Which of the following statements are true for froth floatation process (for a concentration of sulphide ores)?

Options

A. A) Pine oil used as collectors
B. B) Cresol enhance non wettabillity of the mineral particles
C. C) `NaCN` selectively prevents `PbS` from coming to the froth but allows `ZnS` to come with the froth
D. D) The mineral particles become wet by oils while the gangue particles by water.

Explanation

To determine which statements are true for the froth flotation process used for the concentration of sulphide ores, we will analyze each statement based on the principles of the froth flotation process.

### Step-by-Step Solution:

1. **Understanding Froth Flotation Process**:
- The froth flotation process is used to separate hydrophobic minerals from hydrophilic waste materials. Hydrophobic minerals do not wet with water, while hydrophilic materials do.

2. **Analyzing Each Statement**:
- **Statement A**: "Pine oil is used as a collector."
- **Analysis**: This statement is true. Pine oil (or eucalyptus oil) is indeed used as a collector in the froth flotation process for sulphide ores. It helps to wet the metal sulphides, allowing them to attach to air bubbles and rise to the froth.

- **Statement B**: "Crystal enhances non-wettability of the mineral particle."
- **Analysis**: This statement is false. Crystal is used as a froth stabilizer, not to enhance non-wettability. It helps to stabilize the froth but does not affect the wettability of the mineral particles.

- **Statement C**: "Sodium cyanide selectively prevents lead sulphide from coming to the froth but allows zinc sulphide to come with the froth."
- **Analysis**: This statement is false. Sodium cyanide is used as a depressant to selectively allow lead sulphide to come to the froth while preventing zinc sulphide from rising. Therefore, it allows lead sulphide to float and prevents zinc sulphide from coming with the froth.

- **Statement D**: "The mineral particles become wet by oils while the gauge particles by water."
- **Analysis**: This statement is true. In the froth flotation process, the mineral particles (sulphide ores) are wetted by the collector oil (like pine oil), while the waste (gauge) particles are wetted by water.

3. **Conclusion**:
- The true statements are A and D.
- The false statements are B and C.

### Final Answer:
- **True Statements**: A and D
- **False Statements**: B and C