Characterization of surface-modified porous PVDF hollow fibers for refinery wastewater treatment using microscopic observation

► Higher TiO2 amount leads to rougher surface, increased nodule size, and small pore size. ► The number of nodule aggregates at inner surface is more than outer surface. ► TiO2 in PVDF leads to shorter finger-like macrovoids and thicker sponge-like layer. ► AFM, FESEM, and Guerout-Elford-Ferry equation techniques show a same trend of pore size.