Silver metal organic frameworks and copper metal organic frameworks immobilized on graphene oxide for enhanced adsorption in water treatment

Abstract

In this study, copper metal organic frameworks (Cu-MOF) and silver metal organic frameworks (Ag-MOF) were synthesized and immobilized on and between GO sheets using an ultrasonication process. The GO-immobilized MOFs (GO-Ag-MOF and GO-Cu-MOF) showed enhanced physicochemical properties, including enhanced surface area, surface charge, and active adsorption sites confirmed with characterization techniques such as zeta potential, Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD) and scanning electron microscopy (SEM). In addition, the adsorption capacities of Ag-MOF, Cu-MOF, GO-Ag-MOF, and GO-Cu-MOF materials for methylene blue dye (MB), as an organic contaminant model, were thoroughly evaluated at different experimental conditions (pH (3–10), temperature (25–45 °C), and adsorbate concentrations (0–150 ppm)). The kinetics and thermodynamic behavior of the synthesized MOFs revealed that both GO-Ag-MOF and GO-Cu-MOF showed around 10% increase in adsorption capacity in comparison to the pristine Ag-MOF and Cu-MOF at all the tested conditions. GO-Ag-MOF exhibited more than 98 % dye removal, followed by Ag-MOF (90%), GO-Cu-MOF (75%), and Cu-MOF (65%). The main mechanism for adsorption was monolayer adsorption based on electrostatic interactions. All MOFs showed more than 80% re-generability after three regeneration cycles