Sulfur Dioxide Adsorption and Desorption on Various Filter Media

Abstract

Atmospheric sampling for gaseous pollutants in many cases requires removal of suspended particulates preceding the gas sampler. A series of experiments was performed to determine the extent to which sulfur dioxide was adsorbed on the various material of filter holders and filters. Atmospheric concentrations of sulfur dioxide (0.05 and 0.10 ppm) were passed through plastic, aluminum, stainless steel, and Teflon filter holders with and without membrane and glass fiber filters in place. Plastic holders with membrane filters adsorbed very little sulfur dioxide with Teflon, stainless steel, and aluminum removing increasing amounts, in that order. Glass fiber filters cannot be recommended. Adsorption of sulfur dioxide was markedly increased in all cases when the relative humidity was increased from 10 to 50 percent; results show adsorption on the filter holder is more affected by increasing humidity than adsorption on the filter, except for the glass fiber filter. All materials studied would be satisfactory for sampling sulfur dioxide if a long conditioning time is not objectionable. For short sampling times and peak concentrations a plastic holder with a membrane filter is recommended.