Hafnium [Hf, 72]

Hafnium (Hf), a metal of the group 4 in the periodic table of elements, has crystallographic and chemical properties very analogous to those of Zr, a metal of the same group. Its terrestrial abundance ranges between 3 and 5 mg/kg, and similar contents are in igneous rocks. Hafnium is used mainly in filaments and electrodes, and in nuclear industries, especially in power plants. Hafnium oxide nanoparticles were reported to be used in the radiotherapy, as a promising anticancer agent for human patients. The common range of Hf in plants is 0.01–0.4 mg/kg. Although Hf is slightly available to plants, plants growing in soils amended with sewage sludge contain elevated amount of Hf, up to, on an average, 3 mg/kg. The metal dust presents a fire and explosion hazard. It is completely insoluble in water, saline solutions, and body chemicals. Exposure to Hf can occur through inhalation, ingestion, and eye or skin contacts.