Carbon gel-supported Fe-graphene disks: Synthesis, adsorption of aqueous Cr(VI) and Pb(II) and the removal mechanism

Carbon gel-supported Fe-graphene (Fe-G) disks were synthesized via sol-gel polymerization of resorcinol-formaldehyde (RF), followed by carbonization of the polymeric mass. Fe(III)-graphene oxide were in situ doped in the gel at the incipience of polymerization. The Fe(III) served as a crosslinker between graphene oxide and RF matrix as well as the polymerization catalyst. The prepared Fe-G/RF (C) disks were used as an efficient adsorbent for aqueous Cr(VI) and Pb(II). Various analytical techniques were used to characterize the physico-chemical properties of the prepared materials, including surface morphology, surface area and point of zero charge. The compressive strength of the Fe-G/RF(C) disks was measured to be significantly high (0.12 MPa). The maximum adsorption capacities of Fe-G/RF(C) for Cr(VI) and Pb(II) were determined to be 108 and 172 mg/g at the optimized solution pH. Significant adsorption of the metals was attributed to the large surface area (similar to 537 m(2)/g) and microporosity (94%) in the material, high chemical reactivity of graphene, and amenability of the material surface to protonation by pH-adjustment. The synthesized amorphous carbon gel-supported Fe-graphene disks can be effectively used as packed bed materials for the adsorptive removal of toxic metal ions present in industrial aqueous effluents under flow or dynamic conditions. (C) 2017 Elsevier B.V. All rights reserved.