Determination of biodiesel yield and color after purification process using deep eutectic solvent (choline chloride:ethylene glycol)

One of the important challenges after the biodiesel production is the purification process to the extent that satisfies the international standard norms. A lot of research has been carried out on removal of impurities in biodiesel. However, there is lack of knowledge on the effect of DESs on the color changes of biodiesel after the purification process. Therefore, this research aims at biodiesel purification process optimization and investigating its color change using ChCl:Eg. In order to improve the biodiesel purification process and enhance the biodiesel yield and color quality, process parameters including the purification time (X₁) and DES:biodiesel molar ratio (X₂) were optimized, using the response surface methodology approach based on the Box-Behnken (BBD) experimental design. The model predicted the biodiesel yield to be 96.73% and its color parameter values (L^*, a^*, b^*) to be 57.28, − 0.24, and 58.12, respectively. Plot analysis showed that increasing purification time and DES:biodiesel molar ratio increased L^*of the biodiesel color but decreased the a^* and b^* of biodiesel color. The application of ChCl:Eg (1:2) at optimum conditions of purification time 33.91 and DES:biodiesel (1:1) to achieve a commercial biodiesel with value > 96.5% ester content and removal of impurities such as pigments (red and orange) after the biodiesel purification is clearly justified.