Determination And Correlation Of Liquid-liquid Equilibrium Of Methyl Tert-butyl Ether-Cresol/Propionic Acid/Butyric Acid–Water For Treating Highly Concentrated Wastewaters In Coal Chemical Industry

The process of coal carbonization or gasification is usually performed in the temperature range of 400-1000 ° C, which produces a large mount of wastewater containing highly concentrated phenols. The wastewater has a very complex composition, with major phenols of phenol and cresols, main organic acids of acetic, propionic and butyric acids.Extraction technology is commonly used in industry to pretreat wastewater, meanwhile to recover valuable materials. After the wastewater pretreatment, biological treatment is used so that the pollutant concentration in the wastewater will meet the discharge restricts. To develop a good extraction solvent is critical for designing a success extraction process, and liquid liquid equilibrium data is the foundation for simulating and optimizing the solvent extraction process.This thesis focuses on treating coal gasification wastewater with highly concentrated phenols. Based on the composition of this kind of wastewater, we screened various extractants according to their distribution coefficient and selectivity for cresols, propionic and butyric acid and their physical properties, and chose methyl tert-butyl ether(2-methoxy-2-methylpropane, MTBE) to treat the wastewater. Thus, we measured liquid-liquid equilibrium data for various systems consisting of MTBE and studied this solvent’s extraction capability.The liquid liquid equilibrium data of ternary systems, MTBE-(o-cresol/m-cresol/p-cresol)- water, MTBE- propionic acid- water, MTBE- butyric acid- water and the quaternary system,MTBE- propionic acid- butyric acid- water were measured. We employed Bachman equation,Hand equation and Othmer-Tobias equation to verify the consistency and reliability of the experimental data, which showed that, the experimental data are quite consistent.The NRTL and UNIQUAC models were applied to correlate the experimental data to obtain binary interaction parameters of above LLE systems. While each ternary system has six binary interaction parameters, the quaternary system has 12. The results showed that, these two activity coefficient models represented the experimental data very well. The calculated binary interaction parameters should be useful for designing a process to remove phenols and organic acids from wastewater by MTBE extraction.