A Study on the Selective Recovery of Phenol and Formaldehyde from Phenolic Resin Plant Effluents by Liquid-Liquid Extraction

The selective recovery of phenol and formaldehyde from a phenolic resin plant effluent by liquid-liquid extraction has been studied. The selective recovery of phenol was achieved by using an organic phase containing Cyanex 923 extractant in an aliphatic diluent. Equilibrium curves are presented for both the extraction and the stripping. The stripping concentrate can be reused for phenolic resin production. The results of the extraction equilibrium showed that for a mole ratio (Cyanex 923)total/(PhOH)total higher than 0.6, the complex PhOH·Cyanex 923 is the predominant species. When the ratio values are lower than 0.6, the main species are the phenol in the aqueous phase and the complexes 2PhOH·Cyanex 923 and 4PhOH·Cyanex 923. Formaldehyde recovery was also tested by applying liquid-liquid extraction with 1-decanol. Equilibrium curves are presented for both extraction and stripping. An integrated liquid-liquid extraction process was proposed involving the sequential recovery of phenol and formaldehyde from the phenolic resin plant wastewater.