Study On Liquid-liquid Phase Equilibrium Based On Phenolic Wastewater Treatment

Phenol and its derivatives,which commonly exist in various kinds of industrial wastewaters as a prototype toxic substance,are highly toxic or not easy to degrade.At present phenolic wastewater has become one of the most serious industrial wastewater,For the treatment of phenol wastewater in industry,solvent extraction and biochemical treatment are commonly used to achieve emission standards,and solvent extraction is the most important part.In the study,two high-efficient green solvents for phenol remover were selected.Hexyl acetate,tributyl phosphate and n-dodecane composite compound;several kinds of representative phenols were selected: such as phenol,o-cresol,m-cresol,p-cresol,resorcinol and hydroquinone.In the paper,the liquid-liquid equilibrium systems(water + phenols + extractant)were determined,and the feasibility of treating hexyl phenol wastewater with hexyl acetate,tributyl phosphate and n-dodecane composite compound was verified.This study will provide important experimental support and theoretical basis for the recovery and separation of phenolic compounds from industrial wastewater.In this work,the liquid-liquid equilibrium systems for binary(water + phenol),(water + o-cresol),(water + m-cresol),(water + p-cresol),(water + hexyl acetate),and ternary(water + phenol + hexyl acetate),(water + o-cresol + hexyl acetate),(water + m-cresol + hexyl acetate),(water + p-cresol + hexyl acetate),(water + resorcinol + hexyl acetate),(water + hydroquinone + hexyl acetate)and quaternary(water + phenol + n-dodecane + tributyl phosphate)were measured.The Hand,Bachman and Othmer-Tobias equations are used to test the reliability of the experimental data;the correlation coefficients R2 of the linear equations are more than 0.99,which confirms the reliability of the experimental data in this paper.In addition,two activity coefficient models(NRTL and UNIQUAC)were used to correlate the experimental data of each system,and the corresponding binary interaction parameters of the subsystems were obtained;two activity coefficient models(NRTL and UNIQUAC)were used to correlate the experimental data of each system,and the corresponding binary interaction parameters of the subsystems were obtained;the averages of root-mean-square deviations(rmsd's)between the calculated and experimental values for ternary(water + phenols + hexyl acetate)systems were less than 0.3% for the NRTL and UNIQUAC model,thus the two models could well represent the studied systems.The experimental data of the liquid-liquid phase equilibrium for(water + phenol + n-dodecane + tributyl phosphate)system were predicted by the obtained bianry interaction parameters;the average mean square deviation deviations between the calculated results of NRTL and UNIQUAC models were 0.91% and 0.83%,respectively,which were in good agreement with the experimental data.The experimental results show that the distribution coefficient of phenol and o-cresol are about 360 and 1700,respectively,when hexyl acetate is used as extractant for extraction of phenol wastewater;and the corresponding single stage extraction rate are 97.9% and 99.4%,respectively.For the extraction of diphenol wastewater by using hexyl acetate,the distribution coefficients of resorcinol are up to 60,and the corresponding single stage extraction rate is 89.3%.In the use of n-dodecane and tributyl phosphate composite compound for the extraction of phenol wastewater,the distribution coefficient of phenol is as high as 3000,and the single stage extraction rate is 98.89%.The results showed that good extraction effect were obtained in the extraction of phenolic wastewater by the hexyl acetate,n-dodecane and tributyl phosphate composite extractant,and low extraction temperature was helpful for the extraction property of phenols.