High-Performance Oil–Water Separation Using an Additive-Free, Hemp Seed Oil-Based Inherently Hydrophobic Polyurethane Foam

Abstract

This study reports the synthesis of an inherently hydrophobic, bio-based polyurethane foam (Bio-HPUF) derived from hemp seed oil (HSO) for efficient oil–water separation. Unlike conventional polyurethane foams, Bio-HPUF was synthesized without solvents, blowing agents, or catalysts, using HSO-derived polyol and hexamethylene diisocyanate (HDI). Structural characterization via FTIR confirmed successful urethane formation, while SEM revealed an open-cell porous morphology with pore sizes ranging from 163–567 (Formula presented.) m. Thermal analysis showed multi-stage degradation with stability up to 330°C. The foam exhibited a water contact angle of 91° and an oil contact angle of 16°, indicating hydrophobic and oleophilic behavior. It demonstrated selective sorption capacities up to 1–27.8 g/g for oils and organic solvents, rapid oil uptake within 15 s, and high selectivity in water. Reusability studies showed minimal loss in performance over 10 oil adsorption–desorption cycles. The foam also maintained (Formula presented.) 99% of its original mass after 24 h exposure to acidic, saline, and basic media, with no structural degradation. Notably, Bio-HPUF effectively separated toluene-in-water emulsion, showed excellent compression recovery with self cleaning abilities, affirming its applicability in complex systems. These results highlight the material's sustainable synthesis, structural robustness, and high selectivity, positioning it as a promising sorbent for environmental oil remediation.