Soluble Aluminum Research Articles

Highly Selective Lewis Acid Sites in Desilicated MFI Zeolites for Dihydroxyacetone Isomerization to Lactic Acid

Desilication of commercial MFI-type (ZSM-5) zeolites in solutions of alkali metal hydroxides is demonstrated to generate highly selective heterogeneous catalysts for the aqueous-phase isomerization of biobased dihydroxyacetone (DHA) to lactic acid (LA). The best hierarchical ZSM-5 sample attains a LA selectivity exceeding 90 %, which is comparable to that of the state-of-the-art catalyst (i.e., the Sn-beta zeolite); this optimized hierarchical catalyst is recyclable over three runs. The Lewis acid sites, which are created through desilication along with the introduction of mesoporosity, are shown to play a crucial role in the formation of the desired product; these cannot be achieved by using other post-synthetic methods, such as steaming or impregnation of aluminum species. Desilication of other metallosilicates, such as Ga-MFI, also leads to high LA selectivity. In the presence of a soluble aluminum source, such as aluminum nitrate, alkaline-assisted alumination can introduce these unique Lewis acid centers in all-silica MFI zeolites. These findings highlight the potential of zeolites in the field of biomass-to-chemical conversion, and expand the applicability of desilication for the generation of selective catalytic centers.

Aluminium tolerance in bean traditional cultivars from Madeira.

Common bean (Phaseolus vulgaris L.) is the most important legume crop in the world, providing low-cost, high quality protein, minerals and dietary fiber for human nutrition. The crop was originated from diversity centers in America and exhibits adaptation abilities to different environmental conditions, including soil with low pH. Acid soils occupy 30% of the agro ecosystem areas in the world. In Madeira, acid Andosols and unsatured Cambisols are the dominant groups of soils. Generally, under acidic and infertile conditions, besides of H+ toxicity, soluble aluminium (Al) is the most important abiotic factor limiting plant development and crop productivity. In the field, the hidden roots are also affected and the reduction of root growth under Al stress can be clearly observed in early stages. Seedlings of fifty bean accessions from the Archipelago of Madeira were tested under controlled conditions in the presence of 50 µM Al at pH 4.4. In general, the tested germplasm appeared to be sensitive or very sensitive to Al toxicity. However, fifteen traditional cultivars clearly exhibited elevated Al-tolerance, with an average root relative elongation (RRE) exceeding 50%, while top six accessions surpassed the 60% RRE mark. The Madeira bean germplasm is a valuable resource for sustainable crop production in acid soils and it could be used as parental lines in breeding programs aimed for Al tolerance in common beans.

Modelling of the adsorption of phenolic acids onto α,γ–alumina particles

Adsorption of three phenolic acids, namely parahydroxybenzoic acid (4-hydroxybenzoic acid, H2Phb), protocatechuic acid (3,4-dihydroxybenzoic acid, H2Proto) and gallic acid (3,4,5-trihydroxybenzoic acid, H2Gal) onto α,γ–Al2O3 particles was studied vs. ligand concentration at pH 5.0, and vs. pH. The oxide surface was characterized with both potentiometric titrations and electrophoretic measurements; a difference in the point of zero salt effect (PZSE) and the isoelectric point (IEP) was evidenced, which could be attributed to the presence of impurities or to the heterogeneity of the oxide. The potentiometric titration experiments lead to the determination of a PZSE of 8.5. Moreover, the particular shape of the curves were fitted in the framework of the constant capacitance model (CCM), using FITEQL 4.0 software, to determine the oxide parameters (protolytic properties and site density). The electrophoretic measurements were fitted in the framework of the double diffuse layer model (DLM) and an IEP of 9.5 was determined. The constant-pH isotherms of the acids were fitted using the CCM. Constant-pH isotherms of H2Gal and H2Proto onto the Al2O3 surface sites at pH 5 were similar. Two adsorption sites of different affinities were clearly evidenced for H2Gal and can also be proposed for H2Proto. H2Phb showed a lower affinity for the surface than the two other acids, as the logKsorb for H2Phb is one and a half time lower than the one for H2Proto when adsorption is described with one adsorption site. As expected for a carboxylic acid, adsorption of H2Phb decreased with pH and experimental data were well fitted using three adsorbed species (MOH2H2Phb+, MHPhb−, and MPhb−). Adsorption of H2Proto and H2Gal did not change significantly upon increasing pH, meaning that the different functional groups on the aromatic ring (carboxylate and phenolate) were involved in adsorption as pH increases. Dissolution of the oxide was also estimated by measuring the amount of soluble aluminum at pH 5. Increasing acid concentration promoted dissolution, especially for the low concentration range ([acid]<3mmolL−1), but higher acid concentration lowers the increase of the solubility increase, likely due to adsorption on surface of an aluminum–organic complex.

Tschermak's substitution in antigorite and consequences for phase relations and water liberation in high-grade serpentinites

A model for the incorporation of alumina in FeO–MgO–Al2O3–SiO2–H2O (FMASH) serpentinites has been developed by considering ideal Tschermak (Al2Mg−1Si−1) solid solution in antigorite. The antigorite model has been calibrated by fitting the experimental conditions for the decomposition of antigorite to chlorite+olivine+orthopyroxene+fluid in the FMASH system. The antigorite Al-contents predicted with this model are in agreement with natural observations and suggest a maximum alumina solubility in antigorite of 3.6wt.% Al2O3 at 20kbar–650°C and of 4.5wt.% Al2O3 at 3kbar–560°C. In the assemblage antigorite–olivine–chlorite–fluid, the Al-content of antigorite is buffered and temperature sensitive. This temperature sensitivity is the basis for a serpentinite geothermometer at greenschist, amphibolite and eclogite facies conditions. The buffered assemblage is stable in harzburgite compositions for relatively moderate amounts of Al2O3 (>1.8wt.%) and is widespread in lherzolites, where it occurs together with diopside or, in a narrow temperature field, with tremolite.

Comparative Proteome Analyses Reveal that Nitric Oxide Is an Important Signal Molecule in the Response of Rice to Aluminum Toxicity

Acidic soils inhibit crop yield and reduce grain quality. One of the major contributing factors to acidic soil is the presence of soluble aluminum (Al(3+)) ions, but the mechanisms underlying plant responses to Al(3+) toxicity remain elusive. Nitric oxide (NO) is an important messenger and participates in various plant physiological responses. Here, we demonstrate that Al(3+) induced an increase of NO in rice seedlings; adding exogenous NO alleviated the Al(3+) toxicity related to rice growth and photosynthetic capacity, effects that could be reversed by suppressing NO metabolism. Comparative proteomic analyses successfully identified 92 proteins that showed differential expression after Al(3+) or NO treatment. In particular, some of the proteins are involved in reactive oxygen species (ROS) and reactive nitrogen species (RNS) metabolism. Further analyses confirmed that NO treatment reduced Al(3+)-induced ROS and RNS toxicities by increasing the activities and protein expression of antioxidant enzymes, as well as S-nitrosoglutathione reductase (GSNOR). Suppressing GSNOR enzymatic activity aggravated Al(3+) damage to rice and increased the accumulation of RNS. NO treatment altered the expression of proteins associated with cell wall synthesis, cell division and cell structure, calcium signaling and defense responses. On the basis of these results, we propose that NO activates multiple pathways that enhance rice adaptation to Al(3+) toxicity. Such findings may be applicable to crop engineering to enhance yield and improve stress tolerance.

Minimizing residual aluminum concentration in treated water by tailoring properties of polyaluminum coagulants

Aluminum coagulants are widely used in water treatment plants to remove turbidity and dissolved substances. However, because high aluminum concentrations in treated water are associated with increased turbidity and because aluminum exerts undeniable human health effects, its concentration should be controlled in water treatment plants, especially in plants that use aluminum coagulants. In this study, the effect of polyaluminum chloride (PACl) coagulant characteristics on dissolved residual aluminum concentrations after coagulation and filtration was investigated. The dissolved residual aluminum concentrations at a given coagulation pH differed among the PACls tested. Very-high-basicity PACl yielded low dissolved residual aluminum concentrations and higher natural organic matter (NOM) removal. The low residual aluminum concentrations were related to the low content of monomeric aluminum (Ala) in the PACl. Polymeric (Alb)/colloidal (Alc) ratio in PACl did not greatly influence residual aluminum concentration. The presence of sulfate in PACl contributed to lower residual aluminum concentration only when coagulation was performed at around pH 6.5 or lower. At a wide pH range (6.5–8.5), residual aluminum concentrations <0.02 mg/L were attained by tailoring PACl properties (Ala percentage ≤0.5%, basicity ≥85%). The dissolved residual aluminum concentrations did not increase with increasing the dosage of high-basicity PACl, but did increase with increasing the dosage of normal-basicity PACl. We inferred that increasing the basicity of PACl afforded lower dissolved residual aluminum concentrations partly because the high-basicity PACls could have a small percentage of Ala, which tends to form soluble aluminum–NOM complexes with molecular weights of 100 kDa–0.45 μm.

Chemistry of bauxite residue neutralisation and aspects to implementation

Bauxite residue neutralisation is intended to reduce the environmental impact of this highly alkaline material. Also, it can potentially reduce the need for on-going management of disposal impoundments post-closure, as well as open opportunities for re-use of the residue material. In this study bauxite residue neutralisation has been examined using a range of neutralising agents measuring the change in pH, in addition to the quality of leachate produced, specifically alkalinity and solution aluminium concentration. Solution alkalinity is removed by neutralisation and precipitation for mineral acid addition and through precipitation by soluble calcium or magnesium salt addition. Carbonation removes alkalinity through neutralisation and transformation to bicarbonate. An equilibrium pH of less than 10 is achieved only if the solid phase alkalinity is suppressed (Ca/Mg) or dissolved (acid). The kinetics of this process is inhibited by mass transfer limitations (acid processes) and a sustainable presence of a soluble excess (Ca/Mg processes). The solution alkalinity after neutralisation to pH10 is reduced to less than 1% of the initial value using mineral acid or a soluble calcium or magnesium source. Using carbon dioxide the solution alkalinity is only reduced by about 40%. Comparing acid to Ca/Mg treated bauxite residue there is a difference in the mechanism in which the soluble aluminium is precipitated from the solution alkalinity, such that at equivalent pH values, the aluminium solution concentration is higher for acid treated bauxite residue compared to Ca/Mg treated bauxite residue. Aspects of implementing bauxite residue neutralisation within the context of a dry stacking operation are discussed.

Residual Effects of Organic and NPK Fertilizers on Maize Performance at Different Soil pH Levels

Acid soils are highly weathered and are usually excessive in soluble aluminum and manganese and deficient in phosphorous, calcium, magnesium and molybdenum, which may cause their reduced uptake and lead to nutrient imbalances in plants. To address this problem, a field study was carried out in 2012 to evaluate the residual effects of combined rates of poultry manure (PM) and NPK 15-15-15 fertilizers on responses of maize (Zea mays L) in a soil limed to different pH levels. The treatments were four levels of soil pH: pH 5.5 (control), pH 6.0, pH 6.5and pH 7.0 and six levels of combined PM and NPK 15-15-15 fertilizer: T1 (200 kg/ha NPK + 6 t/ha PM); T2 (300 kg/ha NPK + 4 t/ha PM), T3 (400 kg t/ha NPK + 2 t/ha PM); T4 (400 t/ha NPK only), T5 (8 t/ha PM only) and T6 (Control) arranged in a 6 x 4 factorial in randomized complete block design (RBCD) with three replications. The results showed that Treatment T2 (8 t/ha PM only) significantly (P < 0.05) gave the highest dry matter yield while T2 (300 kg/ha NPK + 4 t/ha PM) had the least dry matter yield. Liming also increased the maize dry yield with soil limed to pH 6.0 having the highest dry matter. It was therefore concluded that for second season planting, maize can be efficiently produced in sandy loam ultisols previously applied with treatments T5 (8t/ha PM) and limed to pH 6.0.

Galvanic Production Waste Water Treatment with Electro/coagulation Sludge in Terms of Nickel and Copper Ions

A possibility of nickel ions and copper ions recovery from galvanic waste waters with electro-coagulation sludge that is formed in the process of electro/chemical cleaning of galvanic drainage pipes with the use of soluble aluminum anodes has been demonstrated. Nickel ions recovery from the galvanic waste water in case of the optimal proportion of the sludge has reached at least 55 %.

The apparent solubility of aluminum (III) in Hanford high-level waste

The solubility of aluminum in Hanford nuclear waste impacts on the processability of the waste by a number of proposed treatment options. For many years, Hanford staff has anecdotally noted that aluminum appears to be considerably more soluble in Hanford waste than the simpler electrolyte solutions used as analogues. There has been minimal scientific study to confirm these anecdotal observations, however. The present study determines the apparent solubility product for gibbsite in 50 tank samples. The ratio of hydroxide to aluminum in the liquid phase for the samples is calculated and plotted as a function of total sodium molarity. Total sodium molarity is used as a surrogate for ionic strength, because the relative ratios of mono-, di- and trivalent anions are not available for all of the samples. These results were compared to the simple NaOH-NaAl(OH)4-H2O system, and the NaOH-NaAl(OH)4-NaCl-H2O system data retrieved from the literature. The results show that gibbsite is apparently more soluble in the samples than in the simple systems whenever the sodium molarity is greater than 2M. This apparent enhanced solubility cannot be explained solely by differences in ionic strength. The change in solubility with ionic strength in simple systems is small compared to the difference between aluminum solubility in Hanford waste and the simple systems. The reason for the apparent enhanced solubility is unknown, but could include kinetic or thermodynamic factors that are not present in the simple electrolyte systems. Any kinetic explanation would have to explain why the samples are always supersaturated whenever the sodium molarity is above 2M. Real waste characterization data should not be used to validate thermodynamic solubility models until it can be confirmed that the apparent enhanced gibbsite solubility is a thermodynamic effect and not a kinetic effect.

Inclusion Variations of Hot Working Die Steel H13 in Refining Process

Inclusion variations of die steel H13, including changes of species, morphologies, compositions, amounts and sizes, in the production of EAF→LF→VD→ingot casting→electro-slag refining (ESR) procedure, were investigated by systematic sampling, and analyzed with scanning electron microscope (SEM), energy dispersive spectrum (EDS), and metallographic microscope. The variation mechanism was studied by comprehensive analysis of total oxygen, nitrogen, and acid soluble aluminum as well as chemical test of refining slag. Based on the investigations, technical measures for cleanness improvement were discussed. The results show that oxide inclusions in H13 steel change from irregular Al2O3→near globular CaO-MgO-Al2O3 and CaO-Al2O3-SiO2 complex inclusions→finer CaO-Al2O3-SiO2 inclusions with higher CaO content→CaO-Al2O3-SiO2 inclusions with higher Al2O3 content and irregular MgO-Al2O3 inclusions→fine irregular MgO-Al2O3-CaS inclusions in various steps of the production; the variations are related with changes of acid soluble aluminum content, reactions between slag and steel, re-oxidation of liquid steel during casting, and refining of ESR. It is also found that A12O3 inclusions are modified by refining slag in LF and VD refining; and ESR plays a good role in inclusion removal, especially in controlling the large linear VC-CrC-MoC inclusions distributed in grain boundaries. It is suggested that casting protection should be improved, and the basicity of refining slag and acid soluble aluminum content in steel should be raised.

Tonoplast- and Plasma Membrane-Localized Aquaporin-Family Transporters in Blue Hydrangea Sepals of Aluminum Hyperaccumulating Plant

Hydrangea (Hydrangea macrophylla) is tolerant of acidic soils in which toxicity generally arises from the presence of the soluble aluminum (Al) ion. When hydrangea is cultivated in acidic soil, its resulting blue sepal color is caused by the Al complex formation of anthocyanin. The concentration of vacuolar Al in blue sepal cells can reach levels in excess of approximately 15 mM, suggesting the existence of an Al-transport and/or storage system. However, until now, no Al transporter has been identified in Al hyperaccumulating plants, animals or microorganisms. To identify the transporter being responsible for Al hyperaccumulation, we prepared a cDNA library from blue sepals according to the sepal maturation stage, and then selected candidate genes using a microarray analysis and an in silico study. Here, we identified the vacuolar and plasma membrane-localized Al transporters genes vacuolar Al transporter (VALT) and plasma membrane Al transporter 1 (PALT1), respectively, which are both members of the aquaporin family. The localization of each protein was confirmed by the transient co-expression of the genes. Reverse transcription-PCR and immunoblotting results indicated that VALT and PALT1 are highly expressed in sepal tissue. The overexpression of VALT and PALT1 in Arabidopsis thaliana conferred Al-tolerance and Al-sensitivity, respectively.

A temporal study on fate of Al2O3 nanoparticles in a fresh water microcosm at environmentally relevant low concentrations

This study on a microcosm, brings out the temporal changes in physico–chemical behavior of aluminum oxide nanoparticles (for a period of 210 days), at environmentally relevant concentrations (1000μg/L and below). The dynamics of particle behavior in terms of mean hydrodynamic diameter, specific surface area and dissolution of soluble aluminum and, their possible ecological implications have been presented in this study. A thorough statistical analysis brings out nanoparticle behavior, where a rapid aggregation of particles (79±13nm at 0h to 1464±80nm at 48h), with a decrease in specific surface area (32m2/g at 0h to 1.7m2/g at 48h) was observed. Ion release profile indicated a significant increase in soluble aluminum concentration only after 36h (277±15μg/L at 0h to 462±3μg/L at 36h) which reduced over a period of 60 days (279±20μg/L). A differential response at 1000μg/L concentration was observed, short term exposure (5 days) showed an immediate effect on the resident algal population (∼25% decreased viability) and the long term (7 months/210 days) exposure showed a gradual recovery. Thus, nanomaterials may not have the stipulated toxic response, at low concentration and longer standing period, presumably owing to the complexity of the natural systems.

Aluminum solubility in TiO2 rutile at high pressure and experimental evidence for a CaCl2-structured polymorph

Aluminum incorporation into TiO 2 has been studied in the TiO 2 -Al 2 O 3 system as a function of pressure at temperatures of 900 and 1300 °C using commercial Al 2 TiO 5 nanopowder as starting material. A new orthorhombic TiO 2 polymorph with the CaCl 2 structure has been observed in the recovered samples synthesized from 4.5 to 7 GPa and 900 °C and from 2.5 to 7 GPa at 1300 °C. The phase transition to the α-PbO 2 type TiO 2 phase takes place between 7 and 10 GPa at both temperatures. Two mechanisms of Al incorporation in TiO 2 rutile have been observed in the recovered samples. The substitution of Ti 4+ by Al 3+ on normal octahedral sites is dominant at lower pressures. High pressure induces the incorporation of Al 3+ into octahedral interstices of the rutile structure, which is responsible for an orthorhombic distortion of the TiO 2 rutile structure and gives rise to a (110) twinned CaCl 2 type structure. This phase is probably a result of temperature quench at high pressure. Aluminum solubility in TiO 2 increases with increasing pressure. TiO 2 is able to accommodate up to 9.8 wt% Al 2 O 3 at 7 GPa and 1300 °C. Temperature has a large effect on the aluminum incorporation in TiO 2 , especially at higher pressures. High pressure has a strong effect on both the chemistry and the microstructure of Al-doped TiO 2 . Enhanced aluminum concentration in TiO 2 rutile as well as TiO 2 grains with a microstructure consisting of twins are a clear indication of high-pressure conditions.

Continuous flow analysis method for determination of soluble iron and aluminium in ice cores

Iron and aluminium are the two most abundant metals on the Earth's crust, but they display quite different biogeochemical properties. While iron is essential to many biological processes, aluminium has not been found to have any biological function at all. In environmental studies, iron has been studied in detail for its limiting role in the bioproductivity of high nutrient, low carbon oceanic zones, while aluminium is routinely used as a reference of crustal contributions to atmospheric deposition archives including peat bogs, lacustrine and marine sediments and ice sheets and glaciers. We report here the development of a flow injection analysis technique, which has been optimised for the simultaneous determination of soluble iron and aluminium in polar ice cores. Iron was determined by its catalytic role in the reduction of N,N-dimethyl-p-phenylenediamene (DPD) to a semiquinonic form (DPDQ) and subsequent absorption spectroscopy at 514 nm. Aluminium was determined by spectroscopic analysis of an aluminium-lumogallion complex that exhibits fluorescence at 560 nm. These techniques have been applied to a section of Greenland ice dated to 1729-1733 AD and indicate that volcanism is a source of highly soluble aluminium and iron.

Effects of humic acid on residual Al control in drinking water treatment plants with orthophosphate addition

This study aimed to investigate the effects of humic acid (HA) on residual Al control in drinking water facilities that used orthophosphate addition. The results showed that adding orthophosphate was an effective method for residual Al control for the raw water without HA. When orthophosphate was added at 1.0 min before the addition of poly aluminum chloride (PACl), the concentrations of soluble aluminum (Sol-Al) and total aluminum (Tot-Al) residue were 0.08 and 0.086 mg·L−1, respectively; both were reduced by 46% compared with the control experiment. The presence of HA would notably increase the residual Al concentration. For the raw water with 5 mg·L−1 of HA, the concentrations of Sol-Al and Tot-Al increased from 0.136 and 0.174 mg·L−1 to 0.172 and 0.272 mg·L−1, respectively. For water with a HA concentration above 5 mg·L−1, orthophosphate was ineffective in the control of residual Al, though there were still parts of orthophosphate were removed in coagulation. The amounts of Al removal were positively correlated with the solids freshly formed in coagulation. Similar to the raw water without HA, the best Al control was obtained with orthophosphate salt added at 1.0 min before PACl. HA concentrations in the raw water, solution pH, and the orthophosphate dosage suitable for residual Al control by orthophosphate precipitation were also investigated.

Global estimates of mineral dust aerosol iron and aluminum solubility that account for particle size using diffusion‐controlled and surface‐area‐controlled approximations

Mineral aerosol deposition is recognized as the dominant source of iron to the open ocean and the solubility of iron in the dust aerosol is highly variable, with measurements ranging from 0.01–80%. Global models have difficulty capturing the observed variations in solubility, and have ignored the solubility dependence on aerosol size. We introduce two idealized physical models to estimate the size dependence of mineral aerosol solubility: a diffusion‐controlled model and a surface‐area‐controlled model. These models produce differing time‐ and space‐varying solubility maps for aerosol Fe and Al given the dust age at deposition, size‐resolved dust entrainment fields, and the aerosol acidity. The resulting soluble iron deposition fluxes are substantially different, and more realistic, than a globally uniform solubility approximation. The surface‐area‐controlled solubility varies more than the diffusion‐controlled solubility and better captures the spatial pattern of observed solubility in the Atlantic. However, neither of these two models explains the large solubility variation observed in the Pacific. We then examine the impacts of spatially variable, size‐dependent solubility on marine biogeochemistry with the Biogeochemical Elemental Cycling (BEC) ocean model by comparing the modeled surface ocean dissolved Fe and Al with observations. The diffusion‐based variable solubility does not significantly improve the simulation of dissolved Fe relative to a 5% globally uniform solubility, while the surface‐area‐based variable solubility improves the simulation in the North Atlantic but worsens it in the Pacific and Indian Oceans.

제주도 Andisol 토양의 Al-용해도 특성

The solubility of aluminum for two Andisol profiles formed on pyroclastic materials and basaltic rocks from Jeju Island, Korea was investigated. It is found that high organic carbon content and ratios in the A horizons, suggesting the substantial amounts of reactive Al are associated with organic matter, whereas the low organic carbon content and the ratios in the Bo horizons indicate that a major part of the reactive Al should be bound inorganically. The differential FT-IR spectra following acid-oxalate dissolution and heating up to 150 and , and transmission electron microscope (TEM) observation confirm that imogolite is in the Bo horizon. Our results of equilibration experiments demonstrate that the Al solubility in the Bo horizon for Andisols can be clarified by the congruent dissolution model for imogolite-type material (ITM), rather than by the simultaneous equilibrium with both ITM and Al hydroxy-interlayered aluminosilicate. With results from dialysis and aging procedures, it is noted that the formation of a proto imogolite sol showing its transformation to imogolite, which supports the congruent dissolution of ITM primarily controlling the Al solubility of Andisols in Jeju Island, Korea.

Aluminium heterogeneous speciation in natural waters

The presence of aluminium in natural waters is of major concern at present because of the potential threat for the health of a number of species, including humans. In natural water, aluminium exists in different forms depending on the concentrations of various other species, organic matter, the types of minerals, the pH, etc. The aluminium species in the natural water – gibbsite system is considered in this work. The main approaches for estimating of the individual concentrations of the aluminium species involve the use of reliable thermodynamic data, together with experimental measurements of free or total concentrations of major components. The new type of diagrams based on graphical and computerized methods, which quantitatively describe the distribution of soluble and insoluble, inorganic, and organic, and monomeric and polymeric aluminium species in heterogeneous aquatic systems is presented. This approach utilizes thermodynamic relationships coupled with original mass balance constraints, where the mineral phases are explicitly expressed. The factors influencing the distribution of soluble and insoluble aluminium species in aquatic systems were analyzed. The new type of developed diagrams may be used to interpret data obtained within the framework of water-quality monitoring programs.

Metastable Phases of Dross Particles Formed in a Molten Zinc Bath and Prediction of Soluble Aluminum During Galvannealing Processes

The morphology, chemistry, and crystallographic characteristics of metastable dross particles were identified. These particles are formed during the initial stage of precipitation. The particles had aluminum concentrations of 15 to 80 mass pct, with values that decreased gradually as particle size increased. These metastable dross particles were a mixture of the crystalline phase of FeZn10, which is called the “delta phase,” and the high-aluminum amorphous phase, which covered the surface of the crystalline phase. The new “meta Q” concept was proposed to predict the amount of soluble aluminum in the zinc bath by considering nucleation kinetics and particle growth. The results calculated using the “meta Q” concept were compared with the values measured by the aluminum sensor, which were taken during the same period at the commercial galvanizing line. The mean of the absolute values of the differences between the calculated and measured values was 9.7 ppm.