Removal of phenol(s) from effluent by extraction with solvent mixture

摘要

Issued in week 9742. A process for the extraction of phenols from effluent using a solvent mixture, comprises passing the effluent through a first extraction zone to which the solvent mixture is added and then through a second extraction zone to which at least one of the solvents in the mixture is added. Phenol-enriched solvent mixture is removed from the first zone and then phenol is separated and the solvent is returned to at least one of the two zones.The process involves the following steps : (a) the effluent containing at least one phenol compound and having a pH of 6-10 is introduced into the first zone, through which a mixture of solvents (A) and (B) is passed at 10-60 deg.C ; (b) solvent (B) is passed through the second zone at 10-60 deg.C and then returned to the first zone along with (A) extracted from the effluent by (B), so that the effluent leaving the second zone has a maximum monovalent phenol content of 50 ppm and a resorcinol content reduced by at least 90 % ; (c) the phenol-enriched solvent mixture removed from the first zone is separated in a first distillation column to form a phenol-free mixture of (A) and (B) at the top of the column and a phenol-rich solvent mixture at the base of the column ; and (d) the phenol-free mixture of (A) and (B) is partially separated in a second distillation column to give pure (B), which is returned to the second zone, whilst the remaining solvent mixture is returned to the first zone. (B) has a lower b.pt. and water solubility at 10-60 deg.C than (A), is miscible with (A) and has a water solubility of up to 2 wt.% at 40 deg.C, b.pt. of 50-100 deg.C at 1 bar and a resorcinol distribution factor (D) of at least 0.5. (D) is equal to the equilibrium concentration (C1) of resorcinol in (A) or (B) divided by the equilibrium concentration (C2) of resorcinol in the effluent. (A) has a maximum b.pt. of 172 deg.C at 1 bar, maximum water solubility of 5 wt.% at 40 deg.C and (D) value of at least 5.