Adsorption

Adsorption is the phenomenon of enrichment of solutes (adsorbates) at solid/liquid interfaces, with its core characteristics being:

Physical adsorption: Van der Waals forces, desorption activation energy < 40 kJ/mol

Chemical adsorption: Formation of chemical bonds, desorption activation energy > 80 kJ/mol

Mechanism of Action

Thermodynamic properties

Physical adsorption is reversible (desorption rate > 95% at 25°C)

Chemical adsorption is often irreversible (requires thermal regeneration at >150°C)

■ Adsorbent material system

Material Type Specific Surface Area (m²/g) Typical Application

Water treatment applications

Activated Carbon (GAC) 900-1400 VOC removal (Benzene adsorption capacity 120 mg/g)

Zeolite Molecular Sieve 400-800 Ammonia nitrogen adsorption (Exchange capacity 2.2 meq/g)

Resin Adsorbent 500-1200 Heavy metal capture (Cu²⁺ capacity 3.2 mmol/g)

■ Engineering control parameters

Adsorption isotherm: Freundlich model (1/n=0.3-0.7)

Empty bed contact time (EBCT): 10-20 minutes

Breakthrough point definition: Outlet concentration ≥ 5% of inlet average concentration

Technical Advantages and Limitations

Advantages

Deep removal of PPb-level trace pollutants

Modular design (activated carbon filter tank replacement cycle of 6-24 months)

Limitations

High energy consumption for chemical adsorbent regeneration (＞3kWh/m³)

Competitive adsorption effect (capacity decay of 30-50% in multi-component systems)

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