Structural incorporation of As5+ into rhomboclase ((H5O2)Fe3+(SO4)2 · 2H2O) and (H3O)Fe(SO4)2.

摘要: Iron sulfates represent an essential sink for the toxic element arsenic in arid and semi-arid mining areas with high evaporation rates. Information about structural incorporation of As(5+) iron sulfates, however, remains scarce. Here we present evidence heterogeneous substitution S(6+) by crystal structure rhomboclase ((H5O2)Fe(3+)(SO4)2 · 2H2O) its dehydration product (H3O)Fe(SO4)2. Rhomboclase (Rhc) was synthesized presence molar As/Fe ratios 0, 0.25, 0.5, 0.75 1.0, resulting As loads 0.0, 0.93, 1.44, 1.69 1.87 wt.%, respectively. The unit cell parameters Rhc increase from 9.729(6), 18.303(2), 5.432(1) A a, b, c, to 9.745(9), 18.332(5), 5.436(8) when is crystallized at a ratio 1. Simultaneously, crystallite size decreased 304 176 nm. In situ (H3O)Fe(SO4)2, investigated powder X-ray diffraction, shows that starts dehydrate 76 °C, which completed 86 °C. does not impact start or end temperatures but accelerate dehydration. absorption fine spectroscopy (EXAFS) reveals S(6+), (H3O)Fe(SO4)2 structure, replaced As(5+), while polymerization AsO4-tetrahedra FeO6-octahedra during formation results strong distortion AsO4-tetrahedron.