Chemical phosphoric acid activated carbon production process

The phosphoric acid method for producing activated carbon is a commonly used chemical activation process. It mainly uses phosphoric acid as an activator to convert carbon-containing raw materials (such as wood, coconut shells, fruit shells, etc.) into activated carbon with a high porosity structure at high temperature. The following is a brief introduction to the method:

1. Basic principle
   Phosphoric acid plays the following roles during the heating process:

Dehydrating agent: promotes the removal of moisture and volatiles in the raw materials, inhibits tar formation, and reduces carbon loss.

Oxidant: reacts with cellulose and lignin in the raw materials to form a cross-linked structure and expand the pores.

Template effect: phosphoric acid penetrates into the raw materials, leaving abundant pores (mainly mesopores) after pyrolysis.

2. Production process
   Raw material pretreatment

The raw materials are crushed to a suitable particle size (usually 3-10mm) and impurities are removed.

Impregnation

Mix the raw materials with phosphoric acid solution in a certain proportion and soak for several hours until uniform penetration.

Activation

In an inert atmosphere (such as nitrogen) or oxygen-limited conditions, heat to 400-600℃ for 1-2 hours to allow phosphoric acid to fully react with the raw materials.

Recover phosphoric acid

After activation, wash with water until neutral and recover phosphoric acid (recyclable).

Drying and crushing

The washed activated carbon is dried, crushed, and sieved to obtain the finished product.

3. Product features
   Developed pores: mainly mesopores, suitable for adsorbing larger molecules (such as pigments, organic matter).

High specific surface area: usually up to 1000-1500 m²/g.

Surface oxygen-containing functional groups: phosphoric acid activation will introduce acidic groups and enhance the adsorption of polar substances.

4. Advantages and disadvantages
   Advantages:

Low activation temperature (compared to physical methods) and low energy consumption.

Controllable pore structure and excellent adsorption performance.

Disadvantages:

Waste acid needs to be treated, and the environmental protection cost is high.

The equipment needs to be resistant to acid corrosion (such as enamel or stainless steel).

5. Application areas
   Water treatment: removal of heavy metals and organic pollutants.

Food industry: decolorization, refined sugar solution.

Chemical industry: catalyst carrier, gas purification.

6. Environmental protection and improvement
   Phosphoric acid recovery: reduce waste liquid discharge through evaporation concentration or neutralization treatment.

Green alternative: study the activation process of biomass acid (such as citric acid) or low-concentration phosphoric acid.

The phosphoric acid method occupies an important position in the industry due to its high efficiency and controllability, but it needs to balance performance and environmental protection requirements.