Sj. Macnaughton et Nr. Foster, SUPERCRITICAL ADSORPTION AND DESORPTION BEHAVIOR OF DDT ON ACTIVATED CARBON USING CARBON-DIOXIDE, Industrial & engineering chemistry research, 34(1), 1995, pp. 275-282
Supercritical adsorption isotherms were measured for the priority poll
utant DDT on activated carbon at 313.1 and 318.1 K at a fixed carbon d
ioxide density of 0.658 g/cm(3). Equilibrium loadings, measured at sat
uration DDT solubilities, ranged from 0.5 to 0.7 g/g of carbon, and th
e adsorption isotherms are well described by the Freundlich model. The
desorption of DDT from activated carbon using supercritical carbon di
oxide was examined to assess the influence of temperature, density, an
d flow rate. Concentration-time desorption profiles were measured usin
g a supercritical extraction apparatus that incorporated a high-pressu
re UV cell. The desorption efficiency for this system increases with b
oth temperature and density, and the data indicate that the desorption
process is limited by the adsorption equilibrium at low CO2 flow rate
. Overall the desorption of DDT from activated carbon using supercriti
cal CO2 is unfavorable with less than 60% removal and the bulk of the
desorption occurring at very low relative DDT concentrations. A local
equilibrium model combined with experimental adsorption data was able
to predict the desorption profiles.