The effect of active control of electric potential of filter medium on depth filtration was explored experimentally. Activated carbon particles were selected as the conductive filter medium. The filter medium potential was controlled with an external DC power supply. Kaolin particles were used as the model suspended solid. The activated carbon and kaolin had negative zeta potential around neutral pH. When the filter medium potential against a counter electrode was greater than or equal to + 0.2 V, rejection rate of particles was 1.8 times higher than that when the potential was less than + 0.2 V. Thus adsorption of particles by interaction of electric double layers was enhanced by maintaining a positive charge on the filter media. Desorption of kaolin trapped on the filter media was also confirmed by changing the filter medium potential from positive to negative. The percentage of kaolin particles desorbed was 11% of the kaolin trapped on the filter media. The desorption rate was not high, but this technique will enhance refreshment of the filter media when combined with back washing.
Keywords: depth filtration, electric double layer, particle separation, zeta potential