Technology Of Foam Fractionation And Resin Adsorption For The Enrichment And Purification Of Phenols From Their Aqueous Solution

Foam fractionation has high efficiency in the separation of trace compounds from aqueous solutions,so it has attracted widespread attentions in the field of wastewater treatment.In previous reports on foam fractionation of phenol,both its enrichment ratio and recovery percentage were low.For solving the problem,a three-stage foam fractionation technology was developed to obtain a high enrichment ratio and a high recovery percentage of phenol and achieve the isolation and reuse of phenol and the surfactant in the foamate.For effectively enriching and recovering phenol from its diluted solution,a two-stage foam fractionation technology was developed and optimized using cetyl trimethyl ammonium bromide(CTAB)as a collector.Under the optimal conditions,the total enrichment ratio and recovery percentage of phenol reached 86.1 and 91.1%,respectively.After the two-stage foam fractionation technology,phenol and CTAB existed in the form of co-complex in the foamate.For achieving their further separation,a third-stage foam fractionation technology was developed.By using the third-stage technology,the CTAB concentration in the first-stage foamate decreased from 11.2 g/L to 0.6 g/L while the phenol concentration decreased just from 2.5 g/L to 2.4 g/L.Thus the successful crude separation of phenol and CTAB was achieved.Macroreticular resin was used to purify phenol from the third-stage residual solution.Single-factor experiments were carried out to determine the value ranges of factors that had significant effects on the adsorbing capacity of phenol.On this basis,the adsorption technology was optimized by response surface method.The results show that the adsorbing capacity of phenol was 23.3 mg/g under the optimal conditions.Furthermore,the adsorption of phenol onto the ADS-17 macroreticular resin was well fitted by the Freundlich isothermal adsorption equation.Using the ethanol solution of 70%(v/v)as a de sorption agent,the desorption percentage of phenol reached 81.7%.Based on the above results,the removal of catechol from the aqueous mixtures of catechol,o-cresol and phenol was studied by foam fractionation.It is aimed at achieving the successful foam fractionation of a single compound from the aqueous solution of multi-phenolic compounds.Using the single-factor experiments,the effects of pH and the molar ratio of catechol and CTAB on the recovery percentages of the three phenolic compounds were studied.Response surface method was used to further optimize the foam fractionation process.Under the optimal conditions,the recovery percentages of catechol,o-cresol and phenol were 87.1%,25.3% and 27.7%,respectively.