Research On The Efficiency And Mechanism Of Remediation Of Heavy Metal Contaminated Environment By Zero-valent Iron Nanoparticles

Due to rapid development of industrialization and agricultural production,Heavy maetals discharge into the surface and groundwater, by atmospheric deposition,wastewater discharge, soil erosion, rain leaching and erosion and other ways. Heavy maetals may be immobilized within suspended particles, organisms or some other organic compounds, and eventually enriched in sediment. It result in dramatically incresed pollution of sediment. Under certain environmental conditions(Seasonal variation, disturbance of water p H, redox potential, etc.), heavy metals which are partitioned in the sediment can be potentially remobilized and thereby become bioavailable. This process affects the quality of the upper water and lead to secondary Pollution. Because of their acute toxicity, persistence, non-biodegradable nature and tendency for biological accumulation, Heavy maetals especially Cr(VI), can causes harmful effect to humanity and environment. Therefore, heavy metals have been identified as serious environmental contaminants of worldwide concern. Traditional treatment methods used to heavy metals removal have certain disadvantages such as high cost, energy requirements and generation of secondary pollution. It is thus of necessity to effectively remediate the heavy metal contaminated environment.Recently, nZVI has been widly application for remediation the heavy metal contaminated groundwater and soil because of its high reactivity and larger surface area. In order to more clearly understanding their remediation efficiency and mechanism, we have conducted many studies. Modified nZVI synthesised through liquid phase reduction, was modified with Sodium dodecyl sulfate(SDS) by sonicated. The prepared nanoparticles were characterized by field emission scanning electron microscope(FSEM), energy-dispersive spectrometry(EDS), Fourier transform infrared spectrophotometer(FTIR) and zeta potential. Then we could analysis the basic physical structure of nZVI, such as surface morphology, element composition and surface charge. In order to reveal the stability of prepared SDS-n ZVI, we study the kinetics of particle aggregation and sedimentation, and analysis variation of particle size.The prepared modified nZVI was applied for removal Cr(VI) from wastewater,and studied its removal efficiency. Eventually, the optimal environmental conditions for the removal of Cr(VI) from wastewater by modified nZVI were optimized andselected. We determined the maximum removal capacity and equilibrium time by batch Studies. Additionally, modified nZVI as a reactive media for remediation of Cr(VI) contaminated sediment, and studied its removal efficiency. To estimate the effectiveness of modified nZVI for Cr(VI) immobilization, toxicity characteristic leaching procedure(TCLP) tests were performed. We builded adsorption kinetics model to investigate adsoption capacity of modified nZVI and critical factors limiting the reaction rate, furhter to reveal type and distribution of binding site between modified nZVI and Cr(VI). Meanwhile, we investigate adsorption mechanism of modified nZVI with building adsorption isotherms model. Then we determined the type of sorption. Acoording these studies, we analysis the behavior mechanism of contaminated environment remediation with modified nZVI in detail. This project aims to provide a method reference and scientific support for heavy metals contaminated environment remediation, and promote the development of critical technologies and theories of heavy metals contaminated environment remediation to achieve effective treatment and improve the ecological environment.