Synthesis of interstratified graphene/montmorillonite composite material through organics-pillared, delamination and co-stacking and its application in hexavalent chromium removal from aqueous solution

- An interstratified MAGO was synthesized through delamination and co-stacking.
- The MAGO used as adsorbent for the removal of Cr(VI) ion.
- The adsorption rate was fast and adsorption equilibrium was obtained within 30 min.
- Increasing the acidity of the solution is benefited to the high adsorption capacity.
- The MAGO was shown to be effective through four sorption-desorption cycles.

Layers from two different delaminated dispersions of 3-aminopropyltriethoxysilane (APTES)-intercalated montmorillonite (Mts) and octylamine (OA)-intercalated graphene oxide (GO) could be co-stacked to obtain APTES-intercalated Mts (Mts-APTES)/OA-intercalated GO (GO-OA) interstratified composites (MAGO). The synthesized composites were characterized by XRD, FTIR, BET, TGA, TEM and XPS, which showed that MAGO had been prepared successfully. The optimal concentration of APTES was 8% in anhydrous toluene which avoided self-polymerization of APTES while facilitating the nucleophilic attack of APTES amine groups and the protic character of ethanol to compete with silane for the intimal hydroxyl groups by H-bonding. The MAGO demonstrated an extremely fast Cr(VI) removal from aqueous solution with a high removal efficiency at low pH. Data from batch studies of the adsorption process followed pseudo-second-order kinetics. The results fit a Langmuir model of adsorption, with maximum adsorption capacities of MAGO composites at pH 3.0 being 44.25 mg g−1, 47.46 mg g−1, 49.58 mg g−1 under 30 °C, 40 °C, 50 °C, respectively, which were much higher than capacities of some conventional adsorbents. The reusability of the MAGO composite was also determined through adsorption-desorption studies, providing evidence for the potential use of MAGO composite in the removal of Cr(VI) from acidic wastewater.

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