Results 1 - 10 of 2035
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[en] Effect of pulp density and oxygen addition on the growth of thiobacillus in percolator. Large percolators were used to study the growth of thiobacillus. The treatments were given to 40 kg are consisted of pulp density of 1:1 (B) (w/v). Nine K solutions were used as growth medium. The flow rate of oxygen addition was 0,5 ml/min. T. ferrooxidans F 402 was inocculated into the percolator from 150 ml of enriched culture containing 2.0 x 105 cell/ml. Results of the experiments showed that bacteria grew well either in pulp A or B. The parameters Eh, concentration of Fe2+ and Fe3+ showed good correlation. Growth of bacteria was not affected by oxygen addition. In the leaching treatments with pulp A and B, the solution contained 55 and 16 ppm U respectively. (author). 11 refs.; 7 figs
[en] Ba is the most useful element to get the Ba(Ra)SO4 precipitate. However, when the high concentrations of ions such as sulfate, calcium are existed in the leachate of phosphogypsum stack, it is difficult to get the Ba(Ra)SO4 precipitate. Since this reason, the developed method for the Ba coprecipitate using EDTA was performed to determine the 226Ra concentration in the high sulfate sample. The average concentration of 226Ra in a leachate of phosphogypsum using this method was 0.102 Bq·kg-1 and the minimal detectable activity is 3.4 mBq·kg-1. The mBq·kg-1 method was 0.102 Bq·kg-1 and the minimal detectable activity is 3.4 mBq·kg-1. The 226Ra stock solution and the CRM (Certified Reference Material) were analyzed to verify this method. In analyzed 226Ra stock solution, bias with added concentration was approximately 1% and the correlation curve between 226Ra concentration in simulated standard sample and measured 226Ra concentration showed good agreement with a correlation coefficient (R2) of 0.99. In analyzed CRM, maximum bias with reference value was 5.8% (k=1) and the analytical results were in good agreement with the reference value.
[en] The author presents a new technique for production of yellow cake with double precipitation, thus solving a series of problems for precipitating uranium with traditional double precipitation. The new technique can not only remove ferric ions and sulfate radicals but also make solid-liquid separation easy, utilize effectively the sulfuric acid produced in ferric ions precipitation process, and increase uranium concentration of leaching liquor. To take it as producing yellow cake will save investment, simplify operation, and cut down the consumption of raw materials and energies. It is more competitive than ion-exchange or solvent extraction in the process of extracting-purifying and preparing yellow cake
[en] A large volume of uranium electrokinetic leachate has been generated during the electrokinetic decontamination to remove uranium from contaminated soil. The treatment technology for the reuse of the uranium leachate was developed. The concentration of uranium in the generated uranium leachate was 180 ppm and concentrations of Mg(II), K(I), Fe(II), and Al(III) ions ranged from 20 ppm to 1,210 ppm. The treatment process for uranium leachate consisted mainly of mixing and cohesion, precipitation, concentration, and filtration. In order to obtain the pH=11 of a precipitate solution, the calcium hydroxide needs to be 3.0 g/100ml and the sodium hydroxide needed to be 2.7 g/100ml. The results of several precipitation experiments showed that a mixture of NaOH+0.2g alum+0.15g magnetite was an optimal precipitant for filtration. The average particle size of precipitate with NaOH+alum+0.15 g magnetite was 600 μm. Because the total value of metal concentrations in supernatant at pH=9 was the smallest, sodium hydroxide should be added with 0.2 g alum and 0.15 g magnetite for pH=9 of leachate.
[en] Landfill, a matured and economically appealing technology, is the ultimate approach for the management of municipal solid wastes. However, the inevitable generation of leachate from landfill requires further treatment. Among the various leachate treatment technologies available, advanced oxidation processes (AOPs) are among powerful methods to deal with the refractory organic constituents, and the Fenton reagent has evolved as one promising AOPs for the treatment of leachates. Particularly, the combination of UV-radiation with Fenton's reagent has been reported to be a method that allows both the photo-regeneration of Fe2+ and photo-decarboxylation of ferric carboxylates. In this study, Fenton and photo-Fenton processes were fine tuned for the treatment of leachates from the Colmenar Viejo (Madrid, Spain) Landfill. Results showed that it is possible to define a set of conditions under which the same COD and TOC removals (approx 70%) could be achieved with both the conventional and photo-Fenton processes. But Fenton process generated an important quantity of iron sludge, which will require further disposal, when performed under optimal COD removal conditions. Furthermore conventional Fenton process was able to achieve slightly over an 80% COD removal from a 'young' leachate, while for 'old' and 'mixed' leachates was close to a 70%. The main advantage showed by the photo-assisted Fenton treatment of landfill leachate was that it consumed 32 times less iron and produced 25 times less sludge volume yielding the same COD removal results than a conventional Fenton treatment.
[en] Organic matter, upon dissolution into the aqueous state as dissolved organic matter (DOM), can undergo mineralization by microbes. There has been increasing effort to characterize DOM released from thawing permafrost because it may perpetuate a permafrost carbon feedback. Permafrost-derived DOM often has a composition that can be highly susceptible to mineralization by microbes, but most studies to date that characterize permafrost-derived DOM have been limited to select regions, and tend to focus on a single type of permafrost (sometimes unspecified) that reflects a particular deposit type. Importantly, diversity in the nature of the deposit, formation of permafrost, and thaw modification processes leads to spatial and stratigraphic variability in its properties, but our understanding of variation in the composition of DOM derived from differing permafrost types (end-members) is poor. Here, we used ultrahigh-resolution mass spectrometry to characterize DOM composition derived from a series of permafrost end-member types that are commonly found within the thaw-vulnerable western Canadian Arctic, including: tills (glacially deposited), diamicton (thawed and remobilized material of mixed origin), lacustrine (lake basin sediments into which permafrost has aggraded), peat (partially decomposed organic material), and Yedoma (syngenetic silty loess) deposits. We identified marked variation in DOM composition among permafrost end-member types. Tills were compositionally dissimilar to all other permafrost end-members. Compounds unique to Yedoma were predominantly aliphatic, while compounds unique to peat, lacustrine, and diamicton spanned saturation and oxygenation gradients. All permafrost leachates were generally higher in aliphatics, lower in aromatics, and less oxygenated than active layer leachates. Compositional differences appear to reflect variation in permafrost parent materials, and particularly strong effects from past modification processes while in the unfrozen or thawed state. Constraining DOM composition and assessing its stratigraphic variability will become more pressing as the spatial and stratigraphic extent of thaw increases with future warming. (letter)
[en] We test different amounts of acid and the way of adding it in order to obtain the solubilization of uranium in static leaching. We also test the effects of the temperature. Finally we show the tests of solvent extraction considering the most important variables in it . In leaching we must work with 32 kg/t of acid and 40 d in order to obtain uraniums solubilization over 80%, The pregnant liquors have a high concentration of silica and we must use low organic liquid ( ≤ 3,5 % in amine) and fit the acidity of the pregnant Solutions to 4-8 g H2SO4/I. We show the economy of the process. (Author)
[en] The objectives of the Annual Report are to: (1) describe changes in the volume of liquid seen in each lysimeter, (2) describe concentrations and changes or trends in the concentrations of leachate-indicator constituents in any liquids accumulated in each lysimeter, (3) summarize the finding in regard to the presence or absence of leachate in each lysimeter, (4) make recommendations, if any, limited to vadose-zone study-related variables. The data and analyses contained in this report reflect the initial characterization of construction and consolidation water in Cells 5 and 6 lysimeters.
[en] To understand the long-term leach behavior of a borosilicate waste glass in a repository, the leaching experiment with three kinds of simulated borosilicate waste glasses has been carried out since the middle of 1997. The five years results indicate that a boron would be applied as an indicator of a long-term leachning of their borosilicate waste glasses and that their long-term leach rates have a tendency to be close to about 0.03g/m2-day even though their compositions and their ratios of the surface area to the volume of leachate are different