Evaluation of the Degradation of Methylene Blue Using Photocatalytic Materials

Non-point organic pollutants in groundwater, stormwater, wastewater, and drinking water are a growing problem in the environment, which lack effective and efficient treatment technologies. Photocatalytic treatment of organic contaminants in aqueous or liquid mediums has gained interest due to their potential for effective degradation. Common industrial treatment practices utilize a slurry reactor, suspending the photocatalyst in the contaminated solution. However, photocatalytic slurry reactors are hindered by solution turbidity, dissolved salt content, and absorbance of light. Research presented here introduces two novel engineered material combinations which immobilize the photocatalyst for effective and sustainable degradation of organic pollutants, one in-situ and one ex-situ. Methylene blue was chosen as a surrogate contaminant for both studies considering well studied degradation pathway literature. The in-situ method investigates immobilizing titanium dioxide in cement paste by functionalizing it with maleic anhydride (Ti-MAH). This process not only immobilizes the photocatalyst but also increases the reactivity of the catalysts. Preparation of the Ti-MAH is performed by permanently bonding the maleic anhydride to titanium dioxide in methanol, drying and powdering residual material, and then inter-grinding the preparation with cement during mixing. When compared with OPC, the Ti-MAH cured cement paste is more reactive under a wider range of light wavelengths, possesses a higher band gap, sustains this heightened reactivity over multiple testing iterations, and treats organics effectively. Amorphous silica within the calcium-silica-hydrate, C-S-H, is theorized to bond to the powdered Ti-MAH during curing. Verification of silica bonding to the titanium by way of MAH was demonstrated by FTIR spectra, SEM imagery, and XRD. Creating a sustainable and passive photocatalytic cement that precisely bonds silicon to the Ti-MAH is useful for organic contaminant in urban stormwater but use can translate to other applications because the Ti-MAH bonds readily with any amorphous silica such as glass materials, paints and coatings, optics and LEDS, among many others. The ex-situ method introduces the development and application of a novel, photocatalytic, porous silica-based granular media (SGM) to be used in a packed bed column reactor. SGM retains the cross-linked structure developed during synthesis through a combination of foaming agent addition and activation temperature. The resultant media has a high porosity of 88%, with a specific surface area averaging 150 m²/g. Photocatalytic capabilities are further enhanced as the resultant structure fixes the photocatalyst within the translucent matrix. SGM is capable of photocatalysis combined with diffusion of nucleophiles, electrophiles, and salts from the pore space. The photocatalytic efficiencies of SGM at various silica contents were quantified in batch reactors using methylene blue destruction over time and cycles. Methylene blue concentrations of 10mg/L were effectively degraded (>90%) within 40 minutes. This effectiveness was retained over multiple cycles and various methylene blue concentrations. SGM is a passive and cost-effective granular treatment system technology which can translate to other organic contaminants and industrial processes. The two treatment methods use varying processes and materials to meet the fundamental goal of immobilizing the photocatalysts for a sustained attack on organic pollutants. The studies present the experimental methods of both remedial technologies in sequence from material development and immobilization of the photocatalysts to assessment of reactivity and longevity. Herein, batch reactors are utilized to individually test each photocatalytic material and determine their feasibility to be up-scaled into an onsite pilot-test.

Name thesis:degree_name

M.S. (Master of Science)

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Civil Engineering (UMKC)

Grantor

University of Missouri--Kansas City

Year dc:date.issued

2021

Author dc:creator

• McIntyre, Hannah M.

Advisor dc:contributor.advisor

• Hart, Megan Leanore, 1976-

Handle dc:identifier.uri

https://hdl.handle.net/10355/85281

OAI identifier oai:identifier

oai:mospace.umsystem.edu:10355/85281