Dual separator purification system

Abstract

A dual separator purification system and method for removing particulate as well as ionic contaminants from liquids is disclosed. The present invention is particularly useful in the electrostatic printing industry. The system comprises two disparate separators connected in series. The first separator has a repelling electrode and a rotating drum which collects charged particulate contaminants and debris. A liquid such as spent liquid toner is passed through a gap between the repelling electrode and the rotating drum. The contaminants, including colored toner particles and paper debris, move electrophoretically through the gap and adhere to the rotating drum. Upward motion of the drum surface brings the accumulated deposit out of the gap region and to a scraper blade which removes the deposit from the drum for subsequent disposal. The partially purified liquid is collected and then passed through a second separator which has a spirally-wound laminate of porous and electrically conductive layers. As the liquid passes through the porous layers of the spiral laminate, it is subjected to an electric field created between the conductive layers. The remaining contaminants within the liquid, mostly molecules that were electrically neutral during the pass through the first separator, but which slowly become ionized, move toward a conductive layer. The liquid remains in the second separator and exposed to the electric field for a relatively long time. A highly purified liquid, virtually free of contaminants, emerges from the second separator.