In this work mass transfer enhancement of non-dispersive solvent extraction by use of helical hollow fiber membranes (HHFM) was investigated by means of experiment and model simulation. Purified terephthalic acid wastewater treatment by extraction with p-xylene as solvent was chosen as the application case. Experiments showed that extraction efficiency of the HHFM was doubly enhanced compared with that of the straight hollow fiber. A comprehensive mathematical model of the HHFM extraction was developed in an orthogonal helical coordinate system with an analytical solution of the 3D velocities. Model simulation revealed that Dean vortices circulate the peripheral fluid to the center, which enhances the mass transfer in the lumen side where radial diffusion is the rate determining step of the extraction. Relations of effluent impurity concentration and enhancement factor with the Graetz number and dimensionless curvature, were obtained by model simulation. Optimal parameters were selected for HHFM extraction design. (C) 2017 American Institute of Chemical Engineers AIChE