Tiny Fe-Ni batteries accelerate soil decontamination

Soil contaminated with chlorinated aliphatic compounds can be remediated ten times faster than with biological or iron-based methods by use of a new metallic powder developed by Tosoh Corp. (Tokyo; edlinks.chemengonline.com/6514-532). The powder, called MA-FN20, electrochemically strips the chlorine atoms from the pollutants, producing soluble chloride ions and volatile organic compounds (VOCs), which can then be recovered by conventional methods. MA-FN200 is a powder composed of 50–100-µm particles of iron with 0.3 wt.% nickel. The nickel is present as small spots on the iron particles, and the particles act like tiny batteries when introduced into moist soil. The iron serves as the anode, liberating electrons when Fe metal is oxidized to Fe+2, and the nickel spot works as the cathode, refducing chlorinated aliphatic hydrocarbons (with water) into Cl– (and OH–) ions and VOCs. The MA-FN200 reducing agent is simply dispersed into soil, onsite, in doses of about 1–3 wt.%, and the little batteries do their work during a period of 3–14 days, depending on the temperature (between 5 and 30°C). The process completely decomposes chlorinated aliphatic hydrocarbons, including tetrachloroethylene, trichloroethylene…