Date of Award

8-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Environmental Engineering

Advisor

Karanfil, Tanju

Committee Member

Lee, Cindy M

Committee Member

Ladner, David A

Abstract

Titanium dioxide nanoparticles (TiO2 NPs) are one of the most common nanomaterials used in nano based products. They are used as antimicrobial, antibiotic, and antifungal agents, ultraviolet (UV) blockers, antiscratch additives, and catalysts, because TiO2 NPs have high specific surface area and sorption capacity for ionic and nonionic species, and ultraviolet (UV) reflecting capabilities. However, TiO2 NPs could enter human body through skin, food, inhalation and drinking water, and cause potential adverse effect, including production of oxidation radicals, genotoxic effects, and inflammation and neurotoxic effects.
The main objective of this study was to examine the efficiency of conventional drinking water treatment processes (coagulation, flocculation, sedimentation, and filtration) in removing the TiO2 NPs, since potable water consumption is one of the possible pathways for the NPs to enter the human body. In the absence of regulations, drinking water treatment plants are currently not designed and operated for the removal of NPs. Moreover, there are limited numbers of studies regarding the removal of NPs using conventional treatment process in the literature.
A systematic experimental investigation was conducted to understand the effects of initial TiO2 NP concentration, the TiO2 NP coating, different coagulants (alum vs. ferric chloride), pH and the presence of natural organic matter (NOM) on the removal of TiO2 NPs.
Results showed higher degree of TiO2 NP removal with increasing TiO2 concentration from 0.5 mg/L to 5 mg/L. For 90% removal of uncoated TiO2 NP, 10 and 40 mg/L of alum were required at pH 6.5 in distilled and de-ionized (DDI) water, respectively. Better removal of uncoated than SiO2 coated TiO2 NPs was also observed. The performance of alum (Al2(SO4)3*18H2O) and ferric chloride(FeCl3) were similar (90% removal at 120 mg/L coagulant in Hanahan water at pH 6.5), but ferric chloride was better for NOM removal (40% vs. 30% at 80 mg/L coagulant and pH 6.5). NOM had a significant effect on the removal of NPs. The presence of NOM increased the required alum dose from 20 mg/L in DDI water to 80 mg/L in a 3 mg TOC/L model NOM water to accomplish 85% removal of the NPs. The pH of 5.8 resulted in higher removals of TiO2, turbidity and TOC as compared to pH of 6.5. For TOC removal, 60% was achieved at 60 mg/L alum in pH 5.8 solution, while 31% was removed at pH 6.5, which is related to the properties of NPs, coagulants and NOM.
Overall, this study showed the effect of different factors (initial TiO2 NP concentration, TiO2 NP coating, natural organic matter/natural waters, pH and coagulant type) on the removal of TiO2 NPs from water during conventional drinking water treatment processes. Although conventional treatment processes appear to be effective in removing NPs, it was also noted that removal efficiencies decreased with decreasing NP concentrations in water. Additional research is recommended to further examine the removal of NPs from water at much lower concentrations than used in this study.

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