Hierarchically porous waste human hair/chitosan composite mats enabling reusable capture of fresh and spent motor oils from freshwater and marine environments.

Human hair (HH) waste represents an abundant keratin-rich biopolymer with considerable potential for sustainable environmental remediation. In this study, highly porous and reusable oil sorbent mats were fabricated by integrating discarded HH fibers into a chitosan (CS) matrix through a facile sodium tripolyphosphate-mediated ionic crosslinking strategy. To optimize the composite architecture, a series of HH/CS mats with different HH/CS ratios were systematically prepared and evaluated in terms of porosity, wettability, mechanical properties, and oil sorption performance. All composite mats exhibited lightweight porous structures with porosities ranging from 78.5-81.8% and low bulk densities (0.262-0.302 g cm-3), enabling efficient flotation and oil capture on water surfaces. Among the investigated compositions, HH/CS-2.0 exhibited the best balance between structural integrity and adsorption performance, achieving the highest Young's modulus (146.79 MPa) and a maximum motor oil sorption capacity under bulk oil conditions of 4864.46 mg g-1, corresponding to nearly five times its own weight. The optimized mat demonstrated efficient removal of both fresh and used engine oils from freshwater and seawater surfaces. More importantly, it retained approximately 90% of its initial sorption capacity with less than 9% structural mass loss after five consecutive adsorption-desorption cycles, highlighting its excellent durability and regeneration potential. Post-reuse SEM, FTIR, and XRD analyses further confirmed the preservation of the composite framework after repeated operation. Comprehensive FTIR, XPS, and GC-MS investigations revealed that oil uptake was predominantly governed by physical mechanisms, including hydrophobic affinity, capillary-driven infiltration, and confinement within interconnected hierarchical pores, without inducing significant chemical transformation of either the sorbent matrix or the captured hydrocarbons. This work demonstrates a simple, low-cost, and scalable route for valorizing waste HH into high-performance bio-based sorbents with promising potential for oil spill remediation and oily wastewater treatment.