Agricultural waste/graphene oxide 3D bio-adsorbent for highly efficient removal of methylene blue from water pollution

The objective of this study was to synthesize a novel, efficient and economical bio-adsorbent with three dimensions (3D) structure using a direct assembly method for removal of methylene blue (MB) from aqueous solution. The raw materials were corn straw core (CSC) and graphene oxide (GO). The variables that affected adsorption capacity were tested. GO loading could facilitate the removal rate. When 5 wt% GO was added (CSC-5GO), the removal rate was increased by 21.62% compared to pure CSC (64.58%). Furthermore, the adsorption by CSC-5GO fitted pseudo-second-order kinetic model (R 2 > 0.998) and Temkin model ( R-2 > 0.955). The maximum adsorption capacity was 414.03 mg g(-1 )for MB at pH = 12, 298 K and MB concentration of 1000 mg L-1. The adsorption thermodynamic test results suggested that the adsorption was a spontaneous, exothermic and randomness decrease process. Furthermore, after five cycles of adsorption-desorption test, the adsorbent removal rate was >90%, which implied that CSC-5GO had an excellent reproducibility. (C) 2018 Elsevier B.V. All rights reserved.