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Nien K.C.,National Central University | Chang F.T.,JG Environmental Technology Co. | Chang M.B.,National Central University
Journal of the Air and Waste Management Association | Year: 2015

Activated carbon (AC) is seldom applied for recovering ketone-based volatile organic compounds because of safety concerns. Adsorption of methyl ethyl ketone (MEK) with AC is a highly exothermic reaction that potentially causes fires in AC beds. Moreover, 2,3-butanediol (BDO) is produced in the desorbed solvent, causing yellowing and odor of the recovered solvent. This study applied a continuous adsorption–desorption apparatus for evaluating the operating capacities and BDO concentration in recovered MEK containing modified and original ACs. AC-1 (TAKETA- G2X) was used as the target for modification. The experimental results indicate that using MgO as the modifier increases the ignition point by 12°C and that applying KNO3 as the modifier reduces the AC ignition point by 28°C (compared with AC-1). The BDO concentration of the desorbed MEK solvent can be reduced by increasing the loading of the modifying agent (Ethanolamine) (Im-1: 3.1 wt%; Im-5: 6.2 wt%). Moreover, applying the AC pretreated with nitrogen (Im-6) as adsorbent significantly reduces the BDO concentration (from 0.123 wt% to 0.073 wt%). Because desorption and purging procedures were performed in N2 atmospheres, the BDO concentrations of the desorbed MEK solvents were relatively low and ranged from 0.032 wt% to 0.043 wt%. When the MEK concentration was reduced to 2000 ppm, lower BDO concentrations (0.012–0.022 wt%) were measured in the recovered MEK solvent. The way to modify activated carbon and a better desorbing sequence to effectively inhibit the oxidation of MEK to BDO are developed. The results obtained indicate that the BDO concentration in the desorbed solvent was lower than the original MEK solvent (0.023 wt%). Different approaches can be applied simultaneously to achieve high inhibition effects; however, carbon adsorption performance may be negatively affected. Implications: The study is motivated to improve the quality of recovered solvent and reduce fire hazards, particularly when AC is applied for adsorbing a ketone-based solvent (e.g., MEK). The experimental results indicate that the BDO concentration in the recovered solvent can be reduced and the ignition point of AC can be increased by modifying the AC with an appropriate agent. © 2015 A&WMA.

Lin G.-Y.,National Chiao Tung University | Cuc L.-T.,National Chiao Tung University | Lu W.,National Chiao Tung University | Tsai C.-J.,National Chiao Tung University | And 2 more authors.
Separation and Purification Technology | Year: 2013

This study designed and tested a wet electrocyclone with high efficiency for long-term operation. The inner diameter of the collection electrode is 25 cm, and the discharge electrodes consist of seven circular discs with zigzag-shaped edges for particle charging and removal. The tip of the circular saw-type discs is 20 μm in diameter and the tip to the inner wall (collection electrode) spacing is 4 cm. Cleaning water near the inter wall was used to keep the collection electrodes clean. Experimental results showed that the collection efficiency of the present wet electrocyclone decreased with an increasing air flow rate. The efficiency for oleic acid (OA) particles was reduced only slightly from 78-92% to 75-90% for particles from 22.1 to 805 nm in electrical mobility diameter (dp) after 6 h of micro-Al 2O3 loading test. In the field test, the collection efficiencies of the present wet electrocyclone for submicron SiO2 particles with mass concentration of 20-50 mg/m3 were also found to keep higher than 93% for continuous 14-day operation. A modified Deutsch-Anderson model was developed to predict the charged particle collection efficiency (ηelec,p, %) of nanoparticle as well as larger particles. The present model is ηelec,p(%)=1-exp{- [A(NDeB)+C(NDe)+D]}×100%, where A, B, C and D are regression coefficients, and NDe is the modified Deutsch number. Good agreement was obtained between the present predictions and experimental data. © 2013 Elsevier B.V. All rights reserved.

Ho M.,National Taiwan University | Wu K.-Y.,National Taiwan University | Chein H.-M.,Industrial Technology Research Institute of Taiwan | Chein H.-M.,JG Environmental Technology Co. | And 2 more authors.
Inhalation Toxicology | Year: 2011

The total surface area is known to be an effective exposure metric for predicting the lung toxicity of low solubility nanoparticles (NPs). However, if NPs are dissolved quickly enough in the lungs, the mass may be correlated with the toxicity. Recent studies have found that the toxicity of zinc oxide (ZnO) NPs was caused by the release of zinc ions. Thus, we hypothesized that mass could be used as an exposure metric for the toxicity of ZnO NPs. Healthy Sprague-Dawley rats were exposed to a low, moderate, or high dose of 35 and 250nm ZnO particles or filtered air. Bronchoalveolar lavage fluid was collected to determine lung inflammation, injury and oxidative stress. The lung inflammation induced by ZnO particles according to different concentration metrics, including number, mass and surface area, was compared. The mass concentration was significantly correlated with the percentage of neutrophils (R 2=0.84), number of neutrophils (R 2=0.84) and total cells (R 2=0.73). Similarly, surface area concentration was significantly correlated with the percentage of neutrophils (R 2=0.94), number of neutrophils (R 2=0.81) and total cells (R 2=0.76). There was no correlation between the number and lung inflammation. We found that both mass and surface area were effective as metrics for the toxicity of ZnO NPs, although only surface area was previously indicated to be an effective metric. Our results are also consistent with recent study results that ZnO NPs and released zinc ions may play a role mediating the toxicity of NPs. © 2011 Informa Healthcare USA, Inc.

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