Hydrophobic air pollutants removal at one second gas contact in a multi-channel capillary bioreactor

Abstract

Biological processes are increasingly applied for gas purification as a sustainable and economical alternative to conventional physical-chemical processes (chemical absorption, incineration, adsorption). Although biological gas treatment is accepted as an economical, safe, and reliable air pollution control technology, it faces important limitations when applied for the treatment of poorly water-soluble compounds due to mass transfer limitations. A twenty-five capillary channels bioreactor was studied to characterize mass transfer coefficients and the removal of hydrophobic air pollutants under segmented gas-liquid flow pattern. The removal efficiency of hexane, toluene and α-pinene vapors reached values up to about 75%, 99% and 75%, respectively, at a gas contact time of less than 1 second, which is at least one, but closer to two orders of magnitude shorter than conventional biological gas purification systems. The bioreactor displayed stable operation for 100 days and was robust against common upsets, which opens the new opportunities for expanding the application field of biological processes for air pollution control and the mitigation of greenhouse gases in dilute air streams.