Synthesis of bimetallic Metal-Organic Frameworks composite for the removal of Copper(II), Chromium(VI), and Uranium(VI) from the aqueous solution using fixed-bed column adsorption

Abstract

NiCo(BDC) bimetallic Metal-Organic Framework (MOF) is impregnated with MnO2 particles to synthesize a highly stable NiCo(BDC)@MnO2 composite. This MOF composite is applied for the removal of Copper (II), Chromium (VI), and Uranium (VI) heavy metal ions from aqueous solutions using batch adsorption and the fixed-bed column method. The physicochemical properties of the composite were analyzed by Fourier transform infrared spectrometry (FTIR), powder X-ray Diffraction (PXRD), Scanning Electron Microscope (SEM), and Brunauer−Emmett−Teller (BET) analysis. TG-DTA analysis shown the composite MOF is thermally stable up to 450°C. X-ray Photoelectron Spectroscopy (XPS) analysis confirms the presence of Nickel, Cobalt, and Mn. The fixed-bed column adsorption experiments on Cu(II), Cr(VI), and U(VI) were conducted to understand the effect of bed height, flow rate, and initial concentration on adsorption efficiency. NiCo(BDC)@MnO2 MOF composite showed a high adsorption capacity of 756.82 ​mg/g for Cu(II), 111.22 ​mg/g for Cr(VI), and 365.25 ​mg/g for U(VI) were examined by the Langmuir isotherm model. The equilibrium studies specified that Cu(II), Cr(VI), and U(VI) adsorption follows pseudo-second-order kinetics in the batch adsorption process and Thomas, Yoon-Nelson, Adam, and Bohart model in fixed-bed column adsorption, which indicates that chemisorption and surface complexation are maybe the primary mechanisms.