Nanoparticle Deposition with Controlled Density and Placement

DeStefano, Audra
Hydraulic fracturing utilizes water containing chemical additives and propping agents to increase oil and gas production in low-permeability reservoirs. Recent increase in the use of hydraulic fracturing to develop oil shales has resulted in a rise of water usage in well completion processes. Stimulating a single well can use up to five million gallons of water, with between ten and thirty percent of that water being returned to the surface in the form of flowback water. Flowback water is contaminated with hydraulic fracturing additives and naturally occurring organic compounds, making it unsafe for immediate reuse and resulting in fiscal and environmental costs. Using ultrafiltration membrane modules shows promise in treating flowback water for reuse, but has been held back by fouling attributed to dissolved organic compounds and high total dissolved solids. In this presentation, we focus on addressing membrane fouling resulting from dissolved organics by using catalytic nanoparticles to modify commercial membrane surfaces. Catalytic nanoparticles, such as hydrophilic TiO2, convert fouling organic molecules to smaller molecules such as CO2 and H2O. Existing deposition methods, such as dip coating, result in poor nanoparticle dispersion and, consequently, particle aggregation, which significantly reduces water flux. We demonstrate that this problem can be mitigated by optimizing nanoparticle deposition using polymeric membranes that have different surface properties and pore sizes. We have studied in-situ deposition in liquid phase via covalent bonding and a well-controlled, self-limiting deposition approach in vapor phase. Both methods improved nanoparticle dispersion and performance of the resulting membranes.
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