Comprehensive analysis of alkaline earth metal ion removal from biodiesel using amino polycarboxylate chelating agents: performance and mechanistic insights

Scientists at Kunming University of Science and Technology collaborating with The Hong Kong Polytechnic University have discovered a promising method for removing harmful alkaline earth metal ions from biodiesel using amino polycarboxylate chelating agents. Their study, published in Frontiers in Energy, suggests that this method could improve the quality and stability of biodiesel, a crucial step in promoting its use as a sustainable fuel alternative.

The presence of calcium (Ca²⁺) and magnesium (Mg²⁺) ions in biodiesel has been a significant challenge, causing increased engine wear, reduced oxidation stability, and lower combustion efficiency. Addressing these issues is essential for making biodiesel a competitive alternative to traditional fossil fuels.

The study focused on Jatropha biodiesel, a non-edible feedstock, which is prone to contamination by alkaline earth metal ions. The research team evaluated four chelating agents: ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), 1,2-cyclohexanediaminetetraacetic acid (CDTA), and N-(2-hydroxyethyl)-ethylenediaminetriacetic acid (HEDTA). Among these, CDTA exhibited the highest efficiency, removing 98.6% of Ca²⁺ and 94.3% of Mg²⁺. The oxidative stability of biodiesel also improved significantly, with the induction period increasing from 3.38 to 8.68 hours after CDTA treatment.

The study employed both experimental tests and density functional theory (DFT) calculations to assess the chelating agents' performance. DFT calculations revealed that CDTA forms cyclic complexes by coordinating with metal ions through nitrogen atoms in amino groups and oxygen atoms in carboxyl groups. The DFT analysis provided insights into the molecular interactions, highlighting CDTA's superior ability to form strong cyclic complexes with metal ions.

This research could have significant implications for the biodiesel industry by offering a method to enhance fuel quality and performance. The findings may lead to increased adoption of biodiesel, contributing to cleaner energy production and reduced reliance on fossil fuels. Moreover, the study opens avenues for further exploration of chelating agents in other applications involving metal ion removal.

The study was supported by various grants from Yunnan Province and the National Natural Science Foundation of China. For more detailed insights, the full paper is available in Frontiers in  Energy: https://journal.hep.com.cn/fie/EN/10.1007/s11708-025-1032-2. Future research will continue to explore the potential of chelating agents in improving biodiesel and other renewable energy sources.