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Enhancing Biological Removal Yield of Microplastics Using Advanced Oxidation Processes (AOPs)

Shamsi, Zahra | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 56732 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ghasemian, Saloumeh; Yaghmaei, Soheila; Ghobadinejad, Zahra
  7. Abstract:
  8. Statistics show that plastic production in the world is increasing, with 335 million tonnes in 2016 reaching 367 million tonnes in 2020. Since the presence of plastics in the dimensions of micro and nano, especially in aquatic environments can have adverse effects on human health and other living organisms, it has raised major environmental concerns. Therefore, it is necessary to think of measures to remove them and develop efficient methods for eliminating and decomposing microplastics. Recently, the advanced oxidation processes have attracted much attention because of the ability to eliminate recalcitrant compounds. In this study, electrochemical techniques and Fenton-based techniques for removing two types of microplastics, PVC and LDPE were investigated. The electrochemical oxidation of microplastics was evaluated using a Box-Behnken design using Design Expert software. The effect of 3 variables of time, electrolyte concentration and voltage were studied. It was observed that in optimal conditions, 270 minutes, the electrolyte concentration of 0.135 M and voltage of 10 kV, LDPE microplastic weight loss was 11.2%. In addition, other advanced oxidation methods, including Fenton, Electro-Fenton and Fered-Fenton, were investigated to achieve a more efficient technique. The results showed that the Fered-Fenton method results in the highest percentage of removal, 30.6% for PVC and 27.4% for LDPE. Microplastics were also subjected to SEM-EDX, FTIR, XRD and GC-MS analyzes. SEM images showed fractures and scratches on the surface of the treated microplastics. The EDX elemental analysis indicated the presence of oxygen element in the treated particles; This confirmed the results of FTIR analysis of the creation of oxygen groups after oxidation via Fered-Fenton technique. In addition, XRD analysis indicated the PVC amorphous structure and semi-crystal LDPE. Also reduced peak intensity and reduced crystallinity index for LDPE microplastics, and peaks shift to smaller angles and increased interplanar spacing for PVC microplastics were the results of XRD analysis, which also confirms the emergence of carbonyl and hydroxyl groups on the sides of carbon chains. GC-MS analysis also detect the intermediate compounds created during the process, which mainly included compounds with aldehyde, ether, alcohol, ester and epoxide groups. It is also worth noting that the difference in the weight loss of PVC and LDPE can be attributed to the features of these polymers such as density and amorphous or semi-crystalline structure
  9. Keywords:
  10. Microplastics ; Water Treatment ; Advanced Oxidation Process ; Fenton Method ; Electrochemical Oxidation ; Biological Removal ; Low Density Poly Ethylene(LDPE)

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