Solvent Extraction of Cyclohexanecarboxylic Acid From Waste Fluid by Using a Mixture of Toluene and 1-Octanol

Abstract

Solvent extraction studies have been carried out for the recovery of cyclohexanecarboxylic acid (CCA) from simulated waste fluid. Influences of various parameters including extractant types, pH of the solution, equilibration time, and initial concentrations of CCA, etc., were studied. A mixture of toluene and 1-octanol (90:10, v/v) was found suitable for the extraction. The results showed that solution pH had a great effect on the distribution ratio, and CCA could be efficiently extracted when the pH was lower than 3.5. The extraction was found quite rapidly. The distribution ratio decreased as the initial concentration of CCA increased. The stripping rate of CCA using sodium hydroxide as stripping agent was found to be increased with the increase of alkali concentration. After back extraction once, more than 98% stripping efficiency was achieved with 0.8 mol/L sodium hydroxide solution at aqueous to organic phase (A/O) ratio 1:1 when CCA concentration was lower than 38.3 g/L. The practical extraction process was carried out for the waste fluid (concentration of CCA 36.5 g/L) discharged in the production of caprolactam from toluene. After four extraction stages at A/O ratio 1:1, the cumulative extraction recovery reached 99.3%. The practical stripping efficiency from loaded organic phase reached 98.2% in one single stage.

Keywords:

• caprolactam waste fluid
• cyclohexanecarboxylic acid
• extraction
• recovery
• stripping

ACKNOWLEDGEMENTS

This research was supported by Scientific Research Fund of Hunan Provincial Education Department, the Foundation of Hunan Provincial Key Laboratory of Green Catalysis and Chemical Reaction Engineering (11k062).

Notes

Experimental conditions: initial CCA concentration = 36.5 g/L, pH = 3.5, A/O = 1/1, contact time 10 min. Raffinate CCA means the concentration of CCA in aqueous solution after extraction.