Al Species In Solution Research Articles

Transformation of planar Mögel Al13 coagulant during the dilution and aging process

Transformation of a novel planar Mögel Al13 (Al13(OH)24(H2O)2415+, simplified as M-Al13) coagulant in the dilution and aging process was investigated with Ferron colorimetric method, electrospray ionization mass spectrometry (ESI-MS) and 27Al NMR spectroscopy. Special attention has been paid to the transformation process of M-Al13 to stereo Keggin Al13 (ɛ-AlO4Al12(OH)24(H2O)127+, simplified as K-Al13). M-Al13 was found to be an unstable aluminum species and could be decomposed into oligomers as Al1, Al2 and Al3 when dissolved in solution. These newly formed oligomers were also found to polymerize into K-Al13 by self-assembly during the dilution process. More K-Al13 species could be continuously formed at the initial aging period of the diluted solution. On the whole, the hydrolysis and aging behavior of planar M-Al13 in aqueous solution is quite different from those of the K-Al13 species, which may provide insight into the structure re-organization mechanism of polymeric Al species in solution.

Quantification analysis of polymeric Al species in solutions with electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS)

With the help of Ferron colorimetric method and 27Al NMR spectroscopy, quantification analysis method of electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) on Al speciation was developed and thus Al species in polymeric Al solutions were quantitatively analyzed. Based on the speciation results of mononuclear Al solution and purified Al 13 solution, Al species obtained with ESI-TOF-MS in polymeric Al solutions were classified into three categories as low polymers (i.e., Al 1–Al 10), mid polymers (i.e., Al 13–Al 20), and high polymers (i.e., Al 21–Al 31). Among these polymers, only a certain number of Al species have relative high content and constitute the dominant component of polymeric Al solutions. The quantification analysis results of ESI-TOF-MS agree well with those obtained by the other two traditional methods, which proves the feasibility of the novel method on Al species analysis. Additionally, ESI-TOF-MS can provide more information on Al speciation than 27Al NMR spectroscopy and Ferron colorimetric method, and the quantification analysis results can clearly explain the difference between the two traditional methods.

Effect of aging condition on species transformation in polymeric Al salt coagulants

Effect of aging time and aging temperature on the transformation process of Al species in hydroxyl Al solutions were analyzed by Ferron assay and 27Al NMR spectroscopy with the help of analysis results of pH, turbidity and morphology of samples. Owing to the high chemical energy provided by elevated temperature, aging temperature exerted greater effect on the transformation of polymers than aging time. Elevation of aging temperature enhanced the transformation rate of various Al species in solution. Polymerization or hydrolysis of monomers in solution was not detected under various aging conditions. Polymeric Al species with non-Keggin structure (e.g., hexameric ring structure) were less stable than Keggin-Al 13. The decomposition of Al 13 only occurred at higher aging temperature. The coexistence of oligomers affected the transformation of Al 13. Morphology and species composition of colloidal Al species transformed from Al 13 were different from those from polymeric Al species with non-Keggin structure. Changes in pH, turbidity and morphology of samples agreed well with the distribution of Al species obtained by Ferron assay and 27Al NMR spectroscopy.

Kinetics of Aluminum Uptake by Cell Suspensions of Phaseolus vulgaris L.

Summary The Kinetics of aluminum (Al) uptake by cell suspensions derived from an Al-resistant (Dade) an an Al-sensitive (Romano) cultivar of Phaseolus vulgaris L. were investigated. Uptake of Al from low-volume (3-mL) uptake solutions containing 75 μM AlCl 3 was rapid during the first 20 min with little additional absorption occurring over the remainder of the 180 min experimental period. In contrast studies with excised roots showed a longer rapid phase (30 min) which was followed by a linear phase of uptake. Differences in Al uptake between excised roots and cell suspensions appear to reflect the unique characteristics of our low-volume cell system rather than real differences in uptake between the two systems. The rate, extent, and saturable nature of uptake in this cell system suggested that depletion of Al from uptake solutions may have been responsible for the lacf of an observable linear phase of uptake. However, when the concentration of Al in uptake solutions was increased to 500 and 1000 μM, total accumulation of Al increased, while the general pattern of uptake was not affected. Moreover, mock-uptake experiments at these high concentrations ruled out the possibility of artifacts arising from formation of solid phase phase Al. While increasing the concentration of Al in uptake solutions provided a means of increasing Al available for uptake, Pyrocatechol violet analysis of monomeric Al indicate incomplete recovery of added Al particularly at concentrations above 300 μM. To overcome potential problems associate with the formation of complex Al species in solution, the total amount of Al in solution was increased using a high-volume (100-mL), low-concentration (75-μM AlC1 3 ) system. Under these conditions, a biphasic pattern of uptake was observed, with a rapid phase of uptake during the first 20 min, and a linear phase of uptake over the remainder of the 180 min uptake period. We were also able to isolate the linear phase of uptake after desorption in 9.0 mM citric acid. These results suggest that the basic pattern of Al uptake by cell suspensions (saturated vs. linear) is strongly affected by the speciation of Al, which is indirectly related to the volume of uptake solutions. The biphasic pattern of uptake observed in our high-volume system also supports the hypothesis that the kinetics of short-term Al uptake observed in excise roots reflect transport events occurring at the cellular level. We believe further investigation of the kinetics of Al uptake at the cellular level could provide a more direct means of measuring the uptake of Al across the plasma membrane in plants.

Experimental determination and interpretation of the solubility of the assemblage microcline, muscovite, and quartz in supercritical H 2O

The concentrations of K, Na, Al, and Si in pure H 2O in equilibrium with natural microcline, muscovite, and quartz have been measured between 400 and 600°C at 2 kbar with an extraction-quench apparatus. Silicon is the dominant solute in solution, and its concentration is similar to those reported for quartz solubility in pure H 2O: increasing from 0.05 molal at 400°C to 0.12 molal at 600°C. The small amount of Na in the microcline and muscovite was rapidly leached from the mineral surface into solution so that the initial log molality of Na equaled −2.7 but decreased as pure H 4O was injected into the charge volume. Log molalities of K in equilibrium with the mineral assemblage are between −3.0 and −2.7. The calculated solution compositions are basic, and Al(OH) 4 − is determined to be the dominant Al species in solution. These calculations suggest that both Al(OH) 3 0 and A1(OH) 4 − contribute significantly to the solubility of corundum in pure H 2O at these temperatures and 2 kbar. The logarithm of the equilibrium constant for Al( OH) 3 0 + H 2 O = Al( OH) 4 − + H + is computed to be −4.1, −5.4, and −6.1 at 2 kbar and 400, 500, and 600°C, respectively. No evidence exists for the formation of significant concentrations of alkali-Al complexes despite the fact that Al concentrations in pure H 2O for microcline + muscovite + quartz are an order of magnitude greater than those reported for corundum solubility at the same pressure and temperature.

Empirical models to approximate calcium and magnesium ameliorative effects and genetic differences in aluminium tolerance in wheat

The activities of inorganic, monomeric aluminium (Al) species in the root environment are important in the toxicity of Al to plant roots, which may be ameliorated by increased activities of basic cations. Additionally, it has been suggested that electro-chemical processes in walls of root cells play a role in Al tolerance. Empirical models were proposed to accomodate genetic and calcium (Ca) and magnesium (Mg) ameliorative effects on Al toxicity. The models were tested using data from a solution culture study (with ionic strength 1.6 to 8.6 mM) in which wheat (Triticum aestivum L.) cvv. Warigal (Al-sensitive) and Waalt (Al-tolerant) were grown for 28 d at 0, 10 and 20 μM Al, in factorial combination with 200, 400, 800 and 1600 μM Ca and 100, 200, 400 and 800 μM Mg. There was a poor relationship between relative total dry mass (TDM) (calculated as a percentage of the average TDM of each cultivar in the absence of added Al) and the activity of Al3+ or the sum of the activities of the monomeric Al species in solution. A model based on the ratios of activities of cations in solution, taking valency into consideration, was more successful, accounting for ca 85% of the observed variation in relative TDM. There were no systematic variations between observed values and those estimated by the model.

Comparison between Pyrocatechol Violet and 8‐Hydroxyquinoline Procedures for Determining Aluminum Fractions

AbstractThere is currently considerable interest in quantifying concentrations of Al species in solution because of: (i) concern about the potential toxicity of inorganic forms of Al to plants and aquatic organisms, (ii) the need to better understand the processes contributing to soil development, and (iii) ongoing assessments of the biogeochemistry of Al. This study was conducted to compare the pyrocatechol violet (PCV) and 8‐hydroxyquinoline (oxine) methods for the determination of monomeric Al fractions. A strongly acidic cation‐exchange resin was used in automated PCV and nonautomated oxine procedures to separate aqueous Al into inorganic (labile) and organic (nonlabile) monomeric forms. Both synthetic and natural solutions were used in this analysis. Results showed good agreement between the two methods, suggesting that the PCV method is an acceptable alternative to the oxine method for the estimation of monomeric Al. In addition, the cation‐exchange column fractionation procedure was verified using an F ion‐selective electrode. Interference to the PCV method by Fe, F, and dissolved organic C was not significant across the range of solution concentrations studied.

Structural studies of Silica Springs allophane

AbstractThe structure of Silica Springs allophane from New Zealand has been studied by high-resolution 27A1 and 29Si NMR spectroscopy, IR spectroscopy and electron microscopy. Experimental NMR conditions were chosen to give a quantitative relationship between signal strength and Al content. Aluminium is present in both octahedral (Alvi) and tetrahedral (Aliv) coordination, and the ratio Alvi:Aliv was obtained for three samples with different total Al:Si ratios. In all cases the Aliv:Si ratio was 1 : 3, consistent with the ratio in ideal muscovite. The negative charge arising from Aliv was apparently balanced by positive charge at adjacent Alvi sites. Both NMR and IR spectra indicate that Si exists in a condensed network, probably a sheet, with Si atoms linked (through oxygen) to one, two and, possibly, three other Si atoms, but not four. The spectra are consistent with a mixture of Si-O-Si, Si-O-Al, and Si-OH linkages. A structure based on fragments of single curved 1 : 1 aluminosilicate layers, with the tetrahedral sheet on the outer surfaces, is suggested, the diameter of curvature being 2–3 nm. The tetrahedral sheet is more or less complete and has a Aliv : Si ratio of 1 : 3; the octahedral Alvi sheet is incomplete. Electron micrographs suggest that, at least in some cases, the fragments form more or less complete spherules. This proposal seems to accord with Farmer's concept of “aluminous hydrous feldspathoids”. The minimum pH at which Silica Springs allophane has precipitated corresponds to the initial presence of tetrahedrally coordinated Al species in solution.

Effects of aluminium and calcium in the soil solution of acid soils on root elongation of Glycine max cv. Forrest

In the course of three experiments, soybean (Glycerine max (L.) Merr.) cv. Forrest was grown in 21 soils (four surface soils and 17 subsoils) amended with liming materials (CaCO3 and Mg CO3) and soluble Ca salts (CaSO4.2H20 and CaCl2.2H2O). In most soils, the soluble salts increased concentrations and activities of Al species in solution to levels that restricted root growth, and MgCO3, induced a Ca limitation to root growth. Root lengths after three days were related to so11 and soil solution attributes.Suitable diagnostic indices for the prediction of Ca limitations to root growth were either Ca saturation of the effective cation exchange capacity or Ca activity ratio of the soil solution, which was defined as the ratio of the activity of Ca to the sum of the activities of Ca, Mg, Na, and K. Values corresponding to 90% relative root length (RRL) of soybean were 0.05 for the Ca activity ratio and 11% for Ca saturation. Calcium activity and Ca concentration in the soil solution and exchangeable Ca were less useful for this purpose.Soil Al saturation was not a good predictor of Al toxicity, but soil solution measurements were. The activities of Al3+ and AlOH2+ gave the best associations with RRL, and values corresponding to 90% RRL were 4 8M and 0.5 8M respectively. The results suggested that Al(OH)3� , Al(OH)2+, and AlSO4+, were not toxic species. Soil solution pH and soil pH measured in water were more sensitive indicators of root growth than soil pH measured in 0.01 M CaCl2.Using a Ca activity ratio of 0.05 and an Al3+ activity of 4 8M as diagnostic indices, none of the 20 soils in two experiments were toxic in Al, while 13 (all subsoils) were deficient in Ca. Thus the first limitation on root growth was Ca deficiency and not Al toxicity, in spite of high Al saturations and relatively low pH in these soils. However, Al toxicity could be induced by increasing the ionic strengths of soil solutions.

Experimental determination of the solubility of the assemblage paragonite, albite, and quartz in supercritical H 2O

The concentrations of Na, Al, and Si in an aqueous fluid in equilibrium with natural albite, paragonite, and quartz have been measured between 350°C and 500°C and 1 to 2.5 kbar. Si is the dominant solute in solution and is near values reported for quartz solubility in pure H 2O. At 1 kbar the concentrations of Na and Al remain fairly constant from 350°C to 425°C but then decrease at 450°C. At 2 kbar, Na increases slightly with increasing temperature while Al remains nearly constant. Concentrations of Si, Na, and Al all increase with increasing pressure at constant temperature. The molality of Al is close to that of Na and is nearly a log unit greater than calculated molalities assuming Al(OH) 0 3 is the dominant Al species. This indicates a Na-Al complex is the dominant Al species in solution as shown by Anderson and Burnham (1983) at higher temperature and pressure. The complex can be written as NaAl( OH) 0 4 ± nSiO 2 where n is the number of Si atoms in the complex. The value of n is not well constrained but appears to be less than or equal to 3. The results indicate Al can be readily transported in pure H 2O solutions at temperatures and pressures as low as 350°C and 1 kbar.