Efficient removal and fouling-resistant of anionic dyes by nanofiltration membrane with phosphorylated chitosan modified graphene oxide nanosheets incorporated selective layer

To validate the feasibility of designing composite nanofiltration (NF) with separation layer composed of desired both skin features and loose body by one-step process, in this work, a novel phosphorylated chitosan (PCS) NF membrane was fabricated via surface functionalization with an appropriate amount of graphene oxide (GO) nanosheets through forming covalent bonds. It demonstrated superior surface hydrophilicity, roughness and negative charge (decreasing to 41.9 degrees, 18.7 nm and -56.4 mV, respectively), and showed good anionic dye and salt separation performance. Due to the disruption of the packing of polymer chains with the two-dimensional layered rigid GO nanoplates, porosity of its surface layer increased by 16.8 % concurrently. Compared with the bare PCS membrane, the permeate fluxes of NF2 membrane to aqueous solutions dissolved with direct black 38, xylenol orange, ponceau S, NaCl and Na2SO4 under steady state were higher by 58.8 %, 76.3 %, 75.1 %, 83.1 % and 78.8 %, respectively. Also, it exhibited slightly higher anionic dyes and significantly superior salt removal efficiencies. Furthermore, the optimal GO-PCS membrane also exhibited better antifouling property for achieving the outstanding flux decline ratio of 8.67 % and especially irreversible fouling ratio of only 0.17 % to direct black 38.