Fabrication of foam-like oil sorbent from polylactic acid and Calotropis gigantea fiber for effective oil absorption

Abstract

A variety of oil sorbents with good hydrophobicity and oil-absorption capacity have been reported. However, their practical application is severely hindered by complex preparation process, high application cost and non-biodegradability. Here, Calotropis gigantea fiber (CGF) from plant fibers and polylactic acid (PLA) from renewable resources were utilized to construct a biodegradable foam-like oil sorbent (marked as PCF), by using a tandem freezing-solvent replacement method. CGF has large hollow structure for oil absorption, PLA can provide the oil sorbent with physical rigidity, and additional freezing process is expected to produce the oil sorbent with higher porosity for accommodating more oils. SEM images indicated the stable porous structure of PCF, and stress-strain results gave the support for good mechanical property, as the data showing that PCF remained intact structure at 70% deformation (pressure up to 185 kPa). PCF had the oil-absorption capacity ranging from 22.8 to 48.3 g/g, and could selectively absorb the oils in water for its water contact angle >130°. With added power, PCF also had the ability to transfer the oils from water. After ten “absorption-desorption” cycles, the absorption percentage of PCF reached still 81.3% for soybean oil and up to 88.1% for kerosene, indicating its excellent reusability. Compared with commercial oil sorbent, the treatment cost using PCF could be reduced by more than 80% from a preliminary evaluation, demonstrating that the as-developed PCF showed great commercial viability for treating oily wastewaters to provide a cleaner water environment for humans.