Oil removal from water using carbon aerogels derived from pomelo peel

Abstract

Importance of the work: Agricultural waste material was utilized to make carbon aerogels that can adsorb oils and be reused. Objectives: To investigate the potential of carbon aerogel made from pomelo peel (CAPP) as a potential sorbent for oils from the surface of water. Materials & Methods: The CAPPs were prepared from pomelo peel by cutting, freezing at −20°C for 24 hr and freeze-drying at −55°C or −80°C for 24 hr, followed by carbonization or pyrolyzed at 300°C (5°C/min, 1 hr) to obtain CAPP1-1, CAPP1-2, CAPP2-1 and CAPP2-2, followed by investigations based on the contact angle, morphology, sorption, reusability and grease-trap testing. Results: The average water contact angles of CAPP1-1, CAPP1-2, CAPP2-1 and CAPP2- 2 were 124.1°, 79.1°, 99.1° and 84.3°, respectively. Sorption tests were conducted by immersing the CAPPs in 15 mL of oil on water for 30 s, yielding capacities of 4.35–9.04 g/g. Mean ± SE sorption was highest with diesel oil for CAPP1-1 (6.45 ± 0.35 g/g), with palm oil for CAPP1-2 (8.19 ± 0.56 g/g), with rice bran oil for CAPP2-1 (8.08 ± 0.37 g/g) and with rice bran oil for CAPP2-2 (9.04 ± 0.36 g/g). In household grease-trap testing, CAPP1-2 had the highest palm oil removal (11.71%), followed by CAPP2-2, CAPP2-1 and CAPP1-1. After the second recycle, diesel sorption remained high (73.4–88.6%), decreasing to moderate-to-low levels (36.4–71.4%) after the third recycle. Main finding: The CAPPs derived from pomelo peels could be fabricated based on freeze-drying and carbonization using a muffle furnace or pyrolysis. Palm oil removal from a grease trap was in the range 7.88–11.71%. Reusability was confirmed through absorption-regeneration tests for diesel oil over three cycles.