Immobilization and transformation of co-existing arsenic and antimony in highly contaminated sediment by nano zero-valent iron.

Arsenic (As) and antimony (Sb) are usually coexistent in mine wastes and pose a great threat to human health. The As immobilization by nano zero-valent iron (nZVI) is promising, however, the stabilization for co-occurring As and Sb is not known. Herein, the immobilization and transformation of As and Sb in nZVI-treated sediments were evaluated using complementary leaching experiments and characterization techniques. Raw sediment samples from a gold-antimony deposit revealed the co-existence of ultrahigh As and Sb at 50.3 and 14.9 g/kg, respectively. Leaching results show that As was more efficiently stabilized by nZVI than Sb, which was primarily due to the soluble fraction that was readily absorbed by nZVI of As was higher. As the nZVI treatment proceeds, the oxidation and reduction of As and Sb occur simultaneously as evidenced by XPS analysis. The primary oxidant, hydroxyl radicals, was detected by EPR studies, proving the occurrence of nZVI induced Fenton reaction. This study sheds light on differences in the interaction and immobilization of nZVI with Sb and As in co-contaminated sediments.