Commercial activated carbons from Calgon (207C and OVC) and Cabot Norit (RB2 and GCA 48) were evaluated for use in spacecraft trace contaminant control filters. The Polanyi potential plots of the activated carbons were compared using to those of Barnebey-Cheney Type BD, an untreated activated carbon with similar properties as the acid-treated Barnebey-Sutcliffe Type 3032 utilized in the TCCS. Their adsorptive capacities under dry conditions were measured in a closed loop system and the sorbents were ranked for their ability to remove common VOCs found in spacecraft cabin air. This comparison suggests that these sorbents can be ranked as GCA 48 207C, OVC RB2 for the compounds evaluated

Monje, Oscar

Surma, Jan M.

NASA Technical Reports Server

47th International Conference on Environmental Systems ICES-2017-291 
16-20 July 2017, Charleston, South Carolina 
Polanyi Evaluation of Adsorptive Capacities of Commercial 
Activated Carbons 
Oscar Monje1 
Ascentech, Kennedy Space Center, Florida 32899, USA 
and 
Jan M. Surma 2 
Sierra Lobo, Kennedy Space Center, Florida 32899, USA 
Commercial activated carbons from Calgon (207C and OVC) and Cabot Norit (RB2 and 
GCA 48) were evaluated for use in spacecraft trace contaminant control filters. The Polanyi 
potential plots of the activated carbons were compared using to those of Barnebey-Cheney 
Type BD, an untreated activated carbon with similar properties as the acid-treated 
Barnebey-Sutcliffe Type 3032 utilized in the TCCS. Their adsorptive capacities under dry 
conditions were measured in a closed loop system and the sorbents were ranked for their 
ability to remove common VOCs found in spacecraft cabin air. This comparison suggests 
that these sorbents can be ranked as GCA 48 > 207C, OVC > RB2 for the compounds 
evaluated. 
Nomenclature 
ECLS = environmental control and life support 
FTIR = Fourier transform infrared radiation 
ISS = International Space Station 
KSC = Kennedy Space Center 
LMSC = Lockheed Missiles and Space Company 
TCCS = trace contaminant control system  
VOC = volatile organic compound 
A = adsorption potential (mol-K/ml) 
atm = pressure unit, atmosphere 
Ce = equilibrium chamber concentration 
Cinit = initial chamber concentration 
C = chamber concentration 
d = diameter 
h = hour 
l = length 
L = liter 
min = minute 
mg =   milligram 
ml = milliliter 
mol = mole 
P = contaminant partial pressure (atm) 
Ps = contaminant saturated vapor pressure (atm) 
ppmv = part per million by volume 
q = contaminant adsorptive capacity (ml/g)  
T = temperature (Kelvin) 
Vm = contaminant molar volume at normal boiling point (ml/mol) 
                                                          
1 Research Scientist, Air Revitalization Laboratory, Kennedy Space Center, Fl 32899. 
2 Scientist, Air Revitalization Laboratory, Kennedy Space Center, FL 32899. 
https://ntrs.nasa.gov/search.jsp?R=20170006640 2019-08-31T06:41:55+00:00Z
 International Conference on Environmental Systems 
 
 
2 
α = constant 
β = constant 
µmol = micromole 
µl = microliter 
I. Introduction 
CTIVATED carbon beds are used for controlling trace contaminants produced by metabolic processes and 
material offgassing in spacecraft cabin air. In the 1970’s, a rapid method based on the Polanyi adsorption 
potential theory was developed by the Lockheed Missiles and Space Company (LMSC) for predicting the adsorption 
equilibrium capacities of activated carbons from commonly available adsorbent and adsorbate properties.1 The 
Polanyi adsorption potential theory is useful for sizing and accurately predicting the lifetimes of carbon beds used in 
environmental control and life support (ECLS) systems. This approach has been successfully used for designing 
Trace Contaminant Control System (TCCS) beds for both Spacelab and International Space Station (ISS) programs. 
Recently, a test rig for measuring Polanyi plots was constructed. These measurements were validated by reproducing 
Polanyi plots of ethanol adsorption by Barnebey-Sutcliffe Type 3032 activated carbon collected by LMSC.2 
Barnebey-Sutcliffe Type 3032 is a commercially obsolete (no longer manufactured) treated carbon used in the 
TCCS on ISS. 
In this paper we compare the efficacy of candidate activated carbons for use in the TCCS using Polanyi plots 
measured in our test rig. Four untreated activated carbons were chosen as potential replacements of Barnebey-
Sutcliffe Type 3032 because they target low concentration volatile organic compounds (VOCs): Calgon 207C, 
Calgon OVC, Cabot Norit RB2, and Cabot Norit GCA 48. Calgon OVC and 207C are granular activated carbons 
made from coconut shell by high temperature steam activation. Cabot Norit RB2 is a steam activated extruded 
carbon with a particle diameter of 2 mm. Cabot Norit GCA 48 is a granular activated carbon produced from coconut 
shells by steam activation. Cabot Norit GCA 48 was recently selected for removal of volatile methyl siloxanes on 
ISS because of its high capacity for removal of hexamethyl-cyclotrisiloxane in the presence of an ersatz of ISS 
VOCs and for its low pressure drop.3 
 
 These comparisons are useful for ranking replacements with similar performance characteristics in order to 
mitigate commercial obsolescence, which arises as commercial products are discontinued, or for evaluating newly 
released commercial activated carbons. 
II. Materials and Methods 
 The following discussion presents the concept of adsorption potential and describes the experimental method. 
A. Polanyi Potential Plots 
The adsorptive capacity, q, is determined under closed loop dynamic test conditions whereby the sorbent is 
exposed to an initial contaminant concentration in a sealed chamber and allowed to adsorb until an equilibrium 
concentration is reached. The test rig and methodology for obtaining the Polanyi potential plots is described 
elsewhere.2 Briefly, the potential plot relates the adsorption capacity, q, with the adsorption potential, A. The 
adsorption capacity is define by Eq. 1 and the adsorption potential is defined by Eq. 2.  
 q = αe-βA       (1) 
 A = (T / Vm) log10 (Ps/P)       (2) 
 In Eq. 1, empirical constants (α and β) are determined from the adsorption potential plot. In Eq. 2, T is the 
sorbent temperature (K), Vm is the molar volume at the normal boiling point (ml/mol), Ps is the contaminant vapor 
pressure (atm) at T, and P is the contaminant partial pressure (atm) obtained from the equilibrium concentration. The 
adsorption potential is calculated from the molar volume, the vapor pressure, and the equilibrium concentration.1 
The Polanyi adsorption potential theory has been applied to the study of activated carbon adsorption for VOCs. 4, 5 
B. Closed Loop Apparatus 
The system consists of a 14-liter mixing volume, which includes the 0.4-liter cell of a Gasmet DX-4030 Fourier 
transform infrared radiation (FTIR) spectrometer (Figure 1). The system also includes a diaphragm pump to 
recirculate the test gases, a fan to mix the test gases, and a bypass line with valving to divert the test gases through 
tube containing the adsorbent.2 A sample (4 mm diameter x 20 mm long; 40-60 mg dry sorbent) is placed in a 
thermal desorption tube and fed with a single VOC in the mixing volume.  
A 
 International Conference on Environmental Systems 
 
 
3 
C. Sample preparation 
The adsorbent particles are large compared to the 4 
mm desorption tube so they are crushed into 2-3 mm 
pieces in a pestle. Powder formed during crushing was not 
used. The desorption tubes are loaded with enough 
activated carbon to ensure that the l/d (length/diameter) 
ratio is near 5.  
The adsorbent samples must be dried prior to use 
because they adsorb water vapor during storage. A 
weighed sample (40-60 mg) as received is loaded into the 
4mm ID desorption tube and held in place using 2 glass 
wool plugs. The loaded tube is weighed and heated to 
100°C with a flow rate of 100 ml/min of N2 in a 
desorption tube conditioning oven (Scientific Instrument 
Services, Inc). This dries the adsorbent and removes 
moisture adsorbed during storage and transport to the 
Kennedy Space Center (KSC). The loaded tube is weighed 
after 1 h and after 2 h, until its mass is constant. The mass 
difference is ascribed to water and subtracted from the 
initial sample mass.  
D. Measuring equilibrium loading capacities 
 The sealed mixing volume is loaded with a single VOC (ethanol, acetone, dichloromethane, or toluene) using an 
adsorbent tube injection system (Supelco ATIS) that flash vaporizes a 7 – 10 µl sample into a continuous flow of an 
inert gas which carries the sample into the chamber.2 Once loaded, the VOC circulates through the desorption tube 
and returned to the mixing volume until the equilibrium concentration is reached. The initial concentration, Cinit 
(ppmv) is recorded before circulating the VOC mixture through the adsorbent sample. The change in concentration 
in the mixing volume is measured every 20 seconds using the FTIR until an equilibrium concentration, Ce (ppmv), is 
reached. When the ratio Ce/Cinit becomes constant, the chamber concentration, Ce, is in equilibrium with the 
contaminant concentration in the adsorbed phase in the activated carbon. The Polanyi adsorption potential and the 
equilibrium adsorptive capacity, q, (ml/g) is derived based on data acquired at this condition. The system used for 
the present evaluation was found to leak, thus a correction was applied to the adsorption data.2 
III. Results  
 
 Results pertaining to adsorption potential plots for 
four commercially-available, untreated, activated 
carbons are presented. The closed loop equilibrium 
adsorption capacity apparatus was used to acquire 
equilibrium adsorption capacity data for acetone, 
ethanol, dichloromethane and toluene to construct 
adsorption potential plots. Figure 2 includes the 
LMSC data for the 10% phosphoric acid treated 
Barnebey Sutcliffe Type 3032 and the untreated 
Barnebey-Cheney Type BD activated carbons for 
comparison.1 The Barnebey-Cheney Type BD 
activated carbon has a higher equilibrium adsorption 
capacity than Barnebey-Sutcliffe Type 3032, it lacks 
the NH3 removal capacity imparted by the acid 
treatment, and was used as a baseline for the 
untreated adsorbents tested. 
E. Comparison of Activated Carbons 
The VOC equilibrium capacities of four 
commercially-available activated carbons was 
evaluated (Figure 1). Calgon OVC and 207C had 
 
Figure 2. Polanyi adsorption potential plots for Calgon 
& Cabot Norit Carbon activated carbons. This 
comparison suggests that CGA 48 > OVC, 207C > RB2, 
Barnebey-Cheney Type BD > Barnebey-Sutcliffe Type 
3032 for the compounds evaluated under dry conditions. 
 
Pump
 
Fan
Injection 
Port
Pump
FTIR
Flow Meter
Desorption 
Tube
 
Figure 1. A simplified schematic of the closed 
loop adsorption equilibrium system. The mixing 
chamber is dosed with a known VOC quantity and 
then circulated through the FTIR and sorbent 
tube. 
 International Conference on Environmental Systems 
 
 
4 
similar equilibrium adsorptive capacities to each other and to that of the untreated Barnebey-Cheney Type BD 
activated carbon. The equilibrium adsorptive capacity of Cabot Norit RB2 was lower than that of Calgon OVC, 
Calgon 207C, and Barnebey-Cheney Type BD activated carbons. In contrast, Cabot Norit GCA 48 is a better 
sorbent than Calgon OVC, Calgon 207C, Barnebey-Cheney Type BD, Barnebey-Sutcliffe Type 3032 activated 
carbons for the compounds evaluated.  
IV. Discussion 
 The Polanyi adsorption potential methodology serves as the framework for characterizing equilibrium adsorption 
capacities of candidate activated carbons for controlling trace contaminants in spacecraft cabin air. This approach 
has been utilized in sizing TCCS beds for the Spacelab and ISS programs. Adsorption potential characteristic curves 
are not only useful for adsorbent bed design but also for comparing candidate sorbent replacements for 
commercially-obsolete adsorbent media used for the ISS TCCS. 
 A closed loop method was used to measure the equilibrium adsorptive capacities of four untreated activated 
carbons under dry conditions: Calgon OVC, Calgon 207C, Cabot Norit RB2, and Cabot Norit GCA 48. These 
activated carbons differ in their composition and in the method used for activation, which may cause differences in 
their adsorptive capacities for VOCs. The activated carbons were crushed so that small samples could be used for 
the purpose of reducing test duration. Crushing increases the surface area and may affect kinetics of adsorption in 
flow through methods where mass transfer coefficients matter. In this method, the adsorbent is exposed to the single 
VOC until its pores reach equilibrium so crushing the samples is not expected to affect equilibrium capacity.  
The adsorptive capacities of these activated carbons were compared to that of Barnebey-Cheney Type BD, an 
untreated activated carbon with an improved equilibrium adsorptive capacity than acid-treated Barnebey-Sutcliffe 
Type 3032 utilized in the TCCS. This comparison suggests that these sorbents can be ranked as GCA 48 > 207C, 
OVC > RB2, Barnebey-Cheney Type BD >  Barnebey-Sutcliffe Type 3032 for the compounds evaluated.  
V. Future Work 
The assumption that crushing the samples does not affect equilibrium capacity should be investigated. The 
equilibrium adsorptive capacity measurements should be repeated using humid gas streams because TCCS beds are 
used in the presence of water vapor, which may alter the vapor adsorption of VOCs by activated carbon.6 Including 
the effect of water vapor would be useful in the design of adsorption systems utilizing activated carbon for the 
removal of VOCs from spacecraft cabin air. 
 
Acknowledgments 
The present work was funded by the Life Support Systems Project of NASA’s Advanced Exploration Systems 
Program. 
References 
1Robell, A.J., Arnold, C.R., Wheeler, A., Kersels, G.J., and Merrill, R.P., Trace Contaminant Adsorption and Sorbent 
Regeneration, NASA CR-1582, September 1970, pp. 32-45. 
2Monje, O., Surma, J.M., Kayatin, M.J., and Perry, J.L. “Measuring Polanyi Potentials for Chemsorb® 1000 and Chemsorb® 
3800.” ICES 2016-321, 46th International Conference on Environmental Systems, Vienna, Austria, 2016. 
3Carter, L, Perry, J.L., Kayatin, M.J., Wilson, M., Gentry, G.J., Bowman, E., Monje, O., Rector, T., and Steele, J. "Process 
Development for Removal of Siloxanes from ISS Atmosphere." ICES 2015-074, 45th International Conference on Environmental 
Systems, Bellevue, Washington, 2015. 
4Nirmalakhandan, N.N., Speece, R.E. 1993. Prediction of activated carbon adsorption capacities for organic vapors using 
quantitative structure-activity relationship methods. Environ. Sci. Technol. 27:1512–1516 
5Brown, R.C. 1995. Review: Activated Carbon Filters in Respiratory Protective Equipment, International Journal of 
Occupational Safety and Ergonomics, 1:330-373. 
6Runzhi, G., and Keener, T.C. 1993. A Qualitative Analysis of the Effects of Water Vapor on Multi-Component Vapor-Phase 
Carbon Adsorption, Air & Waste, 43: 864-872. 
 
 


Polanyi Evaluation of Adsorptive Capacities of Commercial Activated Carbons

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server