Pilot scale study and design of a granular activated carbon regeneration process using supercritical fluids

Abstract

A technology which has great potential for environmental control and waste remediation is contaminant removal and separation with supercritical fluids (SCF's) or supercritical fluid extraction (SFE)

Regeneration of Adsorbents by the Use of Liquid, Subcritical and Supercritical Carbon Dioxide

“…The adsorbate must often compete for adsorption sites with other components of the solution, predominantly with water. Tomasko et al (1993) found that the regeneration efficiency of toluene-spent activated carbon was 96% in the absence of water but 85% in the presence of water, although the initial rates of desorption (as indicated by the slope of the desorption profile) were similar in both cases. Apparently water has a shielding effect for low concentrations of toluene, although for the case of 2-chlorophenol the reverse appeared to be true since efficiencies of 85% and 89% were observed in this case under similar conditions.…”

“…A similar estimation was carried out by Tomasko et al (1993) on a pilot plant consisting of a three-element desorber with two-stage flash separation at a yield of 24 tonne adsorbent per day. After optimizing the process by minimizing the cost of recycling supercritical CO 2 through an efficient recompression scheme and employing a cycle configuration in the desorber unit, the processing cost was found to be ca.…”

“…Previous supercritical adsorption studies have found that both the Langmuir (Tan and Liou 1990) and the Freundlich (Madras et al 1993) isotherm models were capable of describing the supercritical adsorption results. Kander and Paulaitis (1983) and Tomasko et al (1993) have applied the Toth isotherm for the description of the loadings of phenol and 2-chlorophenol, respectively, adsorbed from supercritical CO 2 on to activated carbons.…”

“…An alternative method of increasing the solubility would be through the addition of a polar cosolvent (Bott 1982;Ekart et al 1993) or a reactive one (Hills and Hill 1993) to supercritical CO 2 . Dooley et al (1987) found that the addition of methanol to supercritical CO 2 significantly enhanced the fraction of DDT desorbed from soils, but Tomasko et al (1993) noted that the weight of activated carbon actually increased when methanol was used as a cosolvent during the desorption of 2-chlorophenol with supercritical CO 2 .…”

Single-step treatment of 2,4-dinitrotoluene via zero-valent metal reduction and chemical oxidation

“…Alternate methods of regeneration of GAC include supercritical fluids and advanced oxidation (Tomasko et al, 1993;Huling et al, 2005). Supercritical fluids are fluids that are raised above their critical temperature and critical pressure, so that the compound has the density of a liquid but the viscosity of a gas (Levine, 2002).…”