AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Limitations and Modifications of Impregnated Filter Method for Sampling Sulfur Dioxide Gas
Chufan Zhou, CHIH-HSIANG CHIEN, Alexandros Theodore, Chang-Yu Wu, Yu-Mei Hsu, Brian Birky, University of Florida
Abstract Number: 792 Working Group: Instrumentation and Methods
Abstract Collection of sulfur dioxide gas (SO2) using a filter impregnated with a solution containing Na2CO3 and glycerol is a NIOSH method to assess SO2 concentration in the occupational setting. However, this method is subject to relative humidity (RH), and the breakthrough kinetics is unknown. To investigate the issue, a family of filters treated by solutions with an increasing amount of glycerol (0 – 20% v/v) and a constant amount of sodium carbonate (2.5% w/v) were tested under medium (45%) RH condition. The results showed these treated filters did not have enough capacity for sampling 10 ppm of SO2 under both 200-minute sampling and 8-hour occupational exposure conditions. The breakthrough curve illustrated that filters coated with less glycerol had earlier 50% breakthrough, indicating the role of the coated glycerol amount on the filter in building up the water content. Sufficient water content, important to the dissolution and dissociation of Na2CO3, enhances ion transport in the mixture that helps increasing the utilization of the coated Na2CO3. Secondly, experiments were conducted to evaluate the performance with more Na2CO3 coated on the filter (10% and 20%). The results demonstrated that the new protocols successfully increased the breakthrough time under 45% RH for 8-hr. However, early breakthrough still occurred in dry (25%) RH condition due to low utilization of Na2CO3 resulting from the insufficient water absorbed. The results suggest that incorporating more Na2CO3 and glycerol in the coating protocol can further improve performance. Finally, a kinetic model was proposed to describe SO2 sorption behavior on the impregnated filter. This model predicted well when the impregnated filter works under medium RH range or holding sufficient glycerol amount, i.e., when the ion diffusion rate in the liquid phase was high and the coated Na2CO3 could be utilized fully.