In this study, a ternary Zr(IV) system with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and fluoride was chosen on the basis of dispersive liquid–liquid microextraction method. Zirconium was extracted into the fine droplets of dichlorobenzene as extracting solvent. These drops dispersed as a cloud in the aqueous sample with the help of ultrasonic waves, and the procedure was done. Finally, atomic absorption spectrometry was applied for the determination of zirconium. The effects of different factors that influence complex formation and extraction, such as pH, amounts of complexing agents, type and volume of the extracting solvent, as well as sonication and centrifuging time, were optimized. Under optimum conditions, the calibration curve was linear in the range of 150.0–800.0 ng mL?1 with a limit of detection of 44.0 ng mL?1. Relative standard deviation was calculated to be 4.1 % (n?=?7, c?=?400.0 ng mL?1). The enrichment factor was 80. The proposed method was successfully used to determine the zirconium in several water, wastewater, and soil samples. 相似文献
Mining-contaminated sites and the affected communities at risk are important issues on the agenda of both researchers and
policy makers, particularly in the former communist block countries in Eastern Europe. Integrated analyses and expert based
assessments concerning mining affected areas are important in providing solid policy guidelines for environmental and social
risk management and mitigation. Based on a survey for 103 households conducted in a former mining site in the Certej Catchment
of the Apuseni Mountains, western Romania, this study assesses local communities’ perceptions on the quality of water in their
living area. Logistic regression was used to examine peoples’ perception on the quality of the main river water and of the
drinking water based on several predictors relating to social and economic conditions. The results from the perception analysis
were then compared with the measurements of heavy metal contamination of the main river and drinking water undertaken in the
same study area. The findings indicate that perception and measurement results for the water quality in the Certej Catchment
are convergent, suggesting an obvious risk that mining activities pose on the surface water. However, the perception on drinking
water quality was little predicted by the regression model and does not seem to be so much related to mining as to other explanatory
factors, such as special mineralogy of rock and soils or improper water treatment infrastructure, facts suggested by the measurements
of the contaminants. Discussion about the implications of these joint findings for risk mitigation policies completes this
article. 相似文献
ABSTRACTDeveloping countries, which often have emerging or fledgling civil societies, are vulnerable to disasters, and especially devastating earthquakes. The long-term influence of devastating earthquakes on civil societies in developing countries is a critical research topic while receives relatively little attention. From a comprehensive literature review, this study identified four key areas of the civil society: civic participation, voluntary organizations, social capital, and democratic governance, and then examined four devastating earthquakes in India, Iran, Pakistan and China in the first decade of the twenty-first century as case studies, to identify the effects these earthquakes had on these four areas. It was found that from a long-term perspective, while the earthquakes strengthened the civil society, they had beneficial but limited effects. We argue that by promoting local community participation, facilitating extensive non-government organization (NGO) cooperation, and streamlining state-civil society relationships, an enabling environment can be developed to further sustain the advances made by a civil society after a disaster. 相似文献
Nitrogen-doped titanium dioxide (TiO2) and Fe–N-codoped TiO2 layers on fly ash cenospheres (FAC) as floating photocatalyst were successfully prepared through sol–gel method. Photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)–Vis diffuse reflectance spectroscopy (DRS), and nitrogen adsorption analyses for Brunauer–Emmett–Teller (BET) specific surface area. Photocatalytic efficiency of the prepared catalyst was evaluated through using the decomposition of Rhodamine B (RhB) as a model compound under visible light irradiation. Photocatalytic activity and kinetics of catalyst under visible light were detected in details from different Fe/Ti mole ratios by detecting photodegradation of RhB. Experimental results show that when the calcination temperature was 550 °C, the dosage of FAC was 3.0 g, and the mole ratio of Fe/Ti was 0.71 %; the synthesized Fe–N-TiO2/FAC photocatalyst presented as anatase phase and that N and Fe ions were doped into TiO2 lattice. The material’s specific surface area was 34.027 m2/g, and UV–Vis diffuse reflectance spectroscopy shows that the edge of the photon absorption has been red shifted up to 400–500 nm. Fe–N-codoped titanium dioxide on FAC had excellent photocatalytic activity during the process of photodegradation of RhB under visible light irradiation.
• Bi doping in TiO2 enhanced the separation of photo-generated electron-hole.• The performance of photocatalytic degradation of MC-LR was improved.• Coexisting substances have no influence on algal removal performance.• The key reactive oxygen species were h+ and •OH in the photocatalytic process. The increase in occurrence and severity of cyanobacteria blooms is causing increasing concern; moreover, human and animal health is affected by the toxic effects of Microcystin-LR released into the water. In this paper, a floating photocatalyst for the photocatalytic inactivation of the harmful algae Microcystis aeruginosa (M. aeruginosa) was prepared using a simple sol-gel method, i.e., coating g-C3N4 coupled with Bi-doped TiO2 on Al2O3-modified expanded perlite (CBTA for short). The impact of different molar ratios of Bi/Ti on CBTA was considered. The results indicated that Bi doping in TiO2 inhibited photogenerated electron-hole pair recombination. With 6 h of visible light illumination, 75.9% of M. aeruginosa (initial concentration= 2.7 × 106 cells/L) and 83.7% of Microcystin-LR (initial concentration= 100 μg/L) could be removed with the addition of 2 g/L CBTA-1% (i.e., Bi/Ti molar ratio= 1%). The key reactive oxygen species (ROSs) in the photocatalytic inactivation process are h+ and •OH. The induction of the Bi4+/Bi3+ species by the incorporation of Bi could narrow the bandgap of TiO2, trap electrons, and enhance the stability of CBTA-1% in the solutions with coexisting environmental substances. 相似文献