Supercritical Carbon Dioxide as Green Product for Effective Environmental Remediation

Abstract

The extraction of environmental pollutants from associated matrices is the first and the most important step in an environmental pollution study. Many different methods have been employed in order to concentrate organic components from aqueous solution such as liquid-liquid extraction, adsorption on solid adsorbents and passage through capillary polymeric columns.To date, the vast majority of the work with SFE has centered on the extraction of analytes from solid matrices. That which has been reported for SFE of aqueous matrices has been performed on a large scale such as for waste water treatment.A supercritical fluid is a material which can be either liquid or gas, used in a state above the critical temperature and critical pressure where gases and liquids can coexist. It has the ability to diffuse through solids like a gas, and dissolve materials like a liquid since it is able to penetrate anything by changing density to a great extent in a continuous manner. Sequential supercritical fluid extraction (SSFE) technology is widely used in selective fractionation of crude oil to help provide the effective separation of high molecular polycyclic aromatic hydrocarbons (PAHs) and saturated hydrocarbons from oil based matrices Sites. This paper is designed to present a state of art on supercritical fluid extraction (SFE) technology by treating CO2 as super green environmental friendly gas for separation of PAH and hydrocarbons in environmental remediation. It shows the merits and demerits of two conventional approaches for the extraction of aqueous samples i.e.(1) Liquid matrices that first absorbs it on a solid support and (2) direct SEF of matrix using a special extraction cell. Based on comprehensive study at Libyan Petroleum Institute (LPI) it finds critical optimum parameters for outstanding performance of SEF by using a liquid extraction cell at 2000 to 3000 Psi pressure, 40oC and 15minutes extraction time. It demonstrates that how sequential supercritical fluid (CO2) extraction (SSFE) when applied to contaminated soils from diverse sources is capable to elucidate the sorption desorption behavior of high molecular aromatic hydrocarbons (PAHs). The method involves five extraction phases that applies successively harsher conditions by increasing fluid temperature and density to mobilize target from different soil particle. Interesting results from case studies in Libya demonstrate that SEF technology by using CO that applies successively harsher conditions by increasing fluid temperature and density to mobilize target from different soil particle. Interesting results from case studies in Libya demonstrate that SEF technology by using CO that applies successively harsher conditions by increasing fluid temperature and density to mobilize target from different soil particle.