01. PhD Thesis

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Browsing 01. PhD Thesis by Subject "ag2co3"

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    TIO2- AND AG2CO3-BASED PHOTOCATALYSIS FOR REMOVING EMERGING POLLUTANTS FROM WATER
    (Nazarbayev University School of Engineering and Digital Sciences, 2024-09-04) Mergenbayeva, Saule
    Water plays a vital role as an essential natural resource that supports the development of life and human endeavors. Large volumes of water are consistently polluted with various pollutants, including emerging pollutants (EPs). EPs are a group of persistent pollutants like pharmaceuticals and personal care products (PPCPs), dyes, and endocrine-disrupting compounds (EDCs). Many of them result from overuse, and their presence can cause serious health issues. However, conventional water treatment technologies are not specifically designed to remove these kinds of pollutants. In this study, advanced oxidation processes (AOPs) utilizing newly developed TiO2 and Ag2CO3-based photocatalysts were applied to remove several model EPs. The catalysts were synthesized using various preparation methods and then characterized to investigate their crystal structure, morphology, elemental composition, and optical characteristics using XRD, Raman spectroscopy, SEM, TEM, EDS, BET analysis, and UV-Vis DRS spectroscopy. Firstly, TiO2 combined with Ti2O3 (mTiO), calcined at various temperatures, was used to degrade 4-tert-butylphenol (4-tert-BP) under simulated solar light. Among the catalysts, mTiO calcined at 650°C (mTiO-650) achieved the highest degradation and mineralization performance, achieving approximately 90% and 50%, respectively. The phase transformation and surface area of the calcined catalysts played a significant role in enhancing their photocatalytic activity. Additionally, the presence of various anions (NO3−, Cl−, HCO3− and CO32−) and humic acid (HA) in water was evaluated for its effect on 4-tertBP degradation. In addition, potential pathways for the degradation of 4-tert-BP were suggested. This study marks a significant advancement with the successful preparation of mTiO-650 catalyst capable of eliminating of 4-tert-BP in water. Secondly, mono- and co-doped TiO2 catalysts were synthesized using simple impregnation methods. Mono-doped Mo@TiO2 and W@TiO2 improved the adsorption capacity and reduced the energy gap (Eg), while co-doped catalysts, namely CuMo@TiO2 exhibited distinct adsorption properties and slightly enhanced degradation performance. CuMo@TiO2 fully degraded 4-tert-BP under UV light in 60 min and achieved 70% degradation under solar light in 150 min, marking the first application of both mono-doped and co-doped TiO2 catalysts for degrading 4-tert-BP in water, emphasizing their potential in environmental remediation, and introducing a novel pathway for efficient photocatalyst synthesis. Moreover, TiO2 doped with Fe (Fe@TiO2) was successfully synthesized via the wet impregnation method. Surface morphology was analyzed using SEM and TEM, while EDS confirmed the incorporation of Fe into TiO2. Fe@TiO2 demonstrated enhanced light absorption in the 200–365 nm range compared to bare TiO2. The photocatalytic performance of the catalyst was assessed in a continuous flow system for the degradation and mineralization of 4-tert-BP under UV light (254 nm). Fe doping slightly improved the degradation efficiency, with 87% of 4-tert-BP degraded in 60 min, compared to 82% with bare TiO2. Furthermore, Fe@TiO2 catalyst achieved 49.6% mineralization of 4-tert-BP. Additionally, Ag@TiO2 catalysts were also developed for reducing 4-nitrophenol (4-NP) to 4-aminophenol (4-AP), with Ag@TiO2-21 achieving 98.3% 4-NP reduction within 10 min. Moreover, Ag@TiO2-21 displayed strong antibacterial activity, with minimum inhibitory concentration (MIC) values ranging from 0.5 to 1 mg/mL against B. subtilis, E. coli, S. aureus, and P. aeruginosa. This study introduces Ag@TiO2 catalysts for efficient elimination of 4-NP from water, showcasing significant antibacterial activity. This research highlights the potential of Ag@TiO2 catalysts for environmental applications and offers a novel approach to developing effective photocatalysts. Furthermore, TiO2@zeolite (TiO2@Z and TiO2@ZSM) catalysts were tested for the degradation and mineralization of sulfamethoxazole (SMX) under UV (365 nm) light. The TiO2@ZSM1450 catalyst achieved complete SMX degradation within 10 min and mineralized 67% of SMX in 120 min. The effect of anions (NO3−, Cl−, and CO32−) on the photocatalytic performance of the TiO2@ZSM1450 catalyst was also investigated. The study highlights the effectiveness of modifying TiO2 with zeolite for improved photocatalytic performance. Lastly, Ag2CO3 was employed for the photocatalytic degradation of 4-tert-BP, achieving 100% degradation within 60 min under solar light. The effect of key parameters, including 4-tert-BP concentration (2.5–10 mg/L), Ag2CO3 dosage (100–300 mg/L), various light sources, and the presence of different anions, was studied. The re-usability of Ag2CO3 remained effective after three successive experimental runs. This study introduces Ag2CO3 as a novel catalyst for 4-tert-BP elimination in water, emphasizing its potential in environmental applications and offering a new synthesis approach. The results of this Thesis have great significance in advancing water treatment technologies and provide original and novel alternatives for the elimination of EPs in water.