1. 1. Activating reagents 2. Depressants 3. Others (they modify: pH, coagulation, redox, rheology, etc.) AUXILIARY FLOTATION REAGENT

2. Activating action of hydrolyzing cations. Flotation of quartz in the presence of 10 –4 M sulfonate (no flotation in the absence of those cations)

3. Fluoric ions may activate and depress flotation of silicates: a – area of depressed flotation in presence of oleate b) area of activation in the presence of dodecylamine as collector (Manser, 1975)

4. Depressants acting through adsorption Depressing reagents Depressants acting through redox reactions Depressants acting through reactions with flotation reagents

5. Depressors acting through adsorption –MC + D = –MD + C D – depressant ion C – collector ion –MC – collector adsorbed or forming surface compound with mineral –MD – depressant adsorbed or forming surface compound with mineral Barski’s constant (relation) equilibrium const. for bulk reactions equilibrium const. for surface reactions general form of Barski’ relation

6. Depressants acting through adsorption pH modifiers (acids and bases)   k y    OH X based on attachment of partcles to bubble too high and low pH depress flotation of minerals

7.   k y    OH X Values of parameter y for selected mineral-collector system (here pH regulator determines concentration of OH - ions (after Chander, 1988) Mineral–collector y pH range Galena/KEX 0.65 9–12 Galena/KDEDTP 0.53 6–9 Sphalerite/DEDTC 0.56 6–8 Sphalerite/DBDTC 0.72 7.5–10 Sphalerite/DADTC 0.75 8–11 Chalcopyrite/NaDEDTP 0.71 8.5–11 Chalcopyrite/KEX - 11–13 Pyrite/NaDEDTP 0.62 4–6 Pyrite/KEX - 10–12 E - ethyl, D – di, T tio, A- amyl, B- butyl, X- xanthate, P - phosphate, C – carbonate, K- potassium, Na - sodium In highly alkaline environment not working

8. Redox depressants

10. Relationship between flotation recovery of sulfides and potential applied to a platinum wire immersed in aqueous suspension of a sulfide containing ethyl xanthate at 1.44·10 –5 kmol/m 3. After Richardson and Walker, 1985

11. Depressants acting through reactions with flotation reagents 2C 2 H 5 OC(S)SK + 2K 2 SO 3 + 2KHSO 3 + 2O 2  2C 2 H 5 OC(S)SOK  2C 2 H 5 OH + 4K 2 S 2 O 3 + 2CO 2 Removal of xathates from sulfides

13. Dispersion modifiers iep Acids, bases, large organic ions