In order to find an effective method for treating urea wastewater, the experiments on the hydrolysis of urea in wastewater were conducted in a fixed bed reactor with different aluminas (α-Al2O3, γ-Al2O3, and η-Al2O3) as catalysts respectively in contrast with inert ceramic particle. The results indicate that the three alumina catalysts show obvious catalytic activity for urea hydrolysis at 125 °C. The order of activity is η-Al2O3?>?γ-Al2O3?>?α-Al2O3, and the activity difference increases with increasing temperature. According to the characterization results, surface acidity has little impact on the activity of catalyst. However, it was found that surface basicity of alumina catalyst plays an important role in catalytic hydrolysis of urea, and the activity of catalyst may be also influenced by the basic strength. With η-Al2O3 as catalyst, the urea concentration in wastewater is reduced to 4.96 mg/L at a temperature of 165 °C. Moreover, the η-Al2O3 shows a good stability for urea hydrolysis. The hydrolysis of urea over η-Al2O3 catalyst can evidently reduce the reaction temperature and is promising to replace industrial thermal hydrolysis process. 相似文献
The emphasis on participate control from industrial processes has been shifted recently towards fine particulates, having diameters less than 3 microns. There exists an urgent need for more scientific information of fine particle characterization.1,2 Coal and oil fired power plants are among the largest anthropogenic point sources of particulate matter.3 Limited knowledge is available on particle size distribution and trace metal composition in power plant emissions.4-7 The morphological properties of particle emissions have been largely neglected. In this report we present some information on particle characteristics for an oil-fired and coal-fired power plant. 相似文献
Parks with various types of vegetations played an important role in ameliorating air quality in urban areas. However, the attenuation effect of urban vegetation on levels of air pollution was rarely been experimentally estimated. This study, using seasonal monitoring data of total suspended particles (TSP), sulfur dioxide (SO(2)) and nitrogen dioxide (NO(2)) from six parks in Pudong District, Shanghai, China, demonstrated vegetations in parks can remove large amount of airborne pollutants. In addition, crown volume coverage (CVC) was introduced to characterize vegetation conditions in parks and a mixed-effects model indicated that CVC and the pollution diffusion distance were key predictors influencing pollutants removal rate. Therefore, it could be estimated by regression analysis that in summer, urban vegetations in Pudong District could contribute to 9.1% of TSP removal, 5.3% of SO(2) and 2.6% of NO(2). The results could be considered for a better park planning and improving air quality. 相似文献
Nonpoint sources (NPS) pollution has been an important cause for water quality impairment worldwide. To take the temporal
variations of both NPS pollution and in-stream attenuation into consideration, an inverse modeling approach and the load duration
curve (LDC) method were combined for variable nutrient total maximum daily load (TMDL) development. 相似文献
The liquid-to-solid ratio (L/S) of semi-solid Fenton process (SSFP) designated for hazardous solid waste detoxication was investigated. The removal and minimization effects of o-nitroaniline (ONA) in simulate solid waste residue (SSWR) from organic arsenic industry was evaluated by total organic carbon (TOC) and ONA removal efficiency, respectively. Initially, Box-Behnken design (BBD) and response surface methodology (RSM) were used to optimize the key factors of SSFP. Results showed that the removal rates of TOC and ONA decreased as L/S increased. Subsequently, four target initial ONA concentrations including 100 mg kg−1, 1 g kg−1, 10 g kg−1, and 100 g kg−1 on a dry basis were evaluated for the effect of L/S. A significant cubic empirical model between the initial ONA concentration and L/S was successfully developed to predict the optimal L/S for given initial ONA concentration for SSFP. Moreover, an optimized operation strategy of multi-SSFP for different cases was determined based on the residual target pollutant concentration and the corresponding environmental conditions. It showed that the total L/S of multi-SSFP in all tested scenarios was no greater than 3.8, which is lower than the conventional slurry systems (L/S ? 5). The multi-SSFP is environment-friendly when it used for detoxication of hazardous solid waste contaminated by ONA and provides a potential method for the detoxication of hazardous solid waste contaminated by organics. 相似文献
Phthalates (PAEs) in drinking water sources such as the Yangtze River in developing countries had aroused widespread concern. Here, the water, suspended particulate matter (SPM), and sediment samples were collected from 15 sites in wet and dry seasons in Zhenjiang, for the determination of six PAEs (DMP, DEP, DIBP, DBP, DEHP, and DOP) using the solid-phase extraction (SPE) or ultrasonic extraction coupled with gas chromatography-mass spectrometry (GC-MS). The total concentrations of six PAEs (Σ6PAEs) spanned a range of 2.65–39.31 μg L?1 in water, 1.97–34.10 μg g?1 in SPM, and 0.93–34.70 μg g?1 in sediment. The partition coefficients (Kd1) of PAEs in water and SPM phase ranged from 0.004 to 3.36 L g?1 in the wet season and from 0.12 to 2.84 L g?1 in the dry season. Kd2 of PAEs in water and sediment phase was 0.001–9.75 L g?1 in the wet season and 0.006–8.05 L g?1 in the dry season. The dominant PAEs were DIBP, DBP, and DEHP in water and SPM, DIBP, DEHP, and DOP in sediment. The concentration of DBP in water exceeded the China Surface Water Standard. The discharge of domestic sewage and industrial wastewater might be the main potential sources of PAEs. The risk quotient (RQ) method used for the risk assessment revealed that DBP (0.01 < RQ < 1) posed a medium risk, while DIBP and DEHP (RQ > 1) posed a high environmental risk in water, DIBP (RQ > 1) also showed a high risk in sediment.
Environmental Science and Pollution Research - In this study, Mn-doped MgAl-layered double hydroxides (LDHs) were successfully synthesized for efficient removal arsenate from aqueous solution. The... 相似文献
Environmental Science and Pollution Research - Nitrosamines (NAms) are potent genotoxic and carcinogenic but widely detected in drinking water. This study aimed to investigate the occurrence of... 相似文献
A solid-phase microextration-based sampling method was employed to determine the concentrations of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its metabolites, 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), 1,1-dichloro-2,2-bis(p-chlorophenyl)ethene (DDE) and 1-chloro-2,2-bis(p-chlorophenyl)ethene (DDMU), in two estuarine bays, Daya Bay and Hailing Bay, of South China. Six DDT components including p,p′-DDT, o,p′-DDD, p,p′-DDD, o,p′-DDE, p,p′-DDE, and p,p′-DDMU were detected in Hailing Bay, while only p,p′-DDD was found in Daya Bay. p,p′-DDD was the most abundant DDT component in both bays, sharply different from the previous finding in the water column of the Palos Verdes Shelf, California, USA that p,p′-DDE was prevalent. In addition, the occurrence of p,p′-DDMU (with a range of 0.047-0.21 ng/L in Hailing Bay) has not been reported around the globe, and its presence in our study region appeared to stem from dehydrochlorination of p,p′-DDD, favored under aerobic conditions, but further investigations are clearly needed to confirm the mechanism for generation of DDMU in estuarine environments. 相似文献