154 research outputs found
Phase-out of leaded gasoline: approaches and prospects for Lebanon
No full textAir pollution from urban traffic is a growing environmental problem worldwide. Emissions of lead resulting from the usage of leaded fuel are of particular concern due to associated health hazards. While many countries have accomplished or are in the process of phasing-out leaded gasoline, others continue to rely to a large extent on the use of high lead-content gasoline. Such is the case of Lebanon where the use of unleaded gasoline is hindered not only by the lack of direct governmental endorsement but also by the price difference in favour of leaded gasoline. While the phase-out of leaded gasoline is economically feasible, several measures should be undertaken for a successful transition to unleaded gasoline. This paper reviews the problem of lead addition into gasoline and the international experience in its phase-out. Policy measures and technical considerations for a successful transition to unleaded gasoline are described. Available data for Lebanon about the vehicle fleet characteristics, gasoline consumption and quality as well as lead emissions and concentrations in various environments are presented. This information forms the basis for developing a phase-out action plan outlining the interrelation and responsibilities of various agencies as well as measures to be adopted for a successful phase-out process
Socio-economic impacts of leaded gasoline and phase-out prospects in Lebanon - by Zaher Mohammad Hashisho
No full textTheses (M.S.)--American University of Beirut. Interfaculty Graduate Environmental Sciences Program (Environmental Technology), 2000;"Advisor : Dr. Mutasem El-Fadel, Associate Professor, Civil and Environmental Engineering--Member of Committee: Dr. GeorgeBibliography : leaves 171-182Lead is a toxic heavy metal. Nevertheless, it has been mined and used since more than 800 years ago. Among the different contemporary sources of lead pollution, emissions from the combustion of leaded gasoline is of particular concern, as it can constitu
Microwave -Swing Adsorption for the Capture and Recovery, or Destruction for a More Sustainable Use of Organic Vapors
No full text180 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007.The MSA-LR system successfully adsorbed organic vapor from the airstreams, allowed for rapid regeneration of the ACFC cartridge, and recovered the adsorbate as liquid for recycle and reuse. The MSA-SST system allowed accurate and precise control of the organic vapor concentration. Chemical treatment of the ACFC had a significant effect on ACFC's adsorption and regeneration properties. This research contributes to the development of novel vapor control techniques to effectively and economically control vapor emissions.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD
Measurement of Fugitive Greenhouse Gas Emissions from an Oil Sands Tailings Pond
No full textAlberta oil sands tailings ponds are under the concern of releasing greenhouse gases (GHGs) including carbon dioxide (CO2) and methane (CH4). In this research, Eddy Covariance (EC) technique was used to measure GHGs emissions from an oil sands tailings pond. A tower with EC instruments mounted on top was placed at the south bank of the tailings pond from July 27, 2017 to September 29, 2017. EC instruments mainly included gas analyzers for concentration measurements of both CO2 and CH4, and a 3D sonic anemometer for wind speed measurement. Collected data were processed using EddyPro software, and analyzed to show relationships between measured concentrations, calculated fluxes and potential impacting factors such as wind speed, wind direction, and temperature. The median concentration measurements of CO2 and CH4 over the entire measurement period are 385.3 ppmv and 3.0 ppmv, respectively. The median flux measurements of CO2 and CH4 are 6.8 g/m2/d and 6.5 g/m2/d, respectively as flux values over the entire measurement period. The footprint analysis of the flux measurements shows that the majority of source areas contributing to the flux values was within the boundary of the pond, when the EC tower was downwind of the tailings pond. The flux values obtained using EC were compared to previous flux measurements at the same tailings pond by flux chamber technique, and synchronous independent EC, flux chamber, flux gradient, inverse dispersion modelling (IDM) measurements by Environment and Climate Change Canada (ECCC). CH4 concentration measurements and flux calculations from this study were aligned with flux measurements reported by ECCC. The median CH4 flux measurements of this thesis of 6.5 g/m2/d is 12% different from the ECCC’s median flux measurements value of 7.4 g/m2/d. Concurrently historical flux chamber measurements of this target pond are lower than the EC flux measurements due to the inability of flux chamber to capture the heterogeneity of the tailings pond. Therefore, it is recommended to use EC for measuring GHG flux from oil sands tailings ponds
Evaluating the Performance of Activated Carbon, Polymeric, and Zeolite Adsorbents for Volatile Organic Compounds Control
No full textActivated carbon, zeolites, and polymeric adsorbents are commonly used adsorbents to remove Volatile organic compounds (VOCs) from industrial gas streams. To better understand of adsorbents performance for the removal of VOCs, adsorption capacity, cumulative heel and the influence of water vapor on VOCs uptake were investigated. For this purpose, five-cycle adsorption/desorption tests were completed for a single VOC, 1,2,4-Trimethylbenzene (TMB) and a mixture of VOCs (OAC-SST) using a fixed-bed of Optipore V503, BAC, ZEOcat Z700, ZEOcat F603, and ZEOcat Z400. To assess the effect of humidity on the performance of aforementioned adsorbents during the adsorption of TMB, adsorption experiments were conducted at 0% and 75% relative humidity (RH). The effect of water vapor on the adsorption of polar and non-polar VOCs on ZEOcat Z700 and ZEOcat F603 were measured, and the adsorption experiments were completed for TMB (non-polar) and 2-butoxyethanol (polar) adsorbate, at 0%, 45% and 75% RH. TMB adsorption capacities on Optipore V503 and BAC were 51% and 48%, respectively. Adsorption of OAC-SST on the same adsorbents show adsorption capacities of 45% and 43%, respectively. In case of zeolite, the adsorption capacities of ZEOcat Z700, ZEOcat F603, and Z400 were 16.4%, 10.2% and 2.1% for TMB and 16%, 14%, and 10% for OAC-SST, respectively, demonstrating a lower adsorption performance of zeolites compared to Optipore V503 and BAC. Moreover, cumulative heel buildup with Optipore V503 was noticeably lower compared to the other adsorbents used in this study although V503 was regenerated at 200ºC while BAC and zeolites were regenerated at 288ºC. A maximum of 3% impact of RH on TMB adsorption on BAC and Optipore V503 can be observed at 75% RH due to water vapor’s low affinity towards BAC and Optipore V503. However, there were 31% and 51% decrease in TMB adsorption on ZEOcat Z700 and ZEOcat F603, respectively at 75% RH. Moreover, the adsorption capacity of 2-butoxyethanol on ZEO F603 decreased by 7.5% and 18.0% at 45% RH and 75% RH, respectively. However, the adsorption capacity of 2-butoxyethanol on ZEOcat Z700 decreased by 15.6% and 20.8% at 45 % RH and 75% RH, respectively. The results of this study are helpful for understanding the adsorption performance of adsorbents and their capacities for VOC uptake under different humidity conditions
Microwave -Swing Adsorption for the Capture and Recovery, or Destruction for a More Sustainable Use of Organic Vapors
No full textThe MSA-LR system successfully adsorbed organic vapor from the airstreams, allowed for rapid regeneration of the ACFC cartridge, and recovered the adsorbate as liquid for recycle and reuse. The MSA-SST system allowed accurate and precise control of the organic vapor concentration. Chemical treatment of the ACFC had a significant effect on ACFC's adsorption and regeneration properties. This research contributes to the development of novel vapor control techniques to effectively and economically control vapor emissions.Made available in DSpace on 2015-09-25T21:04:23Z (GMT). No. of bitstreams: 2
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Previous issue date: 2007Embargo set by: Seth Robbins for item 84621
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Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDsRestricted to the U of I community idenfinitely during batch ingest of legacy ETDsU of I Only180 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2007
Tailoring Electrical Conductivity of Metal-Organic Frameworks for Electrothermal Swing Adsorption Applications
No full textMetal-organic frameworks (MOFs), particularly CuBTC, have shown the potential to revolutionize pollution control. CuBTC, in particular, has demonstrated superior efficiency and selectivity in removing volatile organic compounds (VOCs) from the air. However, the low thermal stability and strong affinities of MOFs with adsorbed materials complicate the recovery and reuse of the adsorbents.
Electrothermal regeneration utilizes the adsorbent's electrical resistivity against the electrical current to heat it, enabling rapid release and recovery of the adsorbate. However, it is not typically suitable for most MOFs due to their inherent electrical insulating properties, which hinder their ability to conduct electricity and generate heat.
The first phase of this study focused on the adsorption capabilities of CuBTC and FeBTC, two well-known MOFs with the same organic ligand but different metal centers. CuBTC, with its larger surface area, displayed higher efficiency at lower concentrations. FeBTC, on the other hand, showed a comparable ability to adsorb VOCs at higher concentrations, likely due to its larger pore volume. The study also noted challenges in regenerating these MOFs after 2-methylpyridine adsorption, likely due to strong chemisorption. However, effective desorption with other VOCs suggests that these adsorbents could be regenerated. These findings underscore the pollution control potential of CuBTC and FeBTC.
The second phase of this study was dedicated to improving CuBTC's electrical conductivity to facilitate electrothermal regeneration. By integrating carbon nanotubes (CNTs), porous carbon, and graphene during the synthesis process, the study achieved an electrical resistivity within the targeted range of 0.1 to 10 Ω.m while maintaining the MOF's adsorption properties. Notably, modifications with porous carbon effectively preserved CuBTC's surface area and adsorption capabilities, balancing between reduced electrical resistivity and adsorption capacity.
The second objective of the research's second phase was to examine various techniques for modifying CuBTC's electrical resistivity, including in-situ solvothermal, in-situ sonication methods, and post-synthesis modifications. X-ray diffraction (XRD) analysis confirmed that CuBTC's fundamental crystalline structure was preserved, while transmission electron microscopy (TEM) images demonstrated the even distribution of carbon-based materials. Additionally, TEM images revealed that the sonication-assisted synthesis method effectively prevented carbon cluster formation and thus reduced electrical resistivity. Thermogravimetric analysis (TGA) was employed to determine the thermal stability and amount of the modifiers in the final products, confirming their efficacy and ensuring sample durability under operational conditions. The study found that incorporating moderate amounts of carbonaceous modifiers, particularly through sonication, balanced the adsorption capabilities and resistivity of CuBTC. This drawback highlighted the superior effectiveness of carbon-based materials in achieving desired electrical characteristics while maintaining efficient adsorption properties.
In the third phase, electrothermal heating regeneration was compared to traditional thermal regeneration. CNT and porous carbon were incorporated into CuBTC and optimized for the best adsorption and electrothermal regeneration performance. Techniques used included in-situ sonication with CNT, in-situ solvothermal method with porous carbon, and post-synthesis physical mixing of porous carbon with CuBTC. These modifications reduced CuBTC's electrical resistivity while retaining its adsorption capacity. CuBTC was subjected to multiple adsorption-desorption cycles using traditional thermal and electrothermal regeneration techniques, effectively releasing adsorbed VOCs in both methods. However, the electrothermal regeneration process consumed considerably less energy and accelerated the regeneration process. This efficiency allows for shorter cycle times for continuous operation and demonstrates higher desorption efficiencies than traditional methods.
In conclusion, various modification methods were investigated to introduce electrical conductivity into MOFs while maintaining their adsorption characteristics. These methods were successful in producing samples that allowed for electrothermal regeneration. Adding carbonaceous modifiers to CuBTC has preserved its adsorptive properties while reducing its electrical resistivity, making it suitable for electrothermal regeneration processes. Electrothermal regeneration reached the desorption temperature of 120 °C in 13 to 15 minutes, with heating rates ranging from 8.2 to 9.6 °C per minute. The conventional method reached the same temperature in 48 minutes, with a heating rate of approximately 2.5 °C per minute. Over a 2-hour regeneration period, electrothermal regeneration consumed considerably lower energy than conventional, ranging from 142 to 242 kJ/g depending on the sample, compared to a consistent 600 kJ/g used by the conventional method. The electrothermal regeneration technique has outperformed conventional heating methods' energy efficiency and speed, promoting more sustainable and effective pollution control practices
Long-term Performance of Activated Carbon in Cyclic Adsorption/Regeneration of VOCs: Experimental and Modeling Investigation of Fixed Bed Adsorber
No full textActivated carbon (AC) has attracted tremendous interest in adsorption-based air treatment. Nonetheless, a major challenge associated with the use of ACs is the decline in adsorption capacity with time due to heel build-up (i.e., accumulation of non-desorbed species). Designing a reliable adsorption system requires a deeper understanding of the changes occurring during the long-term use of ACs. For this purpose, the effect of ACs' properties such as porosity and operational conditions such as purge gas flow rate on the long-term performance of ACs requires further investigation.
The objective of the present work was two-fold: first, to study the simultaneous effect of purge gas flowrate and activated carbon's porosity during prolonged cyclic adsorption/regeneration of three different ACs. Secondly, develop a model that can predict the long-term performance of ACs during adsorption/regeneration of a representative volatile organic compound (VOC). This section itself comprised two main stages: 1) Modeling the impact of heel on AC's pore size distribution (PSD), adsorption isotherm, and capacity, and 2) verifying the model using cyclic adsorption-desorption of 1,2,4-trimethyl benzene (TMB). The model predicts the cyclic adsorption capacity of AC by applying the Dubinin-Radushkevich-Langmuir (D-R-L) isotherm based on AC's limiting pore volume and adsorbate-adsorbent affinity coefficient.
For the long-term experimental study, six scenarios were investigated by varying the dry air purge gas flow rates 0.5 and 5 SLPM and the porosity of adsorbent used (44%, 60%, and 86% microporosity). The cyclic adsorption/regeneration experiment results indicated that the cumulative heel and the adsorption capacity followed ascending and descending trends with cycle number, respectively. Initially, the porosity and micropore volume of the adsorbents played a more important role in their performance. However, at higher cycle numbers, the effect of purge gas flow rate was more determinant in the performance of ACs. In the first five cycles, the two adsorbents with the highest micropore volume, G-70R, and B101412, showed similar heel build-up formation rates while B100772 with lower micropore volume (0.43 (cm^3)/g as opposed to 0.50(cm^3)/g) had slightly lower heel build-up. Alternatively, at the 20th cycle, purge gas flow rate had a clear effect on the performance and cumulative heel build-up of all three ACs regardless of their porosity. For all three adsorbents used in this study, samples regenerated with 0.5 SLPM all had an average cumulative heel of 31 %. Those regenerated with 5 SLPM Had a cumulative heel build-up average of 21%. The presence of mesopores and a hierarchal pore structure certainly helped reduce heel build-up in the micropores. DTG analysis of the samples showed that with an increase in purge gas flow rate, the nature of heel build-up starts to change and transform into heavier chemically formed compounds.
In the second part, two machine learning (ML) algorithms, multivariate linear regression (MLR) and Decision tree, were applied to predict Micropore volume reduction because of volatile organic compounds (VOCs) cyclic heel build-up on activated carbons (ACs). A dataset of 100 experimental tests of cyclic adsorption/regeneration of different VOCs on ACs with distinct properties was used. It was observed that micropore volume reduction could be predicted with acceptable accuracy with an R2 of 0.85 ± 0.08 using the MLR algorithm by considering the adsorbent characteristics, adsorbate properties, and regeneration conditions. The micropores prediction results were then combined with several mathematical equations to predict the pore size distribution of a used activated carbon. To verify the model, its results were tested against nine samples with various stages of heel build-up. The micropore and PSD were predicted with a mean relative absolute error (MRAE) of 3.5%, 10.8%, and 12.0% for G-70R, B101412, and B100772, respectively. The PSD prediction model was then utilized in conjunction with the DRL isotherm prediction model, and the adsorption capacity of samples at five concentrations of 0, 50, 100, 500, and 1000 ppm were predicted for each adsorbent. The prediction of adsorption capacity on the virgin G-70R, B101412, and B100772 had a MRAE of 0.6%, 8.9%, and 2.7, respectively while for the corresponding used samples the MRAE was 13.2%, 10.1%, and 10.0%. The results of this study are beneficial in improving the long-term performance of activated carbons and making them last longer
Fast preparation of activated carbon from oil sands coke using microwave-assisted activation
No full textMicrobead-assisted high resolution microwave planar ring resonator for organic-vapor sensing
No full textA microbead-assisted planar microwave resonator for organic vaporsensing applications is presented. The core of this sensor is a planarmicrostrip split-ring resonator, integrated with an active feedback loop to enhance the initial quality factor from 200 to ∼1 M at an operational resonance frequency of 1.42 GHz. Two different types of microbeads, beaded activated carbon (BAC) and polymer based (V503) beads, are investigated in non-contact mode for use as gas adsorbents in the gas sensing device. 2-Butoxyethanol (BE) is used in various concentrations as the target gas, and the transmitted power (S21) of the two port resonatoris measured. The two main microwave parameters of resonance frequency and quality factor are extracted from S21 since these parameters are less susceptible to environmental and instrumental noisethan the amplitude. Measured results demonstrate a minimum resonance frequency shift of 10 kHz for a 35 ppm concentration of BE exposure to carbon beads and 160 kHz for the polymer based adsorbent at the same concentration. The quality factor of the resonator also changed for different concentrations, but a distinguishable variation is observed for the BAC adsorbents. The high quality factor of the sensor provides the opportunity of real time monitoring of the adsorbent behaviors in remote sensing mode with very high resolution
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