Removal of Antimony from Water by Nano Zero-Valent Iron/Activated Carbon Composites

Abstract

Nano zero-valent iron/activated carbon (nZVI/AC) composites were prepared via liquid phase chemical precipitation and then characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and Brunauer-Emmett-Teller theoretical methods for an analysis of the structure, morphology, physical and chemical characteristics of the composites. The effects of the reaction system, nZVI loading, initial pH, and dosage on antimony removal were investigated and the removal mechanisms were discussed. These results indicate that nZVI/AC can be successfully prepared via liquid phase chemical precipitation. In an N2 atmosphere, a dosage of 0.2 g·L-1, 15% nZVI/AC with an initial pH of 7.5 (the pH of raw water) was prepared. After a reaction duration of 2 h, the removal rate of Sb(Ⅴ) had reached 76.2% and the effluent concentration had decreased to only 23.8 μg·L-1. These results show that Fe2+ plays a major mechanistic role in the removal of Sb(Ⅴ) from the system and is the major active substance in the reaction process. In combination with an analysis of elemental Sb on the surface of the nZVI/AC before and after reaction, the removal process relies on the reduction of Fe(0) and Fe2+, Sb(Ⅴ) reducted into Sb(Ⅲ) and through adsorption removal.