Over 30 million tons of phosphogypsum are being placed on piles, or gyp stacks, each year. Some productive use for this potential resource is desired. It has been proposed that this phosphogypsum and tailings sand, also associated with the phosphate mining operations, be used to produce high value glass or glass-ceramics products while returning the sulfuric acid back to the mining operations. Phase one successfully demonstrated feasibility of making glass from these materials. The current phase was to research the marketing of a product made from these materials and to complete an initial risk assessment. Glass-ceramics made with high concentrations of calcia or gypsum appear attractive for making a variety of products and yield strong, abrasion and corrosion resistant products. Wall, floor and roof tile were selected as the products. The method for identifying and selecting the product is reported. A preliminary risk assessment indicates that radon exposure attributable to these tile are much lower than for other construction materials. Annual gamma dose from maximal use of tile, all floors and roof, and conservatively exposure times was less than 50 mrem/y. With a more realistic tile use, limited to the kitchen, bathroom and entry way, the estimated exposures were less than 10 mrem/y.
Chris Chapman, Richard Peters, and Bogdan Wojak, Vitrification International Technologies, Inc. April 1999.