Flotation

Indian copper and zinc concentrators (HCL, HZL) rely on flotation after grinding to liberate sulphides. pH lime control for sphalerite/pyrite separation — exam questions on Cu-Pb-Zn flowsheet.

Grade-recovery curve: aggressive conditions increase R but dilute grade — optimise NPV not either alone. First-order kinetics R = 1 − exp(−kt) models batch lab cells.

Singh & Singh flotation chapter lists xanthate collectors for sulphides, fatty acids for oxides.

Relation 1 —

Write this relation with symbols exactly as in Wills Mineral Processing — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 2 —

Write this relation with symbols exactly as in Wills Mineral Processing — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 3 —

Write this relation with symbols exactly as in Wills Mineral Processing — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Recovery R = mass valuable in concentrate / mass in feed × 100%. Combined metal recovery multiplies stage recoveries: R_total = R₁ × R₂ × R₃ for rougher-scavenger-cleaner.

Grade-recovery trade-off: longer flotation time or more collector raises R but entrain gangue — grade drops. Operating point on curve set by smelter payment terms and penalty elements.

Rate constant k: dR/dt ∝ (1−R) — faster k means shorter residence time needed. Plant scale-up from lab k with scale factors.

Reagents: collector makes mineral hydrophobic; frother stabilises bubble; modifier (depressant, activator, pH) shifts selectivity. Eh-pH diagrams predict stable sulphide phases — redox control critical for complex ores.

State assumptions explicitly before using any relation for flotation — steady state, uniform properties, linear elastic material, ideal gas, incompressible flow, etc., as applicable.

Wrong assumptions invalidate the entire solution even when the formula is correct. In Mineral Processing viva and GATE descriptive questions, listing valid assumptions often earns separate marks.

1. Read the question and list given data with SI units (common in Mineral Processing papers).
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to flotation.
4. Use equation 1: .
5. Use equation 2: .
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.

Flotation appears in beneficiation plants. In Indian mining curricula this topic is tested because it connects theory to comminution and separation.

GATE and semester exams often combine flotation with earlier units — revise prerequisites before attempting mixed problems.

Industry interview panels sometimes ask: "Where did you use flotation?" — answer with a lab, mini-project, or plant visit example if possible.

• Adding stage recoveries instead of multiplying
• Grade-recovery point beyond economic optimum ignored
• pH effect on sulphide flotation reversed (e.g. pyrite depressed at high pH with lime)
• Confusing metallurgical recovery with mass recovery

Before attempting flotation problems, confirm you can:

1. Collector, frother, modifier reagents
2. pH and pulp potential affect selectivity
3. Rougher-scavenger-cleaner circuit

Revise the solved examples in Wills Mineral Processing — Standard reference and one previous-year GATE or university paper for this unit.