Over the course of the last several years, essential studies have been conducted in a wide variety of areas using supercritical fluids. It is a technique that has eliminated some of the tedious steps of current liquid-liquid and solid-solid extraction procedures. Supercritical fluid extraction also offers cleaner extracts, less sample handling and equivalent or better recoveries, time efficient and low in solvent waste generation.
Cashew nut shell contains 25% to 30% (by weight) of cashew nut shell liquid (CNSL). Traditional methods for removing CNSL from cashew nut shells (CNS) leads to thermal degradation and polymerization of CNSL components. Extraction of CNSL using supercritical fluid extraction (SCFE) technique gives clear extract without any thermal degradation. This work investigates the extraction of CNSL using supercritical carbon dioxide (SC-CO2). The yield of CNSL increases with increase in extraction pressure, temperature and mass flow rate of SC-CO2. It is observed that at different operating conditions, the CNSL contains different components. However, the concentration of these components is different at different operating parameters. The oil extracted is analysed by Gas chromatography Mass spectroscopy (GC-MS), Fourier Transform Infra Red (FT-IR) spectroscopy, and Ultra-Violet spectroscopy (UV). The GC-MS analysis of CNSL suggests that it contains ‘cardanol’ as a major component. UV spectroscopy gives the concentration of cardanol in the oil and FT-IR is used to find the major functional groups present in the oil. Extraction of natural phenols from cashewnut shell liquid and sugarcane bagasse oil is also discussed in this study. The presence of these in-situ phenols can be advantageous. The cardanol and substituted phenols, so extracted, may be used as natural phenols for making phenol-formaldehyde resins, which reduces the part of petro-based phenols to be added for resin manufacturing.
A simple mathematical model to characterize the supercritical extraction process has been proposed. This model is primarily based on two mass transfer mechanism: solubility and diffusion. Effects of extraction parameters such as pressure, temperature, and particle size on the extraction of oil have been studied at the supercritical fluid extraction system of laboratory scale and the results have been compared with the results obtained from solution of mathematical model. The proposed model developed has been applied for both high initial oil content material (Cashew nut shells) and low initial oil content material (black pepper). The model showed good agreement with experimental data.