Plant-mediated biosynthesis of iron nanoparticles-calcium alginate hydrogel membrane and its eminent performance in removal of Cr(VI)

Iron nanoparticles (FeNPs)-calcium alginate (CaAlg) hydrogel membrane was biosynthesized using green tea extract. Characterization of ultraviolet and visible (UV-Vis) spectra, Scanning Electronic Microscopy (SEM) and Transmission Electron Microscope (TEM) of FeNPs and FeNPs-CaAlg hydrogel membrane confirmed that the FeNPs-CaAlg hydrogel membrane is covered by FeNPs and the FeNPs are spherical in shape and the average particle size is 4.96 +/- 2.03 nm. The composite membrane shows a eminent performance in removing chromium Cr(VI) from wastewater. The FeNPs-CaAlg hydrogel membrane (0.6 g) can remove as high as 99.5% of 1 mg/L (50 mL) Cr(VI) at room temperature (23 degrees C) and original pH (5.41) within 10 min. It is confirmed that the combination of biosynthesized FeNPs and CaAlg hydrogel membrane show synergistic effect on removal of Cr (VI). Furthermore, the superiority and complementary mechanism of the composite membrane were proposed with the aid of X-ray photoelectron spectroscopy (XPS).