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 ([(Mg0.75Al0.25(OH)(2)](A(n-))(0.75/n)center dot mH(2)O, 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, B-11 NMR spectral analyses indicated that the Mg-Al bimetallic oxides captured trigonal B (B-[3]) and tetrahedral B (B-[4]) after the sorption of boron, regenerating hydrotalcite-like compounds. As the initial concentration of boron increased, the percentage of tetrahedral B-[4] in solid residues after the sorption of boron increased. The B-[4]/B-[3] 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. (C) 2015 Elsevier B.V. All rights reserved.