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International audienceBACKGROUND: Hydrophobic volatile organic compounds (VOCs), such as toluene, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), are poorly soluble in water and classical air treatment processes like chemical scrubbers are not efficient. An alternative technique involving an absorption step in an organic solvent followed by a biodegradation phase was proposed. The solvent must fulfil several characteristics, which are key factors of process efficiency, and a previous study allowed polydimethylsiloxane (or PDMS, i.e. silicone oil) to be selected for this purpose. The aim of this paper was to determine some of its characteristics like absorption capacity and velocity performances (Henry's constant, diffusivity and mass transfer coefficient), and to verify its non-biodegradability. RESULTS: For the three targeted VOCs, Henry's constants in silicone oil were very low compared to those in water, and solubility was infinite. Diffusivity values were found to be in the range 10(-10) to 10(-11) m(2) s(-1) and mass transfer coefficients did not show significant differences between the values in pure water and pure silicone oil, in the range 1.0 x 10(-3) to 4.0 x 10(-3) s(-1) for all the VOCs considered. Silicone oil was also found to be non-biodegradable, since its biological oxygen demand (BOD(5)) value was zero. CONCLUSION: Absorption performances of silicone oil towards toluene, DMS and DMDS were determined and showed that this solvent could be used during the first step of the process. Moreover, its low biodegradability and its absence of toxicity justify its use as an absorbent phase for the integrated process being considered. (C) 2010 Society of Chemical Industr

In relation with CO2 capture by chemical absorption into aqueous amine‐based solvents, absorption and regeneration parameters by separate absorption and regeneration tests are determined. An absorption parameter for different types of amine‐based solvents is evaluated by performing absorption tests at 298 K and atmospheric pressure with a gas‐liquid contactor and deducing apparent kinetic constants. The regeneration parameter is obtained from a CO2 concentration temporal profile measured in a regeneration cell at the boiling temperature of each solvent. By combining both parameters it is possible to compare the absorption‐regeneration performances of all the solvents studied. Good absorption‐regeneration performances of cyclical amines, especially of piperidine (PIP) and piperazine (PZ), are highlighted. The interesting potential of 2‐amino‐2‐methyl‐1‐propanol (AMP) and methyldiethanolamine (MDEA) activated with PZ and PIP is also considered.

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A mathematical model was developed for the isothermal absorption of nitrogen oxides into nitric acid solutions containing hydrogen peroxide. This model, based on the two-film theory of absorption with chemical reactions, includes diffusive transport and equilibrium between species in the gas phase and simultaneous absorption of the NO x components with fast irreversible reactions in the liquid phase. Kinetic parameters relative to the absorption of the different NO x species were determined at increasing acidities and for a low concentration of H2O2 from test runs performed in a small packed column at 20 °C and atmospheric pressure for various NO x partial pressures up to 500 Pa and the whole range of NO x oxidation ratios. Only the parameter relative to trivalent NO x was found to increase with the HNO3 molarity, the other ones remaining constant. Interpretation of the experimental results according to the model showed that the hydrolysis is the main controlling step for tetravalent nitrogen oxides and that among the trivalent components nitrous acid is likely to be a major transporting species.