Dye adsorption characteristics of magnetite nanoparticles coated with a biopolymer poly(γ-glutamic acid)

► Biopolymer poly(γ-glutamic acid) (PGA) coated magnetic nanoparticles as dye sorbent. ► Nanoparticles characterized for methylene blue sorption by FTIR, TEM and VSM data. ► An ultrafast kinetics with a Langmuir adsorption capacity of 78.7 mg/g is achieved. ► Raise in pH and drop in salt level increase dye adsorption, while lowering pH favors desorption. ► Sorption is by electrostatic interaction via exchange of α-carboxyl protons on PGA.