Microwave assisted synthesis of alkanolamide surfactant from used cooking oil and diethanolamine

The large consumption of cooking oil by the community causes high waste. This study aims to synthesize and characterize fatty acid diethanolamide (FADEA) surfactants based on used cooking oil (UCO) using various raw material mass ratios and reaction times with microwave technique and to test the performance of surfactants along the liquid surface. Surfactant was synthesized at 630 W with mass ratios of UCO:DEA (1:1), (1:2), and (1:3) and time variations of 15, 20, and 25 min. The fourier-transform infrared spectroscopy (FTIR) spectrum results show that FADEA has been formed but has yet to convert because there are still triglyceride and diethanolamine (DEA) peaks entirely. The products had a pH and 6 out of 9 free fatty acid (FFA) values that fulfilled the commercial specifications. However, free DEA values and total amides did not fulfil that. In addition, the FADEAs could reduce air-water surface tension by 52–71 % when the critical micelle concentration (CMC) value reached a concentration of 0.094–0.117 % w/v. Foam formation was higher with increasing mass ratio and reaction time with foam stability ≥ 88 %. The best FADEA characteristics and performance were achieved at a mass ratio of 1:3 at 25 min. This product can be used as a foaming agent and foam stabilizer in manufacturing.