Computational investigation of the interaction mechanisms of low-density polyethylene (LDPE)/polyurethane and low-density polyethylene (LDPE)/hexane systems as absorbents for oil spill remediation: A DFT study

Abstract

The escalating frequency of oil spill incidents and industrial wastewater discharges necessitates the development of effective remediation strategies. In this study, we conduct a comprehensive computational investigation using density functional theory (DFT) to elucidate the interaction mechanisms within polyethylene (PE) combined with polyurethane (PU) and hexane. The study focuses on adsorption energies, intermolecular interactions, miscibility, and electronic properties, providing a molecular-level understanding crucial for designing advanced absorbent materials. The investigation reveals that the low-density polyethylene/polyurethane (LDPE/PU) system exhibits significantly higher adsorption energies (−12.87 kcal/mol) compared to PE/hexane (−7.66 kcal/mol), indicating a robust binding affinity. This discrepancy underscores the superior performance of PE/PU as an absorbent material. The enthalpy results, with ∆H values of −55.75 kcal/mol for PE/hexane-n-hexadecane and −66.11 kcal/mol for PE/PU-n-hexadecane complexes at 298.15 K, support exothermic adsorption. The more exothermic ∆H for PE/PU indicates stronger interactions during oil absorption than PE/hexane. Additionally, Gibbs free energy change (∆G) values affirm a more favorable process for PE/PU, exhibiting a lower ∆G (−42.54 kcal/mol) compared to PE/hexane (−34.79 kcal/mol). Non-covalent interaction (NCI) studies confirm the importance of van der Waals forces in both systems, validating their role in the adsorption process. Miscibility studies indicate limited interactions, with PE/PU showing positive enthalpy of mixing. Electronic study demonstrates PE/PU's higher energy gap of 9.19 eV, correlating with superior performance. This research contributes to the fundamental understanding of oil absorption processes and informs the design and optimization of environmentally sustainable and efficient oil-absorbing materials for remediation applications. Highlights: DFT explores polymeric systems, PE/PU and PE/hexane, for oil absorbent. PE/PU excels with −12.87 kcal/mol adsorption energy, surpassing PE/hexane (−7.66 kcal/mol). NCI validates van der Waals forces in both systems, crucial for effective adsorption. Miscibility studies reveal limited interactions. PE/PU's superior 9.19 eV energy gap signifies enhanced absorbent performance. PE/PU excels as an oil-absorbent material, underlining its overall superiority.