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

The 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.     

Preparation of aluminium hydroxide by reacting sodium aluminate solutions with mineral acid

The preparation of aluminium hydroxide from sodium aluminate solutions by varying the alkaline concentration at a fixed molar ratio of Na₂O: Al₂O₃ has been investigated on addition of hydrochloric or nitric acids. The resulting materials have been examined by X-ray diffraction study, infrared spectrophotometry, thermogravimetrical and differential analyses. As a result, it was found that precipitates generally exist as pseudoboehmite or bayerite, but the formation of bayerite is enhanced by a low rate of addition of acid, higher temperature or higher alkaline concentration. In this case, the composition of the precipitates was little influenced at different molar ratios of Na₂O: Al₂O₃. When the precipitates from sodium aluminate solutions at low and higher alkali concentrations were aged in the mother liquors, pseudoboehmite therein transformed to hydrargillite and bayerite, respectively.     

Crystallisation processes in aluminium hydroxide gels. IV. Factors influencing the formation of the crystalline trihydroxides

The formation of crystalline aluminium trihydroxides from aqueous suspensions of pseudoboehmite, obtained by the hydrolysis of aluminium s-butoxide, has been examined by X-ray diffractometry, nitrogen adsorption and dilatometry. The results obtained have been interpreted in terms of a mechanism involving dissolution of the pseudoboehmite. For those suspensions with which the recrystallisation was followed dilatometrically, first-order kinetics were found, suggesting that random nucleation of trihydroxide crystals is involved. The rate of recrystallisation was decreased by the addition of organic solvents to the aqueous suspension and also, initially, by an increase in temperature. At the same time the proportion of gibbsite produced in admixture with bayerite was reduced and that of nordstrandite increased. It is concluded that the retardation is due, at least in part, to an increase in the crystallinity of pseudoboehmite which has been found to accompany the introduction of the organic solvents. The increased crystallinity must result in a decrease in the solubility and rate of solution of pseudoboehmite; under these conditions nordstrandite formation appears to be promoted. Neutron activation and spectroscopic analysis of hydroxide samples showed that storage of aqueous suspensions in glassware resulted in pick-up of sodium and silica at the ppm level. The changes in these levels as recrystallisation occurred suggested that retention of the products of glass dissolution was occurring in a way which depended on the surface area of the hydroxide. No variation related to the phase composition of the trihydroxide mixtures was observed.     

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

Pseudoboehmite 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.     

氢氧化铝佐剂配制工艺的优化

目的优化氢氧化铝[A(lOH)3]佐剂配制工艺。方法对A(lOH)3配制工艺中的反应温度、氢氧化钠(NaOH)溶液的滴入速度、气体流量和反应终点pH值进行优化,观察配制的A(lOH)3溶液的状态。分别以原工艺和优化工艺配制的A(lOH)3溶液为佐剂制备重组乙型肝炎疫苗(CHO细胞),比较二者的外观和效力。结果优化的A(lOH)3配制工艺为:反应温度70～72℃;NaOH溶液滴入速度185ml/min,10个点滴入;气体流量0.2bar;反应终点pH值5.80±0.05,以该工艺配制的A(lOH)3胶体颗粒大小均匀,呈淡淡的蓝白色,不发生沉淀。以优化工艺配制的A(lOH)3溶液为佐剂制备的重组乙型肝炎疫苗(CHO细胞)无沉淀,为均匀的胶体,成品放置3年外观无显著变化;疫苗效力略有提高,但不显著。结论优化了A(lOH)3溶液佐剂的配制工艺。     

Filtration characteristics of aluminium hydroxide mixtures (alumina hydrates)

The specific cake resistance of the alumina hydrates obtained from sodium aluminate solutions was investigated against the caustic ratio, ageing and filtration pressure using a laboratory test filter at constant pressure filtration conditions. The alumina hydrate product was produced from sodium aluminate solutions by seeding the aluminium hydroxide crystals of definite size distribution at constant solution temperature. The specific cake resistance was found to increase with the caustic ratio and filtration pressure and to decrease with the ageing of alumina hydrates in aluminate solutions.     

Influence of aluminium sources on the synthesis and catalytic activity of mesoporous AlMCM-41 molecular sieves

Mesoporous AlMCM-41 molecular sieves were synthesized using various aluminium sources, viz., sodium aluminate, aluminium sulphate, aluminium isopropoxide and pseudoboehmite. The influence of different aluminium sources on the framework substitution of aluminium as well as on the catalytic properties of t-butylation of phenol was studied. Among the aluminium sources, the use of sodium aluminate for the AlMCM-41 synthesis showed maximum incorporation of aluminium in the framework. Further, the catalyst also showed good catalytic activity for the chosen reaction.     

Separation of aluminium from beryllium in aqueous solutions by precipitate flotation

A fluoro-complex of aluminium is selectively precipitated by sodium ion from a dilute aqueous solution aluminium, beryllium, fluoride and potassium ions at a pH near 3. Subsequent flotation of this precipitate with long-chain alkylamines is affected by carbon chain length, pH, concentration of fluoride ion, rate of gas flow into the flotation cell and micellar form of the collector. Temperature has little effect on recovery.     

Editorial

This work deals with the preparation of aluminium hydroxide gels by precipitation from pure and mixed solvents in the presence of propylamine acting as proton acceptor in the hydrolysis reaction. As solvents were used water, ethanol and 50% v/v water-ethanol and water-acetone mixtures. Pure acetone could not be used because the aluminium salt used (AlCl₃.6H₂O) was not sufficiently soluble in it. The samples were freeze-dried and activated to temperatures up to 773 K. The samples prepared from aqueous solutions showed the structure of poorly crystallized pseudoboehmite, while the sample prepared from pure ethanol was nearly amorphous and presented the highest specific surface area of all the samples (570 m² g^?1 for thermal activation at 473 K). The sample prepared from aqueous acetone exhibited the highest porosity (about 4 cm³ g^?1) consisting of pores of nearly uniform size. This porosity remained almost constant throughout the range of thermal activation temperatures.     

浸取铝灰制取纳米氧化铝新工艺

介绍了一条回收铝灰中的铝制备纳米氧化铝的新工艺.用硫酸浸取电解铝工业中产生的铝灰,得到硫酸铝溶液,实验研究各参数对浸取过程的影响,得到适宜工艺条件;将硫酸铝溶液和碳酸氢铵反应生成碳酸铝铵沉淀,过滤、洗涤、焙烧碳酸铝铵得氧化铝粉体.实验研究了分散剂类型、分散剂用量、铝盐浓度对氧化铝粒径的影响,得出优化工艺条件.经X射线衍射分析和扫描电镜检测表明所得产品为粒径约70 nm的α-Al2O3.     

Studies of the crystallisation of gallium hydroxide precipitated from hydrochloric acid solutions by various alkalis

Gallium hydroxide precipitated from aqueous gallium chloride solution on addition of alkalis at varying pH have been aged in the mother liquors for different periods of time. The resulting precipitates have been examined by X-ray diffraction and i.r. spectrophotometry. It is found that the precipitate, separated immediately from the mother liquor after preparation, exists in an amorphous type and transforms to α-gallium oxyhydroxide during aging independent of pH.     

The characterisation of aluminium hydroxide gels by nitrogen adsorption

Aluminium hydroxide gels with a range of textures have been prepared by the hydrolysis of aluminium s- butoxide with water, aqueous ethanol and aqueous glycerol. Crystallisation was permitted to take place to varying extents by ageing of precipitates in their mother liquors at room temperature. Adsorption isotherms on the outgassed gels were of Types II and IV of the Brunauer classification. An examination of the data by plotting reduced isotherms (V/V_m versus P/P_o) revealed the existence of reversible capillary condensation on some of the hydroxides, although the isotherms were of Type II. The Lippens de Boer t method has been found useful in locating the onset of capillary condensation in an adsorption isotherm, but the t-plot can be misleading with samples that have a spread of pore dimensions extending into both the micro- and transitional-pore regions. This situation appears to arise in pseudoboehmites aged for extended periods so that cementation is extensive. The principal factors influencing the texture of the gels appear to be the extent of crystallisation and the amount of inter-particle cementation. Thus amorphous material prepared in water was found to be porous whereas that precipitated in glycerol, which apparently protects the surface of the primary particles, was non-porous (or macro-porous). Transitional pore systems with the best definition were obtained with pseudoboehmites, especially with those formed by ageing in aqueous ethanol. In water, the ready conversion of pseudoboehmite to low-area, non-porous, bayerite is a complicating factor.     

低热固相合成碱式碳酸钠铝纳米晶及其数据挖掘

对合成碱式碳酸钠铝的新方法进行了研究,以聚乙二醇-400（PEG-400）为模板,硫酸铝为铝源,用低热固相反应一步法成功合成得到碱式碳酸钠铝.基于均匀设计实验方案以及数据挖掘技术的应用,在数据挖掘成果的指导下进行了实验.XRD表征的结果表明,用最优工艺条件合成得到的产物为4.9 nm的NaAl(OH)₂CO₃,故同时优化控制了碱式碳酸钠铝的组成及粒度,从而得到比较纯净的碱式碳酸钠铝纳米晶体.     

The role of iron(iii) and tartrate in the zincate immersion process for plating aluminium

The zincate immersion process is a commercial process used to treat aluminium prior to electroplating. Superior zinc coatings are obtained through modifications to the original process. One such modification involves the addition of ferric chloride, complexed with potassium sodium tartrate, to the plating baths. This paper describes a detailed investigation into the function of these additives. It was found that the addition of tartrate alone did not significantly affect the rate of zinc deposition, the deposit morphology or the position of the aluminium or zinc polarization curves. This suggests that the role of tartrate is solely as a complexing agent to maintain iron (iii) in solution. In contrast to this, the addition of iron(iii)/tartrate had a marked effect on the reaction. It was found that iron(iii) functioned primarily by reducing the size of the zinc crystals as they formed. This produces a thinner and more compact zinc immersion coating.     

Coelectrodeposition of aluminium and cadmium from aqueous sulphate solutions

Coelectrodeposition of aluminium and cadmium from aqueous solutions is shown to be possible under very restricted conditions. The deposits are in a divided form and contain up to 40% aluminium. Lower cadmium ion concentration in the solutions leads to a higher proportion of aluminium in the deposit and there is an optimum concentration for the sulphuric acid in solution. Faradaic yields for metal electrodeposition are, however, low and hydrogen evolution is the predominant reaction.     

Optimale bedingungen zur gewinnung von Raney-Nickel mit maximaler entschwefelungseigenschaft

Desulphurization properties of Raney Nickel obtained from 50% of nickel-aluminium alloy by treatment with various concentrations of sodium hydroxide at different temperatures were studied as a function of the specific surface absorbed hydrogen as well as of the residual aluminium. The Raney Nickel obtained by treatment of the starting alloy with 10 and 26% of sodium hydroxide at 50°C and 80°C possesses maximum desulphurization ability on low molecular organic compounds. The skeletal metal obtained consists of coarse particals with a minimum content of residual aluminium and a very high specific surface. The Raney Nickel obtained from removal of aluminium from the starting alloy by 2% of sodium hydroxide at 20°C is characterized by a considerable amount of residual aluminium, very low specific surface and high degree of dispersity. The Raney Nickel obtained under these conditions is most effective for desulphurization of high molecular compounds in aqueous medium.     

Electrolytic aluminium oxide membranes — a new kind of membrane with reverse osmotic characteristics

Porous aluminium oxide membranes have been produced by a complete anodic oxidation of thin aluminium folia in acid media. The electronic microscopy investigation had shown that the membranes have an asymmetrical porous structure with a very dense barrier layer and that they are, therefore, potentially applicable, in the reverse osmosis field.Investigation of the membrane pure water permeability under pressure differences from 10 to 30 atm gave high initial permeability values (about 100 times higher than those of thermally untreated cellulose acetate membranes) which decreased rapidly during experiments. By heating the membranes above 600°C, or by their additional hydration in hot water, initial permeability decreases, with further decrease during the experiments. In addition, the hydrated membranes have better mechanical characteristics than untreated ones.The separation characteristics of aluminium oxide membranes were tested with aqueous solutions of sucrose and phenol, under the same conditions as in the permeability tests. The membranes exhibited distinct selectivity in both cases.     

New fibres prepared from cellulose-aqueous solution of sodium hydroxide systems (review)

The following basic conclusions were drawn from the published data examined; cellulose treated in steamblast conditions can form solutions and gelling pastes in an aqueous solution of sodium hydroxide; the solubility of cellulose in aqueous sodium hydroxide solution is primarily a function of the intramolecular bonds in the cellobiose unit with constant DP; intramolecular bonds are most efficiently broken in steamblast treatment in the cellobiose unit of cellulose I and cellulose III; monofilaments and yarns were obtained from solutions and gelling pastes of cellulose in aqueous sodium hydroxide solution; the physicomechanical properties of the monofilaments and yarns obtained from solutions and gelling pastes of cellulose in aqueous sodium hydroxide solution are still significantly lower than these indexes for viscose textile yarn.All-Russian Scientific-Research Institute of Polymer Fibres. Mytishchi. Translated from Khimicheskie Volokna, No. 2, pp. 11–14, March–April. 1996.     

Aluminium as anode in primary alkaline batteries. Influence of additives on the corrosion and anodic behaviour of 2S aluminium in alkaline citrate solution

The inhibitive effects of various additives on the corrosion of 2S aluminium in 4N NaOH containing calcium oxide and sodium citrate (base electrolyte) have been examined by studying the self corrosion, anodic polarization and anode efficiency of 2S aluminium in solutions containing different additives. It has been found that among the different additives investigated, those forming anions in solution act favourably.     

Oxalate as an intermediate in the base-catalysed water-gas shift reaction

The conversion of CO to H₂ and CO₂, in the presence of 1.0 M solutions of sodium carbonate, hydroxide and formate has been studied in the temperature range 200–350 °C. The decomposition of 1.0 M solutions of sodium formate, oxalate and carbonate under argon pressure was investigated using the same reaction conditions. It is shown that carbonate reacts readily with CO to produce oxalate, which decomposes easily to formate and CO₂. The formate is the most stable intermediate under the reaction conditions and only decomposes rapidly to carbonate and H₂ above 300 °C, making the water-gas shift reaction truly catalytic. Sodium hydroxide is not an intermediate in this reaction but first reacts with CO₂, formed during the reaction, to produce carbonate. Based on these results a new mechanism is proposed for the base-catalysed water-gas shift reaction.