The effect of increasing the hydrophobicity of poly(propylene) (PP) fibers, the most frequently used synthetic filter materials, on depth filtration performance was investigated. Reduced graphene oxide (RGO) was employed to fabricate highly hydrophobic surfaces by a dip-coating method. The anchoring of RGO on the surface of the PP fibers was confirmed by the appearance of signals corresponding to RGO in Raman and X-ray photoelectron spectra. In addition, scanning electron microscopy images revealed the presence of wrinkled and folded RGO sheets on the PP fibers. The water contact angle increased from 108° to 125° after the first RGO coating, and it was saturated at about 135°. Using kaolin as model hydrophilic particles, the depth filters with RGO-coated PP fibers showed a superior performance in terms of water flux and trans-filter pressure in comparison with those with the pristine and hydrophilic PP …