Showing papers on "Aluminium hydroxide published in 1990"

Coprecipitation of yttrium and aluminium hydroxide for preparation of yttrium aluminium garnet

Abstract: Coprecipitation of yttrium and aluminium hydroxide for the preparation of pure yttrium aluminium garnet (YAG) powder with small grain size is the subject of this study. Starting materials are sulphates and chlorides of yttrium and aluminium. To obtain pure YAG (Y3Al5O12), the pH during flocculation of the precursor must be chosen carefully. The presence of water increases the degree of agglomeration. To minimize agglomeration, the influence of dispersion liquids has been studied, leading to optimized conditions for precipitation.

Value of serum aluminium monitoring in dialysis patients: a multicentre study.

Abstract: The clinical relevance of regular serum aluminium monitoring in dialysis patients was investigated in a multicentre study by 6-monthly determination of the serum aluminium during 4 consecutive years. In a group totalling 1193 patients, a striking decrease of mean serum aluminium was observed the last 2 years of the study. This phenomenon was accompanied by a substantial reduction of the prescribed dose of aluminium hydroxide (Al(OH)3) and its partial replacement by calcium carbonate (CaCO3) and/or magnesium hydroxide (Mg(OH)2). Under this policy serum phosphate control remained satisfactory. In all the centres, water treatment was found to be adequate, yielding dialysate aluminium around 2 micrograms/l. Dialysis patients with clinically overt liver disease showed a significantly greater median serum aluminium concentration than that observed in a control dialysis population. Compared to the latter group, the median serum aluminium concentration of dialysis patients with diabetes mellitus did not differ significantly. Results further indicated that patients with biopsy-proven osteomalacia presented a significantly greater median serum aluminium compared to that of patients without osteomalacia. We demonstrated that a serum aluminium of 60 micrograms/l provides a relatively sensitive (82%) and specific (86%) index for the detection of aluminium-related bone disease (ARBD). Provided the aluminium determinations are performed by a qualified laboratory, serum monitoring in dialysis patients (a) allows the safer use of aluminium-containing phosphate binders, and (b) is of value in the diagnosis of overload/toxicity.

Method for the preparation of metal matrix composite materials

Abstract: A method for preparing deagglomerated fibres and/or particles and for providing the fibres and/or particles with a substantially uniform protective coating, the fibres and/or particles being of a material selected from the group consisting of carbides, oxides, nitrides, silicides, borides, metals and graphite, including SiC, TiC, ZrC, WC, NbC, AlN, TiN, BN, Si3N4, MgO, Al2O3, SiO2, ZrO2, Fe2O3, Y2O3, steel, tungsten, molybdenum and carbon, the method comprising (a) preparing an inorganic colloid sol, and (b) mixing the fibres and/or particles with the inorganic colloid sol to produce a dispersion in which the fibres and/or particles are deagglomerated and substantially homogeneously distributed. The fibres and/or particles, e.g. SiC whiskers provided with an aluminium oxide coating by treatment with an aluminium hydroxide-based sol, are used for the preparation of metal matrix composite materials, e.g. based on aluminium or an aluminium alloy.

Recovery of sodium hydroxide and aluminium hydroxide from etching waste

Abstract: A method for the recovery and recycling of sodium hydroxide from the waste solution of aluminum etching operations. The method utilizes a dialysis membrane column or stack to initially remove sodium hydroxide from the waste solution and return it to the etch tank base solution sufficiently concentrated to carry on the basic etching operation. The method permits the recovery of salable quantities of aluminum hydroxide.

Residual Aluminium Concentration in Drinking Water After Treatment with Aluminium or Iron Salts

Abstract: In recent years a potential connection between human intake of aluminium and Alzheimer’s disease has drawn attention to the aluminium concentration in drinking water. In the present paper the aluminium concentration in drinking water from treatment plants using aluminium or ferric coagulants is compared with the solubility of aluminium hydroxide, reviewed from the literature. Aluminium hydroxide is least soluble at about pH 6.3. At lower pH, positively charged aluminium hydroxide complexes, and at higher pH, negatively charged aluminate ions are formed, and at these pH values, solubility is higher. Complexing agents increase the solubility.

The dehydroxylation of aluminium hydroxides and the kinetics ofα-Al2O3 formation

Abstract: Studies were made of the dehydroxylation of several aluminium hydroxide modifications and the kinetics ofα-Al2O3 formation. The investigated samples differed in both mineral composition and the level of alkali admixtures. It was found that the rate of formation and the quantity ofα-Al2O3 depend mainly on the purity of the aluminium hydroxides, while the transition forms of alumina depend on the initial type of the aluminium hydroxide.

Flame retardant polymer compositions

Abstract: The composition comprises a blend of polyethylene and an ethylene-vinyl acetate copolymer having a hydrated mineral flame retardant dispersed therein, the composition further containing an oligomeric polyester resin dispersant. The hydrated mineral flame retardant is typically aluminium hydroxide, optionally together with magnesium hydroxide. Artefacts made from the composition are useful for protecting electrical and fibre optic cables where stringent flame resistance properties are required.

Basic calcium aluminium hydroxide di:carboxylate(s) - useful as heat stabilisers for halogen-contg. thermoplastics, esp. PVC

Abstract: (1) Basic calcium aluminium hydroxide dicarboxylates of formula CaxAl2(OH)2(x+2)A.mH2O (I) are claimed; x = 2-8; m = 0-12; A = anion of an aliphatic, aromatic or heteroaromatic dicarboxylic acid or a combination. (2) (I) are produced by reaction of mixts. of Ca(OH)2 and/or CaO, Al(OH)3 and NaOH, or of Ca(OH)2 and/or CaO and NaAlO2, with the corresp. acid AH2 in the amts. required in aq. medium, followed by sepn. and working up by known methods. Pref. x = 3-6, m = 2-4, and A = fumarate or phthalate; reaction is carried out at 25-100 deg.C.

Process for the production of aluminium hydroxide from bauxite

Abstract: Process for the production of aluminium hydroxide by digesting bauxite with alkali solution and precipitating aluminium hydroxide from the digestion solution, comprising: a combining bauxite and alkali solution having a caustic concentration of at least 180 grams per litre expressed as sodium carbonate and digesting partly the bauxite in the combined product in a first digestion step at relatively low temperature, b separating reaction product obtained in step a into a liquid phase and a solids/liquid slurry, c combining liquid phase and solids/liquid slurry obtained in step b and digesting the combined product in a second digestion step at relatively high temperature, d releasing heat from the reaction product obtained in step c to preheat liquid phase obtained in step b , e separating the reaction product obtained in step d into a supersaturated sodium aluminate solution and undissolved material, f precipitating aluminium hydroxide from the supersaturated sodium aluminate solution obtained in step e and separating aluminium hydroxide from the spent liquor, and g recycling spent liquor obtained in step f to step a for use as alkali solution

Process for the preparation of polyaluminium compounds.

Abstract: The present invention relates to a process for the preparation of polyaluminium hydroxychloride complexes having the general formula Al(OH)xCly in solution or in solid form and intended to be used as flocculants and coagulants at water purification, sludge dewatering, plant dewatering and paper production, whe-reby one reacts aluminium chloride in solution with aluminium hydroxide, or aluminiumoxide hydrates at a temperature of 120-170°C at an elevated pressure for 1.5-5 hrs, whereby the rela-tionship AlCl3:Al(OH)3 is thus adjusted that the relationship OH:Al in the resulting compound Al(OH)xCly becomes 0.5 to 1.5, preferably 0.8 to 1.2.

Aluminium-Containing Polymethylsiloxane as a New Solid Acid Catalyst

Abstract: An aluminium-containing polymethylsiloxane (AMS) was prepared in an aqueous system using methyltrichlorosilane, dimethyldichlorosilane, and aluminium hydroxide as the starting materials, and its applicability as a new solid acid catalyst was examined. AMS is an amorphous hydrophobic solid with a high surface area (ca. 250 m2 g−1) and a relatively high thermal stability (max. 573 K in air). The adsorption of basic indicators indicated that acid sites with a medium strength (pKa=1.5) exist on AMS, and protic acid sites were detected on AMS by the IR spectra of adsorbed pyridine. These acid sites differ from the aprotic sites found on alumina. Though those on AMS are able to catalyze the dehydration of pinacol in the vapor phase, they are inactive for the hydrolysis of methyl acetate in an aqueous system.

Process for obtaining oxynitride powders and their application to the preparation of ceramics

Abstract: Process for obtaining oxynitride powders and more particularly gamma AlON or a mixture of alumina and AlON, starting with the nitriding of aluminium hydroxide or transition alumina powders at a temperature higher than approximately 900 DEG C. The invention also relates to the application of the oxynitride powders obtained to the preparation of ceramics.

Removal efficiency of heavy metals from laboratory wastewater containing ligands by an aluminium hydroxide co‐precipitation system

Abstract: The aluminum co‐precipitation process is one of the usual methods to remove heavy metals from laboratory wastewater: however, ligands contained in the wastewater can interfere with the process. Hea...

Oral pharmaceutical compositions comprising a mixture of ibuprofen and aluminium hydroxide and process for their preparation

Abstract: A pharmaceutical composition for oral administration comprising a mixture of ibuprofen or a pharmaceutically acceptable salt thereof and aluminium hydroxide, the amount of aluminium hydroxide being sufficient to mask the bitter taste of the ibuprofen, or the salt thereof which would be evident in the absence of aluminium hydroxide. The ratio of aluminium hydroxide (expressed as equivalent aluminium oxide) to ibuprofen may be in the range 1:50 to 5:1 parts by weight.

Method for producing mullite

Abstract: A synthetic mullite is produced by mixing 41-62 wt.% of at least one refractory of agalmatolite, kaoline and clay, 38-59 wt.% of at least one slimanite of calcined alumina, aluminium hydroxide and bauxite with 0.1-6.5 wt.% zircon or zirconia, and sintering the mixt. at 1600-1750 deg. C. The mullite has a good refractory property.

Flame retardant polymer composition

Abstract: 2054693 9013594 PCTABS00002 The composition comprises a blend of polyethylene and an ethylene-vinyl acetate copolymer having a hydrated mineral flame retardant dispersed therein, the composition further containing an oligomeric polyester resin dispersant. The hydrated mineral flame retardant is typically aluminium hydroxide, optionally together with magnesium hydroxide. Artefacts made from the composition are useful for protecting electrical and fibre optic cables where stringent flame resistance properties are required.

The precipitation and hydrothermal crystallisation of alkaline‐earth. Metal aluminosilicate hydrates from aqueous solution: Crystalline phases and precipitation and recrystallisation mechanisms

Abstract: The preparations, precipitations and recrystallisations of magnesium and calcium aluminosilicate hydrates, from aqueous suspensions of microcrystalline silica, aluminium hydroxide (and oxohydroxide) and magnesium (calcium) hydroxides at ambient temperatures to 400 °C, are surveyed. The phases reported in systems of different Mg(Ca)/(Al + Si) and Al/(Al + Si) composition ratios are tabulated and precipitation and recrystallisation mechanisms are proposed.

Maintenance method for forming device for electrode foil used for aluminum electrolytic capacitor

Abstract: PURPOSE:To make it possible to perform the maintenance of a forming device easily by dissolving and removing aluminum hydroxide attaching to a converting tank, making an acid aqueous solution circulate in the forming tank CONSTITUTION:Particles of aluminium hydroxide produced in a forming process are chemically amphoteric compounds, and it is very difficult for them to dissolve in aqueous solutions almost neutral but it is very easy for them to dissolve in acid aqueous solutions By utilizing this property and making an acid aqueous solution circulate in a tank, aluminum hydroxide particles attaching to the forming tank are dissolved and removed For example, if solid aluminum hydroxide 10g is tried to be dissolved in an aqueous solution 100cc of sulphuric acid or nitric acid (density 5%) under a condition of 60 degC, 30min, it can be dissolved completely In addition, it is very easy to wash out the aqueous solution and its removal is simple This makes it possible to dissolve and remove the aluminum hydroxide easily Accordingly, the efficiency of the maintenance of the forming device and the quality of electrode foils can be enhanced

Process for the preparation of short prismatic aluminium hydroxide and its use as filler or pigment

Abstract: A process for preparing a short-prismatic aluminium hydroxide by decomposing a supersaturated sodium aluminate hydroxide and the use of the product as pigment and filler in the paper industry, as a flame-retardant filler in plastics and as a white pigment in colours and paints.

Alternative phosphate binders for aluminium hydroxide

Abstract: In this chapter, we discuss the use of high doses of CaC03 and other alkaline salts of calcium as well as of magnesium hydroxide and magnesium carbonate as alternative phosphate binders for Al(OH)2.

Aluminium hydroxide and fibrous-based insulating material, in particular for injection onto a floor surface

Abstract: The invention relates to an insulating material designed in particular to be blown onto the surface of a floor. This material is characterized in that it consists of a mixture of organic fibrous particles, of powdered aluminum hydroxide obtained by drying and spraying an aluminum hydroxide slurry, a hygroscopic agent and a starch powder.