Wang, ShaobinDuan, XiaoguangHu, Kunsheng2023-04-122023-04-122022https://hdl.handle.net/2440/137898Microplastics (MPs) have been discovered in different ecosystems around the world due to their light weight, and facile formation from large-size plastic fragmentation. Though the effects of MPs on human are still vague, evidence of their negative impacts has been discovered in various microorganisms and marine animals. Wastewater treatment plants (WWTPs) could remove most of MPs in water, but a large amount of MPs is still being discharged to the environment. In the meantime, additives and raw materials of plastics could be released and cause negative effects. Therefore, a system that can in-situ degrade MPs in the aqueous environment is required for water security. However, current plastic treatment technologies are more suitable to centralized plastic treatments or in the soil environment. Advanced oxidation processes (AOPs) have been demonstrated as a powerful method to degrade recalcitrant organic pollutants. Thus, this PhD research aims to utilize and develop AOP systems and find methods that can remove MPs and corresponding additives and raw precursors. In this thesis, the properties, types and effects of MPs have been summarized, and the recent research progress of plastic treatment methods in aqueous systems have been illustrated (Chapter 2). This section aimed to understand the current technologies in MPs removal, and figure out that AOPs are of high potential for in-situ MPs removal in water compared to traditional MPs removal technologies. The first experimental part presented in this thesis focuses on developing AOPs hydrothermal systems to degrade MPs with high efficiencies. In Chapter 3, a thermal Fenton system was designed to degrade MPs at hydrothermal reactions. It was found this system could cause over 90 wt% of MPs weight loss after 12 hours of reaction. The degradation was mainly attributed to the mass production of •OH. In addition, the filtrated solution demonstrated non-toxic effects on microorganisms, indicating the generated intermediates are totally green to the environment. In Chapter 4, in reducing the oxidant dosage in the remediation process, peroxymonosulfate (PMS) was used with MnOx as the catalysts. It was found that -MnO2 was the most stable catalyst that could achieve a reasonable weight loss of MPs. The second research part of this thesis emphasized on the removal of MPs additives and plastic feedstock, because the manufacture of primary MPs or fragmentation of macroplastics could release additives and unreacted raw feedstock to the environment. In Chapter 5, annealed nanodiamonds (NDs) was used as the co-catalyst to enhance the Fenton system to degrade diethyl phthalate (DEP), which is a commonly used plasticizer. It is proposed that the higher sp2/sp3 ratio of NDs could enhance the Fe(III)/Fe(II) circulation and result in higher DEP removal efficiency. In Chapter 6, phenol was chosen as the plastic raw feedstock pollutant to test the efficiency of porous carbon on PMS activation. In this study, a hierarchically ordered porous carbon doped with Co single atoms was synthesized. The porous architecture enhanced the mass transfer and increased active site exposure for PMS activation, eventually enhancing the radical generation and electron-transfer processes. To sum up, in this thesis we introduce the current development of plastic treatment and show current AOPs to remove not only MPs but also the accompanied released additives and raw feedstock chemicals. The outcomes provide foundations for future research on finding a one-pot universal system to remove MPs-related pollutants.enMicroplastics, Advanced Oxidation Processes, Additives, Carbonaceous materialsThesis