A new approach to the environmental remediation of trichloroethylene (TCE) using functional iron/silica aerosol particles.

摘要

The objective of this dissertation is to remediate groundwater contaminants such as trichloroethylene (TCE) by functional particles. The porous silica particles with zero valent iron were synthesized by an aerosol-assisted process and subsequent gas or liquid phase reduction. The surface properties of these particles were carefully controlled through silanol modification to realize the suitable particle affinity with target contaminants.; While aerosol silica particles incorporating nanoscale zero valent iron are reactive for groundwater TCE remediation, environmentally benign silica particles serve as effective carriers for nanoiron transport through soil. The presence of surface silanol groups on silica particles makes possible the surface property control via silanol modification using organic functional groups. This leads to preferred partition of particles on TCE/water interface. Additionally, aerosol silica particles with functional groups such as ethyl tails on the surface preferentially adsorb hydrophobic TCE during environmental remediation. This increases the local concentration of TCE in the vicinity of iron, thus promoting TCE degradation by iron.; The morphology of silica particles with iron can be controlled through introducing cetyltrimethyl ammonium bromide (CTAB) as the template. Solid silica particles with disordered mesostructure can be obtained at low CTAB concentration. A novel translation from solid particles to hollow spheres was observed at increased CTAB concentration. Low solubility of ferric chloride in ethanol has been found to be the key for such transition and a reasonable formation mechanism of hollow spheres will be proposed. Further thermal reduction of encapsulated ferric ions produces zero valent iron nanoparticles inside silica hollow spheres. The reactivity and partition characteristics of hollow particles with iron will also be discussed.