Inclusion of bimetallic Fe0.75Cu0.25-BDC MOFs into Alginate-MoO3/GO as a novel nanohybrid for adsorptive removal of hexavalent chromium from water

Abstract

Metal–organic frameworks (MOFs) as porous materials have recently attracted research works in removal of toxic pollutants from water. Cr(VI) is well-known as one of the most toxic forms of chromium and the selection of efficient and effective Cr(VI)-remediation technology must be focused on a number of important parameters. Therefore, the objective of this work is to fabricate a novel nanohybrid adsorbent for removal of Cr(VI) by using assembled bimetallic MOFs (Fe0.75Cu0.25-BDC)-bound- Alginate-MoO3/Graphene oxide (Alg-MoO3/GO) via simple solvothermal process. The aimed Fe0.75Cu0.25-BDC@Alg-MoO3/GO nanohybrid was confirmed by FTIR, SEM, TEM, XRD and TGA. Adsorptive extraction of Cr(VI) from aqueous solution was aimed by various optimized experimental parameters providing optimum pH = 3, dosage = 5–10 mg, starting concentration of Cr(VI) = 5–15 mg L−1, shaking time = 5–10 min. The point of zero charge (pHPzc) was 3.8. For Cr(VI) removal by Fe0.75Cu0.25-BDC@Alg-MoO3/GO, four isotherm models were estimated: Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) with calculated correlation coefficient (R2 = 0.9934) for Langmuir model which was higher than others. The collected results from the kinetic study clarified that pseudo-second order model is the most convenient one for describing the adsorption behavior of Cr(VI) and therefore, the adsorption process was suggested to rely on a chemisorption mechanism. Thermodynamic parameters referred that the adsorption mechanism is based on a spontaneous and exothermic process. Finally, the emerged Fe0.75Cu0.25-BDC@Alg-MoO3/GO nanohybrid was confirmed as an effective adsorbent for extraction of hexavalent chromium from real water specimens (tap, sea water and wastewater) with percentage recovery values > 98%.