multivariate modelling showed that sediment properties and experimental set-ups had the highest influence on the heavy metal removal indicating that they should be modelled and analysed separately. Clean-up levels of Cu, Pb and Zn were significantly higher for the cell designs, implying that longer time and relatively more electric charge and energy would be necessary to achieve similar clean-up levels in the stack design experiments.In the studied experimental domain, the optimal current density for the 2- and 3-compartment cells was 0.12 mA/cm2 (center value) removing the highest quantity of Cu, Pb and Zn per Wh. The highest percentages removed were 82% Cu, 81% Pb and 92% Zn were however achieved at higher current density. For the stack experiments conducted at same electric charge per unit sediment, energy consumption was a magnitude higher and the highest clean-up levels were 21% Cu, 42% Pb and 73% Zn.