Experimental and Monte Carlo simulation study on a core–shell NiFe2O4@HKUST-1/graphene oxide nanocomposite for Congo Red adsorption

Abstract

A copper-based metal–organic framework, nickel ferrite and graphene oxide were prepared as constituents of a new core–shell nanocomposite formed by a layer-by-layer method, then it was applied to absorb Congo Red dye as an organic contaminant. The nanocomposite was studied by XRD, FTIR, EDS, FESEM and VSM methods. Investigating the main factors affecting the adsorption shows that the optimum pH of the dye solution is 7, the best contact time is 60 min with an initial solution concentration of 5 ppm and 0.05 g of adsorbent is the optimum amount. Adaptation of Langmuir, Freundlich, Temkin and Dubinin–Radushkevich adsorption isotherms showed that the dye adsorption process is consistent with two first isotherm models. Regarding the adsorption kinetics and according to the calculations, it was found that the adsorption process follows second-order kinetics. The composite NiFe₂O₄@HKUST-1/GO demonstrated a maximum adsorption capacity of 25.64 mg g⁻¹ for Congo Red dye removal from aqueous solutions. Monte Carlo simulations were used to simulate the adsorption nature between NiFe₂O₄ (311) molecules and the HKUST-1 surface, GO molecules and NiFe₂O₄@HKUST-1, and CR and NiFe₂O₄@HKUST-1/GO.