Description of the polymer: Liquid latex type of flocculant;

NHPA (Ammonium poly-acrylate) , anionic charged with MW about 18 million;

The product ingredients are : WATER , ACRYLIC ACID to make the polymer , LIQUOR AMMONIA to neutralised the polymer, LOW ODOUR PARAFINIC SOLVENT , OLEIC ACID , polymerization iniziators and finished residuals.

The polymer dilution is made in a 0,25M NaOH and 10(-3) NaCl solution. We suspect anionic charge very high.  The polymer is used in Alumina plant in red mud thickening clarifiers and it is similar to CYTEC HX-6300

Anionic flocculants play a crucial role in the alumina industry, especially in the processing of red mud through thickening clarifiers. The application of these flocculants in alumina plants is a complex and intricate process, involving multiple stages and requiring a detailed understanding of both the chemical properties of the flocculants and the physical characteristics of red mud.

Understanding Red Mud

Red mud is a by-product of the Bayer process, which is the principal method for refining bauxite to produce alumina (aluminum oxide). In this process, bauxite ore is digested in a high-pressure and temperature environment with sodium hydroxide. The result is a separation of alumina, which can be further processed into aluminum, from the bauxite's impurities, primarily iron oxides, silica, and other compounds. These impurities form a thick, slurry-like substance known as red mud, named for its distinctive color.

Challenges in Red Mud Processing

The management and processing of red mud pose significant challenges due to its high alkalinity, fine particle size, and the large volume generated. Efficient processing and disposal of red mud are crucial for both environmental and economic reasons. One of the primary methods to handle red mud is through thickening and clarifying, which involves the separation of solid particles from the liquid.

Role of Anionic Flocculants

Anionic flocculants are key agents in the red mud thickening process. These are large, water-soluble polymers that carry negative charges. When introduced into the red mud slurry, these negatively charged polymers interact with the positively charged particles in the mud, causing them to aggregate and form larger particles, known as flocs.

Selection of Anionic Flocculants

The selection of an appropriate anionic flocculant depends on various factors:

1. Molecular Weight: The molecular weight of the flocculant determines its bridging capability for particle aggregation.
2. Charge Density: The charge density affects the flocculant's ability to neutralize the surface charges of red mud particles.
3. Compatibility: The flocculant must be compatible with the specific composition of the red mud and the conditions of the Bayer process.

Application in Thickening Clarifiers

In thickening clarifiers, the red mud slurry is treated with anionic flocculants to enhance particle settling. The process typically involves the following steps:

1. Mixing: The flocculant is mixed with the red mud slurry, promoting contact between the polymer and the particles.
2. Flocculation: Aggregation of particles forms larger and heavier flocs.
3. Settling: The flocs settle at the bottom of the clarifier due to their increased weight and size.
4. Clarification: The top layer of the clarifier becomes clearer as the solid particles settle.

Advantages of Using Anionic Flocculants

• Improved Settling Rate: They significantly increase the settling rate of the fine particles in red mud.
• Enhanced Clarity: The clarity of the supernatant liquid improves, which is crucial for recycling and reuse in the Bayer process.
• Reduced Footprint: Efficient settling reduces the area required for red mud disposal.
• Operational Efficiency: Enhanced sedimentation leads to improved operational efficiency and cost savings.

Environmental and Safety Considerations

While anionic flocculants enhance the processing of red mud, their use also raises environmental and safety concerns. It is crucial to ensure that:

• The flocculants do not introduce harmful substances into the environment.
• The treated red mud is disposed of or reused in a manner that minimizes environmental impact.