Biomedical subjects

Juu-En Chang

Publications and source records attributed to Juu-En Chang.

7 recordsLinked to original sources

PubMed2007

Influence of start-up on PCDD/F emission of incinerators.

This study aims to evaluate the influence of start-up on polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) concentration in the stack flue gas of incinerators and its contributing PCDD/F emission. The PCDD/F emission of the first sample among three consecutive stack flue gas samples of five intermittent incinerators, which sampled at a stable combustion condition after start-up, is 2-3 times higher than the mean of the others. For verifying the PCDD/F characteristics of incinerators during start-up, one continuous MSWI was investigated for two years. The elevated PCDD/F emissions of the MSWI during start-up could reach 96.9 ng I-TEQN m(-3) and still maintained a high PCDD/F emission (40 times higher than the Taiwan emission limit) even 18 h after the injection of activated carbon, indicating the memory effect. Taking the MSWI for example, which consists of four incinerators, the estimated annual PCDD/F emission from normal operational conditions was 0.112 g I-TEQ. However, one start-up procedure can generate approximately 60% of the PCDD/F emissions for one whole year of normal operations. And the PCDD/F emission, which is the result of the start-ups of four incinerators, was at least two times larger than that of a whole year's normal operations, without consideration for the PCDD/F emission contributed by the long lasting memory effect.

Air Pollutants, Occupational↗

PubMed2006

Tracking of copper species in incineration fly ashes.

Speciation of copper in the incineration waste heat boiler (HB) and the down stream electrostatic precipitator (EP) fly ashes during the flue gas cooling down (1123-->473 K) has been studied by X-ray absorption near edge structural (XANES) spectroscopy in the present work. Copper species such as Cu(OH)(2) (59-67%), CuCl(2) (5-12%), CuO (24-26%), and a small amount of CuS (3-4%) in fly ashes were determined by semi-quantitative analyses of the XANES spectra. In the toxicity characteristics leaching procedure (TCLP) tests, about 83 and 20% of copper were leached from the EP and HB fly ashes, respectively. The relatively high leachability of copper for the EP fly ash might be due to the fact that CuCl(2) was enriched on the surfaces as observed by X-ray photoelectron spectroscopy (XPS). On the contrary, CuCl(2) was mainly encapsulated in the HB fly ashes.

Carbon↗

PubMed2006

Comparisons of levels of polychlorinated dibenzo-p-dioxins/dibenzofurans in the surrounding environment and workplace of two municipal solid waste incinerators.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the surrounding environment (outdoor) and workplace air of two municipal solid waste incinerators (MSWIs, T and M) were characterized and compared. T and M represented two typical municipal solid waste incinerators in the north of Taiwan, which have different processes for controlling the PCDD/F emissions. The results of this study are summarized as follows. (1) The total PCDD/F and the total PCDD/F WHO-TEQ concentrations in the workplace air were 5-13 and 5-15 times higher than those in the outdoor air, respectively. Obviously, it is worthwhile to explore more on health risk assessment for exposure of PCDD/Fs emitted from MSWIs, particularly in the workplace air. (2) Mean total PCDD/F I-TEQ concentrations in the outdoor air ranged between 0.0216 and 0.155 pg I-TEQ/Nm(3) and averaged 0.0783 pg I-TEQ/Nm(3) (0.0828 pg WHO-TEQ/Nm(3)) during two seasons for two MSWIs, which were 6.5-fold higher than that of a remote site (0.0119 pg I-TEQ/Nm(3) or 0.0132 pg WHO-TEQ/Nm(3)) in Taiwan. However, the above outdoor air concentration levels in the MSWIs were still much lower than the air quality limitation of PCDD/Fs (0.6 pg I-TEQ/Nm(3)) in Japan []. (3) PCDFs were the primary toxicity distributors for PCDD/Fs in the outdoor air, since the ratios of PCDDs/PCDFs (I-TEQ) at all sampling sites ranged from 0.180 to 0.492 and were less than unity. (4) The OCDD, OCDF, 1,2,3,4,6,7,8-HpCDD and 1,2,3,4,6,7,8-HpCDF were the four dominant species in both workplace and outdoor air near MSWIs. (5) By spraying water on and wetting both the fly and bottom ashes, the mean total PCDD/F I-TEQ concentration in the workplace air was reduced 86.9% in the T MSWI. The above results indicate an appropriate improving action did inhibit the fugitive emission of PCDD/Fs and reduce the health risk of workers during work handling ashes in MSWIs.

Air Pollutants↗

PubMed2003

Effects of leaching parameters on swelling behaviors of compacted mudstone used in landfill liner.

This study attempt to determine the swelling deformation of compacted mudstone using the free swell test, and the leaching parameters using a pH meter, a conductivity meter, and ion chromatography (IC) techniques. Closely examining chemical characteristics indicated that natural mudstone is saline-alkali soil. The maximum swelling deformation obtained from the free swell test is about 15.7%. The swelling developed relatively rapidly after the start of soaking, stopping after 7 days. The leaching characteristics in compacted mudstone involve the hydrolysis of Na+ ions, the precipitation of CaCO3 and slightly dissolution of Mg2+ ion. The relationship of swelling deformation to sodium adsorption ratio (SAR) value indicated that the SAR value in soaking suspension significantly affects the amount of swelling. Additionally, the pH of the soaking suspension importantly affects swelling behavior. Overall, the early swelling behaviors of compacted mudstone are posited to involve directly the concentration of Na+ ions in the soaking suspension and the precipitation of CaCO3 in compacted mudstone. Furthermore, the very slight swelling after the 3-day soaking is related to the dissolution of Mg2+ ions in compacted mudstone.

Aluminum Silicates↗

PubMed2003

Leaching behavior and ESEM characterization of water-sensitive mudstone in southwestern Taiwan.

This investigation attempts to understand the critical soluble salts in natural mudstone and the leaching, microstructural, and microchemical characteristics in soaked mudstone using scanning electron microscopy (SEM)/energy-dispersive X-ray analysis (EDAX), X-ray fluorescence spectrometry (XRF), X-ray diffractometry (XRD), conductivity measurement, ion chromatography (IC), and environmental scanning electron microscopy (ESEM)/EDAX techniques. Natural mudstone probably includes soluble salts such as Na2SO4, NaCl, NaCO3, and CaCO3. The dissolution of Na2SO4 controls water-sensitive mudstone very susceptible to slaking and dispersion. ESEM micrographs clearly show evidence of mudstone-slaking during soaking since the visible pores are filled with small aggregative masses. A calcium-bearing precipitate from the soaked mudstone is speculated to be attributable to the decomposition of the hydrated product of the fresh mudstone.

Chemical Precipitation↗

PubMed2002

Integrated copper-containing wastewater treatment using xanthate process.

Although, the xanthate process has been shown to be an effective method for heavy metal removal from contaminated water, a heavy metal contaminated residual sludge is produced by the treatment process and the metal-xanthate sludge must be handled in accordance with the Taiwan EPA's waste disposal requirements. This work employed potassium ethyl xanthate (KEX) to remove copper ions from wastewater. The toxicity characteristic leaching procedure (TCLP) and semi-dynamic leaching test (SDLT) were used to determine the leaching potential and stability characteristics of the residual copper xanthate (Cu-EX) complexes. Results from metal removal experiments showed that KEX was suitable for the treatment of copper-containing wastewater over a wide copper concentration range (50, 100, 500, and 1000 mg/l) to the level that meets the Taiwan EPA's effluent regulations (3mg/l). The TCLP results of the residual Cu-EX complexes could meet the current regulations and thus the Cu-EX complexes could be treated as a non-hazardous material. Besides, the results of SDLT indicated that the complexes exhibited an excellent performance for stabilizing metals under acidic conditions, even slight chemical changes of the complexes occurred during extraction. The xanthate process, mixing KEX with copper-bearing solution to form Cu-EX precipitates, offered a comprehensive strategy for solving both copper-containing wastewater problems and subsequent sludge disposal requirements.

Anti-Infective Agents↗

PubMed2002

EXAFS study of adsorbed Cu(II) on fly ashes with different residual carbon contents.

This work studied the speciation of copper species adsorbed onto the surface of fly ash using X-ray absorption spectroscopy (XAS). Experimental results verified that the chemical bond between Cu(II) and the surface of the fly ash was Cu-O. The data set was optimally fitted into the two atomic shells: the first shell containing O atoms and the second shell containing Cu atoms. The extended X-ray absorption fine structure (EXAFS) data also show that, in the first shell, about 2.03-2.41 nearest oxygen atoms surround the center Cu atom with a Cu-O bond distance of 1.96-1.99 A. The results further demonstrated that the bond distance slightly increased with an increasing carbon content of the fly ash.

Adsorption↗