Some metal etching operations emit limited flow rates of waste gases with reddish-brown NO2 fume, which may cause visual and acidic-odor complaints, as well as negative health effects. In this study, tests were performed by passing caustic-treated waste gases vented from Al-etching operations through columns packed either with virgin or regenerated granular activated carbon (GAC) to test their adsorptive conversion performance of NO2 in the gases. The gases contained 5–55 ppm NO2 and acetic and nitric acids of below 3 ppm. Exhausted carbon was regenerated by scrubbing it with caustic solution and water, and dried for further adsorption tests. Results indicate that with an (empty bed residence time (EBRT) of 0.15 sec for the gas through the GAC-packed space, around 60% of the influent NO2 of 54 ppm could be removed, and 47% of the removed NO2 was converted by and desorbed from the carbon as NO. GAC used in the present study could be regenerated at least twice to restore its capacity for NO2 adsorption. Within EBRTs of 0.076–0.18 sec, the adsorptive conversion capacity was linearly varied with EBRT. In practice, with an EBRT of 0.20 sec, a conversion capacity of 0.80 kg NO2 (kg GAC)?1 with an influent NO2 of 40 ppm can be used as a basis for system design.Implications: Some metal etching operations emit waste gases with reddish-brown (yellow when diluted) NO2 fume which may cause visual and acidic-odor complaints, as well as negative health effects. This study provides a simple process for the adsorptive conversion of NO2 in caustic-treated waste gases vented from metal-etching operations through a GAC column. With an EBRT of 0.20 sec, a conversion capacity of 0.80 kg NO2 (kg GAC)?1 with an influent NO2 of 40 ppm can be used as a basis for system design. Saturated GAC can be regenerated at least twice by simply scrubbing it with aqueous caustic solution. 相似文献
Journal of Material Cycles and Waste Management - Efforts to improve the performance of hydrothermal treatment (HT) in producing high-quality solid fuel from sewage sludge were carried out by... 相似文献
The purposes of this research are to quantify the concentration of heavy metals (Zn, Cu, As, Pb, Cd, and Hg) in the water and fish tissues of common carp (Cyprinus carpio) in the upper Mekong River and to thereby elucidate the potential dietary health risks from fish consumption of local residents. Surface water and fish tissues (gill, muscle, liver, and intestine) from four representative sample areas (influence by a cascade of four dams) along the river were analyzed for heavy metal concentrations. Results revealed that the levels of heavy metals in fish were tissue-dependent. The highest Cu and As levels were found in the liver; the highest Zn and Pb levels occurred in the intestine, and the highest Hg level was found in the muscle. The total target hazard quotient (THQ) value for residents is > 1 for long-term fish consumption, and local residents are, therefore, exposed to a significant health risk. Results from the current study provide an overall understanding of the spatial and tissue distribution of heavy metals in water and fish body along the upper Mekong River under the influence of cascade dams and highlight the potential health risk of As for the local residents of long-term fish consumption.