Study On The Stability And Microbial Toxicity Mechanism Of Embedded Nanometer Zero - Valent Iron

Nano zero-valent iron(n ZVI), as an inexpensive and environmentally friendly reducing agent, has been widely used for polluted soil, groundwater and wastewater remediation with both in situ or ex situ applications. At present, studies have demonstrated that n ZVI was effective for degrading a range of common environmental contaminants. However, one of the major issues associated with n ZVI was that it was easy to agglomerate into large particles due to intrinsic magnetic interaction and van der waals forces, limiting the practical application of n ZVI. In addressing this issue, it is necessary to modify n ZVI with several types of coatings or to load n ZVI onto an appropriate support to enhance its stability and reactivity. Despite the widespread and enormous potential use of n ZVI for environment remediation, there are growing concerns about the biological harm that may be caused by the n ZVI materials because these particles are easily exposed to human, animals and microorganisms. Therefore, it is necessary to assess and address the toxic effects of these n ZVI materials on microbial activity.In this paper, n ZVI/partly-graphitized carbon(n ZVI/PGC) composites were prepared using a carbothermal synthesis method,and the synthesized n ZVI particles were distributed uniformly on the graphitized carbon skeleton, which has the advantage in surface area, stability and reactivity. The composite materials were characterized using X-ray diffraction(XRD), nitrogen adsorption/desorption, thermogravimetry(TG), Scanning electron microscopy(sem), and to investigate the removal capacity of pollutants by degradating Rh B. At the same time, n ZVI and Si O2 coated n ZVI(n ZVI@Si O2) were prepared by a solution reduction method, and to investigate the toxic effects of the three kinds of n ZVI particles on E coli cells.The results show that:(1)The most stable and active Fe/Fe3O4/PGC composite exhibits high removal efficiency of rhodamin B(Rh B), and the removal efficiency of Rh B was improved by increasing dosage of sample, and decreasing p H value and concentration. There were no obvious difference of the main crystalline phases among the samples before and after use, and storage for 15 days in air, which indicate that the Fe/Fe3O4/PGC composite is quite stable.(2)Through the measure of growth curve and the number of baterial colonies, we can see that could inhibit the growth of E coli, and the inhibitory activity is more evident in intoxicated group.(3)By investigate the comparative effects of the three kinds of n ZVI composites on E.Coli cells fluid conductivity and the biochemical index, we can see that the most obvious inhibitory effect is caused by the n ZVI without modified, which shows more toxicity than the other materials. This result shown that the n ZVI could attack E.coli cells when contacted with it to produce reactive oxygen free radicals, and lead the occurance of lipid peroxidation, the higher concentration, and the higher damage.