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This paper reports a modeling and experimental study of the mass transfer enhancement of water deoxygenation by using a helical hollow fiber membrane (HHFM) to enable Dean vortices. Experiments demonstrated that the HHFM deoxygenating rate was doubled compared with straight hollow fiber deoxygenation. A new model to describe the HHFM deoxygenation mass transfer was derived combining the helical coordinate system mass continuity equation on the lumen side and a modified dusty gas model for the mutual gaseous diffusion in the porous membrane. The model simulation showed that Dean vortices induce transverse fluid disturbance in the fiber, which significantly promotes lumen side mass transfer. The key parameters influencing the strength of Dean vortices are the Reynolds number of the lumen side and the curvature of HHFM. Operating and membrane structure parameters were optimized for HHFM deoxygenation design. The new model could be employed to describe quantitatively the mass transfer behavior of all types of HHFM gas-phase separation processes.

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.