Structural incorporation of As5+ into hematite.

Hematite (α-Fe2O3) is one of the most common iron oxides and a sink for the toxic metalloid arsenic. Arsenic can be immobilized by adsorption to the hematite surface; however, the incorporation of As in hematite was never seriously considered. In our study we present evidence that, besides adsorption, the incorporation of As into the hematite crystals can be of great relevance for As immobilization.

Ba2Gd2(Si4O13): a silicate with finite Si4O13 chains.

The title compound, dibarium digadolinium(III) tetrasilicate, crystallized from a molybdate-based flux. It represents a new structure type and contains finite zigzag-shaped C(2)-symmetric Si(4)O(13) chains and Gd(2)O(12) dimers built of edge-sharing GdO(7) polyhedra. The [9+1]-coordinated Ba atoms are located in voids in the atomic arrangement.