A four-step, bench-scale process has been developed that is capable of removing at least 92 percent of the soluble fluoride from feldspar flotation process wastewaters at a projected cost of $1.03/kkg ($0.93/ton) of feldspar. For a 163,000 kkg/year (180,000 ton/year) plant, the initial capital expenditure would be about $200,000. The wastewater is pretreated with sodium hydroxide, lime, and calcium chloride, which removes an initial 50 to 60 percent of fluoride. The clarified water is then passed through a bed of activated alumina for further fluoride removal. The activated alumina is regenerated with a 1-percent sodium hydroxide solution, and fluoride in the caustic liquor is effectively precipitated with calcium chloride. The fluoride can be recovered in concentrated form as insoluble calcium fluoride filter cake.

Includes bibliographical references (page 22). Prepared for U.S. Environmental Protection Agency, Office of Research and Development, Industrial Environmental Research Laboratory, Cincinnati, Ohio, submitted by Versar, Inc., under grant no. Contract Number: R-804377.