Integrating DFT and experiments to elucidate Pb2+–surfactant interactions for micelle-enhanced water remediation

Abstract

Lead ions (Pb²⁺) are highly toxic, bioaccumulative, and non-biodegradable, making their removal from contaminated environments a critical global challenge. In this work, an integrated quantum–experimental framework was developed to investigate Pb²⁺ adsorption by two anionic surfactants N-lauroylsarcosine (LS) and sodium dodecyl sulfate (SDS) and a nonionic surfactant (Tween 80). Density Functional Theory (DFT) calculations of molecular electrostatic potential, Mulliken charge distribution, and adsorption energy (ΔEₐdₛ) revealed that LS exhibited the strongest affinity for Pb²⁺, followed by SDS, while Tween 80 showed negligible binding. Experimental validation through surface tension isotherms (Szyszkowski and Szyszkowski–Frumkin model fitting) and dynamic light scattering (DLS) measurements confirmed these trends. Pb²⁺ complexation significantly reduced micellar aggregation numbers (from 73 to 18 for LS and from 78 to 29 for SDS), while Tween 80 displayed minimal variation. The strong agreement between theoretical and experimental results demonstrates that Pb²⁺ ions destabilize micelles by reducing their aggregation capacity, with LS showing the most efficient Pb²⁺ removal. This study provides a systematic correlation between DFT-predicted adsorption energetics and experimental interfacial behavior in Pb²⁺–surfactant systems, establishing a predictive strategy for the rational design of eco-friendly, surfactant-assisted remediation technologies for heavy metal pollutants.