Phosphine-functionalized electrospun poly(vinyl alcohol)/silica nanofibers as highly effective adsorbent for removal of aqueous manganese and nickel ions

Phosphine-functionalized PVA/SiO₂ (pgf-PVA/SiO₂) composite nanofiber adsorbent (porous) was prepared using a facile electrospinning technique. The successful fabrication of the pgf-PVA/SiO₂ nanofibers was confirmed by field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) analyses. The nanofiber adsorbent was evaluated for water sensitivity, N₂ adsorption-desorption isotherms, pore size distribution, and manganese (Mn⁺²) and nickel (Ni⁺²) ions removal from aqueous solution at various pH, contact times, and adsorbent dosages as well as at different regeneration/reuse cycles. The composite pgf-PVA/SiO₂ nanofibers (with 0.5g/L fiber loading) can remove almost completely (96-98%) the aforementioned ions from aqueous solutions (initial concentration of 120mg/L, pH 6) within 15min of contact time. A reasonably simple acid treatment (with a 1M HCl solution) was found to be extremely effective in regenerating the nanofiber adsorbent, and 92.5% of the metal ions were removed from the adsorbent even in the fifth regeneration/reuse cycle. Additionally, the adsorption equilibrium studies revealed the excellent adsorption capacities of the pgf-PVA/SiO₂ nanofiber for both Mn⁺² and Ni⁺² ions (234.7 and 229.9mg/g, respectively).