Comparison of Hydrogen Peroxide Quenching with Activated Carbon and Mineral Catalysts

1 online resource (48 pages) : PDF

2016

University of North Carolina at Charlotte

Advanced oxidation is an advanced water treatment process used for treating impaired drinking water sources, among other applications. Commonly, hydrogen peroxide (H2O2) is used with ultraviolet (UV) light to create hydroxyl radicals that oxidize organic matter. Due to the low molar absorptivity of H2O2, not all of it gets used for oxidation and residual H2O2 will remain after treatment. When advanced oxidation is used for drinking water treatment, residual chlorine is required for distribution purposes. Any residual H2O2 is oxidized by free chlorine and ultimately more chlorine is needed to achieve a target chlorine residual concentration. In order to create a more efficient chlorine residual addition, the residual H2O2 is removed prior to disinfection. Highly porous granular activated carbon (GAC) is commonly used as a catalyst to quench the H2O2 residual. The pores can be fouled over time by organic matter and surface can be oxidized by the H2O2 that is present in the water, and therefore GAC must be reactivated periodically increasing overall cost of water treatment. This study explored other alternatives for quenching the H2O2 residual, specifically mineral catalysts that would not be as susceptible to fouling by organic matter. Reaction rates for several mineral catalysts were evaluated in batch experiments and normalized to the mass and surface area of the catalyst. The catalysts performed during batch tests in the order of GAC>activated alumina> aluminum oxide>iron (III) oxide> titanium oxide> zinc >magnesium oxide. Column testing was performed with the most feasible mineral catalysts based on rate of H2O2 decomposition and applicability to full-scale processes, and compared to GAC. Further column testing was done with the most promising catalysts aluminum oxide and iron (III) oxide. Through column optimization, the aluminum oxide catalyst was able to successfully lower initial H2O2 concentrations from 10 mg/L to 2.2 ± .3 mg/L at a 60 minute empty bed contact time (EBCT), time the solution is exposed to the catalyst, for 2.5 hour run time. Past the 2.5 hour run time, the hydroscopic nature of aluminum oxide caused a decrease in catalytic activity due to exposure to aqueous H2O2 solutions which was further confirmed through batch testing. Column testing with iron (III) oxide confirmed it to be an effective inorganic catalyst in quenching 10 mg/L H2O2 influent to 0.070 ± 0.004 mg/L effluent concentration at a 2.5 minute EBCT, proving it to be a viable alternative to GAC.

masters theses

Environmental engineering

M.S.

Advanced Oxidation
Hydrogen Peroxide Quenching
Mineral Catalyst

Civil Engineering

Keen, Olya

Amburgey, James
Khire, Milind

Thesis (M.S.)--University of North Carolina at Charlotte, 2016.

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Gleason_uncc_0694N_11198

http://hdl.handle.net/20.500.13093/etd:1175