Patent ID: 8231006

Claim:
A method for separating and recovering silicon particles from silicon saw kerf resulting from slicing silicon wafers from a silicon ingot, the saw kerf comprising a lubricating fluid and a mixture of solid particulate comprising abrasive grains, silicon particles, metal particles and oxide particles, the method comprising: separating at least a portion of the lubricating fluid from the solid particulate mixture; washing the solid particulate mixture with an acidic solution comprising hydrogen fluoride and hydrochloric acid in which (i) the silicon particles are substantially insoluble, and (ii) the metal particles and oxide particles are soluble, metal particles and oxide particles being dissolved from the solid particulate mixture, the acidic solution creating a flotation froth with the solid particulate mixture, the froth comprising the silicon particles and the abrasive grains; collecting the washed solid particulate mixture, the washed mixture comprising silicon particles and abrasive grains; and, separating the silicon particles from the abrasive grains in the washed solid particulate mixture by subjecting the froth to a density-dependent separation technique selected from sedimentation centrifugation, filtration centrifugation, and hydro-cyclone separation and, prior to the density-dependent separation, contacting the silicon particles with a source of iodine, in order to convert at least a portion of the silicon present therein to SiI 4 , wherein the separated silicon particles have a carbon content of less than about 50 ppma and have a content of metal contaminants of less than about 150 ppma.