Marine algae-mediated PVDF/ZnO nanocomposite ultrafiltration membranes: superior performance in Cr(VI) removal from aqueous solutions.

Nano-membrane technology continues to expand its role in water purification. However, this technological advancement faces significant challenges, such as potential toxicity issues and membrane fouling, necessitating the development of sustainable and environmentally benign filtration solutions. In the present study, zinc oxide nanoparticles (ZnO NPs) derived from blue-green algae Arthrospira platensis were used in fabrication of polyvinylidene fluoride (PVDF) ultrafiltration (UF) nanocomposite membranes for the removal of Chromium (VI). This approach ensures environmental compatibility while minimizing ecotoxicological concerns often associated with conventionally synthesized materials. The membrane fabrication process employed the phase inversion technique, with subsequent comprehensive characterization utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), energy-dispersive X-ray analysis (EDX), and water contact angle (WCA) measurements to thoroughly assess their physicochemical properties and structural morphology. The functional performance of these membranes was evaluated through water flux measurements and Chromium (VI) removal efficiency tests. Various concentrations of biosynthesized ZnO nanoparticles (0.5, 1, 2, and 3 wt%) were systematically incorporated into the PVDF matrix, with experimental results demonstrating that the optimized membrane containing 3 wt% ZnO NPs exhibited exceptional performance characteristics, achieving 91.69% removal efficiency for Chromium (VI), an adsorption capacity (q_e) of 10.92 µg/cm², and superior hydrophilicity with a significantly reduced contact angle of 48.9°. Additionally, the water permeability of this optimized nanocomposite membrane demonstrated a substantial 50% enhancement compared to the neat PVDF membrane. Kinetic analyses indicated that the adsorption process followed a pseudo-second-order model, while isotherm studies revealed that the Langmuir model provided the most accurate representation of the adsorption mechanism, suggesting monolayer coverage on homogeneous surface sites. This research not only introduces an environmentally responsible approach to nanocomposite membrane synthesis but also demonstrates the exceptional efficacy of these membranes in heavy metal remediation, offering a sustainable and economically viable solution for industrial wastewater treatment with considerable potential for practical environmental applications and technological scale-up.