Preparation of Mg/Al bimetallic oxides as sorbents: microwave calcination, characterization, and adsorption of Cr(VI)

In the study, Mg/Al bimetallic oxides as sorbents have been successfully prepared via a novel and facile approach (Microwave Calcination). The characterizations of Mg/Al bimetallic oxides were performed using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, N-2 adsorption/desorption, and pH(PZC) analyses. The results showed that microwave calcination resulted in enhanced crystallinity, pH(PZC), and specific surface area of the Mg/Al bimetallic oxides, compared to conventional calcination. Comparison of the performance of Cr(VI) adsorption between Mg/Al bimetallic oxides prepared by conventional (CHTC) and microwave (CHTM) calcination was made and discussed. The results demonstrated that the adsorption experiment data from the CHTC and CHTM were both fitted well to Langmuir-Freundlich isotherm model and pseudo-second-order kinetic model, and the adsorption process was chemisorption and controlled by diffusion. Microwave calcination did not change the adsorption properties for Cr(VI), but the Cr(VI) adsorption capacities of Mg/Al bimetallic oxides obtained by microwave calcination were improved.