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Pesavento M Biesuz R Profumo A Soldi T 《Environmental science and pollution research international》2003,10(5):317-320
SCOPE: The detection and investigation of metal ions bound in strong complexes in natural waters is a difficult task, due to low concentration of the metal ions themselves, and also of the strong ligands, which, moreover, are often not of a well-defined composition. Here, a method is proposed for the investigation of the speciation of metal ions in natural waters. OBJECTIVE AND METHOD: It is based on the sorption of metal ions on strongly sorbing ion exchange resins, i.e. complexing resins. For this reason the method is called Resin Titration. It has been shown in previous investigations that the concentration of metal ion totally sorbed by a particular resin, and its reaction coefficient in the solution phase in the presence of the resin, can be determined from the sorption data using a simple relationship. Here, a data treatment (the Ruzic linearization method) is proposed for also determining the concentration of the ligands responsible for the complex in equilibrium with the resin. RESULTS: The method was applied to data obtained by Resin Titration of a freshwater and a seawater. Copper(II) and aluminium(III) were considered, using Chelex 100 as a titrant, due to its strong sorbing properties towards these metal ions. The results were: the total metal concentration in equilibrium with the resin, the side reaction coefficients, and the concentration of ligands. In all these cases the ligands forming very strong complexes were found to be at concentration lower than that of the metals. CONCLUSION: The Ruzic linearization method allows the determination of the concentration of the ligands forming very strong complexes in equilibrium with Chelex 100. The reaction coefficient was better determined by the calculation method previously proposed for RT. The ligands responsible for the strong complexes were found to be at low concentration, often lower than that of the metal ions considered. The metal in the original sample is partly bound to these ligands, since the complexes are very strong. Only a part of the metal is linked to weaker ligands, or free. 相似文献
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Removal of metal ions from the complexed solutions in fixed bed using a strong-acid ion exchange resin 总被引:4,自引:0,他引:4
Fixed bed removal of equimolar metal ions (Co2+, Ni2+, Mn2+, Sr2+) from aqueous solutions using a strong-acid resin was examined. The solution contained a water-soluble complexing agent including ethylenediaminetetraacetic acid, nitrilotriacetic acid, and citric acid. Experiments were performed under different solution pH and molar concentration ratios of complexing agent to the total metals. It was shown from batch studies that the equilibrium exchange of metals and the resin mainly depended on solution pH, and partly on the type of complexing agent used. A mass transfer model was proposed to describe the breakthrough curves of the resin bed, which contained two parameters (τ and k) estimated from the observed breakthrough data. The calculated breakthrough curves agreed well with the measured ones (standard deviation <6%). In fixed bed tests at low pH (=2), the type of complexing agent had little effect on the breakthrough data. For a given complexing agent, the metal with a larger overall formation constant (Kf) showed a smaller exchange capacity. For a given metal ion, the complexing agent with a larger Kf also revealed a smaller exchange capacity. 相似文献
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固定相络合萃取剂处理水中苯酚的性能研究 总被引:12,自引:0,他引:12
采用固定相络合萃取剂 YH- 1对水中苯酚进行了萃取与反萃取实验研究 ,考察了组成比、废水 p H、起始浓度、流速及再生次数对 YH- 1萃取性能的影响。结果表明 ,当络合萃取剂与聚合物质量比为 2∶ 1,废水 p H<8时 ,通过单级或多级操作 YH- 1能有效地萃取高浓度含酚废水中的苯酚 ,且再生率达 99.3% ,明显优于活性炭。总之 ,固定相络合萃取剂 YH- 1是一种操作范围广、高效、易再生的处理含酚废水的新体系 相似文献
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Pirkanniemi K Vuorio AM Vilhunen S Metsärinne S Sillanpää M 《Environmental science and pollution research international》2008,15(3):218-221
Goal, Scope and Background Complexing agents are one of the major environmental concerns in electrolytic and chemical surface treatment (ECST) industry;
e.g. the EU reference document on the best available technology (BREF) pays special attention to the usage of EDTA. However,
no comprehensive studies are available on usage of EDTA or other complexing agents or their load to the receiving waters from
ECST industry. In this study, the concentrations of complexing agents were analyzed to get an overview of their usage and
load and also to recognize their relevance in the environmental permitting and compliance monitoring of such facilities.
Methods Complexing agent concentrations of treated waste water samples of 23 ECST plants with vat volume exceeding 30 m3 was studied. HPLC and GC-MS were used to analyze and identify complexing agent concentrations, ICP-AES to analyze metals,
and TOC to analyse the organic load. The number of the plants in this study equals around 50% of such installations in Finland
subject to environmental permit as the IPPC directive provides.
Results EDTA, DTPA, and NTA were found in 11 samples out of 23 mainly in rather small concentrations. Their annual load to the receiving
waters may be estimated to be 0.3 tons and the total load from Finnish ECST industry can be extrapolated to be up to 1 ton.
Compared to the estimated use of 5–10 tons in the industry this finding is rather low, even though in Finland cast-off treatment
baths are typically delivered to the hazardous waste treatment plants.
Discussion Since the load of complexing agents is rather low, the chemical waste water treatment seems to be either capable of reducing
complexing agent concentrations to some extent or their usage is lower than expected. On the other hand, it is possible that
not all complexing agents were identified from the samples. The metal concentrations and TOC were well hand in hand with concentrations
found in the Finnish environmental database, which proves that the samples were of average quality of the waste water from
the facilities.
Conclusions According to the results, complexing agents cannot be considered as an environmental risk in the ECST industry in Finland;
EDTA concentrations are clearly below PNECaqua (2.2 mg/l) and the total discharge is very marginal compared to the discharge from the pulp and paper industry. However,
DPTA seems to be as commonly used as EDTA, but also biodegradable NTA was found.
Recommendations and Perspectives Since EDTA has gained plenty of attention in the BREF, DTPA and other, poorly biodegradable complexing agents should also
be taken into account when the BREF is updated within a few years. Also an EU risk assessment report especially for DTPA should
be supplied, since its use is obviously increasing. 相似文献
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Degradation of chelating agents in aqueous solution using advanced oxidation process (AOP) 总被引:5,自引:0,他引:5
This article presents an overview with critical analysis of technical applicability of advanced oxidation process (AOP) in removing chelating agents from aqueous solution. Apart from the effect of metals for chelating agents as a major influencing factor, selected information such as pH, oxidant’s dose, concentrations of pollutants and treatment performance is presented. The performance of individual AOP is compared. It is evident from our literature survey that photocatalysis with UV irradiation alone or coupled with TiO2, ozonation and Fenton’s oxidation are frequently applied to mineralize target pollutants. Overall, the selection of the most suitable AOP depends on the characteristics of effluents, technical applicability, discharge standard, regulatory requirements and environmental impacts. 相似文献
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A laboratory experiment was used to investigate the mobilization kinetics of heavy metals from the sediment of a contaminated river located in northern Taiwan with varied concentrations of NTA and EDTA. We found that there were two stages of desorption in the mobilization of heavy metals from the sediment. As the concentrations of NTA and EDTA ranged 0–3.9 x 10‐4M (0–100mg/l) and 0–2.7 x 10‐4M (0–100mg/l) respectively, the mobilization percentages of heavy metals were proportional to the logarithm values of the concentrations of NTA and EDTA. The physical meaning of the multiple first‐order reaction was significant for the actual condition, but occasionally, it had more errors for Cu and Zn in the initial phase. The two‐constant model was most appropriate for describing the rates of mobilization of Pb, Cu, Zn, and Cr. The agreement between the diffusion model and the experimental data was satisfactory for Pb, Cu, Zn, and Cr only in the initial 5 h. 相似文献
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