Investigation of fine activated carbon as a viable flow electrode in capacitive deionization

Flow capacitive deionization is a variant of capacitive deionization allowing continuous/semi continuous desalination. Performance of electrode is linked to factors such as applied voltage, feed electrode hydrophilicity, carbon loading, conductivity of the feed electrolyte, particle size, viscosity etc. In this paper, a new approach was adopted in reducing particle size of the carbon used as flow electrode by dry milling method at different time intervals. The particle size and hydrodynamic diameter of the ground activated carbon (fine activated carbon FAC) was reduced after milling in comparison with pristine activated carbon (PAC) but an increase in viscosity was observed in FAC flow electrode. Increase in viscosity stems from increase in particles loosening which correlates to more stability of the slurry due to higher zeta potential with consequent less particles agglomeration effect and greater repulsion force. Physico-chemical analysis such as scanning electron microscopy (SEM) and particle size analyzer confirmed the reduction in particle size. On verification as flow electrode at 10 % wt (carbon loading), fine activated carbon exhibited a significant increase in desalination over pristine activated carbon. The improvement is linked to lower particles aggregation that enables higher ions migration and contact to the carbon pores; thus this simple method shows that fine activated carbon can be a viable flow electrode in FCDI.