Application of nanoscale metallic particles for removal of VOCs from contaminated air | |
| Author | Amornpon Changsuphan |
| Call Number | AIT Diss. no.EV-12-03 |
| Subject(s) | Volatile organic compounds Nanoparticles |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Engineering and Management |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. EV-12-03 |
| Abstract | The performance of ZnO nanoparticle (nZnO) coatingson 13X zeolite and activated carbon (AC)inadsorption and catalytic oxidation of benzene at ambient temperature,and the performance of nZnO coatingson 13X zeolite incatalytic oxidation ofbenzene, toluene and ethylbenzene(BTE) were investigated using laboratory scale systems. Morphology analysisbyscanning electron microscope(SEM),wavelength dispersive X-ray Spectroscopy(WDX)and Brunauer EmmettTeller(BET) surface area analysiswere conducted to confirmthat the adsorbentsurface was properly coated by nZnO at the anticipated ratios of Zn to adsorbent materials. The results of the BET surface area analysis showed that the coating with nZnO resulted in a reduction of surface area of both zeolite and AC as compared to the virgin adsorbents. Theexperimentson removal efficiency (RE)were conducted in presence of UVandO3separately and UV+O3combined.For benzene adsorption and catalytic oxidation at ambient temperature, an airstream containing 5ppm of benzene was fed into a reactor filled with either of the coated adsorbents investigated, zeolite or AC,at the Zn to adsorbent ratioof0.5:1.0.The differences betweenthe experiments in average removal efficiency (Avg RE)for benzene were notsignificant except for the experiment with coated zeolite which showeda higher Avg RE of97.9±0.9%as compared to the94.2±2.4%ofthe virgin zeolite experiment. Thecombination of nZnOand eitherUV,O3orUV+O3 could combinetheeffectsof adsorptionand oxidation, thusslightlyincreasingtheAvg REfor benzene. Thebedbreakthrough test results revealed thatthe coating significantly reduced the service time (the period before breakthrough)ofbothcoated adsorbents (zeolite and AC) underall experimental conditions. The final product (CO2) and various intermediate products found in the outlet stream confirmed a potential competing adsorption.To investigate thecatalytic oxidation, the coated adsorbents were first saturated with VOCs by purging an inlet air stream containinga mixture of benzene, toluene and ethylbenzene (BTE) at 5ppmfor 28 min through the coated adsorbents. Coated 13X zeolite ataZn to zeolite ratio of 0.5:1.0 waschosento study its catalystcapacity. At ambient temperature, the highest Avg RE was observed for the coated adsorbentwith O3while at 100oC bed temperature,the coated zeolitecombined with UV+O3yielded the highest RE. Withafurther increase in bed temperatureto 400oC, significant improvements in the RE were observedforall three compounds. A decrease in the Gas Hour Space Velocity (GHSV) showedto increasetheAvg RE which was attributed to the corresponding increase in residence time resulting in morecompleteoxidation reactions. WiththeZn to zeolite ratio increasingfrom 0.2:1.0 to 0.5:1.0, the benzene Avg RE increased by 0.5%/%Zn increasedwhile therewereno significant differencesintoluene and ethylbenzeneremoval. AtaZn to zeolite ratio of 1.0:1.0,the BTE Avg RE decreased for all 3 compounds. Theeffects of the BTE inlet concentration on RE were investigated and the results show that theBTE AvgREdecreased with an increase in the inlet concentration from 5 ppm to 50 ppm while a further increase from 50 ppm to 100 ppm hadno significant effect. Over anoperation time extended to 6 hours, the BTE Avg.RE stabilizedat 50%, 70% and 90%for benzene, toluene and ethylbenzene,respectively. Beside the final productof CO2in the outlet streamandvariousintermediate VOC products were also observed.A Preliminary cost analysis shows that the coated zeolite with a Znto zeolite ratio of 0.2:1.0under the experimental conditionswith a combination ofUV+O3,a GHSV of 818h-1and a bed temperature of 300oC wasmore cost efficient (32 USD/g of BTE removed) thanvirgin zeolite and virgin ACwithout UV+O3input at ambient temperature. The continuous ivadsorption-regeneration process achieved under said conditions largelyeliminated the need for regeneration and also resulted in the lowest waste generation (4.5g/g BTE removed)as compared to the other two adsorption systems. Further studies should be conducted at a bigger scale and with higher VOC inlet concentrations inorder to develop this system towards application in industrial emission control |
| Year | 2012 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. EV-12-03 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Environmental Engineering (EV) |
| Chairperson(s) | Nguyen Thi Kim Oanh |
| Examination Committee(s) | Visvanathan, Chettiyappan ;Nazhad, Mousa M, ;Tepwitoon Thongsri |
| Scholarship Donor(s) | National Science and Technology Development Agency(NSTDA), Thailand |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2012 |