BACKGROUND Silica coated magnetite nanoparticles (SCMNPs) were synthesized via a co-precipitating method and functionalized with carboxylic acid and percarboxylic acid groups for the preparation of microporous polyethersulfone (PES) nanocomposite membranes and used in bovine serum albumin (BSA) and dye separation. There is no published report about the use of this nanoparticle in the preparation of mixed matrix membranes. RESULTS Different concentrations of these nanoparticles were used. The 0.5 wt% SCMNPs-COOOH NPs-PES membrane had the lowest irreversible fouling resistance (R-ir) value (8.33%) and the highest FRR value (91.7%), suggesting that the prepared mixed matrix membrane is easily recovered by water washing. The introduction of percarboxylic acid groups has a positive impact on rejection of the three dyes (Rhodamine B, Direct Black 38, Reactive Green 19), and all membranes presented rejections of more than 90% due to improved electrostatic repulsion between the dye and the membrane surface by incorporation of the nanoparticles. CONCLUSION The membranes modified by SCMNPs-COOOH had significantly higher permeability and BSA solution flux compared with the bare PES membrane. The nanocomposite membranes had enhanced hydrophilicity because of water affinity enhancement of the membrane surface due to the presence of hydrophilic nanoparticles. It is concluded that SCMNPs-COOOH nanoparticles could be an ideal additive to modify PES membrane for water filtration applications. (c) 2018 Society of Chemical Industry