The groundwater remediation based on injection of nanoscale zero-valent iron (nZVI) particles is a well-known technology successfully demonstrated at numerous localities and supported by array of laboratory studies. The main target application of such technology is the reduction of various chlorinated solvents (like TCE, PCE, etc.) and Cr(VI), but laboratory-scale experiments proved the nZVI applicability for elimination of tens organic and inorganic compounds. However, the main limitations of such technology include low selectivity of nZVI particles (including unwanted side-reactions), low stability of nZVI suspension (i.e., during storage) and limited migration of nZVI particles in groundwater conditions. To avoid such handicaps, various surface modifications have been employed (using of surfactants, polymers and chemical modifications) and broad range of nanocomposites have been developed where nZVI particles are deposited on inorganic substrates (carbon black, clay minerals, nanoscale TiO<sub>2</sub>, etc.). Out of many different approaches to enhance above-mentioned aspects of nZVI functionality, the chemical modification of nZVI particles by sulfur turned out recently to be technologically simple, cheap and environmentally acceptable. In this presentation, results of four different modification methods will be demonstrated: three wet-chemical and one gas-solid method to modify pre-formed nZVI particles (NANOFER 25P from NANO IRON Company, Czech Republic), with non-modified nZVI as a reference. The modified nZVI particles were characterized in detail by robust combination of XRD, XPS, HR-TEM with elemental mapping, <sup>57</sup>Fe Mössbauer spectroscopy and SQUID magnetometry (and also BET surface area and Zeta-potential measurement); mobility in 1D geometry (glass columns filled with quartz sand); reactivity (removal of CHC and CrVI from model solutions and from real contaminated waters); toxicity and evaluation of long-term stability. The results shows that sulfidation process does not significantly alter the key characteristics of nZVI particles (metallic iron content, particle size and other physical parameters), but it led to the dramatic increase of nanoparticle reactivity, migration and long-term stability of nZVI suspension. The suggested modification method (i.e., surface sulfidation of pre-formed nZVI particles) turned out to be one of the highly-promising and cheap way, how to significantly enhance nZVI performance in technologies of groundwater treatment.

Sulfidized nZVI particles for groundwater treatment: Synthesis, complex characterization and laboratory-scale testing

253rd National Meeting (2017)

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