Particles having different properties (e.g. particulate fly ash and carbon) are separated by driving the particles by means of a vibratory feeder (12) forwards along a horizontal electrode plate (1) above which is mounted a second electrode (2) having at least one plate (4) mounted at an acute angle (a) to the horizontal. Preferably, two plates (4) each extend sideways from a central block (3) of dielectric material. An alternating electric field is generated between the electrodes (1, 2) by a high voltage AC power source (14). The potential across each plate (4) varies (in particular, decreases) in the lateral direction, the variation being continuous or stepwise. The field lines (16) from each plate (4) curve to the side and impart centrifugal forces to particles charged by friction or conductive induction, which forces separate lighter, more heavily charged particles from the others. The separated particles are collected in bins (13) arranged around the lower electrode (1).