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

- Mechanically strong, porous carbon disk-supported Fe-graphene was synthesized.
- In situ doped Fe served as crosslinker and adsorption sites for Cr(VI) and Pb(II).
- Fe-G/RF(C) showed large surface area (∼537 m2/g) with 94% microporosity.

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 (∼537 m2/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.

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