SEPARATION OF AROMATIC NITRO-COMPOUNDS FROM AQUEOUS-SOLUTION USING SUPERCRITICAL CARBON-DIOXIDE

Direct separation of aromatic nitro compounds from aqueous solution using supercritical carbon dioxide was studied. Then aqueous nitrobenzene (NB) solution was added to an extractor to remove NB by blowing supercritical carbon dioxide, the removal ratio of NB depended upon the temperature, pressure, quantity and velocity of supercritical carbon dioxide or an amount of aqueous solution. The ratio was independent of the concentration of NB (less than 400 ppm). The temperature dependence of removal ratio was small under less than 75 kg/cm(2) of pressure, and a certain amount of NB in 100 ppm of NB aqueous solution was removed under less than 50 kg/cm(2) of pressure. This result was different from that of the regeneration of activated carbon adsorbing NB, but the differrence was explained by the difference of the removal mechanism of NB, between the direct separation from aqueous solution and the regeneration of activated carbon. The removal ratios of 6 kinds of aromatic nitro compounds were observed to relate to regeneration ratios of activated carbons adsorbing these compounds, but not to relate to their aqueous solubilities. The removal ratios tend to decrease in both the cases where the electron affinity of substituent group is too strong or too weak.