The separation of catechol and phenol with each other by two-stage batch foam fractionation

Abstract

Abstract A great amount of phenolic compounds are considered as carcinogens even at low concentrations and they are highly toxic and widely coexist in effluent discharges. It is a very meaningful work to respectively separate a few trace phenolic compounds from their aqueous solution by foam fractionation. The studies of surface activity and surface excess revealed that catechol had a stronger competitive adsorption on the bubble surface than phenol by using cetyltrimethyl ammonium bromide (CTAB) as a collector. A two-stage batch foam fractionation technology was developed for the respective separation of catechol and phenol from their diluted aqueous solution. In the first stage batch foam fractionation, catechol was effectively separated with a high enrichment ratio of 32.2 and a high removal percentage of 90.25% while the removal percentage of phenol was only 2.32% under the suitable operating conditions. A high selectivity coefficient of catechol over phenol could reach 35.25. Then, phenol existed in the residual solution, which was used as the feeding solution in the second stage. In the second stage batch foam fractionation, the small bubbles were used to enhance the adsorption of phenol. At the same time, the foam fractionation column of an inclined foam phase was used to enhance foam drainage and then phenol was effectively removed with a high enrichment ratio of 44.4 and a high removal percentage of 90.23% under the suitable operating conditions. The results indicated that it was practicable to successfully and respectively separate catechol and phenol from their aqueous solution by using the two-stage batch foam fractionation.