Acid-Impregnated Coconut-Shell Activated Carbon

Enhanced Adsorption for Acidic Gases & Heavy Metals

Activated Carbon Products

What Is Acid-Impregnated Activated Carbon?

Impregnated (acid) activated carbon is standard coconut-shell AC that’s been chemically enhanced by treating with strong acids (e.g., phosphoric, sulfuric, or nitric acid). This process introduces functional groups and metal-binding sites on the carbon surface—boosting its affinity for specific contaminants such as acidic gases (H₂S, SO₂) and heavy metals (lead, mercury).

How Acid Impregnation Works

Feedstock & Base AC Preparation

Use high-quality coconut-shell GAC or PAC as the substrate
Pre-clean via steam activation to maximize pore structure

Acid Treatment Processes

Phosphoric Acid Impregnation: Introduces phosphate groups for metal complexation
Sulfuric/Nitric Acid Treatments: Enhances acidity and sulfur/nitrogen functionalities for gas adsorption
Controlled Concentration & Temperature: Optimize acid strength (20–50 wt%) and soak at 60–90 °C

Post-Treatment Washing & Drying

Thorough rinse until pH neutral
Oven-dry at 105–110 °C to remove moisture
Optional mild re-activation to restore pore volume

Key Physical & Chemical Properties

Property	Typical Range or Value
Surface Area	700–1,000 m²/g
Pore Volume	0.5–0.8 cm³/g
Acidic Functional Groups	0.5–2.0 mmol/g (varies by acid type)
pH of Wash Slurry	6.5–7.5 (after washing)
Bulk Density	0.45–0.60 g/mL
Moisture	≤ 5 %
Ash Content	≤ 8 %

Applications of Acid-Impregnated AC

Acidic Gas Removal

H₂S & SO₂ Scrubbing: Natural gas sweetening, biogas purification
VOCs & Acidic Fumes: Industrial off-gas treatment

Heavy Metal Adsorption

Lead, Mercury, Cadmium: Wastewater polishing and remediation
Metal-Complex Removal: Electroplating rinse waters

Industrial & Environmental Uses

Chemical Processing: Catalyst support, reagent recovery
Air Purifiers & Mask Filters: Enhanced removal of acidic irritants
Soil & Groundwater Remediation: Targeted heavy-metal clean-ups

Benefits of Acid-Impregtrated AC

Targeted Selectivity: Functional groups tuned for specific contaminants
Enhanced Capacity: Up to 2–3× more adsorption of acidic species vs. untreated AC
Versatile Formats: Available as GAC, PAC, beads, and pellets
Regenerable: Many grades withstand thermal or chemical regeneration

Choosing the Right Grade

Type of Acid: Phosphoric for metals, sulfuric/nitric for gases
Particle Size: GAC for fixed beds; PAC for slurry/contactors
Functional Group Density: Higher mmol/g for greater capacity
Mechanical Strength: Crucial for backwashing or fluidized beds

Regeneration & Disposal

Thermal Regeneration

Desorb fouling contaminants at 800–900 °C under inert gas
Recover > 80 % of initial capacity for multiple cycles

Chemical Regeneration

Acid/base wash to remove bound metals or acidic species
Rinse and re-dry before reuse

Disposal

Classify spent AC based on adsorbed contaminants
Non-hazardous: landfill per regulations
Hazardous: incineration or secure hazardous waste disposal

Impregnated AC vs. Untreated AC

Feature	Impregnated AC	Untreated Coconut-Shell AC
Contaminant Selectivity	High for acidic gases & metals	Broad-spectrum organics & VOCs
Adsorption Capacity	2–3× higher for target species	Moderate, general-purpose
Regeneration Cycle Life	Depends on impregnant stability	Typically > 20 cycles thermal
Cost	Premium grade	Standard grade