خيارات البحث
النتائج 2671 - 2680 من 4,936
Decomposition of 2-Propanol in the Liquid Phase Using a Photocatalyst Immobilized on Nonwoven Fabric and Ozone Microbubbles النص الكامل
2019
Yasui, Fumio | Sekiguchi, Kazuhiko | Tamura, Hajime
2-Propanol (IPA) is a highly water-soluble volatile organic compound that is used in the cleaning and drying processes during semiconductor fabrication. IPA is also used as a disinfectant in the pharmacy field. Water scrubber processing is one of the methods used for IPA collection. However, water scrubbing requires wastewater treatment. In this study, we propose a decomposition system for IPA in the liquid phase based on a TiO₂ photocatalyst immobilized on nonwoven fabric (TiO₂ nonwoven fabric) and ozone microbubbles (MBs). The thick nonwoven fabric with immobilized TiO₂ exhibits a higher IPA removal rate than that exhibited by the pleated fabric. IPA decomposes to produce acetone, which can be further decomposed and possibly undergo mineralization. The entire water tank can be supplied with ozone by introducing the MB-forming ozone, which considerably affects the decomposition of IPA. The efficient decomposition of IPA was achieved by combining ozone MBs, TiO₂ nonwoven fabric, and ultraviolet irradiation, presumably because the photocatalyst promotes the mineralization of the decomposition product. Thus, the OH radicals from the O₃ MBs competitively captured in the decomposition product strongly promote the decomposition of IPA, enhancing the IPA decomposition rate.
اظهر المزيد [+] اقل [-]Simultaneous removal of nitrate/phosphate with bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin النص الكامل
2019
Shen, Zhanhui | Dong, Xinyi | Shi, Jialu | Ma, Yuanhao | Liu, Daoru | Fan, Jing
Given the prevalence of nitrate and phosphate in surface and groundwater, it is important to develop technology for the simultaneous removal of nitrate and phosphate. In this study, we prepared the bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin DOW 3N (D-Fe/Ni and D-Fe/Cu) for removing nitrate and phosphate simultaneously. XPS profiles revealed that Cu has better ability than Ni to increase the stability of Fe nanoparticles and prevent nZVI from oxidation. The results showed that nitrate removal efficiencies by D-Fe/Ni and D-Fe/Cu were 98.7% and 95.5%, respectively and the phosphate removal efficiencies of D-Fe/Cu and D-Fe/Ni were 99.0% and 93.0%, respectively. Besides adsorption and coprecipitation as reported in previous studies, the mechanism of phosphate removal also includes the adsorption of the newly formed polymeric ligand exchanger (PLE). Moreover, in previous studies, the presence of phosphate had significant negative effects on the reduction of nitrate. However, in this study, the removal efficiency of nitrate was less affected with the increasing concentration of phosphate for D-Fe/Cu. This was mainly because D-Fe/Cu had higher adsorption capacity of phosphate due to the newly formed PLE according to the XPS depth profile analysis.
اظهر المزيد [+] اقل [-]Understanding corporate surplus food donation in China: testing the roles of environmental concern, altruism, past experience, and perceived risk النص الكامل
2019
Liao, Chuanhui | Hong, Jin | Zhao, Dingtao
This paper investigates the motives behind corporate giving and determines whether perceived risk plays a major role in corporate surplus food donation intention. A conceptual model is developed from the perspectives of perceived risk, economic concern, past behavior, and moral motives. A questionnaire survey is conducted among food manufacturers and retailers in the Sichuan Province in China. A total of 143 valid observations are used to conduct structural equation modeling analysis. The results show that corporate reputation, legislation, and business risks are the main sub dimensions of risks that corporations perceive. Perceived risk, past behavior, environmental concern, and altruism affect corporate donation intention significantly. Implications of the findings for promoting surplus food donation are also discussed.
اظهر المزيد [+] اقل [-]Exposure index of methyl isocyanate (MIC) gas disaster and a comprehensive spectrum of cytogenetic analysis after 30 years النص الكامل
2019
Ganguly, Bani Bandana
Severity of clinical expression and high mortality could not facilitate establishing exposure index/association following MIC disaster in Bhopal. Mortality-based exposure stratification was critiqued by the International Medical Commission on Bhopal (IMCB). IMCB stratified exposure considering distance as surrogate at 2 km intervals after 10 years. The first follow-up cytogenetic screening of the pre-screened survivors after 30 years has demonstrated chromosome abnormalities (CA). Exposure stratification was attempted considering cytogenetic screening conducted during 1986–1988. Elevation of CA appeared proportional to exposure status and authenticated the initial mortality-based stratification. The one-on-one comparison of the previous and present cytogenetics has described the individual response to MIC exposure over 30 years. Chi-square test has been carried out for checking the cytogenetic changes at the individual level statistically, which revealed that differences of chromosomal aberrations collected immediately post-disaster and 30 years later are nonsignificant. The prominence of interindividual variation was noticed in general. The impact of overall exposure was higher in males. Constitutional abnormalities in 8.5% of the study population, including translocation, inversion, deletion, fragile sites, etc., necessitate screening of blood-linked members. The incidence of acrocentric association was prominent in the study population. Normal karyotype in children born to severely exposed parents with congenital anomalies indicates necessity of molecular karyotyping and/or screening of mutations. The study highlights follow-up of the health of the index cases at shorter (3–6 months) intervals. This comprehensive spectrum of cytogenetic report highlights immediate post-disaster chromosomal aberrations, the changes that occurred over 30 years in conjunction with other environmental factors at the individual level, constitutive genomic aberrations, polymorphic variations, and chromosomal patterns in congenitally malformed children of the survivors, which collectively indicate the possibility of acquisition/persistence of stable aberrations in MIC-exposed lymphocytes through interaction with environmental/biological confounders.
اظهر المزيد [+] اقل [-]Single and combined effects of microplastics and roxithromycin on Daphnia magna النص الكامل
2019
Zhang, Peng | Yan, Zhenhua | Lü, Guanghua | Ji, Yong
There is a rising concern about the pollution of microplastics (plastic particles < 5 mm) in water due to their physicochemical properties, especially their interaction with organic contaminants; however, such knowledge is still limited. The mass production and consumption of medication for the treatment of infectious diseases in human and animals have led to the ubiquity of antibiotics in the environment. We studied the single and joint effects of microplastics (1-μm and 10-μm polystyrene particles, PS) and roxithromycin (ROX) on Daphnia magna through the acute and sublethal toxicity tests. The 48-h median effective concentration (EC₅₀) of 1-μm and 10-μm PS to D. magna was 66.97 mg/L and 199.94 mg/L, respectively, while the value of ROX was 20.28 mg/L. Malondialdehyde (MDA) levels and the activities of four enzymatic biomarkers, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione S-transferase (GST), were further detected to assess the oxidative stress caused in D. magna caused. The results showed that 48-h exposure to PS (0.1 mg/L) or ROX (0.01 mg/L) alone activated the activities of CAT and GST and MDA levels. When compared with the ROX alone, the responses of GPx and MDA in D. magna co-exposed to 1-μm PS were significantly decreased, while co-exposure to 10-μm PS significantly decreased the responses of GST and MDA. Furthermore, the integrated biomarker response version 2 (IBRv2) analysis revealed that co-exposure to 1-μm PS and ROX led to the strongest biological responses in D. magna. Our findings underlined that microplastics should be a concern when they interact with the co-existence of pollutants in the aquatic environment.
اظهر المزيد [+] اقل [-]Modification of the Relative Abundance of Constituents Dissolved in Drinking Water Caused by Organic Pollution: a Case of the Toluca Valley, Mexico النص الكامل
2019
de Oca, Reyna María Guadalupe Fonseca-Montes | Ramos Leal, Alfredo | Solache-Ríos, Marcos José | Martínez-Miranda, Verónica | Fuentes Rivas, Rosa María
Drinking water contains geogenic elements to which human beings are exposed; in the long term, these elements can be either harmful (As) or beneficial (Mg and Ca) to health. The composition and relative abundance of the constituents in groundwaters are conditioned by the balance between dissolution, precipitation, and oxide-reduction processes also by the nature and spatial arrangement of the materials interacting with the water. In recent decades, human activities and changes in the use of land have led to the accumulation of organic materials and their degradation into nitrogen and phosphorus, which has resulted in a change of the physicochemical composition and quality of drinking water. The main target of the study was to evaluate the effect of contamination by nitrogen and phosphate organic matter on the physicochemical composition of water used for human consumption. The study was conducted in the Toluca Valley aquifer. The determination of parameters in situ and analysis in the laboratory of physicochemical parameters revealed the presence of NO₃⁻ (1.0–119 mg L⁻¹), SO₄²⁻ (6.81–24.70 mg L⁻¹), PO₄³⁻ (2.50–32.20 mg L⁻¹), and N-NH₄⁺ (0–5.40 mg L⁻¹), which suggested the presence of punctual anthropogenic contamination; this was confirmed using 3D fluorescence to identify the presence of organic matter. The results of Na⁺ (15.75 mg L⁻¹), K⁺ (2.66 mg L⁻¹), Ca²⁺ (8.73 mg L⁻¹), and Mg²⁺ (8.01 mg L⁻¹) using the ICP technique showed that the water supplied in the area has a low mineral content. Correlation between P and cations Ca²⁺ (0.844) > Na⁺ (0.720) > Mg²⁺ (0.694) > K⁺ (0.60) indicates that anthropic contamination affects the relative abundance of dissolved constituents in water. The scarcity of essential nutrients in water impacts on public health; it has been reported that deficiency of Ca²⁺ and Mg² implies a wide variety of clinical conditions, mainly in the development of cardiovascular diseases.
اظهر المزيد [+] اقل [-]Shift of Soil Polycyclic Aromatic Hydrocarbons (PAHs) Dissipation Pattern and Microbial Community Composition due to Rhamnolipid Supplementation النص الكامل
2019
Lu, Lu | Zhang, Jing | Peng, Chao
Biosurfactants are promising substitutes for chemical surfactants during polycyclic aromatic hydrocarbon (PAH) bioremediation. However, recent studies have revealed contrasting findings and critical knowledge gaps regarding the impacts of biosurfactants on the soil PAH biodegradation efficiency and microbial community. Here, a laboratory study was conducted to evaluate the impact of rhamnolipid on the PAH dissipation efficiency and microbial community structure during the time-course incubation. The data showed that the contribution ratio of biotic loss and abiotic loss depended on the ring number of PAH. In the microcosms supplemented with 20 μg g⁻¹ rhamnolipid, the biodegradation efficiencies of phenanthrene, fluoranthene, and pyrene increased by 10.1%, 12.3%, and 22.0%, respectively, compared to those in the rhamnolipid-free treatment after incubation for 7 days. In contrast, rhamnolipid either had no impact on or inhibited PAH degradation in the later time points (21–35 days). The abundance of bacterial 16S rRNA and phnAc genes showed significant increase in soil amended of both PAH and rhamnolipid. MiSeq sequencing results revealed that potential PAHs-degrading Massilia, Bacillus, Lysobacter, Archrobacter, and Phenylobacterium became dominant genera in PAH treatment, irrespective of the rhamnolipid added. Nevertheless, PAH addition in the presence of rhamnolipid also significantly stimulated the growth of Delftia, Brevundimonas, Tumebacillus, and Geobacillus. In contrast, the rhamnolipid altered the microbial community composition through the selection of Gaiella, Solirubrobacter, Nocardioides, and Bacillus. The results reveal the intensive selectivity effect of PAH and rhamnolipid on the soil microbes that are involved in bioremediation, and highlight the positive effect on PAHs biodegradation.
اظهر المزيد [+] اقل [-]Improving the Growth of Rapeseed (Brassica chinensis L.) and the Composition of Rhizosphere Bacterial Communities through Negative Pressure Irrigation النص الكامل
2019
Zhao, Xiujuan | Gao, Xiang | Zhang, Shuxiang | Long, Huaiyu
Negative pressure irrigation (NPI) is a new water supply technology that can save water and improve fertilizer utilization efficiency. The objective of this study was to determine the effects of different irrigation treatments on the yield and quality of rapeseed, nitrate distribution in soil, and the composition of rhizosphere bacterial communities in a greenhouse. During the entire rapeseed growth period, NPI reduced water consumption by 23 and 23% compared to that reduced by conventional irrigation (CI) and drip irrigation (DI), and NPI improved water use efficiency (WUE) by 67 and 59% more than CI and DI, respectively. Under NPI, the soil water content remained relatively stable within the range of 9.7–11.7%, which was a lower range of variation than that under CI and DI of 8.6–13.3%. NPI significantly improved the yield, quality, and plant nutrients of rapeseed. The NO₃-N content was always lowest at the different sampling times and soil layers under the NPI-L treatment. NPI significantly increased the microbial diversity in the rhizosphere soil of rapeseed and increased the abundance of Actinobacteria while decreasing that of Proteobacteria and Acidobacteria. Simultaneously, the performance of rapeseed was better under the NPI-L fertilizer concentration (0.15%) than under NPI-H (0.20%). Eventually, the combination of the evaluated regimes demonstrated that NPI is the best irrigation technique for saving water and obtaining relatively high rapeseed yields and quality while improving nitrogen utilization and the composition of rhizosphere bacterial communities. The results of this study provide a scientific basis for planting rapeseed in agricultural facilities.
اظهر المزيد [+] اقل [-]Dinitrodiazophenol industrial wastewater treatment by a sequential ozone Fenton process النص الكامل
2019
Gu, Zhepei | Pan, Xuqin | Guo, Shengpeng | Zhang, Aiping
The ozonation process is efficient in degrading aromatic substances and substances with unsaturated bonds, but cannot effectively destroy small-molecule organic compounds, which accumulate. Likewise, the Fenton process is a classic wastewater treatment method, but requires strict pH control and produces secondary pollution when the concentration of organic substances is high. In this study, we applied a 1stO₃-2ndFenton sequential process to treat diazodinitrophenol (DDNP) industrial wastewater and provide suitable reaction conditions for Fenton process. For the 1stOzone process, organics removal increased as O₃ dosage increased. At optimized operation, the 1stO₃ process provided an acidic effluent (pH = 3) and reduced the organics concentration to a level suitable for the 2ndFenton process. Benzene ring substances as well as nitro group and diazo group compounds were greatly degraded in the 1stO₃ process and were further mineralized in the 2ndFenton process. Additionally, the biodegradability of DDNP industrial wastewater was greatly improved. This is the first reported time that ozonation and the Fenton process have been integrated sequentially to treat an explosive production wastewater. The study provides a feasible chemical oxidation method for treating DDNP industrial wastewater by simply combining two classic treatment processes.
اظهر المزيد [+] اقل [-]Application of Carboxymethyl Cellulose–Stabilized Sulfidated Nano Zerovalent Iron for Removal of Cr(VI) in Simulated Groundwater النص الكامل
2019
Zhao, Lingzi | Zhao, Yongsheng | Yang, Bingjun | Teng, Honghui
Carboxymethyl cellulose–stabilized sulfidated nano zerovalent iron (CMC-S-nZVI) was tested for its capacity to the removal of Cr(VI) in this study. The effect of synthesis approaches on morphology and properties of CMC-S-nZVI was studied. Results revealed CMC-S-nZVI prepared by the surface corrosion method had favorable homogeneity and corrosion resistance. The structure and morphology of CMC-S-nZVI particles were investigated by transmission electron microscopy, X-ray powder diffraction, and Fourier-transform infrared spectrometry. Batch experiments showed that the removal efficiency of Cr(VI) by the CMC-S-nZVI particles was influenced by the S/Fe molar ratio, initial pH, initial Cr(VI) concentration, and the reaction temperature. Increasing S/Fe molar ratio from 0 to 0.35 enhanced Cr(VI) removal efficiency from 65.37 to 85.08%. Reducing pH value and improving the reaction temperature have a positive impact on Cr(VI) removal. The removal amount was 535 mg/g (total iron) CMC-S-nZVI with initial Cr(VI) concentration of 50 mg/L. Compared with CMC-nZVI, CMC-S-nZVI had better performance in Cr(VI) removal in a simulated groundwater system. The results indicated that CMC-S-nZVI might be applicable for in situ treatment of the Cr(VI)-containing groundwater.
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