By employing the novel sulfonated polyphenylenesulfone (PPSU) polymer with super-hydrophilic nature as membrane material, triangle-shape tri-bore hollow fiber (TBF) ultrafiltration (UF) membranes have been fabricated via a newly designed dual-layer tri-needle spinneret. The sulfonation degree of PPSU not only plays a key role in forming a fully sponge-like structure, but also enhances membrane hydrophilicity. The separation performance and fouling behavior of the newly developed TBF membranes were systematically studied for oil/ water separation. The critical and threshold fluxes of TBF UF membranes were determined as a function of sulfonation degree through pressure stepping experiments. Above threshold fluxes, their UF behaviors were studied under the same experimental conditions to filtrate a 5000 ppm petroleum/water emulsion. Interestingly, the sulfonated TBFs always exhibit higher permeate fluxes and lower total resistance than the pristine PPSU membranes. In addition, analyses by the resistance-in-series model indicate that the sulfonated PPSU membranes display much lower resistances from static foulant adsorption and irreversible fouling. Clearly, the sulfonated membranes become less fouled and easier to regenerate. After UF through TBF membranes, the permeate water appears quite clean with low turbidity and high TOC rejection larger than 95.4%. (C) 2014 Elsevier B.V. All rights reserved.