Extraction of Phenolic Compounds with the Highly Efficient Novel Coextractants Cyclohexanone and Methyl Isobutyl Ketone

Extractant selection is the most important aspect for the extraction treatment of phenolic wastewater from the coal chemical industry. Highly efficient extractants are urgently needed. To our knowledge, we identified for the first time one set of coextractants, cyclohexanone and methyl isobutyl ketone (MIBK), after spending plenty of time and energy for the extraction of phenolic compounds, including polyhydroxyphenol, from wastewater. Fourier transform infrared (FTIR) spectroscopy of the solvents before and after extraction shows that intermolecular hydrogen bonding between the molecules of the extractants and phenols is established, contributing to the high performance. The effects of pH, temperature, and salt concentration on the extractant performance were then studied. The extraction favors acidic and neutral pH values. Increasing the temperature has a negative influence on the extraction. The salt effect by putting inorganic salt can obviously enhance the extractant performance. Compared with single extractants such as MIBK and diisopropyl ether (DIPE), coextractants have significantly improved recovery rates of resorcinol and phloroglucinol. To learn if this set of coextractants also has good performance in practical extraction processes for the treatment of industrial wastewater, three-stage countercurrent extraction experiments were carried out with these coextractants for the extraction of phenolic compounds from coal chemical wastewater. Cascade experiments were used to simulate and verify the countercurrent extraction process in actual industry. According to the results, it is observed that this set of coextractants also has good performance in practical extraction processes for the treatment of industrial wastewater.