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The nanoscaled zero-valent iron (nZVI) supported zeolite MCM-41 composites (nZVI/MCM) were synthesized, and applied for the immobilization of Cr(VI) from aqueous solutions. The precise role of MCM-41 and nZVI in the immobilization and reduction of Cr(VI) was characterized using SEM, TEM, HRTEM, HRTEM-EDS, XPS and EXAFS techniques. Comparing to the bare nZVI nanoparticles, the as-synthesized nZVI/MCM composites showed higher efficiency on Cr(VI) immobilization due to the high synergistic effect of Cr(VI) reduction by nZVI and sorption by MCM-41. The morphology and visualizing analysis indicated that nZVI was uniformly distributed on the surfaces of MCM-41, which reduced the aggregation of nZVI apparently and thereby increased the reduction activity. XPS and EXAFS analysis showed that nZVI could promote Cr(VI) reduction into Cr(III), and the sorption and reduction reactions were occurred on bare nZVI. MCM-41 acted as a scavenger for the insoluble products, which could improve the reduction activity of nZVI. The high performance of nZVI/MCM composites showed the promising strategy for the efficient decontamination of Cr(VI) pollution in environmental pollution cleanup. [ABSTRACT FROM AUTHOR]

In this paper, nanoscale zero-valent iron (NZVI), which has great potential in environmental purification is introduced. However, NZVI is easy to accumulate and oxidize, which limits its ability to remove pollutants. Hence several modified NZVI are proposed to overcome its shortcomings in this paper. The heavy metal ions, radionuclides and organic pollutants in the environment are removal by NZVI based materials, and their removal behaviors had been analyzed. This paper also reviews the factors affecting the removal of pollutants by NZVI-based materials, such as pH, ionic strength, contact time, reaction temperature, interfering ions and humic acids. In addition, it is also introduced that NZVI is toxic in the environment, and it also can be recovered and has different removal effects in different water environment. In short, this paper gives a comprehensive summary of NZVI, including its modification methods, pollutants removal, influencing factors of pollutants removal and implication to environment. It provides a strong theoretical basis for the future development of NZVI based materials. [Display omitted] • The characteristics of NZVI-based materials are briefly introduced and summarized. • The removal mechanisms of different pollutants are highlighted. • The influence factors and environmental implications are analyzed. • Future researches of NZVI-based materials in water remediation are discussed. [ABSTRACT FROM AUTHOR]