Reduction of Adsorption Capacity of Coconut Shell Activated Carbon for Organic Vapors Due to Moisture Contents

Abstract

In occupational hygiene, activated carbon produced from coconut shell is a common adsorbent material for harmful substances including organic vapors due to its outstanding adsorption capacity and cost advantage. However, moisture adsorption of the carbon generally decreases the adsorption capacity for organic vapors. In a previous report, we prepared several coconut shell activated carbons which had been preconditioned by equilibration with moisture at different relative humidities and measured the breakthrough times for 6 kinds of organic vapor, in order to clarify the effect of preliminary moisture content in activated carbon on the adsorption capacity in detail. We found that the relative percent weight increase due to moisture adsorption of the carbon specimen had a quantitative effect, reducing the breakthrough time. In this report, we carried out further measurements of the effect of moisture content on the adsorption of 13 kinds of organic vapor, and investigated the relationship between moisture adsorption and the reduction of the breakthrough time of activated carbon specimens. We also applied the data to the Wood's breakthrough time estimation model which is an extension of the Wheeler-Jonas equation.

Estimation of Organic Vapor Breakthrough in Humidified Activated Carbon Beds: —Application of Wheeler‐Jonas Equation, NIOSH MultiVapor™ and RBT (Relative Breakthrough Time)

“…We found that the relative percent weight increase due to moisture adsorption of the carbon specimen had a quantitative effect 2,3) on reducing the breakthrough time. That is, the data plots of the breakthrough times versus water adsorption showed good agreement with quadratic functions approximating a wide range of water adsorption in the graphs 2,3) .…”

“…Activated carbon plays an important role in occupational and industrial hygiene as an adsorbent of harmful substances, particularly various types of organic vapor. In the actual use of an activated carbon bed in respirator gas filters, the breakthrough characteristics of organic vapors are very important, and these characteristics are affected by water adsorption of the activated carbon bed and humidity in the test gas [1][2][3] . Previously 2,3) , we prepared several activated carbon beds using coconut shell activated carbon preconditioned by equilibration with moisture at different relative humidities (RH), and measured the breakthrough times for several types of organic vapor.…”

Micropore characterization of activated carbons of respirator cartridges with argon, carbon dioxide, and organic vapors of different vapor pressures

“…However, the molecular probes technique is tedious and time-consuming in terms of the experimental procedure [12]. Despite several studies describing adsorption of OV onto activated carbon [3,[18][19][20]22,23] and using only one type of OV and a reference compound to characterize the pore structure, this approach may not be suitable for all compounds.…”

“…Activated carbon is the preferred adsorbent material for the removal of toxic organic vapors given its low cost, high specific surface area, extensive pore volume, and tunable pore size distribution depending on the activation process used [1][2][3][4]. Particularly, activated carbon is widely used in the removal of toxic vapors from the ambient air by a process known as physical adsorption [5][6][7][8].…”

A Micropreconcentrator Design Using Low Temperature Cofired Ceramics Technology for Acetone Detection Applications

“…There are a lot of papers where the results for micropreconcentrators are given. In [17] and [18] the CF for benzene for different adsorbent materials, various adsorption conditions and benzene mixture with other gases are featured. However, it is difficult to find an information about acetone densification using micropreconcentrator structures.…”