Pore-scale investigation of the use of reactive nanoparticles for in situ remediation of contaminated groundwater source.

Nanoscale zero-valent iron (nZVI) particles have excellent capacity for in situ remediation of groundwater resources contaminated by a range of organic and inorganic contaminants. Chlorinated solvents are by far the most treated compounds. Studies at column, pilot, and field scales have reported successful decrease in contaminant concentration upon injection of nZVI suspensions in the contaminated zones. However, the field application is far from optimized, particularly for treatments at-or close to-the source, in the presence of residual nonaqueous liquid (NAPL). The knowledge gaps surrounding the processes that occur within the pores of the sediments hosting those contaminants at microscale limit our ability to design nanoremediation processes that are optimized at larger scales. This contribution provides a pore-scale picture of the nanoremediation process. Our results reveal how the distribution of the trapped contaminant evolves as a result of contaminant degradation and generation of gaseous products. We have used state-of-the-art four-dimensional (4D) imaging (time-resolved three-dimensional [3D]) experiments to understand the details of this degradation reaction at the micrometer scale. This contribution shows that the gas released (from the reduction reaction) remobilizes the trapped contaminant by overcoming the capillary forces. Our results show that the secondary sources of NAPL contaminations can be effectively treated by nZVI, not only by in situ degradation, but also through pore-scale remobilization (induced by the evolved gas phase). The produced gas reduces the water relative permeability to less than 1% and, therefore, significantly limits the extent of plume migration in the short term.

Enhanced anaerobic digestion performance of food waste by zero-valent iron and iron oxides nanoparticles: Comparative analyses of microbial community and metabolism.

The effects of zero-valent iron (ZVI) and iron oxides nanoparticles on anaerobic digestion (AD) performance of food waste (FW) were comparably clarified in this study. Results indicated that the nanoparticles supplement effectively enhanced the methane yields. As observed, these nanoparticles accelerated organics transformation and alleviated acidification process. Also, the enriched total methanogens and functional bacteria (e.g., Proteiniphilum) were consistent with the promotion of oxidative phosphorylation, citrate cycle, coenzymes biosynthesis and the metabolisms of amino acid, carbohydrate, methane. Additionally, these nanoparticles stimulated electron transfer potential via enriching syntrophic genera (e.g., Geobacter, Syntrophomonas), primary acetate-dependent methanogens (Methanosaeta, Methanosarcina) and related functions (pilus assembly protein, ferredoxins). By comparison, ZVI nanoparticle presented the excellent performance on methanogenesis. This study provides comprehensive understanding of the methanogenesis facilitated by ZVI and iron oxides nanoparticles through the enhancement of key microbes and microbial metabolisms, while ZVI is an excellent option for promoting the methane production.

α-Hydroxy acids modified ß-cyclodextrin capped iron nanocatalyst for rapid reduction of nitroaromatics: A sonochemical approach.

This study reports a sonochemical approach for the synthesis and catalytic performance of zerovalent iron nanoparticles (nZVI) capped with two cyclodextrin (CD) crosslinked polymers derived from Lactic acid and Citric acid (CDLA and CDCA respectively). The polymers and the catalysts were characterized by NMR, FTIR, HRTEM, DLS, Zeta potential, FESEM, EDAX, VSM, XRD, XPS, TGA analysis. The catalysts proved to be sustainable and recyclable for rapid sonochemical reduction of nitroaromatics under ambient conditions. The isolated yield of the derivatives was found to be greater than 90%. The results suggest excellent dispersibility, stability, high iron content and smaller size of CDLA polymer capped nZVI compared to CDCA capped nZVI, leading to two-fold higher catalytic activity. The effect of various crucial catalysis parameters was investigated and optimized. The scope of the reaction was extended to other nitroaromatics under the optimized conditions. Being magnetically separable, the cost effective and non-toxic catalysts exhibited high recycling efficiency (~13 cycles), high turnover number (TON) and turnover frequency (TOF). The recyclable catalysts could be low-cost and sustainable options for organic transformation in water via sonochemical approach in aqueous medium.

ROS-mediated heme degradation and cytotoxicity induced by iron nanoparticles: hemoglobin and lymphocyte cells as targets.

Nanoparticles (NPs) due to their small size and high surface area induce remarkable adverse effects on the biological systems. However, the exact mechanism by which NPs interacted with biological system and induce their adverse effects is still an enigma. Herein, the interaction of zero valent iron NPs (ZVFe NPs) with human hemoglobin (Hb) was evaluated using a variety of techniques including circular dichroism, fluorescence, and UV-visible (UV-vis) spectroscopy methods. Also, the cytotoxicity of ZVFe NPs on the human lymphocyte cell line as a model of blood system cell line was investigated by reactive oxygen species (ROS), caspase-9, and caspase-3 activities assays. It was revealed that ZVFe NP interaction resulted in heme displacement and degradation and induction of protein cabonylation. It was also shown that ZVFe NPs impaired the complexity of lymphocyte cells through ROS generation and apoptotic pathway. Together, these data suggest that NPs influence the biological system and induce adverse effects through ROS generation.

Probing the interaction of zero valent iron nanoparticles with blood system by biophysical, docking, cellular, and molecular studies.

Human exposure to nanoparticles (NPs) is inevitable as NPs become more widely applied and, as a result, nanotoxicology study is now gaining attention. Herein, the interaction of zero valent iron NPs (ZVFe-NPs) with human hemoglobin (Hb) was evaluated using a variety of techniques including fluorescence spectroscopy, far circular dichroism (CD) spectroscopy as well as docking study. Also, the cytotoxicity of ZVFe-NPs on the human lymphocyte cell line as a model of blood system cell line was investigated by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), acridine orange/ethidium bromide (AO/EB) staining, flow cytometry, and real-time PCR assays. Fluorescence studies revealed that ZVFe-NPs bind to Hb via hydrogen bonds and induced conformational changes of Hb in a static denaturation mechanism. CD experiment showed that Hb retained its native structure in the presence of ZVFe-NP. Molecular docking study also demonstrated that polar residues of Hb provide convenient medium to establish hydrogen bonds with water molecules on ZVFe-NP surface. Likewise, it was also revealed that ZVFe-NPs impaired the viability of lymphocyte cells through apoptotic pathway. For NPs to move into the clinical area, it is crucial that nanotoxicology research provide pivotal information about the adverse effect of NPs against biological systems.