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

Abstract 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 (GS EEO-modified ) was used as an adsorbent to remove caffeine from solution. Experimental results indicate that GS EEO-modified effectively adsorbs caffeine and that the adsorptive ability of GS EEO-modified prepared with KMnO 4 is obviously higher than that of GS EEO-modified prepared with H 2 O 2 or S 2 O 8 2− . The optimal preparation conditions for GS EEO-modified were 1.2 M H 2 SO 4 , 0.1 M KMnO 4 , 80 °C, and an applied voltage of 4 V. GS EEO-modified of 4.0 g L −1 efficiently adsorbed 95% of the caffeine (C 0  = 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 GS EEO-modified , which maintained a high adsorptive ability (81%) after seven cycles of adsorption-regeneration treatment.