Sustainable functional electrospun polyamide 11/halloysite derivatives nanofibrous membranes for water treatment applications

Membrane-based approaches are an exciting alternative for the filtration and remediation of polluted water and for the removal of different traditional and emerging contaminants. This work focuses on the design and development of sustainable bio-polymeric blends based on polyamide 11 (PA11) employed to produce different Electrospun Nanofiber Membranes (ENMs) through the electrospinning process. Moreover, different eco-friendly functional nanofillers based on hybrid halloysite (HNT) derivatives were employed as dopant agents of the starting polymeric blends in a ratio of 1, 2 and 5 wt% of PA11 to achieve better mechanical and thermal features as well as retention performances of specific wastewater organic contaminants. Chemical-physical and structural-morphological characterizations, concerning all the nanofillers and the obtained sustainable membranes, are reported as well as the removal and separation studies of two selected anionic and cationic dyes, methyl orange (MO) and methylene blue (MB) in a dead-end filtration apparatus. The newly developed composite ENMs, compared to pristine PA11 ones, show good tensile mechanical and thermal properties, and increased MO and MB removal rates, modulated by the different HNT derivatives employed. Dead-end filtration experiments were performed using 1 and 3 layers of each type of ENM revealing, for 1-layer PA11 ENMs containing HNT modified with octadecylphosphonic acid and (3-aminopropyl)triethoxysilane (PA11@C18_HNT_NH2) and dimethyloctadecyl[3(trimethoxysilyl)propyl]ammoniumchloride (PA11@HNT_N + C18), a selectivity towards the removal of the cationic dye MB with a separation efficiency of 69.8 and 73.3 % respectively. Hence, 3-layer PA11 ENMs doped with HNT functionalized with (3-aminopropyl)triethoxysilane (PA11@HNT_NH2) display the highest retention rate for MO and MB respectively of 100 and 89.8 %. Graphical abstract