Removal Efficiency of Volatile Organic Compounds using Different Types of Activated Charcoal in the Fume Hood

Abstract

In laboratories, fume hoods are used to handle most chemicals, with the goal of protecting the health of workers and preventing the deterioration of indoor air quality. However, there is no obligation to install air purifiers in fume hood systems in Korea. As a result, harmful vapors and gases form fume hoods can be emitted directly into the atmosphere through the exhaust duct. This study compared the breakthrough time of three different types of activated charcoal adsorbent, and evaluated their capacity to adsorb volatile organic compounds (VOCs) within a local exhaust ventilation (LEV) system. Acetone was used as a surrogate for polar volatile organic compounds (VOCs) and toluene was used as a surrogate for non-polar VOCs. Both were tested against three different kinds of adsorbent: an activated carbon fiber (ACF), granular activated carbon (GAC), and an ACF + GAC mixture. Approximately 10 and 50 ppm of the tested solvents were evaporated by a syringe pump in a hood, and the breakthrough time was determined by comparing the concentrations measured by a real-time monitor before and after adsorption. The adsorbents were installed 5 m from the hood as part of the LEV system. The breakthrough time for toluene was on average two times longer (>1.1 - 2.8 times) than for acetone for all three adsorbents. When the 50 ppm concentration was used, the breakthrough time was 3.1 times shorter (>1.3 - 4.4) than when the 10 ppm concentration was used. The ACF + GAC mixture had the longest breakthrough time for both acetone and toluene regardless of the concentration used, followed by GAC and then ACF. The breakthrough time was reduced by 7.4 - 9.1 times when the length of the ACF + GAC was shortened from 14 to 7 cm. The adsorption efficiency for acetone and toluene was 75.6 and 80.7% of the total evaporated amount before breakthrough, respectively. The ACF + GAC mixture was proven to have a long breakthrough time and the adsorption rate was relatively stable until breakthrough. Among the three types of adsorbent the ACF + GAC mixture was found to have the longest breakthrough time for both toluene and acetone. An ACF + GAC mixture is therefore considered suitable for use within a laboratory LEV system to improve air quality.