Chitosan Eco-Friendly Approach to Oil Spill Cleanup: A Combined 2D TD-NMR Relaxation and Computational Modeling Study

Abstract This study elucidates the molecular interactions governing the destabilization of petroleum emulsions by chitosan, using 2D Time-Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry and molecular docking simulations. To that end, we applied a commercial medium molecular weight chitosan (75.50% deacetylated, 7.25 x 10⁴ g/mol) to a series of six petroleum emulsions, which exhibited viscosities ranging from 32.52 to 103.95 mm²/s at 20°C. Our findings demonstrate chitosan's ability to flocculate petroleum emulsions by primarily interacting with water molecules, subsequently affecting the oil phase. Molecular docking simulations confirmed that chitosan binds most strongly to water molecules (via hydrogen bonds) and exhibits only minor interactions with naphthalenes and paraffins (via London dispersion forces). This observation suggests that chitosan's preferential water binding disrupts the oil-water interface and destabilizes the surfactant layer, thereby promoting emulsion breakdown. Marked shifts in T₂ relaxation times that correlate with water content evidence chitosan’s water-centric binding mechanism. Our analysis highlights chitosan’s role as an effective adsorbent for petroleum pollutants, advancing polymer science for addressing crucial environmental remediation challenges.