Removal mechanisms for volatile organic compounds in the atmosphere and in waste gas streams

Abstract

Atmospheric lifetimes were calculated from OH radical and Cl atom rate constants measured using a relative rate - smog chamber technique for a series of haloalkanes and aliphatic and cyclic ketones. The reactivities of these organics with respect to OH radicals and Cl atoms were observed to be affected by the presence and position of halogen atoms and the presence of a carbonyl oxygen atom for haloalkanes and ketones respectively; polarity effects and stenc contributions were also observed to influence the magnitude of the rate constant values. The atmospheric lifetimes calculated for the organics under investigation were all sufficiently short to ensure that they would undergo transformation in the troposphere and thus could not be considered a threat to stratospheric ozone. O f the organic compounds investigated in this work dichloromethane is the most commonly used chemical in the industrial work place, therefore methods of monitoring and removing this compound are important. Biofiltration techniques are currently being considered for tlus purpose as they are efficient, cheap and clean. In this work a laboratory-scale biofilter unit containing peat fibre as the filter material was used to remove dichloromethane from an artificially generated gas stream. Inlet and outlet gas concentrations were monitored and the percentage removal and the elimination capacity of the biofilter calculated over a time period of 32 weeks. The percentage removal was calculated to be between 40 - 80% and the elimination capacity was found to be a function of the inlet gas concentration