Nano-zero-valent iron (nZVI) nanopowder is an iron particle with a particle size between 1 and 100 nm. Its specific surface area and reactivity are much larger than ordinary iron filings and iron powder. It can be directly injected into the heavily polluted area of the water environment to form an efficient in-situ reaction zone, which can control water pollution flexibly, efficiently and at low cost. nZVI nanopowder can not only degrade various halogenated hydrocarbons, but also degrade some organic pollutants containing no halogen elements, adsorbing or degrading heavy metal ions and various inorganic anions in water. nZVI water repair technology has been applied in developed countries and is rapidly being promoted. The influence of in-situ site factors on nZVI water repair effect is an important development direction in this field in the future. The effective dispersion and migration of nZVI in water environment is the main breakthrough point for nZVI for water restoration in the future.

1. Characteristics of nano zero-valent iron

Nano-zero-valent iron has large specific surface area and high reactivity. The specific surface area analysis (BET) results are 35m2·g-1. The nano-zero-valent iron has strong reducibility and is easily oxidized into iron oxide Fe2O3 or Fe3O4 during the reaction.The nano-zero-valent iron has a spherical structure with an average size of 60 nm and an 80% particle size of between 50 and 100nm.The nano-zero-valent iron has a core-shell double structure, and the core is a solid zero-valent iron Fe0, which is a diffusion ring structure of a metal iron body-centered cubic crystal, surrounded by a thin oxide shell FeOOH, and the shell thickness is mostly 2~ The 4 nm, FeOOH shell structure is considered to be intrinsic to nano-zero-valent iron, that is, the FeOOH passivation layer is formed when nano-zero-valent iron is synthesized. Due to the magnetic and electrostatic attraction, the nano-zero-valent iron tends to form a chain structure, which is usually cluster-like and has a continuous oxidation shell, but the metal core is separated from each other by a thinner oxide film. And the oxide layer is amorphous, which may be because the radius of the nano-zero-valent iron is small, the curvature of the oxide layer is large, and a large tension is generated to hinder the formation of crystals.

2.Nano-zero-valent iron degrading pollutants

Nano-iron can catalyze the reduction of various organic halides, such as halogenated alkanes, halogenated olefins, halogenated aromatic hydrocarbons, organochlorine pesticides and other refractory organic pollutants can be converted into non-toxic or low-toxic compounds. At the same time, it improves its biodegradability and creates favorable conditions for further biodegradation. Whether it is nano-iron or zero-valent iron, when the surface is loaded with a metal catalyst, the dehalogenation rate is significantly improved. At present, more palladium-iron bimetals are studied, but the price of palladium is relatively expensive. The method of modifying nano zero-valent iron can significantly improve the dechlorination effect, and has the advantages of wide application range and high degradation efficiency.

3.Degradation of inorganic substances

3.1Nitrogen and phosphorus removal

By adding nano-iron in the SBR system, it is found that the addition of nano-iron promotes the removal effect of the disc acid salt, and the removal efficiency of the disc acid salt increases with the increase of the concentration of nano-iron. The iron concentration was 400 mg/L and the rate reached 97.69%. When the concentration of nano-iron is 20 and 50 mg/L, there is no significant effect on the removal of nitrogen. However, when the concentration of nano-iron is 200 mg/L, although the ammonia nitrogen can be completely removed, the rate of ammonia reduction is significantly lower than that of the other groups.

3.2 Bromate

Supported nano-zero-valent iron (nZVI/AC) particles were prepared by liquid phase reduction using activated carbon as carrier and FeSO4 and NaBH4 as raw materials, and their structures were characterized by XRD, SEM and TEM. In addition, the effects of different materials, initial pH, nZVI dosage and coexisting ions on the removal of bromate from nZVI/AC were investigated. The results indicate that the removal mechanism of BrZ3- by nZVI/AC includes two mechanisms of adsorption and reduction and a synergistic effect between nZVI and AC.

At all, as a potential water environment restoration method, nano-zero-valent iron provides a new technology platform for the water environment.

SAT NANO can supply nano iron powder nZVI to used on water treatment, if you have any enquiry, please feel free to ask us a price and samples.