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%.