Adsorption behaviors of U(VI) in aqueous solution by cetyltrimethylammonium bromide modified montmorillonite-hydroxyapatite composite adsorbent

In this task, a novel montmorillonite composite (CMH) was successfully prepared by surfactant modifying with cetyltrimethylammonium bromide (CTAB) and compounding with hydroxyapatite (HAP). In contrast to nature montmorillonite (MMT), CMH showed better U(VI) adsorption properties (R > 99 %) in a wide adsorbent dose range (0.2 to 1.0 mg/L) with the initial U(VI) concentration of 10 mg/L at pH = 5.0 and T = 298 K. The adsorption capacity of CMH for U(VI) reached 678.6 mg/g, which was much higher than most of reported clay-based adsorbents, suggesting that the adsorption performances of CMH were at the upper-middle level among clay-based adsorbents. In addition, CMH also performed good recoverability with the adsorption efficiency of 96.2 % after five cycles and could still maintain relatively high U(VI) adsorption capacity even during complex water system, which was expected to be used for adsorbing U(VI) from various water environment. In terms of the differences in morphology, structure and composition between MMT and CMH, the excellent U(VI) adsorption performances of CMH could be explained by the rougher surface, larger interlayer spacing and more pores and functional groups, thus providing more binding sites. The adsorption mechanism involved electrostatic interaction, ion exchange and complexation. This job supplied a novel opinion for the explore of low cost and highly efficient adsorbent synthesis for U(VI) adsorption.