Research Article Received: 28 November 2017 Revised: 12 March 2018 Accepted article published: 25 March 2018 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/jctb.5640 Microwave-assisted optimized route for the synthesis of CoSe 2 nanoflakes: an efficient material for adsorptive removal of Rhodamine B Swapnil K Warkhade, Sangesh P Zodape, Umesh R Pratap and Atul V Wankhade * Abstract BACKGROUND: Ample 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. RESULT: Asymmetrical, smooth CoSe 2 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 CoSe 2 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 CoSe 2 nanoflakes follows a pseudo-second-order model. Despite their smaller surface area (13.20 m 2 g -1 ), CoSe 2 nanoflakes possess significant adsorption capacity (178.59 mg g -1 ). The synthesized CoSe2 nanoflakes have been successfully reutilized for five adsorption cycles with retention of about 100% adsorption efficiency. CONCLUSIONS: The CoSe 2 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. © 2018 Society of Chemical Industry Supporting information may be found in the online version of this article. Keywords: thermogravimetric analysis; adsorption kinetics; nanoflakes INTRODUCTION In last few decades, the growth of industrialization has become the curse to the environment and human beings, due to rea- sonably contaminate most of the aquatic sources. The literature reveals that a significant cause of water pollution is the accumu- lation of textile and industrial dyes in natural water resources. About 15–20% of the total world production of dyestuffs was lost during industrial dyeing processing as industrial effluent into freshwater sources. 1,2 The removal of organic pollutants from water bodies is very challenging due to their high solubil- ity and poor biodegradability. This dye accumulates in ecosys- tems and causes eutrophication, leading to hazardous effects on aquatic life, and health impacts, especially from carcinogenic dyes, on humans. Various physical and chemical techniques including photocatalysis, 3 ultra-filtration, 4 chlorination, 5 ozonolysis, 6 reverse osmosis 7 and coagulation 8 have been used for removal of pollu- tants from water, yet there is a need for better decontamination methods. Adsorption is one of the most admired methods among the var- ious water treatment methods due to its simplicity in handling and effectiveness in the process. 9 Owing to its large surface area (500–2000 m 2 g -1 ) area and high porosity, most of dye manufac- turing industries use activated carbon for the removal of dye from polluted water. 10 However, the regeneration of activated charcoal requires a high pressure water stream, which adds to operational costs. This provokes the need for alternative low cost and highly efficient adsorbents to remove dyes from industrial effluent. Recently, nanomaterials have fascinated many researchers due to their exceptional physical properties, chemical inert- ness and availability large numbers of active sites due to an enhanced surface area. 11 Nanomaterials have been successfully employed for miscellaneous applications including adsorption of the organic dye, 12 catalyzing organic reactions, 13–15 photocatalytic ∗ Correspondence to: AV Wankhade, Department of Chemistry, Visvesvaraya National Institute of Technology, Nagpur, India. E-mail: atulwa2006@yahoo.co.in Department of Chemistry, Visvesvaraya National Institute of Technology, Nagpur, India J Chem Technol Biotechnol (2018) www.soci.org © 2018 Society of Chemical Industry