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Development of an activated carbon filter to remove NO<sub>2</sub> and HONO in indoor air
Yoo, Jun Young,Park, Chan Jung,Kim, Ki Yeong,Son, Youn-Suk,Kang, Choong-Min,Wolfson, Jack M.,Jung, In-Ha,Lee, Sung-Joo,Koutrakis, Petros Elsevier 2015 Journal of hazardous materials Vol.289 No.-
<P><B>Abstract</B></P> <P>To obtain the optimum removal efficiency of NO<SUB>2</SUB> and HONO by coated activated carbon (ACs), the influencing factors, including the loading rate, metal and non-metal precursors, and mixture ratios, were investigated. The NO<I> <SUB>x</SUB> </I> removal efficiency (RE) for K, with the same loading (1.0wt.%), was generally higher than for those loaded with Cu or Mn. The RE of NO<SUB>2</SUB> was also higher when KOH was used as the K precursor, compared to other K precursors (KI, KNO<SUB>3</SUB>, and KMnO<SUB>4</SUB>). In addition, the REs by the ACs loaded with K were approximately 38–55% higher than those by uncoated ACs. Overall, the REs (above 95%) of HONO and NO<I> <SUB>x</SUB> </I> with 3% KOH were the highest of the coated AC filters that were tested. Additionally, the REs of NO<I> <SUB>x</SUB> </I> and HONO using a mixing ratio of 6 (2.5% PABA (<I>p</I>-aminobenzoic acid)+6% H<SUB>3</SUB>PO<SUB>4</SUB>):4 (3% KOH) were the highest of all the coatings tested (both metal and non-metal). The results of this study show that AC loaded with various coatings has the potential to effectively reduce NO<SUB>2</SUB> and HONO levels in indoor air.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study developed an activated carbon to simultaneously remove both NO<SUB>2</SUB> and HONO. </LI> <LI> We investigated various factors (loading rate, metal precursors, and mixture ratios). </LI> <LI> NO<SUB>2</SUB> and HONO could be efficiently removed by an improved activated carbon filter that was impregnated with two types of compounds (2.5% PABA+6% H<SUB>3</SUB>PO<SUB>4</SUB> and 3% KOH). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Diaz, Edgar A.,Chung, Yeonseung,Papapostolou, Vasileios,Lawrence, Joy,Long, Mark S.,Hatakeyama, Vivian,Gomes, Brenno,Calil, Yasser,Sato, Rodrigo,Koutrakis, Petros,Godleski, John J. Informa Healthcare 2012 Inhalation toxicology Vol.24 No.5
<P>The study presented here is a laboratory pilot study using diluted car exhaust from a single vehicle to assess differences in toxicological response between primary emissions and secondary products resulting from atmospheric photochemical reactions of gas phase compounds with O<SUB>3</SUB>, OH and other radicals. Sprague Dawley rats were exposed for 5 h to either filtered room air (sham) or one of two different atmospheres: (i) diluted car exhaust (P)+Mt. Saint Helens Ash (MSHA); (ii) P+MSHA+secondary organic aerosol (SOA, formed during simulated photochemical aging of diluted exhaust). Primary and secondary gases were removed using a nonselective diffusion denuder. Continuous respiratory data was collected during the exposure, and bronchoalveolar lavage (BAL) and complete blood counts (CBC) were performed 24 h after exposure. ANOVA models were used to assess the exposure effect and to compare those effects across different exposure types. Total average exposures were 363 ± 66 μg/m<SUP>3</SUP> P+MSHA and 212 ± 95 µg/m<SUP>3</SUP> P+MSHA+SOA. For both exposures, we observed decreases in breathing rate, tidal and minute volumes (TV, MV) and peak and median flows (PIF, PEF and EF50) along with increases in breathing cycle times (Ti, Te) compared to sham. These results indicate that the animals are changing their breathing pattern with these test atmospheres. Exposure to P+MSHA+SOA produced significant increases in total cells, macrophages and neutrophils in the BAL and <I>in vivo</I> chemiluminescence of the lung. There were no significant differences in CBC parameters. Our data suggest that simulated atmospheric photochemistry, producing SOA in the P+MSHA+SOA exposures, enhanced the toxicity of vehicular emissions.</P>