This study aims to develop a more efficient method for separating magnesium from nickel and cobalt in leach solutions, addressing the challenges of traditional metal separation techniques. Nickel and cobalt are vital for various applications, especially in lithium-ion battery production, but their extraction from low-grade laterite ores is complicated by impurities like magnesium. Magnesium’s presence is particularly problematic in solvent extraction processes used for nickel and cobalt separation, as it can degrade the performance of battery cathodes. The proposed solution employs ethylenediaminetetraacetic acid (EDTA) to selectively form complexes with nickel and cobalt, reducing their co-precipitation with magnesium. Through thermodynamic simulations and kinetic experiments at temperatures of 25, 50, and 75 °C, this study optimizes the complexation process. Results indicate that increasing the temperature accelerates complexation, enabling magnesium separation efficiency over 98% and reducing nickel and cobalt loss to below 2% at 75 °C. The research highlights the recyclability of EDTA, enhancing the method’s economic and environmental viability. This novel approach offers a significant advancement in metal processing for lithium-ion battery manufacturing, providing a viable alternative to conventional magnesium separation methods and setting a promising direction for further research in metal recovery and purification.