Biodiesel production from recycled waste oil in chamistry classes: an approach to recyclingand sustainability

The aim of this study was to produce biodiesel from recycled waste oils using an alkaline transesterification reaction, and to evaluate the most suitable experimental conditions, as well as its potential as a teaching resource for chemistry, whilst promoting recycling and sustainability. The research adopted an experimental approach using pre-treated waste cooking oil, which was subjected to different transesterification tests, varying the type of alcohol, the catalyst, the oil/alcohol molar ratio, the temperature and the reaction time. Nine tests were carried out and the biodiesel obtained was assessed in terms of visual appearance, combustibility and density. The results indicated that six trials produced biodiesel, whilst three resulted in a lack of phase separation and saponification. The best results were obtained using methanol as the solvent in combination with potassium hydroxide (KOH), which produced a biodiesel with a yellow colour, a clear appearance, efficient combustion and a density of between 0.863 and 0.872 g/mL, which is consistent with data in the literature. It is concluded that the efficiency of the process depends on the interaction between the reaction variables and the quality of the raw material, confirming the viability of waste oil recovery and its potential as an educational strategy in the teaching of chemistry and the promotion of sustainability.