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 incorporating 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.