Supercritical CO2 extraction of vetiver essential oil & economic incentive for use of vetiver grass in phytoremediation

Vetiver grass (VG) can be used for soil phytoremediation of various pollutants. The plant is of high tolerance for extreme climatic variations and hostile soil conditions and can produce high biomass. Vetiver can accumulate high concentrations of heavy metals as well as absorb and promote biodegradation of organic wastes.Essential oil extracted from roots of VG has aromatic and biological properties employed in several applications. VG oil and its fractions are extensively used for blending in oriental types of perfumes, cosmetics, foods and aromatherapy, and have applicable potential as pharmaceutics, insecticides and herbicides.The effect of Pb, Zn and Cu on vetiver oil yield and chemical composition was investigated. Oil content and yield are not affected at low and moderate concentrations of Cu and Zn. However, Pb has a significant detrimental effect on plant growth, oil yield and composition. Vetiver oils extracted by hydrodistillation were free of heavy metals. Results show that phytoremediation of Cu and Zn contaminated soils by vetiver can generate revenue from the production of oil extracts.To improve growth, oil yield and quality of VG grown on lead contaminated soils, the addition of CaCO3 was investigated. Calcium treatment increased vetiver growth and survival, but did not improve vetiver oil yield and chemical composition.A response surface method was applied to optimize the extraction yields produced by supercritical CO2 extraction (SCE). Operation at optimal conditions (190 bar, 50ºC and 100 minutes) produced vetiver oil yield about four times higher than that of hydrodistilation. Extraction pressure has a major linear effect on oil yield, whilst temperature and time have a lesser impact.The addition of ethanol increased extraction efficiency of SCE. At optimal conditions of 190 bar, 50ºC and 15 vol% ethanol, ethanol-modified-SCE produced a yield nearly double that of SCE without modifier operated at 190 bar and 50ºC. The operation at 100 bar, 40ºC and 15 vol% ethanol had nearly the same yield as that of optimal conditions. This finding allows extraction operated at low pressure and temperature. Metals accumulated in vetiver roots were not co-extracted with essential oils by either ethanol-modified SCE or SCE without modifier