A sustainable hydrophobic luffa sponge for efficient removal of oils from water

A sponge was designed for separating oils from water, which is based on the natural luffa sponge functionalized with stearic acid (L-SA), both natural and abundant renewable resources. Several sponges were prepared using a simple, inexpensive and easily scalable immersion method. The L-SA sponges showed an absorption capacity of 15 +/- 2,14 +/- 2 and 12 +/- 3 g g(-1) with vegetable, used motor and motor oils respectively, after an immersion time of 240 s. The final concentration of oil remaining in water after separation process was 69 +/- 11 mg L-1 which indicates that more than 99% of oil was removed. The L-SA sponges were re-used twelve times and after a steep decrease after the first use, the absorption capacity decreased slowly. These sponges were designed incor-porating circular economy principles. Specifically, we show that after being used, the sponges can be cleaned by removing the remaining oil and stearic acid; leaving the sponge clean as the pristine luffa which then can be used as a regular sponge or it can be functionalized again with stearic acid and re-used to separate oils from water. (C) 2021 Elsevier B.V. All rights reserved.