Aggregation and Transport of Nanoscale Zerovalent Iron Particles in Model Groundwater Systems

Released on by Mohan Basnet
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  • Aggregation and Transport of Nanoscale Zerovalent Iron Particles in Model Groundwater Systems Book Detail

  • Author : Mohan Basnet
  • Release Date : 2015
  • Publisher :
  • Genre :
  • Pages :
  • ISBN 13 :
  • File Size : 49,49 MB
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Aggregation and Transport of Nanoscale Zerovalent Iron Particles in Model Groundwater Systems by Mohan Basnet PDF Summary

Book Description: "Nanoscale zerovalent iron (NZVI) particles are promising engineered nanomaterials for the in situ remediation of various environmental contaminants into innocuous products. In field applications, direct injection of NZVI into the subsurface has been suggested as a promising technique for achieving rapid remediation. However, challenges have been encountered in field application that includes passivation, aggregation and limited transport. Therefore, the success of site remediation using NZVI depends on the progress made to increase nanoparticle reactivity, reduce aggregation and improve mobility. The overall objective of this research was to evaluate the aggregation and transport behavior of NZVI particles in environmentally relevant model groundwater environments. Palladium-doped NZVI (Pd-NZVI) was chosen to ensure heightened reactivity towards the contaminants to address the passivation problem whereas particle surface-modification with stabilizing polymers was investigated to reduce particle aggregation and concurrently improve transport. In this study, rhamnolipid biosurfactant was proposed for the first time as a novel stabilizing surface-modifier and its efficacy was compared with previously proposed surface-modifiers (carboxymethylcellulose and soy protein). By monitoring changes in particle hydrodynamic diameter as a function of time using dynamic light scattering followed by a systematic assessment of transport behavior in sand packed columns, it is shown that while bare Pd-NZVI is prone to rapid aggregation surface-modified Pd-NZVI exhibited good colloidal stability and improved transport at low ionic strengths (10 mM). In particular, rhamnolipid significantly enhanced transport even at much lower concentrations than the other surface modifiers (10 mg/L compared to 100 mg/L). However, an increase in solution ionic strength influenced both aggregation and transport behavior. Nonetheless, at the highest ionic strength tested, the transport of rhamnolipid-coated Pd-NZVI was significantly higher than that of Pd-NZVI coated with other surface modifiers suggesting that rhamnolipid is most suitable in field application.The transport potential of surface-modified Pd-NZVI was further examined in granular matrices of varied complexities: in quartz sand, in loamy sand and clay-amended quartz sand over a wide range of environmentally relevant ionic strengths. Data suggests that collector geochemical composition and heterogeneity can dramatically alter Pd-NZVI transport potential; markedly reduced transport potential was observed in loamy sand than in quartz sand.Given that microbes and biofilms are ubiquitous in the subsurface environment, the role of biofilm on Pd-NZVI transport was investigated by using biofilm-coated quartz sand to pack transport columns. Transport results showed heightened Pd-NZVI retention in the presence of biofilms suggesting that biofilms may act as a collector surface for nanoparticle retention in the groundwater environment. A viability assay suggests that the retained Pd-NZVI is non-toxic to the Pseudomonas aeruginosa cells in biofilms. However, some inhibitory effect was observed to planktonic bacterial cells. Finally, considering the cost associated with the use of Pd, an alternative reactive nanoparticle, sulfidated NZVI (S-NZVI), was also studied whereby the aggregation and transport behavior of S-NZVI was systematically investigated in a wide range of environmentally relevant water chemistries. Data suggests that sulfidation can influence NZVI surface electrokinetic properties, and thus its stability and transport in granular matrices.Overall, this study makes a major impact in the field of environmental remediation as it addresses key aspects of nanotechnology-enabled site remediation, particularly aspects pertaining to nanoparticle surface coating, collector grain physical, geochemical and biological heterogeneity, and groundwater chemistry." --

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