Amorphous Aluminum Hydroxide Research Articles

Properties of Carbonate-Containing Aluminum Hydroxide Produced by Precipitation at Constant pH

Carbonate-containing aluminum hydroxide was precipitated at constant pH at intervals of 0.5pH units from pH 6 to 10 by pumping 0.5M AlCl3 into the reaction vessel at a constant rate of 2mL/min and infusing 2M Na2CO3 at a rate necessary to maintain the desired pH. The pH of precipitation affected both the particle size and the composition of the precipitate. The particle size of the precipitate decreased as the pH of precipitation was increased from 6 to 10. The precipitates formed between pH 7.5 and 9.5 contained crystalline sodium aluminum hydroxycarbonate (dawsonite) in addition to amorphous carbonate-containing aluminum hydroxide.

Anion-induced metal binding in amorphous aluminium hydroxide

Anion-induced metal binding in amorphous aluminium hydroxide

The Heterogenoues Reactions of Amorphous and Micro-Crystalline Aluminium Hydroxide Precipitates with Alkaline-Earth Metal Hydroxide Solutions: Kinetics and Mechanisms

Article The Heterogenoues Reactions of Amorphous and Micro-Crystalline Aluminium Hydroxide Precipitates with Alkaline-Earth Metal Hydroxide Solutions: Kinetics and Mechanisms was published on January 1, 1984 in the journal Zeitschrift für Physikalische Chemie (volume 265O, issue 1).

The Reclamation of Acidic Colliery Spoil. III. Problems Associated with the Use of High Rates of Limestone

(1) Growth of Trifolium repens in acidic colliery spoil was suppressed by more than 90% when agricultural ground calcitic limestone was applied at above 5 t ha-l whereas Lolium perenne was unaffected at rates up to o00 t ha-'. (2) The inhibitory effect of ground limestone on T. repens was reduced by high phosphorus fertilization and disappeared within 34 weeks of treatment. (3) There was some evidence that high liming caused an imbalance of the Ca/Mg ratio in freshly limed spoil, contributing to growth inhibition. (4) Growth of L. perenne was improved and the inhibitory effect on T. repens was alleviated by substituting magnesian limestone (dolomite) for calcitic limestone. (5) Phosphate adsorption of spoil was similar after low and very high limestone applications but increased by 100% after liming at 25 t ha-' to pH 5. 1. (6) It is suggested that phosphate adsorption at pH 5.1 is caused by freshly precipitated, amorphous aluminium hydroxide. (7) The practical implications of the results are discussed.

The adsorption sites of oxovanadium(IV) ions in amorphous aluminum hydroxide: A spectroscopic characterization

Electron spin resonance spectra and optical spectra have been used to characterize the environment of VO2+ ions adsorbed on amorphous aluminium hydroxide gels. The ion is found to occupy sites of well-defined symmetry uniformly distributed throughout the amorphous structure.Both ESR and bonding parameters give evidence that delocalization of the vanadium(IV) unpaired electron takes place, due to covalency in the binding of the ion.

Structural analysis of the amorphous sodium salt and aluminium hydroxide salt of sucrose sulphate

Download options Please wait... Article information DOI https://doi.org/10.1039/F19817700629 Article type Paper Download Citation J. Chem. Soc., Faraday Trans. 1, 1981,77, 629-639 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Structural analysis of the amorphous sodium salt and aluminium hydroxide salt of sucrose sulphate H. Morikawa, M. Miyake, S. Iwai, Y. Nawata and M. Shiba, J. Chem. Soc., Faraday Trans. 1, 1981, 77, 629 DOI: 10.1039/F19817700629 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Hideki Morikawa Michihiro Miyake Shin-Ichi Iwai Yoshiharu Nawata Motoyasu Shiba

Preparation of gelatinous aluminium hydroxide from aqueous solutions of organic aluminium salts by reaction with alkali

AbstractThe preparation of gelatinous aluminium hydroxide from aqueous solutions of the formate, citrate or tartrate of aluminium on addition of aqueous sodium hydroxide has been investigated under different conditions. The precipitates from aqueous solutions of aluminium formate consist of amorphous aluminium hydroxide, pseudoboehmite, bayerite, hydrargillite or their mixtures, depending on the condition of preparation. A mixed solution of aluminium citrate and sodium hydroxide yields no solid‐phase product without aging on heating to enhance the hydrolysis of aluminium citrate. The resulting precipitate exists as pseudoboehmite, independent of the preparation conditions. In contrast, aluminium tartrate is not hydrolysed to precipitate aluminium hydroxide even by aging on heating.

Die Bildung von kristallinem B�hmit in gemeinsam gef�llten AlFe(III)-Hydroxiden unter hydrothermalen Bedingungen

Under mild hydrothermal conditions originally amorphous aluminium hydroxide coprecipitated with iron(III)ions as Al0,5Fe0,5(OH)3 transforms into aluminium hydroxide crystalline phases which are not observed in products of ageing of pure aluminium hydroxide. By X-ray diffraction analysis, IR spectroscopic studies and microscopic observations it has been found that due to the presence of iron(III) hydroxide it is possible to stabilize the trihydoxide of aluminium i.e. bayerite until 130–140°C. Moreover, with increasing temperature well crystallized boehmite is obtained instead of the usually formed pseudoboehmite. Experiments revealed that the formation of crystalline boehmite does not take place as a process of pseudoboehmit crystallites growth but only as a result of bayerite→boehmite transformation.

Preparation of gelatinous aluminium hydroxide by urea from aqueous solutions containing chloride, nitrate and sulphate of aluminium

AbstractThe preparation of gelatinous aluminium hydroxide from aqueous solutions containing a mixture of the chloride, nitrate or sulphate of aluminium and urea by heating at 95°C has been investigated under different conditions. The pH value of aqueous solutions, on heating for a given period of time, gradually increases, rises steeply at pH 4.0–7.5 and finally approaches a constant value. The precipitate appears at about pH 7 in the presence of chloride or nitrate ions and about pH 4 in the presence of sulphate ions. Although the gelatinous precipitates in the chloride and nitrate systems are apparently different from the granular, filterable one in the sulphate system, their compositions are not influenced by the species of aluminium salt. The fresh precipitates exist in an amorphous state, and go to pseudoboehmite by ageing. It seems that the amount of pseudoboehmite increases as the concentration of aluminium salt in aqueous solution decreases. However, the transformation from amorphous aluminium hydroxide to pseudoboehmite is reduced in the presence of sulphate ions. Furthermore, it is found that the X‐ray diffraction peak for the (200) plane, as an orthorhombic structure, in the pseudoboehmite precipitated from chloride or nitrate solution is more intense than that from sulphate solution.

Reversible control of aqueous aluminum and silica during the irreversible evolution of natural waters

Primary aluminosilicates are transformed at low temperature into a sequence of metastable and thermodynamically stable secondary minerals by an irreversible process. The aqueous concentrations in the associated solution may continuously change during the process or they may be maintained constant through hydrodynamic or chemical steady-state mechanisms or through chemical equilibrium with a reversible metastable solid. Disequilibrium indices calculated for 152 natural waters and experimental solutions show that the solutions are unsaturated with amorphous aluminum hydroxide, microcrystalline gibbsite, amorphous silica and amorphous aluminosilicate, and they are supersaturated with gibbsite and kaolinite. The disequilibrium index for halloysite varies widely from unsaturation to supersaturation. Only the index for the reversible metastable cryptocrystalline aluminosilicate whose composition is pH dependent is very close to zero indicating saturation. The index varies in a narrow range. This, supported by electron micrographs and the results of X-ray fluorescence spectroscopy presented by other authors, suggests that this metastable solid, and not the secondary aluminosilicate minerals, controls the concentrations of alumina and silica in natural waters.

Interactions between H-bentonite and aluminous chlorite-like complexes

In synthetic chlorite-like complexes, amounts of amorphous and/or crystalline hydrous aluminum oxide were determined through use of H-bentonite that converts into Albentonite by reaction with Al-gel or gibbsite. In Al(OH) x-complexes with less than 1,000 mequiv. of Al per 100 g of clay, hydrous aluminum oxide gel remains held on clay surfaces without crystallizing for a long time. The neutralization reaction between a one-symmetry-concentration of H-bentonite and chlorite-like complexes at 10°C is initially very fast and seems to affect exclusively the hydrous oxide in suspension or adsorbed on the external surfaces and edges of clay particles. After a few hours, the interlayer Al-gel begins to be neutralized and the reaction rate decreases according to first-order kinetics. In complexes of equal ages, more time is required to neutralize the hydrous oxide precipitated in the presence of clay than added to the clay, because of a different interlayering. The kinetics of reactions between complexes characterized by amorphous and crystalline aluminum hydroxide (more than 1,000 mequiv. aluminum per 100 g of clay) and H-bentonites were studied. H-bentonite reacts with gibbsite much more slowly than it does with amorphous forms, always according to first order kinetics.

The Influence of the Activity of Water on the Phase Composition of Aluminum Hydroxides Formed by Reaction of Amalgamated Aluminum with Water

AbstractThe influence of the activity of water on the phase composition of aluminum hydroxides obtained by reaction of amalgamated aluminum with water has been studied. The reaction was carried out in solutions of water and dioxane, and in sodium chloride solutions of different concentrations; amorphous aluminum hydroxide was precipitated initially. The aging of this primary product to bayerite, pseudoboehmite, or an amorphous gel was controlled by the water content of the system. The pseudoboehmite has shown a significant reactivity when used as a source of alumina in the hydrothermal syntheses of kaolinite at relatively low temperature and pressure.

Structural Survey of Carbonate-Containing Antacids

A series of carbonate-containing antacids was examined by IR and X-ray analysis to establish the role of carbonate and to compare the structure of the antacids to naturally occurring carbonate minerals. Based on IR analysis, the relative degree of perturbation of carbonate increases in the order calcium carbonate, carbonate-containing aluminum hydroxide gel, and dihydroxyaluminum sodium carbonate. The crystalline carbonate-containing antacids were poorly organized forms of the minerals calcite, CaCO3; dawsonite, NaAI(OH)2CO3; and hydrotalcite, Mg6Al2CO3(OH)16.4H2O. Amorphous carbonate-containing aluminum hydroxide gel can be classified mineralogically as amorphous aluminum hydroxycarbonate. IR and X-ray evidence indicates that magaldrate has a hydrotalcite-like structure with sulfate as the major interlayer anion and carbonate also present in the interlayer space.

Adsorption of inorganic and organic phosphorus by amorphous aluminum hydroxide

Abstract The adsorption of inorganic ? (Pi) and organic ? (Po) compounds by amorphous aluminum hydroxide was studied over the equilibrium ? concentration range of 8 × 10‐7 to 1 × 10‐4 M under normal lake pH conditions using the Langmuir adsorption isotherm. The isotherms for Pi and Po adsorption plotted according to a modified Langmuir equation generally exhibited multiphasic behavior indicative of more than one population of sorption sites differing in their affinity for P. Adsorption maxima and binding energy constants for the adsorption of inorganic and organic phosphorus compounds are reported. Cations, anions, and chelating agents typical of natural waters greatly affected Po adsorption. In general, Po adsorption increased with anionic charge, number of reactive phosphate groups, decreasing steric hindrance and decreasing molecular size. Results indicate that a significant fraction of the native Po in lakes differs from the model Po compounds studied.

Arsenate adsorption on amorphous aluminum hydroxide

Arsenate adsorption on amorphous aluminum hydroxide was studied as a model system for aqueous anion adsorption on oxide surfaces. Adsorption and electrophoretic mobility of the suspended adsorbent particles were measured as functions of equilibrium pH. A transformation of variables allowed the adsorption to be explained in terms of the chemical and physical forces controlling the adsorption reaction. When used in conjunction with the Langmuir adsorption equation, the results allow calculation of levels of arsenate removal for any given amount of adsorbent and any pH.

The nature of pseudoboehmite and its role in the crystallisation of amorphous aluminium hydroxide

The nature of pseudoboehmite and its role in the crystallisation of amorphous aluminium hydroxide

The nature of pseudoboehmite and its role in the crystallisation of amorphous aluminium hydroxide

AbstractPseudoboehmite samples were prepared by ageing the amorphous hydroxide obtained by the hydrolysis of aluminium s‐butoxide using water or aqueous ethanol. Further ageing resulted in the formation of a mixture of crystalline trihydroxides. The two re‐crystallisation stages are accompanied by similar but opposite changes in the volume of the aqueous suspension but pseudoboehmite can only be identified by X‐ray diffraction in a separated xerogel. Crystallinity of the latter was shown to be enhanced by preparation in 80% ethanol but at concentrations providing only a little more than the water needed for hydrolysis of the alkoxide a new modification of pseudoboehmite was observed.X‐ray line broadening and displacement indicated that it possessed an even greater degree of lattice strain than exists in the common form. The composition and specific surface of a number of pseudoboehmite xerogels suggest that the major part of the water, in excess of that in the basic structures AlOOH, is present in a surface monolayer with a minor amount responsible for lattice strain.

The thermal transformation of Gelatinous Aluminium Hydroxide

AbstractThe thermal transformation of the gelatinous aluminium hydroxides (amorphous and pseudoboehmite) prepared from aqueous aluminium chloride solution on addition of sodium hydroxide at various pH, have been studied by X‐ray diffraction, infrared spectra and thermal analyses. As a result, it is concluded that the gelatinous aluminium hydroxides transform thermally as follows: amorphous aluminium hydroxide → amorphous alumina →γ‐alumina → θ‐alumina → α‐alumina, pseudoboehmite → γ‐alumina → θ‐alumina → α‐alumina.Further the thermal transformation of bayerite, prepared from the aqueous solution at higher pH, and of boehmite, prepared hydrothermally from gelatinous aluminium hydroxide, have been investigated in comparison with those of gelatinous aluminium hydroxide.

Studies on amorphous aluminium hydroxide precipitates (gels)

Amorphous (and partly micro-crystalline) aluminium hydroxide precipitates were prepared by controlled hydrolysis of aluminium isopropoxide and aluminium sulphate solutions: the kinetics of their dissolution in well-stirred sodium hydroxide solutions (0.25 to 3 g ion/l) in large excess was studied at 5° to 35°C.

The phase composition of carbonized aluminum hydroxide

1. In the carbonization of aluminate solutions under conditions of pH 10–11.5 and 25–40°C, amorphous aluminum hydroxide precipitates. 2. The gelatinous precipitates, which are products of aging of the amorphous aluminum hydroxide during the process of washing, are not any definite crystalline modification of aluminum hydroxide, but occupy an intermediate position between the amorphous and crystalline states. The molecules of aluminum hydroxide form a more or less ordered steric structure, including elements of boehmite and bayerite structures.