Foam Separation of Lead(ll) and Cad mi urn (II) from Waste Water

Abstract

Foam separation techniques are evaluated to determine if they would be feasible for removing lead(II) and cadmium(II) from highly contaminated waste water. Variables such as pH, ionic strength, collector concentration, and interfering ions were studied to determine their effects on ion flotation. Increased ionic strength, calcium(II), and phosphate interference made ion flotation impractical. Precipitate flotation of lead sulfide and cadmium sulfide left approximately 0.20 ppm lead(II) and 0.08 ppm cadmium(II) in the bulk solution under optimum conditions—somewhat above the levels considered safe to release into the environment. Adsorbing colloid flotation gave excellent results; lead sulfide and cadmium sulfide were adsorbed to ferrous sulfide which was then removed by foaming with hexadecyltrimethylam-monium bromide. Lead(II) levels were reduced from 0.80 to 0.025 ppm in 34 min foaming with 15 ppm iron(III) added. Cadmium(II) levels were reduced from 1.0 to 0.008 ppm in 45 min foaming with 25 ppm iron(III) added.