Sorption properties of boron on Mg-Al bimetallic oxides calcined at different temperatures

Mg-Al bimetallic oxides produced via the calcination of hydrotalcite-like compounds ([(Mg_0.75Al_0.25(OH)₂](A^n-)_0.75/n·mH₂O, where A is an anionic species) exhibited high potential for the removal of boron from aqueous solutions. X-ray diffraction patterns for the produced bimetallic oxides revealed that MgO was the primary phase within the range of investigated calcination temperatures. In addition, ¹¹B NMR spectral analyses indicated that the Mg-Al bimetallic oxides captured trigonal B (^[3]B) and tetrahedral B (^[4]B) after the sorption of boron, regenerating hydrotalcite-like compounds. As the initial concentration of boron increased, the percentage of tetrahedral ^[4]B in solid residues after the sorption of boron increased. The ^[4]B/^[3]B ratios in the solid residues increased with time along with the regeneration of hydrotalcite-like compounds. Furthermore, the Mg-Al bimetallic oxides produced from hydrotalcite-like compounds were more favorable than other bimetallic oxides and effective than single-phase MgO produced from MgCO₃ at the same temperature, indicating that Mg-Al bimetallic oxides are stable materials with the potential for use in the remediation of contaminated sites and water.