Surfactant-modified adsorptive electrospun nanofiber membrane impregnated with akageneite for phosphorus recovery from wastewater

Abstract

Phosphorus (P) recovery from wastewater is essential for eutrophication control, water reuse initiatives, and recovery of this depleting non-renewable resource. Herein, a polyacrylonitrile (PAN) electrospun nanofiber membrane (ENM) was fabricated with akageneite (Ak), and modified with benzyldimethyldodecylammonium chloride (BDDA), a cationic surfactant, for phosphorus recovery from wastewater. We examined the influence of BDDA concentration on membrane properties, including fiber diameter, surface area, surface charge, and contact angle. Membrane performance was then evaluated using adsorption isotherms and kinetics, in the presence of competing ions such as Cl-, SO42- and CO32-, using synthetic wastewater and through a total of 7 adsorption-desorption cycles. Akageneite was found to be the only active ingredient responsible for P removal by the membrane. We observed that the increase in BDDA concentration from 0 % to 3 % resulted in a linear increase in P adsorption capacity from 0.30 to 0.61 mmol P/g Ak. No increase in adsorption was observed at concentrations beyond 3 % BDDA. Membranes made of PAN and BDDA alone exhibited a negligible uptake of P at any concentration of BDDA. Since P uptake happened only in the presence of Ak, the improved performance with the addition of BDDA was attributed to increased hydrophilicity and influence of the Donnan membrane effect. The membranes had the highest affinity towards CO32- followed by P. The P adsorption capacity of PAN-Ak membrane was not affected by the presence of other competing ions (Cl-, SO42-). The results also confirmed the reusability of PAN-Ak without loss of adsorption capacity, even after seven cycles. This work demonstrated the potential of surface modification of adsorptive membranes for improved phosphorus recovery.