The effects of salt and alkali in coagulation bath for the synthesis of Pluronic F127/polyacrylonitrile/bentonite (PF127/PAN/bentonite-) blended polyvinyl chloride (PVC) ultrafiltration (UF) membrane with ultralow water contact angle and tunable surface pore size distribution have been established and the synthesized membrane has been tested for the purification of oily wastewater. The UF membranes are prepared via a single-step phase inversion technique using different coagulation baths involving (i) water, (ii) KCl, (iii) aqueous KOH solution, and (iii) KCl + aqueous KOH solution, and the effect of coagulation on membrane morphology, structure and performance have been studied. The best performing membrane is obtained by maximizing pure water flux using casting solution involving PF127, PAN and bentonite, and KOH-induced KCl-salt coagulation bath. The optimally synthesized membrane performs very well for the purification of oilfield oily wastewater, and a significant increment in permeate flux is obtained with oil rejection > 97.0%. The optimally synthesized UF membrane results in reduced surface pore size distribution with exceptionally high surface pore density, ultralow oil-adhesion, and improved antifouling performance maintaining with stable permeate flux for a long-time run. The synthesized PVC/PF127/PAN/bentonite-blended UF membranes using KOH-induced KCl-salt coagulation bath have shown great promise for the purification of oilfield oily wastewater, especially with low oil concentration below 200 ppm.