Tuning Surface Properties of PLA for Capturing Nonpolar Compounds from Water

In the available literature, the surface wettability of polylactic acid (PLA), a compostable polymer, has been tuned for oil capture by employing multistep processes and incorporating non-biodegradable materials. Such processes are complicated to scale up for industrial production, and the addition of multiple components reduces the compostability of PLA. In this work, we report on the surface wettability tuning of PLA by an easily scalable, solvent-induced recrystallization process, termed Dip-Dip-Dry (DDD), without adding any other materials into PLA. The increase in crystallinity by DDD treatment increases the intramolecular coupling interaction of C=O and C–O groups in PLA, thus reducing the polar component of surface energy to zero, rendering it nonpolar. Surface-modified PLA selectively captures non-polar compounds from water mixtures: discs uptake 0.11 g of oil/g of PLA and 0.06 g of diesel/g of PLA and powders uptake 2.6 g of oil/g of PLA. The selective oil capture capacity of surface-modified PLA is also confirmed in real world conditions by testing them in acidic, basic, and salt water–oil mixtures. The oil-saturated PLA can be regenerated by washing in isopropanol. The durability of this material was tested by exposing it to DI water and simulated seawater for more than 30 days. Hence, this work proposes DDD treated PLA as an industrially scalable sustainable material for non-polar compound capture that prevents secondary pollution.