Regeneration of Activated Carbon loaded with Nitrobenzene by Supercritical Carbon Dioxidet

Abstract

The regeneration of activated carbon loaded with nitrobenzene (N B) by supercritical carbon dioxide was studied. Supercritical carbon dioxide was introduced to the extraction cell packed with NB loaded activated carbon, and the fluid containing extracted NB was passed through heigh-pressure flow cell for spectrophotometry, and then was carried to a pressure reducing valve. The pressure reduced fluid was carried to a glass trap for collection of precipitated NB, and to a gas meter for measuring the volume of carbon dioxide used.
The ultraviolet and visible spectra of NB in supercritical carbon d ioxide were similar to that in hexane soltuion. The spectrum of aqueous solution of extracted NB precipitated in the glass trap was the same as that of the reagent NB used for initial loading. It was estimated that NB extraction was not accompanied with chemical change. The fractional regeneration calculated from the specific surface area of regenerated activated carbon measured by N₂ adsorption was smaller than that calculated from NB amount adsorbed from aqueous solutions. Above the, pressure of 200 kg/cm², the fractional regeneration increased as temperature increased, but below 150 kg/cm², the fractional regeneration decreased reversely as ternperature increased. The phenomenon was considered to be caused by the reversal of the effect of temperature on the solubility of NB in supercritical carbon dioxide. t Separation of Chemicals by Supercritical Fluid. I