Formulation of NZVI-supported lactic acid/PAN membrane with glutathione for enhanced dynamic Cr(VI) removal

The current technologies for production of nanoparticle-membrane are apt to involve complicated multi-step process and/or toxic chemicals and other defects. This study provides a green and clean cryogel manufacture method for fabrication of hydrophilicity Polyacrylonitrile (PAN) membrane with highly porous structure for supporting nano zero-valent iron (NZVI) via a surface modification by employing biodegradable lactic acid. Non-toxic natural compound, glutathione (GSH) was adopted not only as modifiers but also as chelators to promote the capture capacity of hexavalent chromium (Cr(VI)). The specific surface area of the prepared composite (GLPN, 193.16 m2/g) was larger than the previously studied NZVI-membrane (PPN, 131.61 m2/g), and NZVI was distributed uniformly and not agglomerated on the membrane. Compared with NZVI, the efficiency of GLPN removed Cr(VI) has increased by 39.80%. At low pH and Cr(VI) initial concentration, GLPN can completely remove Cr(VI) when the GSH concentration is increased to 50 mM, and the removal efficiency can still reach 86.96% after 6 regenerations. Visual MINTEQ model and experimental results show that the mechanism of GLPN removing Cr(VI) includes the synergy of electrostatic adsorption, chelation, reduction and co-precipitation. The process conforms to two-parameter nonlinear dynamics and Redlich-Peterson isotherm model. This novel strategy shows that GLPN has excellent stability, reducibility and green reproducibility, and can efficiently remove and recycle heavy metal in the natural water matrices or wastewater.