<p>Treatment of oily wastewater by membrane distillation (MD) has been used for the purposes of meeting environmental release, reuse water quality and freshwater demand. The modified polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) hollow fiber membranes were fabricated for treating oily wastewater via an air gap membrane distillation (AGMD) process. The dip-coating of cellulose acetate (CA) on the inner surface was performed to improve oil-fouling resistance and durability of the MD operation. From field emission scanning electron microscopy (FESEM) analysis, the CA-coated membrane exhibited an open structure regarded as finger-like and sponge-like morphologies, achieving an overall porosity of approximately 80%. The CA coating on the PVDF-HFP surface was confirmed by Fourier transform infrared spectroscopy (FTIR) analysis as the hydroxyl and carboxylic groups were observed. There was a notable improvement in surface hydrophilicity of the CA-coated membrane, as indicated by a reduction in the WCA from about 92° to 58°. The N₂ permeance and mean pore size of the CA-coated membrane were measured at 5450 GPU and 22.2 nm, respectively. The CA-coated membrane demonstrated stable performance, achieving a water flux of about 23 kg/m²·h and an oil rejection of 99% during 72 h operation. However, a significant decline in water flux and oil rejection was observed for the pristine membrane. The CA-coated membrane exhibited enhanced oil-fouling resistance, with a flux recovery ratio (FRR) of approximately 92%. Langmuir oil adsorption and atomic force microscopy (AFM) analysis were further confirmed the marginal oil fouling on the CA-coated membrane surface. Therefore, the combination of improved hydrophilicity, structural integrity, and resistance to fouling makes the CA-coated membrane as a promising solution for efficient oily wastewater management.</p> Graphical abstract <p></p>