Aditya Rianjanu, Alex Triputra Lumban Tobing, Merry Crisdayanti Gultom, Rizky Aflaha, Kuwat Triyana, Tarmizi Taher, Wei-Song Hung, Erwin Peiner, Hutomo Suryo Wasisto, Januar Widakdo
Composite nanofiber membranes are one of the most investigated yet promising adsorbent structures for wastewater treatment, where oxide-type nanoparticles are typically used as a functional filler. The impact of this filler on membrane adsorption performance is determined by its material quality and fabrication parameters. Here, we develop electrospun polyacrylonitrile/polyvinylpyrrolidone/niobium pentoxide (PAN/PVP/Nb2O5) nanofiber membranes and enhance their performance for cationic dye adsorption by optimizing the Nb2O5 content and post-fabrication thermal stabilization temperature. The best-performing membrane is obtained at 0.5 g Nb2O5 loading and 150 °C treatment, retains the largest fraction of polymer functional groups and Nb2O5 cation-exchange sites, while higher temperatures progressively eliminate the surface PVP (N–C=O) groups and the exchangeable NH4+. This membrane achieves a pseudo-second-order equilibrium capacity of 26.9 mg/g for methylene blue (MB), with Langmuir monolayer capacities of 23.8 mg/g (MB) and 20.6 mg/g (crystal violet), consistent with a specific cation-exchange interaction. The adsorption process is endothermic (ΔH° = +48.3 kJ/mol) and entropy-driven (ΔS° = +234.7 J/(K·mol)), and spontaneous across the studied temperature range (ΔG° = −22.8 to −27.5 kJ/mol). Higher treatment temperatures (≥250 °C) cause PVP decomposition, PAN cyclization-induced densification, and thermal release of the exchangeable NH₄⁺, reducing the adsorption capacity to 11–17 mg/g. These findings provide a transferable framework for thermally tuning composite nanofiber adsorbents toward efficient cationic dye remediation in textile wastewater. However, reusability is limited, in which under thermal regeneration the removal efficiency can only retain around 10% of its initial value after five cycles, whereas an ion-based (NaCl/ultrasonic) regeneration is more durable, retaining around 36% despite its only partial capacity recovery. © 2026 The Author(s)
Department of Materials Engineering, Faculty of Industrial Technology, Institut Teknologi Sumatera, Terusan Ryacudu, Way Hui, Jati Agung, Lampung Selatan, 35365, Indonesia; Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Gadjah Mada, Sekip Utara, BLS 21, Yogyakarta, 55281, Indonesia; Department of Environmental Engineering, Faculty of Infrastructure and Regional Technology, Institut Teknologi Sumatera, Terusan Ryacudu, Way Hui, Jati Agung, Lampung Selatan, 35365, Indonesia; Advanced Membrane Materials Research Center, Graduate Institute of Applied Science and Technology, National Taiwan University of Science and Technology, Taipei, 10607, Taiwan, China; Institute of Semiconductor Technology (IHT) and Laboratory for Emerging Nanometrology (LENA), Technische Universität Braunschweig, Braunschweig, 38106, Germany; PT Biostark Analitika Inovasi, Bandung, 40375, Indonesia; Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Indonesia, Depok, 16424, Indonesia