Organic dyes removal using magnetically modified rye straw

•Rye derivatives can be considered as efficient adsorbents for organic dyes.•Magnetic modification of straw by microwave-synthesized magnetic iron oxides.•Citric acid–NaOH modification increased the maximum adsorption capacities.

Rye straw, a very low-cost material, was employed as a biosorbent for two organic water-soluble dyes belonging to different dye classes, namely acridine orange (acridine group) and methyl green (triarylmethane group). The adsorption properties were tested for native and citric acid–NaOH modified rye straw, both in nonmagnetic and magnetic versions. The adsorption equilibrium was reached in 2 h and the adsorption isotherms data were analyzed using the Langmuir model. The highest values of maximum adsorption capacities were 208.3 mg/g for acridine orange and 384.6 mg/g for methyl green.