BACKGROUNDAmple literature on the use of conventional materials as an adsorbent for detoxification of water emphasizes the proven superiority of the adsorption technique. However, limited literature on the use of inorganic materials as adsorbents has inspired us to use nanomaterials as an adsorbent for the adsorptive removal of organic pollutants from industrial wastewater. RESULTAsymmetrical, smooth CoSe2 nanoflakes were synthesized by optimizing the concentration of KOH solution abetted with polyethylene glycol-400 via an effective microwave-assisted technique. The adsorption capability of CoSe2 nanoflakes was studied using an aqueous solution of Rhodamine B dye as a model organic pollutant. Adsorption study reveals that the adsorption follows a Langmuir adsorption isotherm, while the adsorption kinetics of CoSe2 nanoflakes follows a pseudo-second-order model. Despite their smaller surface area (13.20m(2)g(-1)), CoSe2 nanoflakes possess significant adsorption capacity (178.59mgg(-1)). The synthesized CoSe2 nanoflakes have been successfully reutilized for five adsorption cycles with retention of about 100% adsorption efficiency. CONCLUSIONSThe CoSe2 nanoflakes synthesized by optimized microwave-assisted technique possessed high adsorptivity and reusability for the adsorption of Rhodamine B from aqueous solution. Additionally, this optimized synthesis protocol can be used for the synthesis of a variety of transition metal selenides. (c) 2018 Society of Chemical Industry