EXTRACTION OF ORGANIC MATERIAL IN MINERAL COAL BY USING SUPERCRITICAL-FLUID EXTRACTION, SOXHLET, AND SONICATION METHODS

Soxhlet and sonication techniques have been widely used for extracting semivolatile organic compounds from solid matrices regardless of the fact that these methods are time consuming and costly in amount of sol vent required. In recent years, supercritical fluids have gained incre ased interest as extraction solvents for organic compounds due to thei r unique and well-known properties. This article describes the prelimi nary results of the use of Soxhlet, sonication, and supercritical flui d extraction (SFE) methods for the recovery of organic compounds from a high-ash Brazilian mineral coal. In both Soxhlet and sonication extr actions the solvent was dichloromethane. Supercritical isopropanol was utilized for SFE. The extracts were fractionated by the preparative l iquid chromatography (PLC-8) method into eight well-defined fractions. Although all three extracts presented almost the same qualitative pro file, SFE was more efficient than Soxhlet and sonication extractions. Moreover, SFE was faster and more convenient than the two conventional methods. Quantitative analyses are being carried out and will be pres ented elsewhere. (C) 1998 John Wiley & Sons, Inc.