Adsorption is an effective method of removing contaminants from water, however, desorption often becomes more difficult after adsorption process, due to the strong binding force between the adsorbent and pollutants, so that the desorbent cannot be reused. In this paper, Co0.85Se nanosheets prepared through a hydrothermal reaction have been used to remove cationic dye methylene blue from aqueous solution in the presence of sodium borohydride. The results show that adsorption/desorption properties of the Co0.85Se nanosheets to MB can be greatly changed in the presence/absence of sodium borohydride (NaBH4), and the equilibration time of the adsorption/desorption depends on the amount of NaBH4. When NaBH4 or Co0.85Se nanosheets existed together, the residual quantity of MB in solution was less than one-twentieth of that in the system alone using either NaBH4 or Co0.85Se nanosheets; while a large number of MB (ca.90%) was released once again into the solution after NaBH4 was decomposed because of catalysis of Co0.85Se. The zeta potential and pH tests have been elucidated the mechanism for the adsorption of MB onto Co0.85Se nanosheets. The efficient adsorption and recovery of dyes indicate that the prepared Co0.85Se nanosheets have potential application in wastewater treatment under the assistance of NaBH4. (C) 2014 Elsevier B.V. All rights reserved.