The oil (7 g of WCO or fresh soybean oil), methanol
(2.02/3.03/4.04 mL, molar ratio of 1:6, 1:9, 1:12 oil:methanol,
respectively), and obtained CaO (0.3/0.5/0.7/1/1.2 g) were mixed
in a 50 mL round-bottom flask and placed in a temperaturecontrolled
water bath (25 ± 3 C).