Electrospinning preparation and flame-retardant properties of tailings-based lightweight nanofiber membranes

[Objective] The high-value utilization of tailings is restricted by their complex components and poor interfacial compatibility with polymers.This study aims to address the interfacial problem through surface-modified electrospinning, prepare tailings-based lightweight nanofiber membranes, and explore the regulation mechanism of interfacial interaction on flame retardancy.[Methods] First, tailings were ball-milled and sieved through a 200-mesh sieve to control particle size.The resulting micropowder was dispersed in an aqueous hydrochloric acid solution, mechanically stirred for 4 h to remove soluble impurities, then filtered, rinsed with deionized water until neutral, and dried to obtain unmodified tailings(TA).For modification, a mixture of 50 mL ethanol/10 mL deionized water was combined with 0.075 g silane coupling agent(KH550)and stirred at(25±2)℃ for 25 min to complete hydrolysis.After adding 5 g pretreated TA, the mixture was stirred at 70 ℃ for 1.5 h.The modified slurry was vacuum-dried at 80 ℃ for 12 h, then sieved through a 200-mesh sieve to obtain uniformly sized modified tailings(MTA).Subsequently, polyacrylonitrile(PAN)/MTA composite nanofiber membranes were fabricated via electrospinning using a 10% PAN/N, N-dimethylformamide(DMF)solution with MTA, employing a 19G needle and an applied voltage of 24 kV.Characterization included X-ray fluorescence spectrometry(XRF)for tailings composition, field emission scanning electron microscopy(SEM)for fiber morphology(Image J, ≥500 fibers for average diameter), electronic universal testing machines(with three parallel samples)for mechanical properties, Fourier transform infrared spectroscopy(FTIR)/X-ray diffraction(XRD)for structural/crystalline phases, thermogravimetric analysis(TGA)for thermal stability, limiting oxygen index(LOI)tester for flame retardancy, and mercury porosimeter/Brunauer-Emmett-Teller(BET)analyzer for porosity/specific surface area.[Results] MTA formed stable hydrogen bonding networks with PAN through surface active groups introduced by KH550 modification, which significantly improved interfacial bonding and dispersion uniformity.In contrast to unmodified TA, which caused severe agglomeration and fiber breakage in PAN/10TA, resulting in an average diameter of 300 nm and uneven distribution, PAN/10MTA composite membranes exhibited uniformly distributed nanofibers with a well-defined morphology and an average diameter of 293 nm.Even PAN/5MTA showed slight agglomeration, further confirming the superiority of 10% MTA in dispersion.Mechanically, the PAN/10MTA composite membrane exhibited a tensile strength of 1.59 MPa and an elastic modulus of 12.04 MPa.While these values were lower than those of pure PAN(4.5 MPa tensile strength, 17.32 MPa elastic modulus), the composite membrane maintained good deformation adaptability—no fiber breakage or delamination occurred after cyclic bending and folding—owing to the uniform MTA dispersion that avoided local stress concentration.Moreover, the interfacial hydrogen bonding synergized with the skeleton support effect of tailing oxides.This synergy effectively promoted the formation of a dense, stable char layer during combustion:TGA showed that PAN/10MTA had a higher char residue(53.5% at 1 200 ℃)than pure PAN(40.7%)and an increased initial weight loss temperature.As a result, the LOI of the composite membrane increased from 17.0% to 25.6%, and it showed rapid self-extinguishing behavior in open flame tests.Additionally, the composite membrane retained a porous structure(porosity of 73.3% for PAN/10MTA, compared to 78.2% for pure PAN)with a specific surface area enhanced from 15 m2/g to 18 m2/g.This porous feature provided more active sites for interfacial interaction and char formation, further supporting the improved interfacial adhesion and flame-retardant performance of PAN/10MTA.[Conclusion] Surface modification and electrospinning successfully resolved the interfacial incompatibility between tailings and PAN.The synergistic effect of interfacial hydrogen bonding and the oxide skeleton in tailings effectively enhanced the mechanical strength and flame-retardant properties of the composite membrane.This study not only achieves the high-value utilization of tailings but also provides a novel strategy for designing flame-retardant functional materials using industrial solid wastes, offering insights into sustainable material development.