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| Non-dispersive solvent extraction of p-toluic acid from purified terephthalic acid plant wastewater with p-xylene as extractant |
| Qing-ran Kong, You-wei Cheng, Li-jun Wang, Xi Li |
| College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China |
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Abstract Non-dispersive solvent extraction (NDSE) with p-xylene as extractant was employed as a novel separation method to recover both p-toluic (PT) acid and water from purified terephthalic acid (PTA) wastewater. The mass transport behavior of PT acid from aqueous solution to p-xylene was investigated by experiments and numerical simulation. Experiments showed that NDSE is feasible and effective. Residual PT acid in the raffinate can be reduced to lower than the permitted limit of wastewater re-use (100 g/m3) with extraction time longer than 60 s in industrial conditions. A mathematical model of PT acid mass transport was developed to optimize the membrane module performance. The model was validated with the experimental results with relative errors of less than 6%. Numerical analysis for mass transfer through the lumen side, the porous membrane layer, and the shell side showed that PT acid transport in the aqueous solution is the rate determining step. The effects of the membrane and operating parameters on membrane module performance were investigated by means of computational simulations. The key parameters suggested for industrial NDSE design are: fiber inner radius r1=200–250 μm, extraction time te=50–60 s, aqueous/ organic volumetric ratio a/o=9.0, and temperature T=318 K.
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Received: 23 October 2015
Published: 08 October 2016
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