This work targets the preparation and characterization of an inexpensive TiO -fly ash composite membrane for oily wastewater treatment. The composite membrane was fabricated by depositing a hydrophilic TiO layer on a fly ash membrane via the hydrothermal method, and its structural, morphological and mechanical properties were evaluated. The separation potential of the composite membrane was evaluated for 100–200 mg·L synthetic oily wastewater solutions. The results show that the composite membrane has excellent separation performance and can provide permeate stream with oil concentration of only 0.26–5.83 mg·L . Compared with the fly ash membrane in the average permeate flux and performance index (49.97 × 10 m ·m ·s and 0.4620%, respectively), the composite membrane exhibits better performance (51.63 × 10 m ·m ·s and 0.4974%). For the composite ash membrane, the response surface methodology based analysis inferred that the optimum process parameters to achieve maximum membrane flux and rejection are 207 kPa, 200 mg·L and 0.1769 m·s for applied pressure, feed concentration and cross flow velocity, respectively. Under these conditions, predicted responses are 41.33 × 10 m ·m ·s permeate flux and 98.7% rejection, which are in good agreement with the values obtained from experimental investigations (42.84 × 10 m ·m ·s and 98.82%). Therefore, we have demonstrated that the TiO -fly ash composite membrane as value added product is an efficient way to recycle fly ash and thus mitigate environmental hazards associated with the disposal of oily wastewaters.