In froth flotation, which reagent is added primarily to promote air-bubble attachment by rendering selected mineral surfaces hydrophobic?

Introduction / Context:
Froth flotation separates valuable minerals from gangue using differences in surface hydrophobicity. Reagents play distinct roles: collectors make target mineral surfaces hydrophobic; frothers stabilize bubbles; modifiers adjust conditions; activators and depressants tune selectivity.

Given Data / Assumptions:

• Goal: enhance air adhesion to mineral surfaces.
• Common collectors: xanthates, dithiophosphates, fatty acids (depending on mineral class).

Concept / Approach:
Collectors adsorb onto mineral surfaces, increasing contact angle so that bubbles attach and carry particles into the froth. Without adequate collector action, particles remain hydrophilic and do not report to the froth product.

Step-by-Step Solution:

Verification / Alternative check:
Flowsheets and reagent schemes categorize xanthates/dithiophosphates as collectors; pine oil/MIBC as frothers; lime/soda ash as modifiers; CuSO4 as an activator for sphalerite.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing frother action with collecting; overdosing collectors leading to non-selective flotation.

Final Answer:
Collector