PhD Oral Exam - Mitra Bahri, Civil Engineering

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Every year, indoor air pollution is responsible for the premature death of millions of people worldwide. This fact highlights the importance of improving indoor air quality (IAQ) in in areas including sustainable buildings. Among different air pollutants, volatile organic compounds (VOCs) constitute a major part of indoor pollutants. The proven negative impact of these compounds in occupants’ health has motivated researchers to develop different air treatment technologies for the removal of VOCs.

Development of plasma-based methods, and their remarkable capabilities for VOCs degradation, has motivated designers to employ these methods as indoor air purification. It has been demonstrated that utilizing a dual functional adsorbent/catalyst (DFA/C) in a plasma system can significantly enhance the VOCs removal and energy efficiency of such an air purifier. However, selecting an appropriate DFA/C is a challenge to achieve the best performance in these systems.

For the first time, this research attempted to utilize metal organic frameworks (MOFs) as DFA/Cs for a plasma-driven catalytic reactor. Accordingly, three different MOFs, MIL-101 (MIL: Metal institute Lavoisier), MIL-53, and CPM-5 (CPM: Crystalline Porous Material-5), were synthesized through microwave, solvothermal and mechanochemical methods. To test the performance of these DFA/Cs, a dielectric barrier discharge (DBD) system was designed and implemented as a non-thermal plasma (NTP) set-up. During preparation and evaluation experiments, different characterization and analytical instruments, including X-ray diffraction (XRD), Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), BET surface area analyzer, Fourier transform infrared spectroscopy (FTIR), Gas Chromatogram/Mass Spectrometer (GC/MS), Ozone monitor, and VOC Photoionization detector (PID), were utilized.

Several adsorption and oxidation experiments were conducted to study physical and chemical behaviors of MOFs for the removal of one (1) ppm toluene and isobutanol on MIL-101, MIL-53 and CPM-5. Also, the effect of the presence of 30% relative humidity on the adsorption capacity and oxidation ability of each MOF was investigated. Results showed physisorption of VOCs on all MOFs during the course of adsorption tests. Moreover, the stable structure of the examined MOFs before and after plasma-catalytic reactions indicated a facile regeneration of catalysts. During the plasma-catalytic oxidation of toluene and isobutanol, different organic by-products and ozone were detected either in dry or humid conditions for all MOFs.

MIL-101 and MIL-53 exhibited much higher adsorption and oxidation ability compared to CPM-5 in most of the experiments. Results demonstrated a higher adsorption capacity and almost the same oxidation efficiency of MIL-101 compared to MIL-53 in dry air. Nevertheless, the negative influence of humidity on adsorption and oxidation efficiency of MIL-101 was more significant than in MIL-53.

In conclusion, results demonstrated the potential capacity of MOFs as DFA/Cs in a NTP system.