ANTIBACTERIAL ACTIVITY OF METAL OXIDE NANOPARTICLES UNDER VISIBLE LIGHT AND IN DARK

Author

Peerzada Ibna Far Madany, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2020

Degree Name

Master of Science

Department

Civil Engineering

First Advisor

Liu, Jia

Abstract

Due to a scarcity of water resources in different places across the world, treatment and reuse of wastewater come up as one of the first options for coping with this problem. Treatment and use of contaminated natural water bodies is another option. Application of nanoparticles (NPs) is an emerging technology for sustainable water treatment and use at a comparatively low cost. The main target of the first study was to establish an innovative and cost-effective disinfection method using metallic NPs to inactivate the bacteria in wastewater effluent. That is why in this study, a cutting-edge methodology using nanotechnology, to cure specific microbial contaminants, was investigated for treatment of wastewater effluent for its reuse. Five different types of metal oxide NPs named of γFe2O3, chitosan coated γFe2O3, αFe2O3/TiO2, TiO2 and γFe2O3/TiO2 were synthesized. For the synthesis of γFe2O3 and chitosan coated γFe2O3 wet chemical method was followed. In the case of γFe2O3/TiO2 and αFe2O3/TiO2 oxidation and co-precipitation method was followed. Characterization of the NPs was done by Dynamic Light Scattering (DLS), and Scanning Electron Microscopy (SEM)/ Energy Dispersive X-ray Spectroscopy (EDS). Characterization results showed that the NPs synthesized were uniformly sized, and the chitosan coated NPs were uniformly coated. Gram-negative Escherichia coli (E. coli) and Enterococcus concentrations of the collected wastewater samples were analysed. The effects of these NPs under both visible light and dark conditions on the E. coli and Enterococcus coliforms were analysed. The number of bacteria present after 1 h interaction was quantified by the nutrient agar plate cultivation after serial dilution. The γFe2O3 NPs (0.1-1000 mg/L) promoted the growth of bacteria under visible light condition. The αFe2O3/TiO2 NPs cured 89.6% of the bacteria colonies at 1 g/L concentration in dark condition. The TiO2 NPS showed the best result at a concentration of 1 mg/L in dark, which could cure 62% of the bacteria. Similar inactivation results were achieved using the chitosan coated γFe2O3 and γFe2O3/TiO2 NPs. These two NPs could totally cure bacterial contamination at a concentration of 1 g/L. To supplement the agar plate cultivation results, quantitative PCR tests were also conducted and compared with the agar plate test results under the same conditions. In the second study, the disinfection effect of γFe2O3/TiO2 NPs and chitosan coated γFe2O3/TiO2 NPs after direct interaction with wastewater effluent was tested. The wastewater samples were collected from Carbondale South East (SE) and Northwest (NW) Wastewater Treatment Plants. The NPs were mixed with wastewater effluent and allowed to interact in dark and under visible light conditions for 1 h. Both of these NPs cured at least 95.7% bacteria from wastewater effluent. The best results were again obtained from the application of γFe2O3/TiO2 NPs in dark condition, which cured 98.8% of total coliforms and 99.5% of E. coli from wastewater effluent. Also, the effect of presence of organic contaminant Perfluoro octane sulfonic acid (PFOS), Perfluoro nonanoic acid (PFNA) in wastewater effluent was investigated. And the result showed that the bacteria inactivation was more than 96% for all the samples. In the third area of study, the effect of γFe2O3/TiO2 NPs on harmful algal blooms (HABs) present in the Campus Lake of Southern Illinois University Carbondale was investigated. Cyanobacteria (also called blue-green algae) are known microorganisms that can produce HABs. The γFe2O3/TiO2 NPs were synthesized in the lab in the same way as in the previous two chapters. Water samples from different points of the lake was collected. The amount of algae present in the lake water was quantified by both quantitative PCR method and chlorophyll A test. The effect of γFe2O3/TiO2 NPs on the toxic cyanobacteria species after 1 h interaction was quantified by the qPCR method. The results after interaction with the γFe2O3/TiO2 NPs indicated significant decrease in the toxic cyanobacteria species as well as the total cyanobacteria concentration in the lake water.