Liquid-liquid Equilibrium And COSMO-SAC Model Predictions Of Extraction Of Xylenol From Phenolic Wastewater In Coal Chemical Industry By Ketones

A large amount of high-concentration phenol-containing wastewater generated from coal chemical industries such as Lurgi gasification,low-temperature carbonization,and coal classing and upgrading.The wastewater contains phenol,cresol,dihydric phenol,and xylenol,etc.Compared with other phenols,the content of xylenol is relatively small,but its total amount is still several hundred ppm.When common extractants were used to extract phenols from coal chemical industry wastewater,xylenol can also be extracted.So in this work,the extraction effect of common extractants on xylenol was investigated.According to the industrial practice and the present extraction technology for phenolic wastewater,the liquid-liquid phase equilibrium data for extraction of xylenol with different solvents were determined at different temperatures,and some thermodynamic models were used to correlate and predict the phase equilibrium data.The extraction efficiency of five ketone extractants(methyl propyl ketone,methyl isopropyl ketone,methyl butyl ketone,methyl tert-butyl ketone,and methyl isobutyl ketone)on xylenols(2,3-xylenol,3,4-xylenol,and 3,5-xylenol)in aqueous phase were studied by experiments.Liquid-liquid equilibrium data of 15 ternary systems of ketone-xylenol-water were measured at 25-70?.After the distribution coefficients and selectivity coefficients of each group of data were calculated,it was found that all extractants can effectively extract xylenols from aqueous phase.The order of their extraction performance was: methyl isobutyl ketone > methyl isopropyl ketone > methyl butyl ketone > methyl propyl ketone > methyl tert-butyl ketone.Liquid-liquid equilibrium data of experimental measurement were correlated by the NRTL and UNIQUAC activity coefficient models,and the corresponding simulated data and binary interaction parameters were obtained.The root mean square deviation(RMSD)between simulated data and experimental data didn't exceed 0.0082,and it indicated that both models could accurately correlate these ternary systems.The COSMO-SAC model was used to predict the liquid-liquid equilibrium data of each ternary system at different temperatures,and the RMSD values between the predicted data and corresponding experimental data were calculated.The small RMSD values indicated that the COSMO-SAC model was suitable to predict liquid-liquid equilibrium behavior.Meanwhile,the screening charge distribution(?-profile)of five ketone extractants,three xylenols and water were analyzed.It was found that the interaction between ketone and xylenol was stronger than that between xylenol and water.Therefore,all ketones in this study can effectively extract xylenols from water.