Experimental Study of Biodegradation of Ethanol and Toluene Vapors

(paint shop effluents, for instance). Synthetic zeolite has a much greater adsorption
capacity than carbon at low solvent concentrations, but carbon has a higher capacity at
high concentrations (Hussey and Gupta, 1998). Treatment with adsorption merely
transfers the contaminants from one phase to another, rather than transforming it into
less harmful compounds. Therefore, a further oxidation process is required to destroy or
recover the contaminants.
Absorption
Packed towers are used most of the time for absorption. The main application
fields are refineries, petrochemical plants, and the pharmaceutical industry (Dueso,
1994). Absorption efficiency depends on:
- The transfer coefficient of organic compounds between the gaseous phase and
the absorbing liquid phase (water or organic liquid depending on whether the
organic compounds are soluble or insoluble in water);
- The efficiency of the gas/liquid contact in the counterflow washing column;
- The contact time.
Similar to treatment with adsorption, absorption also transfers the contaminants from
one phase to another, therefore, a further oxidation process is required to destroy or
recover the contaminants.
Condensation
Condensation is obtained by increasing pressure beyond the saturation pressure,
or by decreasing temperature below the saturation temperature, or by combining the
two. This type of process requires a low temperature as compounds to be trapped are
volatile. Therefore, this process is relatively expensive and rarely used.
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