Browsing by Author "Fan, Jingjing"
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Item Biodegradation of graphene oxide-polymer nanocomposite films in wastewater(Environmental Science: Nano, 7/20/2017) Fan, Jingjing; Grande, Carlos David; Rodrigues, Debora F.The synthesis of polymer nanocomposites has been extensively investigated by many researchers, however, the end of life fate of polymer nanocomposites is still largely unknown. It is expected that at the end of their service life, these polymer nanocomposites will most likely end up in soil and water systems where microorganisms will interact and, perhaps, even biodegrade them. In this study, we investigate the ability of wastewater microorganisms to biodegrade nanocomposite films containing different graphene oxide (GO) loads (0% to 0.6%, (w/w%)) embedded in a model biopolymer (i.e. chitosan). The ability of wastewater microorganisms to grow and form biofilms on the surface of the nanocomposite films was determined by live and dead staining assisted with confocal laser scanning microscopy. The capability of wastewater biofilms to biodegrade nanocomposites was assessed through nanocomposite film weight losses, Fourier transformed infrared (FTIR) and scanning electron microscopy (SEM) analyses. Results showed that microorganisms present in the activated sludge can grow on the surface of the nanocomposites and biodegrade the polymer surrounding the graphene oxide nanoplatelets. As the biopolymer gets degraded, there is increasing exposure of GO on the surface, which yields microbial inactivation and biofilm growth inhibition. To determine the evolution of the toxicity of the nanocomposite during biodegradation. We determined the emergence of the sharp edges of GO on the surface of the nanocomposite through atomic force microscopy (AFM), as well as the production of reactive oxygen species (ROS) with the Ellman's assay before and after biodegradation of the nanocomposites. The results show that as GO surfaces the nanocomposite film during biodegradation, there is increasing production of ROS, which explains the increasing inactivation of the microorganisms.Item Real-Time Monitoring Technology and Nanotechnology Applications on Different Environmental Scenarios(2018-05) Fan, Jingjing; Rodrigues, Debora F.; Rifai, Hanadi S.; Vipulanandan, Cumaraswamy; Louie, Stacey M.; Willson, Richard C.Sensing technology has been widely applied in environmental oil detection. This research proposes for the first time the use of confocal laser fluorescence microscopy (CLFM) as an enabling technology to quantify oil prior to produced water disposal. This method takes advantage of the self-fluorescing properties of oil to visualize and quantify in 3D oil droplets in water in real-time. This study initially involves the optimization of CLFM measurement parameters, followed by investigation of CLFM measurement accuracy and precision changes under various environmental condition. Interfacial tension analyses in combination with the Derjaguin, Landau, Verwey, and Overbeek (DLVO) calculation were employed to gain a better understanding of how environmental conditions affect oil droplets stability and therefore impact the precision of CLFM measurements. Finally, the quantification of oil content in three different real produced water samples were compared between CLFM and the EPA 1664 method. This technology has several advantages over other methods, such as solvent free and can be automated for real-time online applications. In addition of investigating CLFM as a sensing technology, this research also explores nanotechnology for environmental applications. We demonstrate for the first time that suspensions of single-layered MoS2 nanosheets can act as photocatalytic antimicrobial materials under visible light in the presence of electron donor. Ex-MoS2 with the presence of EDTA could inactivate 97% and 65% of planktonic and mature E.coli K12 biofilms, respectively, without significant cytotoxicity to mammalian fibroblast cells. The suspension of single-layered MoS2 nanosheets opens up new opportunities for the development of advanced functional nanomaterials for biomedical and environmental applications. In addition, the end of life fate of nanocomposites is also an important aspect to take into consideration for nanotechnology application. In this study, we investigate the ability of wastewater microorganisms to biodegrade nanocomposite films containing different graphene oxide (GO) loads embedded in a model biopolymer (i.e. chitosan). Results showed that microorganisms present in the activated sludge can grow on the surface of the nanocomposites and biodegrade the polymer surrounding the graphene oxide nanoplatelets. As the biopolymer gets degraded, there is increasing exposure of GO on the surface, which yields microbial inactivation and biofilm growth inhibition.Item The Influence of Salinity, pH, Temperature and Particles on Produced Water Oil Quantification Precision and Accuracy with Confocal Laser Fluorescence Microscopy(Energy and Fuels, 5/24/2018) Fan, Jingjing; Louie, Stacey M.; Rodrigues, Debora F.The present study investigates the effects of different produced water parameters, such as salinity, pH, temperature, and presence of colloidal particles, in oil quantification using confocal laser fluorescence microscopy (CLFM). The study simulates different produced water samples, which typically contains a mixture of oil, salts, and different concentrations of particles. The accuracy of the quantification was not affected by the environmental condition for any of the conditions investigated. On the other hand, under extreme environmental conditions, such as high pH (pH 8), salinity (250000 ppm), and temperatures (60 °C), the precision of the CLFM oil quantification was reduced. Changes in the average oil droplet size upon variation of the environmental conditions generally correlated with the change in CLFM measurement precision. Interfacial tension and DLVO interactions were further evaluated to gain a better mechanistic understanding of how the environmental conditions affect the size or colloidal stability of the oil droplets and therefore impact the precision of CLFM measurements. To obtain an overall understanding of the relationship of the different environmental parameters and oil droplet properties with the level of CLFM measurement precision, multiple correspondence analysis (MCA) and multiple regression analysis were employed. The results showed that conditions of lower salinity, temperature, and SiO2 concentration, as well as neutral pH (pH 7), favor smaller oil droplet sizes (close to 4 ?m) in the oil-in-water emulsion and more precise CLFM measurements. The better understanding of the impact of different water chemistries on oil droplet stability will be essential for decision-makers on conditions that could impact the precision of the method. This work presents a new perspective of investigating CLFM as an oil-in-water quantification technology and guidance for engineers operating this novel technology on the optimum environmental conditions to achieve the best performance of the technology.Item The synergism of temperature, pH and growth phases on heavy metal biosorption by two environmental isolates(Journal of Hazardous Materials, 8/30/2014) Fan, Jingjing; Okyay, Tugba O.; Rodrigues, Debora F.In real environmental applications, such as heavy metal bioremediation, microorganisms are generally not kept at their optimum growth conditions; therefore, it is imperative to investigate their heavy metal removal performance under diverse environmental conditions. The present study aims to investigate the effects of pH, temperature and growth phases on the removal of Cu2+ and Cr6+ by two environmental isolates identified as Ochrobactrum intermedium LBr and Cupriavidus metallidurans CH34. Results showed that cells in logarithmic phase presented better biosorption capacity than cells in stationary phase for both isolates. The Cr6+ metal was removed more efficiently by live O. intermedium LBr than dead cells; while dead C. metallidurans CH34 biosorbed better than live ones. It was also found that the pH and temperature affected the biosorption capacity. The optimum temperatures were determined to be 37 °C and 27 °C, and the optimum pH values were 6 and 7 for O. intermedium LBr and C. metallidurans CH34, respectively. Additionally, both microorganisms preferentially adsorbed Cu2+ in Cu2+/Cr6+ mixtures. The main mechanism of adsorption was determined to be through carboxylic, hydroxyl, and amino functional groups.