Volatile Loss Testing Using Activated Carbons: Methods & Applications
What Is Volatile Loss in Activated Carbons?
Volatile loss (also called moisture content or volatile matter content) is the percentage of mass lost by an activated carbon sample when heated under defined conditions. It measures the combined content of adsorbed water, physisorbed organic vapours, and thermally labile surface functional groups that desorb at elevated temperature — providing an important quality indicator of activated carbon condition and adsorption capacity.
Activated carbons are highly porous carbonaceous materials with surface areas of 500–3000 m²/g, used for gas phase and liquid phase adsorption of organic pollutants, trace metals, odours, and taste compounds in air purification, water treatment, catalyst support, and industrial process streams.
Why Volatile Loss Testing Is Important for Activated Carbon Quality
Adsorption Capacity Indication
Volatile loss — primarily moisture content — reduces available adsorption capacity. Pre-loaded moisture or adsorbed organic species occupy active adsorption sites on the carbon surface, competing with the target adsorbate. High volatile loss indicates that the carbon has partially pre-loaded its pore volume with water or other volatiles from storage or handling — reducing its effective working capacity.
Quality Consistency Verification
Batch-to-batch volatile loss measurement verifies that activated carbon products are delivered at consistent moisture content — important for precise dosing in continuous treatment systems where carbon is weighed into application equipment by mass.
Activity Index
For fresh, unused activated carbon, low volatile loss indicates that the carbon retains its full adsorption potential. Elevated volatile loss — above specification limits — may indicate improper storage, moisture ingress during transportation, or contamination with adsorbed organic compounds.
Test Methods for Volatile Loss
ASTM D2867 — Moisture Content of Activated Carbon
ASTM D2867 is the primary US standard for moisture content measurement of activated carbon. A weighed sample is dried at 150°C ± 5°C for 3 hours in a circulating air oven and reweighed. Mass loss is calculated as moisture content (%). This method specifically targets adsorbed water at low desorption temperature and is used for routine quality control.
ASTM D7582 — Proximate Analysis by Thermogravimetry
ASTM D7582 uses a thermogravimetric analyser (TGA) to sequentially determine moisture (mass loss during nitrogen heating to 107°C), volatile matter (further mass loss during nitrogen heating to 950°C), and ash (residue after oxidation in air) in a single automated analysis run. This provides a complete proximate characterisation of activated carbon alongside volatile loss.
ISO 6253 — Activated Carbon Moisture Content
ISO 6253 is the equivalent international standard, using a 150°C oven drying procedure equivalent to ASTM D2867 but with slightly different sample preparation requirements and reporting conventions.
Loss on Ignition (LOI) for Ash Content
While not directly measuring volatile loss, LOI testing (heating at 600–1000°C in air) measures the total combustible fraction and residual ash — providing information on organic loading and mineral content of activated carbon.
Typical Volatile Loss Specifications
Fresh granular activated carbon (GAC) for water treatment typically has moisture content of 2–8% (from manufacturing cooling). Powdered activated carbon (PAC) may have higher moisture up to 15% from wet handling. Most specifications define maximum volatile loss of 5–8% for dry-shipped products; saturated (water-wet) GAC shipped in slurry may contain >30% water by mass.
Industrial Applications
In water treatment, GAC volatile loss monitoring verifies carbon condition before loading into filter vessels — ensuring that the carbon’s adsorption capacity is as expected. In solvent recovery activated carbon systems, volatile loss measurement after regeneration verifies that previous adsorbate loading has been fully removed. In gas mask filters and military CBRN protection, precise moisture content control ensures the carbon retains its designed capacity against toxic agents.
Why Choose Infinita Lab for Activated Carbon Volatile Loss Testing?
Infinita Lab provides ASTM D2867 and ASTM D7582 volatile loss, moisture, and proximate analysis for activated carbon through our nationwide accredited analytical testing laboratory network, supporting activated carbon product qualification and quality control programmes.
Looking for a trusted partner to achieve your research goals? Schedule a meeting with us, send us a request, or call us at (888) 878-3090 to learn more about our services and how we can support you.
Frequently Asked Questions (FAQs)
Why is activated carbon dried at 150°C rather than 105°C in ASTM D2867? 150°C is used because some strongly adsorbed water requires temperatures above 100°C to fully desorb from the hydrophilic surface oxides and narrow micropores of activated carbon. At 105°C, moisture desorption may be incomplete for carbons with high oxygen surface functional group content, leading to under-reporting of true moisture content.
Does high moisture content in activated carbon permanently damage its adsorption performance? No. Moisture is physically adsorbed and can be completely removed by drying. After drying to <2% moisture, the activated carbon recovers its full adsorption capacity. However, activated carbon exposed to moisture for extended periods may develop surface functional group changes (increased oxygen content from hydrolysis) that alter its adsorption selectivity for non-polar organics.
What is the difference between moisture content and volatile matter in activated carbon? Moisture content (ASTM D2867, 150°C drying) measures adsorbed water plus low-boiling organic adsorbates below ~150°C. Volatile matter (ASTM D7582, heated to 950°C in nitrogen) measures all thermally decomposable surface groups and pre-adsorbed organics. For quality control of fresh carbon, moisture content is the primary parameter; volatile matter is more relevant for characterising used or regenerated carbons.
Can TGA replace oven drying for volatile loss measurement in activated carbon? Yes. TGA provides equivalent or better data compared to oven drying — with the added advantage of providing real-time mass loss curves that reveal whether mass loss is complete at the specified temperature. TGA is faster, requires smaller sample sizes (~5–20 mg vs. 1–5 g for oven methods), and provides the full desorption profile rather than a single endpoint measurement.
What is the volatile loss specification for fresh granular activated carbon in water treatment? AWWA B604 (Standard for Granular Activated Carbon for Water Treatment) specifies maximum moisture content of 8% by weight for fresh, dry-packaged GAC. Some product specifications allow up to 10% to accommodate seasonal humidity variation. Water-wet GAC shipped in slurry is excluded from this limit.
