FERRIC ALUM

Ferric Alum, technically known as Ferric Aluminum Sulfate (or more commonly in industrial chemistry as Iron-Free Alum or Ferric Sulfate depending on the specific grade), is a chemical compound primarily used as a powerful coagulant in water treatment and industrial processes.

In the context of Bangladesh’s massive textile and water treatment sectors, it is a staple for cleaning wastewater.

1. Chemical Composition

While "Alum" usually refers to Aluminum Sulfate, Ferric Alum is produced by adding sulfuric acid to bauxite/aluminum hydroxide in the presence of iron salts.

• Standard Formula: Typically represented as $Al_2(SO_4)_3 \cdot nH_2O$ with a specific percentage of Iron ($Fe$) content.

• Appearance: It usually appears as brownish or yellowish lumps, kibbles, or powder (the color comes from the iron content).

2. Key Functions

• Coagulation & Flocculation: It neutralizes the negative electrical charge on suspended particles (dirt, bacteria, organic matter). This causes them to clump together into "flocs" that are heavy enough to sink to the bottom.

• Decolorization: It is exceptionally effective at removing dye colors from industrial effluent, which is why it’s a favorite in the Textile and Dyeing industries.

• Phosphate Removal: It helps in removing phosphates from sewage, preventing algae growth in water bodies.

3. Common Applications

4. Advantages vs. Non-Ferric Alum

• Cost-Effective: Ferric alum is generally cheaper than "Iron-Free" (Non-Ferric) alum.

• Heavier Flocs: The presence of iron often creates heavier, faster-settling flocs compared to pure aluminum sulfate.

• Efficiency: It works well over a relatively wide pH range, though it is slightly more acidic.