USE OF LOW-GRADE AND RECYCLED MATEWRIALS AS SELECTIVE ARSENATE AND ANTIMONATE SORBENTS

Arsenic (As) and antimony (Sb) are elements with similar chemistry and geochemistry, but their environmental risk differ depending on the origin and degree of the pollution. As and Sb are both very toxic, particularly their inorganic substances in the oxidation states of III and V, which also represent the most common As/Sb forms in the environment. In environmental systems, As mostly occurs as the tetrahedrally coordinated, pentavalent arsenate AsO43- (in oxidising environment), and the trivalent arsenite AsO33- (under weakly reducing to reducing conditions), while Sb is entirely found as the octahedrally coordinated, pentavalent antimonate Sb(OH)6-, over a wide redox potential range. Several low-grade materials (zeolite, biochar) and building waste (concrete slurry waste) in original and surface modified forms were tested as selective adsorbents of As and Sb oxyanions from contaminated waters. The adsorption stability of oxyanions was verified by the Langmuir adsorption model. In natural systems As oxyanions demonstrated the preferential affinity for iron (Fe) oxides/hydroxides, while Sb oxyanions were more selectively binded to organic matter (OM). The adsorption of tested oxyanions on Fe/Mn modified sorbents ran with a higher efficiency (?95%) compare to original materials, with a decreasing trend: As(V) ? Sb(V).