Cr(VI), Pb(II), Cd(II) adsorption properties of nanostructured BiOBr microspheres and their application in a continuous filtering removal device for heavy metal ions

Uniform well-defined nanostructured BiOBr microspheres have been fabricated via a simple hydrothermal method in the presence of cetyltrimethylammonium bromide (CTAB) and ethylene glycol (EG). The heavy metal ion adsorption on the as-synthesized nanostructured BiOBr microspheres was systematically assessed by measuring the residual concentration during the adsorption process using a colorimetric method for Cr(VI) concentration, and an extraction-colorimetric method for Cd(II) and Pb(II) concentrations. The nanostructured BiOBr microspheres showed good removal capacity for heavy metal ions (Cr, Cd, Pb), and excellent adsorption properties for low concentration heavy metal ions, indicating potential applications in water purification. Based on the quick and efficient heavy metal ion removal ability of nanostructured BiOBr microspheres, a continuous filtering-type water purification device was designed and constructed. In using this continuous filtering type water purification device, 1 g of adsorbent can purify about 4900 g of Pb(II) contaminated water, 5900 g of Cd(II) contaminated water, or 21 500 g of Cr(VI) contaminated water having initial concentrations of 200 mu g L-1 to successfully attain the World Health Organization standard for drinking water. The good removal capacity can be attributed to the hierarchical nanostructure, which displays a large specific surface area and strong adsorption of heavy metal ions.