Document Detail


Feasibility of ultraviolet-light-emitting diodes as an alternative light source for photocatalysis.
MedLine Citation:
PMID:  22010378     Owner:  NLM     Status:  In-Process    
Abstract/OtherAbstract:
The objective of this study was to determine whether ultraviolet-light-emitting diodes (UV-LEDs) could serve as an efficient photon source for heterogeneous photocatalytic oxidation (PCO). An LED module consisting of 12 high-power UV-A (lambda max = 365 nm) LEDs was designed to be interchangeable with a UV-A fluorescent black light blue (BLB) lamp for a bench scale annular reactor packed with silica-titania composite (STC) pellets. Lighting and thermal properties of the module were characterized to assess its uniformity and total irradiance. A forward current (I(F)) of 100 mA delivered an average irradiance of 4.0 mW cm(-2) at a distance of 8 mm, which is equivalent to the maximum output of the BLB, but the irradiance of the LED module was less uniform than that of the BLB. The LED and BLB reactors were tested for the oxidization of ethanol (50 ppm(v)) in a continuous-flow-through mode with 0.94 sec residence time. At the same average irradiance, the UV-A LED reactor resulted in a lower CO2 production rate (19.8 vs. 28.6 nmol L(-1) s(-1)), lower ethanol removal (80% vs. 91%), and lower mineralization efficiency (28% vs. 44%) than the UV-A BLB reactor. Ethanol mineralization was enhanced with the increase of the irradiance at the catalyst surface. This result suggests that reduced ethanol mineralization in the LED reactor relative to the BLB reactor at the same average irradiance could be attributed to the nonuniform irradiance over the photocatalyst, that is, a portion of the catalyst was exposed to less than the average irradiance. The potential of UV-A LEDs may be fully realized by optimizing the light distribution over the catalyst and utilizing their instantaneous "on" and "off" feature for periodic irradiation. Nevertheless, our results also showed that the current UV-A LED module had the same wall plug efficiency (WPE) of 13% as that of the UV-A BLB, demonstrating that UV-A LEDs are a viable photon source both in terms of WPE and PCO efficiency.
Authors:
Lanfang H Levine; Jeffrey T Richards; Janelle L Coutts; Robert Soler; Fred Maxik; Raymond M Wheeler
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of the Air & Waste Management Association (1995)     Volume:  61     ISSN:  1096-2247     ISO Abbreviation:  J Air Waste Manag Assoc     Publication Date:  2011 Sep 
Date Detail:
Created Date:  2011-10-20     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9503111     Medline TA:  J Air Waste Manag Assoc     Country:  United States    
Other Details:
Languages:  eng     Pagination:  932-40     Citation Subset:  IM    
Affiliation:
Engineering Support Contract-Team QinetiQ North America, Kennedy Space Center, FL 32899, USA. lanfang.h.levine@nasa.gov
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