High–performance nanofiltration membrane blended by Fe3O4@SiO2–CS bionanocomposite for efficient simultaneous rejection of salts/heavy metals ions/dyes with high permeability, retention increase and fouling decline

[Display omitted] •High pure silica was extracted from wheat straw as agricultural by–product.•Bio–silica was applied for synthesis of Fe3O4@SiO2–CS bionanocomposite.•Fe3O4@SiO2–CS was successfully used for modification of PES NF–membrane structure.•The efficiency of blended NF–membranes with Fe3O4@SiO2–CS significantly increased. A high–performance nanofiltration (NF) membrane was fabricated by blending Fe3O4@SiO2–CS biocompatible and green bionanocomposite, which was synthesized by a core–shell of Fe3O4 magnetic nanoparticles and amorphous SiO2 extracted from wheat straw and functionalized by chitosan groups. The characteristics analyses confirmed fine structure of the synthesized bionanocomposite and the fabricated NF–membranes. Among the fabricated membranes, the unblended membrane (NFM–1) by 47.3 L m–2h−1 showed the lowest pure water flux, while it was significantly increased for the blended membranes (NFM–2, NFM–3 and NFM–4) and in the best case reached 70.6 L m–2h−1 for NFM–3 membrane. All the membranes showed the highest salt rejection for Na2SO4 with ~ 90% and the lowest salt rejection for MgCl2 with ~ 10%, confirming the nanofiltration behavior of the fabricated membranes. The removal of heavy metals ions by NF–membranes increased from NFM–1 membrane by 14.95, 15.45 and 16.11% to NFM–3 membrane by 98.11, 98.61 and 98.86% for Pb2+, Cu2+ and Cd2+, respectively. All the NF–membranes indicated more than 98.2% dyes retention for both cationic and anionic dyes such as MB, CR and RB5. Also, the efficiency of NFM–3 membrane was very high for the filtration of multicomponent solutions and increasing the concentration of Na2SO4 had a limited effect on the removal of Pb2+ and MB. Regarding the 120 h continuous filtration test, NFM–3 membrane depicted a slight reduction in water flux and rejection of Na2SO4, Pb2+ and MB.