| 1. |
- He, Ming, et al.
(författare)
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A controllable approach for the synthesis of titanate derivatives of potassium tetratitanate fiber
- 2004
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Ingår i: Journal of Materials Science. - 0022-2461 .- 1573-4803. ; 39, s. 3745-3750
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Tidskriftsartikel (refereegranskat)abstract
- Three types titanate derivatives, K2Ti6O13 fiber, K2Ti8O17 fiber and anatase TiO2 fiber, were synthesized by ion-exchange reaction from potassium tetratitanate fiber (K2Ti4O9) based on the hydrate conditions predicted by a thermodynamic model. These products were formed by a heat treatment of the corresponding hydrate intermediates K1.33H0.67Ti4O9·H2O, KHTi4O9·0.5H2O and H2Ti4O9·1.2H2O which were quantitatively obtained by controlling the pH value and the equilibrium concentration of potassium ion. The mole ratio of Ti/K in solid phase (R) of the target products was taken as the controlling aim in the hydrate process. The temperature for heat treatment of hydrate intermediates was determined by thermogravimetry (TG) and differential scanning calorimetry (DSC). All products retained fibrous morphology similar to that of K2Ti4O9 used as the starting material.
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| 2. |
- Lu, Ming
(författare)
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Pit lakes from sulphide ore mining, geochemical and limnological characterization before treatment, after liming and sewage sludge treatments : cases studies at Rävlidmyran and Udden, Sweden
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to the increasing number of acidic mining-pit lakes and a growing awareness of the environmental risks associated with them, pit lakes have attracted more and more attention. This study started with a full-year- round investigation of two abandoned sulphide mine pit lakes, the Rävlidmyran and Udden pit lakes in northern Sweden, followed by studies of two full-scale remediation treatments, liming and sewage sludge treatment, respectively, in the Rävlidmyran pit lake. The aim of this study is to understand the geochemistry of pit lakes and the factors influencing pit lake water quality. Based on this knowledge, effects of different remediation methods are investigated and possible improvement of these methods is explored. Furthermore, the possibility of manipulating the pit lakes to obtain efficient metal attenuation is also explored in this study. The results showed that these two pit lakes have some common characteristics; they have low pH, they are oligotrophic and have high metal and sulphate contents. However, they have developed distinctly different limnology and geochemistry. Rävlidmyran is a meromictic lake, which has a rather stable stratification due to more saline groundwater inflow at depth. Three layers have been developed: the mixolimnion at the top, in which the water is well mixed and saturated with oxygen; the monimolimnion in the deeper lake, which is poor in oxygen and which does not mix with upper water; and the chemocline, which separates the upper and deeper water. The distribution of elements such as Ca, Mg, Na, K, S, Mn, Fe and Zn is seen to be strongly controlled by the stratification with lower concentrations in the upper layer and higher concentrations in the deeper water. The Udden pit lake is a dimictic lake without permanent stratification; only seasonal thermal strata develop. The water is well mixed, which results in rather uniform distribution of parameters such as pH, dissolved oxygen, conductivity and elemental concentrations. It is concluded that a careful characterization of the limnological situation of a pit lake is very important, both for designing reasonable remediation treatment methods or being able to use pit lakes for disposal of contaminants such as mine waste. Rävlidmyran was chosen for full-scale studies of remediation. Liming treatment proved to be an effective method with respect to increased pH. The effects of the liming on the dissolved elemental concentrations in the lake water were distinct, especially in the upper oxic water layer. Elements such as Fe, Mn, Zn and Mg were largely removed in the upper oxic water, probably due to formation of oxyhydroxides. Some elements such as Na, K and S were barely influenced. Al and Cu were almost completely removed from the water throughout the profiles, due to pH increase and precipitation of minerals such as gibbsite (Al(OH)3). Sorption of Cu was probably removed from the water by to gibbsite and Fe-oxyhydroxides, since pH was rather high. However, liming is not a long-term solution as long as the acidic sources flow continuously into the lake. Therefore, the liming effect will not last long and it will be rather costly to continue liming. The sewage sludge treatment did not show distinct effects on the water quality during the monitoring period. However, particulate elemental concentrations were influenced, especially during the early stages of the treatment. Concentrations of total organic carbon increased in the water column after sewage sludge treatment. However, most of the organics and nutrients settled rapidly and accumulated at the lake bottom.
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| 3. |
- Ming, Lu
(författare)
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Aqueous geochemistry of pit lakes : two cases studies at Rävlidmyran and Udden, Sweden
- 2002
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Two abandoned pit lakes in northern Sweden were studied in order to improve the understanding of the geochemistry of pit lakes, Rävlidmyran Pit Lake and Udden Pit Lake. Both lakes show strong similarity with other mining lakes in terms of low pH and high metal and sulphate contents. Still, the two lakes have distinctly limnological and geochemical characteristics. Rävlidmyran Pit Lake is oligotrophic and meromictic. The lake is permanently stratified and three layers, the mixolimnion at the top, the chemocline below and the monimolimnion further below, are identifiable. Groundwater filling and stratification strongly control the elemental distributions in the lake. Most elements such as Ca, Mg, Na, K, S, Mn, Fe and Zn have lowest and constant concentration in the mixolimnion. Concentrations increase in the chemocline and keep rising in the monimolimnion. These elements show quite similar behaviour in the water with strong correlations. Groundwater is supposed to be the major source. Fe is removed from the mixolimnion due to oxidation and precipitation, but it is redissolved in the monimolimnion. Udden Pit Lake is a dimictic lake. Distinct overturning in spring and autumn occurs in the lake, during which the whole lake circulates and most of the parameters and chemical components become homogeneously distributed. The lake is thermally stratified in summer and winter. Three layers, the epilimnion at the top, the metalimnion below and the hypolimnion at depth could be identified. The thermal strata do not control the elemental distribution. During stratification, the concentrations of dissolved elements appear to be constant at most depths. Variations mainly occur in the top and bottom waters. Most elements such as Ca, Mg, Na, K, S, Mn, Cu Al and Zn have lowest concentration in the epilimnion. Concentrations increase in the metalimnion and kept constant in the hypolimnion. Fe concentration distribution reflects the changes of redox potential. High amounts of Fe2+ reaching the surface water by drainage waters from closely situated waste rock dumps cause higher dissolved Fe concentration and lower redox potential in the top water. Precipitation of dissolved Fe into suspended Fe occurs in deeper water where the redox potential is higher. In both lakes, a strong relationship between Cu and Al is found. Gibbsite is important since it controls both dissolved Al and Cu concentrations in the lake through processes of adsorption and precipitation. Otherwise scavenging processes by particles are not a significant factor controlling trace metal distributions due to the low suspended particle concentration in both lakes. Sulphate reduction was neither observed in Rävlidmyran nor in Udden, even though the oxygen concentration is poor in the deep waters. The high redox potential limits the formation of sulphides, thus precluding an important precipitation of trace metals as metal sulphides.
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| 4. |
- Rauch, Sebastien, 1971, et al.
(författare)
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Heterogeneity of platinum group metals in airborne particles
- 2001
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Ingår i: Environmental Science & Technology. ; 35, s. 595-599
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Tidskriftsartikel (refereegranskat)abstract
- The emission of three of the platinum group metals (PGMs), Pd, Pt, and Rh, from automobile catalysts and into the urban environment is a potential concern for human health. The analysis of low concentrations of PGMs in air particles is an analytical challenge, and it is demonstrated that interferences in inductively coupled plasma-mass spectrometry (ICP-MS) can be corrected mathematically for Pt and Rh and, at higher concentrations, for Pd. The PM10 concentrations of PGMs in urban air collected in Göteborg are 0.1-10 pg m-3 (Pd), 0.9-19 pg m-3 (Pt), and 0.3-4 pg m-3 (Rh), with higher values for greater traffic intensity. These concentrations provide a general background for the urban atmospheric environment, and the Pt:Rh ratio (4.2:1) agrees with known automobile catalyst composition. The analysis of filters from 10 parallel samplers indicated the significant heterogeneity of PGMs in samples of urban air particles. Scanning laser ablation ICP-MS provided the m spatial resolution required to identify individual particles. Ablation across the filter surface demonstrated the presence of relatively few particles with a high concentration of PGMs. These occasional high concentration particles, which might be overlooked in conventional air sampling with total analysis, have a high Pt:Rh ratio (12.3:1), which can be attributed to catalyst aging during vehicle operation.
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