High reactive nano zero-valent iron produced via wet milling through abrasion by alumina

Abstract

The performance of new nano zero-valent iron (nZVI) particles produced by a promising new milling method in organic solvent was examined. The basic feature of the new process involves the addition of abrasive alumina particles having an average particle size of 5 μm during milling. The milled particles with alumina had a specific surface area exceeding 20 m2·g−1 as well as high percentages of Fe(0) content of 75–80%. The reactivity against Cr(VI), Trichloroethylene, and Tetrachloroethylene was determined and in all cases, the removal capacity of the milled particles was higher than that of commercial available nZVI particles. This high reactivity may be related to the absence of a thick and continuous oxide layer on the surface, the high disorder levels of the metallic structure and the large number of reaction sites. Sedimentation tests revealed very good suspension stability, while in mobility tests, the particles could be distributed throughout the column length. The results showed a low tendency to agglomerate in aqueous solution. This behaviour has been attributed to two factors related to the milling process: first, the high ζ-Potential found in the particles, which enhances electrostatic repulsion. The second factor is the significant decrease of saturation magnetization of the milled particles with alumina in comparison with the values of the commercial nZVI particles, leading to a reduction in magnetic interparticle interaction. This decrease may be related to the introduction of a significant carbon content in the iron particles (0.65–1.35%wt, depending on the sample) and the presence of a highly deformed nanostructure.