How to treat wastewater containing lead (for manufacturing plants) Lead is a toxic heavy metal that can be harmful to human health and the environment. Therefore, it is important to properly treat wastewater containing lead before discharging it into the

The presence of lead in water above permissible levels will seriously affect human health and have a huge impact on the environment. The issue of treating wastewater containing lead is extremely urgent. Let's explore more information with Toan A to find the most appropriate way to treat wastewater containing lead!

Methods for treating wastewater containing lead (for manufacturing plants)

Chemical precipitation method

The chemical precipitation method involves adding chemicals to precipitate toxic heavy metal ions in water. These precipitates are then removed by sedimentation or filtration.

The most common method is precipitation with hydroxide, for heavy metals like lead, chemicals with alkaline properties such as NaOH, Ca(OH)2 can be used to increase the pH and obtain precipitates:

• Pb2⁺ + 2NaOH    → Pb(OH)₂ ↓ + 2Na⁺
• Pb2⁺ + Ca(OH)₂  → Pb(OH)₂ ↓ + Ca2⁺

In this process, additional adhesive substances such as phenol, iron salts, organic polymers, etc., are added to enhance the removal of lead or other heavy metals.

Note: Each hydroxide precipitate will settle at different pH levels.

Advantages

• Easy to find raw materials, simple, easy to implement, and use.
• Besides lead, this method also removes many other metals simultaneously.
• High treatment efficiency.

Disadvantages

• Generates a large amount of precipitate after sedimentation.
• Alkaline solution in the precipitate is difficult to adjust the pH concentration.
• If the metal concentration is too high, it cannot be treated thoroughly.
• If there are complexing agents with hydroxide in the water, treatment efficiency will be reduced.

Ion exchange method

This method uses insoluble solid materials, usually polymers with groups of ions capable of exchanging with lead ions in water.

Note: For this method, if the pH of the wastewater is only between 7 - 9, lead will exist in the form of precipitate and will not carry an electric charge. This means this method will not be effective. But if the pH is greater than 10, lead will exist in a negatively charged state, effectively responding to the separation and retention of ions on the surface of the ion exchange material layer.

Advantages

• Simple, easy to use.
• Small processing space, reasonable.
• Effective treatment.
• Recovery of valuable lead, no secondary waste generation.

Disadvantages

High cost.

RO filtration method

This method is widely applied in water treatment industries, providing high efficiency, simple operation, and maximum space savings. Apart from filtration membranes like ultrafiltration UF, nanofiltration NF, electrodialysis, the reverse osmosis RO filtration device is widely used.

RO filtration devices use reverse osmosis membrane layers with very small pores to retain hidden contaminants in wastewater and effectively remove inorganic impurities, including lead.

Advantages

• Ultra-small filter core, removing almost all dirt.
• Water from RO membranes can be reused.

Oxidation-reduction method

This is one of the common methods used for treating wastewater containing lead or heavy metals.

The main principle of operation of this method is based on the transformation of the oxidation state of substances, from one form to another by adding oxidizing or reducing agents.

The most commonly used oxidizing agents are: Cl2, O3, HClO,...

Adsorption method

Operating mechanism

Adsorption is the process where volatile gases or water-soluble substances are absorbed by the surface of a foam. Materials capable of adsorption in this method include: activated carbon, sludge carbon, or some inorganic materials like iron oxide, manganese oxide, slag, chemical or biological polymers.

During the adsorption process, two types usually occur:

- Physical adsorption: Due to the electrostatic attraction force between ions and the adsorption center on the surface of the adsorbent, weak and reversible interactions occur. The bonding of substances is quite weak, creating favorable conditions for this process.

- Chemical adsorption: It is a process where chemical bonds are formed between lead ions and functional groups of the adsorption center. Naturally, this relationship is often very strong and difficult to break.

After using the adsorption method to treat hazardous substances in water including lead, people often proceed with desorption to regenerate or recycle the adsorption material.

Advantages

• Thorough treatment of low-concentration lead in wastewater.
• Easy to use, operate, simple.
• Utilize waste materials from other industries such as Fe₂O₃.
• Easy desorption and regeneration of adsorption materials.

Disadvantages

High cost of treatment application.

Above are the provided knowledge about commonly used methods for treating wastewater containing lead specifically and heavy metal-containing wastewater in general. To understand more about the appropriate treatment procedures, please contact Toan A for dedicated support and advice!