Phase Transfer Catalyzed Extraction of Phenolic Substances from Aqueous Alkaline Stream

Abstract

Experimental investigations are presented on the extraction/removal of such phenolic compounds as phenol, m-cresol, and resorcinol from alkaline medium via reaction with benzoyl chloride dissolved in toluene as the solvent under two-phase conditions using hexadecyltributyl phosphonium bromide as a phase transfer catalyst. Two types of experiments were performed in order to assess the utility of the reaction scheme for treatment of industrial wastewater. The results of stirred cell experiments revealed that the reactions of phenolics conform to a diffusion-limited fast pseudo-first-order regime. The rate enhancement of the reaction was found to be reasonably low as compared to that reported when Aliquat 336 was used as the catalyst. The specific rate of extraction decreases for the phenolics in the order phenol > m-cresol > resorcinol. Batch experiments conducted in a baffled agitated reactor with individual phenolic compounds as well as mixtures of all components, representing compositions typical of industrial wastewater, revealed that the volumetric rate of extraction is dependent on the stirring speed under otherwise identical conditions. Conversion of phenolics in a batch agitated reactor was found to be more than 99.5% under suitable conditions of stirring speed and reaction time, and the products of reaction, essentially esters, are completely partitioned to the organic phase. Some aspects of product recovery, solvent, and catalyst recycle are discussed.