Functionalized PVDF Membrane-immobilized Fe/Ni Bimetallic Nanoparticles for Catalytic Degradation of Methyl Orange Dye: A Comparative Study

Herein we report on the use of Fe/Ni bimetallic nanoparticles supported on a polyacrylic acid (PAA)-functionalized commercial polyvinylidene fluoride (PVDF) filtration membrane, in the degradation of methyl orange dye. Two methods of PAA grafting onto the PVDF membrane were compared; viz. dip-coating method in which an already polymerized acrylic acid was grafted, and the in situ polymerization method wherein acrylic acid (AA) was polymerized in-situ and grafted onto the membrane. The Fe/Ni bimetallic nanoparticles were then immobilized onto the functionalized membranes. In both cases, the PAA grafting and incorporation of the metal nanoparticles onto the PVDF membranes was confirmed by ATR-FTIR. SEM/EDS analysis showed the presence of metal agglomeration and non-uniform metal distribution on the surface of the nanocomposite membrane prepared by the dip-coating method, while a uniform metal distribution without agglomeration was observed in the in situ polymerization method-prepared nanocomposite membrane. The nanocomposite membranes were assessed for the catalytic degradation of methyl orange dye at both acidic and neutral testing media. High catalytic activity at both acidic and neutral pH conditions, as well as lower metal leaching at neutral pH, was observed with the nanocomposite membrane prepared by in situ polymerization of AA and this was attributed to the uniform metal dispersion obtained with the method. The membranes could potentially be used for the treatment of water containing organic pollutants at moderate pH.