Extraction of Cu²⁺ and Ni²⁺ Ions from Aqueous Media Using Biodegradable Oil from Phaseolus vulgaris Seeds

Abstract

The persistent contamination of aquatic environments by metal ions such as Cu²⁺ and Ni²⁺ poses serious environmental and public health risks. This study explores the use of oil extracted from Phaseolus vulgaris (common bean) as a green, biodegradable extractant for the removal of Cu²⁺ and Ni²⁺ from aqueous solutions. The oil was extracted using Soxhlet extraction with n-hexane and characterized by Gas Chromatography–Mass Spectrometry (GC-MS) to identify its fatty acid composition. Batch solvent extraction experiments were performed to evaluate the effects of extractant volume, pH, temperature, and contact time on metal ion removal efficiency. Under optimized conditions, removal efficiencies ranged from 97.50% to 99.96%, with performance strongly influenced by pH, favoring near-neutral conditions (pH 6). Thermodynamic analysis revealed that the extraction process is non-spontaneous and endothermic, with positive entropy changes indicating increased molecular disorder during metal-ligand interaction. The fatty acid profile of the oil revealed a rich presence of linoleic, oleic, and palmitic acids, whose carboxylic groups serve as active sites for complexation with divalent metal ions. These findings demonstrate the potential of Phaseolus vulgaris oil as an effective, sustainable, and low-cost medium for removing metal ions from contaminated water. The work lays a foundation for further research and application of plant-derived oils as environmentally friendly alternatives in wastewater treatment and environmental remediation.