The preservation of marine ecosystems from human activity is one of the most severe challenges of our days. In particular, the oil/water separation from oil spills and oily wastewater is particularly important. For this reason, a low-cost, effective, and sustainable solution is highly demanded. In this work, a controlled-wettability membrane for selective oil-water mixtures and emulsions was developed. The nanofibrous membrane was prepared via the facile and cost-effective electrospinning technique, using environmentally sustainable materials such as recycled polyethylene terephthalate (r-PET) and chitosan. The effect of different concentrations of chitosan on the morphology, chemical composition, mechanical properties, wettability, and separation performance of the membrane was evaluated.