Experimental and computational studies on isolation of cardanol from cashew nut shell liquid using diethanolamine‐based deep eutectic solvent at different molar ratios

Abstract BACKGROUND Amine‐based deep eutectic mixtures composed of choline chloride and a DEA‐based hydrogen‐bond donor (HBD) can be used in various molar ratios such as 1:2, 1:3, 1:4, 1:5, 1:6 and 1:7 for isolation of cardanol from cashew nut shell liquid (CNSL). RESULTS In this study, green techniques were created to extract cardanol from CNSL by utilizing a deep eutectic solvent (DES) based on diethanolamine with various molar ratios [hydrogen‐bond acceptor (HBA): HBD] of 1:2, 1:3,1:4,1:5, 1:6 and 1:7. To enhance cardanol's solubility in DES, promote phase separation, and increase cardanol yield, ethyl acetate (EA) and isobutyl methyl ketone (IBMK) could be utilized as co‐solvents. At temperatures ranging from 293 to 343.15 K and 1 atm, the density of various molar ratios of DES was determined. Additionally, the prepared DES pH behaviour as well as the relationship between pH and temperature were investigated. All investigated DES temperature increases caused a decrease in pH value. By using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), similar molar ratios of amine‐based DESs were studied for their thermal stability in terms of decomposition temperature, mass loss and melting temperature. The melting temperature and thermal stability were both increased when the HBD increased. The thermal stability of DES, which mostly depends on intermolecular interactions, is greatly influenced by HBD. Finally, at T = 298.15 K and 1 atm, cardanol was extracted from 50 mL CNSL using different volumes of various molar ratios of DES (100 mL, 75 mL, 50 mL and 25 mL) together with 25 mL IBMK and 25 mL EA. The extracted cardanol was evaluated using Fourier transform infrared spectroscopy and gas chromatography–mass spectrometry. CONCLUSION It was observed that the yields of cardanol from each prepared molar ratios ratio of 100 mL DES were 96.57%, 95.38% and 92.87%, respectively. In this study, the sigma potential and sigma profile of chosen HBA and HBD were determined using conductor‐like screening model for real solvents (COSMO‐RS), and the interactions between the molecules during the extraction process were analyzed. The findings demonstrated the viability of using the chosen DESs for the polyphenol extraction process. © 2024 Society of Chemical Industry (SCI).