During the last decade use of supercritical fluids in environmental applications have increased due to their unique properties. Technologies have already been developed for extraction of organic compounds from aqueous and solid environmental matrices and research on extraction of metals is in progress. In most applications, supercritical carbon dioxide is the solvent of choice because it is environmentally benign, safe, and abundant at a low cost. Recent research focus is on use of supercritical fluids as separation and reaction media. Especially as the reaction media, supercritical fluids offer properties that may significantly affect reaction rates and selectivities. The most important property is the control of solvency power through density. This aspect may be used to eliminate side reactions, exceed thermodynamic yield limitations, or control polymer chain lengths and molecular weight distributions. In the separations area, supercritical fluids can be exploited for adsorptive separations of structurally very similar compounds and for selective extraction of thermally labile compounds from natural products.

The supercritical fluid extraction liquid phase oxidation (SELPhOx) process is being developed as a highly flexible means of remediating and destroying both high and low concentrations of light aliphatic to heavy aromatic contaminants from solid matrices. The process employs two distinct technologies: extraction of organic contaminants with supercritical carbon dioxide and wet air oxidation (WAO) destruction of the extracted contaminants. A separation step links the two process stages. Supercritical fluid extraction tests are conducted over wide ranges of temperature, pressure, and CO2/contaminant ratios with soils from a wood treatment plant and two manufacturing gas plant sites. Extraction of polynuclear aromatic hydrocarbons (PAHs) from these soil samples are studied experimentally. The addition of methanol as an extraction modifier was also explored. At comparable CO2-to-contaminant ratios and extraction conditions of 48 degrees C and 137 atm, the total PAHs removed from the three soils ranged from 76.9 to 97.9 percent with CO2 alone and from 88.4 to 98.6 percent with methanol added. Results of these tests are presented and analysed. A skid-mounted Field Test Unit (FTU) based on the laboratory bench-scale test results is being constructed which allows on-site testing of the integrated SELPhOx process with contaminated soils.

The selection of chromatographic techniques in determination of physicochemical properties over conventional static methods is due to quick data turnaround with such systems and readily available commercial equipment. Supercritical fluid chromatography is and can be applied to physicochemical property estimation and its use for this purpose has received considerable attention especially more recently. Moreover, some techniques that are used for determining properties of gas-solid systems using gas chromatography can easily be applied to supercritical fluid chromatography.

The development of “green” alternatives to chemical pesticides could play a crucial role in integrated pest management (IPM). Their use is considered either as a substitution for or in addition to hazardous synthetic products. We analysed the influence of three concentrations of tansy (Tanacetum vulgare L.) essential oil (EO), previously characterised by GC-MS, on the survival and moulting of the 2nd instar and the nutritional indices of the 4th instar gypsy moth (Lymantria dispar L.) larvae. In a residual contact toxicity assessment, the exposure to tansy EO caused low mortality (< 10%) while larval development was significantly slowed down, i.e., the percentage of larvae that moulted into the 3rd instar was reduced. On the other hand, when tansy EO was incorporated into the diet (digestive toxicity assay), high mortality and a lack of moulting after 120 h of eating were recorded for the highest applied concentration of EO. During 48 h of feeding on EO-supplemented food at concentrations of 0.5 and 1% (v/v), the relative growth rate (RGR) of the 4th instar larvae significantly decreased, which can be explained by a significant reduction of the relative consumption rate (RCR) and significantly or marginally significantly lower efficiency of conversion of ingested food into insect biomass (ECI). Although the RCR was also reduced with the lowest applied EO concentration (0.1%), the ECI was not affected which meant the RGR was as high as it was for the control larvae. ECI changes, when two higher EO concentrations were applied, were due to a reduction in the efficiency of conversion of digested food into biomass (ECD), while approximate digestibility was unaffected by the presence of EO in the food. Our results on the significant negative effects of tansy EO on gypsy moth larval survival, development time, and nutritional physiology suggest that it could be considered in future designs for botanical insecticides for gypsy moth control.