pH Modifiers

Froth flotation is a process of material separation considering water association and the density of minerals. It separates gangue and ore minerals. The physical-chemical properties of various chemicals are different. This principle is used for the separation of minerals using froth flotation and has vast practical applications. Some of the uses of froth floatation include low-grade mineral separation, differentiating plastics, recycling and wastewater processing. To perfectly process, every flotation reagent has to contribute equally. pH modifier is one such important chemical.

Froth flotation

Froth flotation is a mineral separation process considering the properties of flotation reagents and surface properties of minerals. It is far better considered than magnetic separation and gravity separation, and it does not depend on the nature of minerals. The properties of flotation reagents are the key. 

Froth flotation process

 First, we have to treat impure ore before processing. Roughing, scavenging and cleaning are the processes that help to remove a large number of peripheral impurities. 

• Liberation is the process by which ore is divided  into different mineral particles.
• A process called conditioning forms a hydrophobic layer around minerals using flotation chemicals.
• Flotation is the step where the mineral slurry is added to the flotation column with froth forming flotation reagents. 
• Frothing is when air is introduced from the bottom and the frothing agent from the top. They form bubbles to which mineral particles adhere.
• Separation is the last process of separating high-grade mineral froth particles from the primary ore.

List of chemicals 

 Different kinds of reagents are used in froth flotation, most of which exist in liquid form. Dry reagents should be processed dry and never wet. One ton of ore might need at least one pound of reagent.

• Collectors

We have to reduce the water-loving property of the desired mineral to make it bind to the air bubble. Collectors are a base for making minerals hydrophobic, and collectors enhance the mineral’s property of floating, making them separate better. 

Examples: Fatty acids and xanthates like potassium isobutyl xanthate and sodium ethyl xanthates

2. Activators 

 Activators promote the binding between a mineral and its collector.

 Example: Copper sulphate

3. Frothers

Frothers form foams. The small air bubbles formed along with the froth adhere to the mineral. The surface tension of water decreases by this activity.

Example: Pine oil, acrylic acid and poly glycol

4. Modifiers

The binding of the collector and mineral is important for froth flotation. Modifiers change the mineral’s surface property and insist it attaches to the collector.

Example: Lime and soda ash (pH modifier), phosphates and silicates (anionic modifier), starch and dextrin (cationic modifier).

Overview of pH modifiers

Modifiers are the flotation reagents used to change the properties of minerals and encourage their attachment with froth bubbles. A modifier binds to a froth bubble when it is already attached with a desirable mineral.

Minerals bear a positive charge under acidic conditions and a negative charge under alkaline conditions. These changes in the surface chemistry of minerals are affected by the pH. This is where the importance of a pH comes in.

pH modifier’s importance 

pH modifiers cause the gangue particle to levitate less using their pH difference. Lime and soda ash are the common pH modifiers. Soda ash is a deflocculating agent too. It wets the gangue to make it less levitating. pH modifiers should be added to the process to maintain the alkalinity of the mineral pulp.

Examples of pH modifiers

pH modifiers are selected according to the collectors. Some collectors can perform better in acidic pH, and some work better in alkaline pH. So the examples given here include both acidic and alkaline pH modifiers.

Lime or slaked lime: Added as a slurry – pH regulation

Soda ash, NaOH: Added as a dry component – pH regulation by dispersing gangue slime

Caustic soda: Added as 5 to 10% solution – pH regulation by dispersing gangue slime

Sulfuric acid: Added as 10 % solution – pH regulation

Conclusion

Froth flotation is a more considerable practice than gravity separation and magnetic separation. Modifiers change the characteristics of a mineral and ensure it attaches to the collector. They are one of the floatation reagents that are used to increase the attachment detachment of minerals using change in pH. With the help of a modifier, a mineral pulp can be alkaline or acidic. This changed nature enhances the selectivity of minerals for collectors.