Water softening using packed bed of polypyrrole from flowing solutions

Packed bed of polypyrrole/polystyrene sulfonate (PPy/PSS) electrodeposited porous carbon electrode was prepared and used for continuous water softening from flowing artificial hard water solutions. Careful preparation of the packed bed was performed in order to obtain the greatest possible degree of uniformity of the PPy/PSS-within the porous carbon matrix. The porous carbon electrode was of the type, reticulated vitreous carbon (RVC) of grades 20, 45 and 80 PPI. Cyclic voltammetry and scanning electronmicroscopy (SEM) were used to characterize the prepared electrodes. The porous electrode was used in removal of Ca2+ ions from flowing 0.0125 M CaCl2 solution at different conditions. Removal efficiencies of about 10% were obtained at some conditions. This low conversion per pass calls for using multi-electrode systems or recirculation of the solution (filters) to obtain the desired Ca2+ and water softening levels. The energy consumption and coulombic efficiency of the overall removal process was determined at a given set of experimental conditions. Regeneration of the PPy bed was affected by the presence of dissolved oxygen in the flowing solutions.