Effect of oxygen plasma pre-treatment on the surface properties of Si-modified cotton membranes for oil/water separations

Hydrophobic and oleophilic Si-based cotton fabrics have recently gained a lot of attentionin oil/water separation due to their high efficiency. In this study, we present the effect of O2 plasmapre-treatment on the final properties of two Si-based cotton membranes obtained from dip coatingand plasma polymerization, using polydimethylsiloxane (PDMS) as starting polymeric precursor.The structural characterizations indicate the presence of Si bond on both the modified cotton surfaces,with an increase of the carbon bond, assuring the success in surface modification. On the otherhand, employing O2 plasma strongly changes the cotton morphology, inducing specific roughnessand affecting the hydrophobicity durability and separation efficiency. In particular, the wettabilityhas been retained after 20 laundry tests at 40 C and 80 C, and, for separation efficiency, evenafter 30 cycles, an improvement in the range of 10-15%, both at room temperature and at 90 Ccan be observed. These results clearly demonstrate that O2 plasma pre-treatment, an eco-friendly,non-toxic, solvent-free, and one-step method for inducing specific functionalities on surfaces, is veryeffective in enhancing the oil/water separation properties for Si-based cotton membranes, especiallyin combination with plasma polymerization procedure for Si-based deposition.