Facile modification of graphite sheet by novel electrochemical exfoliation/oxidant method and its adsorption of caffeine from water

Graphite is an abundant natural material, but its specific area and adsorptive ability are low. In this study, a graphite sheet modified by an electrochemical exfoliation/oxidant process (G(SEEO-modified)) was used as an adsorbent to remove caffeine from solution. Experimental results indicate that G(SEEO-modified) effectively adsorbs caffeine and that the adsorptive ability of GSEEo-modified Prepared with KMnO4 is obviously higher than that of G(SEEO-modified) Prepared with H2O2 or S2O82-. The optimal preparation conditions for G(SEEO-modified) were 1.2 M H2SO4, 0.1 M KMno(4), 80 degrees C, and an applied voltage of 4 V. G(SEEO-modified) of 4.0 g L-1 efficiently adsorbed 95% of the caffeine (Co = 50 mg L-1) within 30 min. Langmuir isotherms describe the adsorption behavior well (q(max) = 1000 mg L-1, b = 0.001, R-2 = 0.9912). Additionally, 0.1 M acetone effectively regenerated exhausted G(SEEO-modified), which maintained a high adsorptive ability (81%) after seven cycles of adsorption-regeneration treatment. (C) 2017 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.