Precipitation Of Aluminum Hydroxide Research Articles

Recovery of lithium from waste liquid of rock salt brine using aluminum hydroxide precipitation method

An integrated process consisting of Li+ precipitation by Al(OH)3, roasting, water leaching, evaporation, and Li2CO3 precipitation was used to recycle Li+ from the waste liquid of rock salt brine (0.099 g/L Li+). Waste liquid from roc salt brine was discharged wastewater after NaCl crystallization and the removal of impurities in the salt manufacturing plant of the good rock salt mine. The influences of Al3+/Li+ mole ratio, Na+/Al3+ mole ratio, precipitation temperature, and time on the recovery of Li+ were investigated during Li+ precipitation by Al(OH)3 stage. The results showed that the optimal condition was Al3+/Li+ mole ratio = 2.5, Na+/Al3+ mole ratio = 2.2, precipitation temperature of 60℃ (333.15 K) for more than 20 min, whose recovery of Li+ reached 97.25%. The thermodynamic analyses of the simulated Li+–Al+–Mg2+–Cl––H2O system were conducted to construct the potential-pH (φ-pH) diagrams. The results showed that the pH value should be located in the LiCl · 2Al(OH)3 · 2H2O salt region with no formation of Mg(OH)2, which started at pH = ~6.5 and ended at pH from 10.09 to 8.55 as the temperature changed. Subsequently, the Li+precipitate was roasting for the transformation of insoluble LiCl · 2Al(OH)3 · xH2O salt to soluble LiCl, followed by the water leaching to obtain the enriched Li+ solution (1.951 g/L Li+) with Li+ recovery of 85.52%. To meet the requirement of Li2CO3 precipitation, the enriched Li+ solution was evaporated, and Na2CO3 was added to precipitate the Li2CO3 product after SO4 2–, Ca2+, and Mg2+ removal. The total recovery of Li+ was 66.69% after the experimental process, and the purity of Li2CO3 product was 99.3%, which can be regarded as industrial-grade Li2CO3. In conclusion, the success in lithium recovery using the aluminum hydroxide precipitation method provided a new perspective for preparing Li2CO3 from the waste liquid of rock salt brine, which could be considered as a newly developing lithium resource to meet the dramatically increasing demand for lithium in new energy vehicle industry.

Investigation of the conditions (nature) of pentacoordinated aluminum oxide formation

Aluminum oxide is widely used as a catalyst carrier, including in internal combustion engine systems, where operating temperatures exceed 1000 °C. As such, aluminum oxide must exhibit enhanced thermal stability. This property is linked to the presence of pentacoordinated centers on the surface of the γ-phase of Al2O3. This paper examines the effect of the pH during aluminum hydroxide precipitation on the formation of pentacoordinated centers on the surface of aluminum oxide. The samples of aluminum hydroxide were synthesized via controlled double-jet precipitation, followed by thermal decomposition into oxides. Precipitation was carried out at constant pH levels, and for comparison, parallel samples were synthesized at pH values of 5, 6, 7, 8, and 9. The precursors for precipitation were a 1 M aluminum nitrate solution (Al3+) and a 10 wt. % ammonia solution (NH4OH). The solutions were introduced into the reactor in a dropwise mode with continuous stirring. The resulting aluminum oxide samples were analyzed using X-ray diffraction and nuclear magnetic resonance techniques. The data show a direct correlation between the pH of aluminum hydroxide precipitation and the presence of pentacoordinated centers on the aluminum oxide surface: the higher the pH, the lower the content of pentacoordinated atoms. Additionally, a relationship was observed between the pH value and the size of the coherent scattering region, with an increase in coherent scattering observed at higher pH levels.

The influence of process parameters on the morphological characteristics of fine precipitated hydrate

<p>In this paper, the influence of process parameters on the morphological properties of fine precipitated hydrate was examined. The research was conducted with the aim of synthesizing fine precipitated aluminum hydroxide from the aluminate solution obtained by the Bayer process. Fine precipitated hydrates obtained in this way are mostly used in the non-metallurgical industry. The synthesized fine precipitated hydrate should comply with certain quality requirements such as granulometry (average particle diameter), purity, specific surface area, whiteness, etc. This paper shows the influence of certain technological parameters, namely the initial precipitation temperature, the amount and specific surface area of the seed, the influence of the NaOH/Al(OH)3 molar ratio on the characteristics of the synthesized fine precipitated hydrate in terms of the specific surface area, mean diameter and morphology of the obtained particles.</p>

ТЕРМОХИМИЧЕСКИЙ РАСЧЕТ РАВНОВЕСНЫХ СООТНОШЕНИЙ ФАЗ ГИДРОКСИДА АЛЮМИНИЯ

A search and analysis of thermodynamic data on the phases formed during the precipitation of aluminium hydroxide from acidic salts’ solutions was carried out in order to further study the equilibrium relations of aluminium hydroxide. The study of literature on the thermodynamic properties of various aluminium hydroxides modifications obtained by low-temperature calorimetry revealed a contradiction in the calorimetric data on boehmite, which is explained by the difference in thermochemical properties between the phases of crystalline and gelatinous boehmite (boehmite and pseudoboehmite). Saturation indices of aluminium hydroxide phases were plotted, which, in turn, made it possible to compare these phases in terms of their stability and confirm certain regularities characterizing the precipitation conditions

Straight synthesis of α and γ alumina from kaolin by HCl acid leaching

In this work the preparation of alumina from kaolinite by leaching with hydrochloric acid is studied. Crude kaolin was calcined at 850?C and then leached with 6 M hydrochloric acid at 90?C. Aluminum hydroxide was precipitated by adding 6 M HCl solution to the leaching water. Finally, the precipitated aluminum hydroxide was heated at 1100?C and converted to aluminum oxide. The materials were identified by XRF, XRD and SEM-EDX techniques. The percentage of alumina recovery was determined at different kaolin particle sizes (?200 to ?400 standard Tyler sieve), different times (1, 2, 3 and 4 h), different leaching temperatures (80, 90, 100 and 104?C) and different concentrations of hydrochloric acid (20, 25, 30 and 37%). The phase changes of alumina were also investigated at two calcination temperatures (1100 and 1200?C). The purity of aluminum oxide obtained by this method is about 97% and the percentage of recovery is about 98%. It was observed that the kaolin granulation with dimensions smaller than 75 ?m had no significant effect on the percentage of alumina recovery. It was also found that the percentage of alumina recovery increased with increasing leaching temperature.

Neutron tomography of porous aluminum electrodes used in electrocoagulation of groundwater

In this work, neutron computed tomography (CT) is employed to investigate the dissolution of porous aluminum electrodes during electrocoagulation (EC). Porous electrodes were chosen in efforts to reduce electric power requirements by using larger surface-area electrodes, having both inner and outer surface, for the EC process. Neutron CT allowed 3D reconstruction of the porous electrodes, and image analysis provided the volume of each electrode vs. thickness, which can indicate whether the inner surface is effectively involved in EC reactions. For the anode, the volume decreased uniformly throughout the thickness of the electrode, indicating that both the outer and inner surface participated in electrochemical dissolution, while the volume of the cathode increased uniformly vs. thickness, indicating deposition of material on both the outer and inner surface. The attenuation coefficient vs. thickness, increased for both anode and cathode, indicating surface chemistry changes. For the anode, the attenuation coefficient increased slightly but uniformly, probably due to aluminum oxide formation on the surface of the anode. For the cathode, the attenuation coefficient increased more than for the anode and nonuniformly. The higher increase in the attenuation coefficient for the cathode is due to precipitation of aluminum hydroxide on the electrode surface, which added hydrogen. Image analysis also showed that, although the attenuation coefficient increased throughout the thickness of the electrode, most of the hydroxide deposition occurred on the outer surface. Energy analysis showed that porous electrodes can be used to reduce process energy requirements by as much as 4 times compared to solid electrodes.

Multilayer adsorption improving the organic removal by foam flotation from sodium aluminate solutions

Effective enrichment of organics by foam flotation will notably contribute to the removal of organics from the Bayer liquor. The present study shows that the removal efficiency increased with increasing concentration of sodium laurate (SL) and sodium stearate (SS). Over 29% SS removal with a concentration ratio of 2.92 was obtained from the Bayer liquor. The surface pressure increased with increasing spreading concentration, while the mean molecular area decreased. From the remarkable difference in the π-A isotherms of SS on the surface of sodium aluminate solution and water, a minimum molecular area of 2.39 Å2 occurred in the sodium aluminate solution, which was notably lower than 24.6 Å2 in water. Adding sodium palmitate (SP) into SS increased the minimum molecular area, while the addition of sodium oleate (SO) raised the maximum surface pressure. From Langmuir-Blodgett films, the micellar size of SS and SL increased with increasing spreading concentration. Adding SP and SO into SS enlarged the micellar size owing to the synergistic interaction between organics. As a result, the complicated interfacial structure, multilayer adsorption of micelles at the air/solution interface, and precipitation of aluminum hydroxide synergistically promoted the removal efficiency of organics from the sodium aluminate soluion.

Isotopic Substitution Reveals the Importance of Aluminate Diffusion Dynamics in Gibbsite (Al(OH)3) Crystallization from Alkaline Aqueous Solution

Understanding molecular-scale factors governing the precipitation of aluminum hydroxides, such as gibbsite, under alkaline conditions is important for the formation of laterite deposits, as well as aluminum processing. However, mechanisms enabling tetrahedral aluminate ions to assemble into octahedral sites of the gibbsite lattice remain unclear. Formation of oligomeric complexes has been hypothesized as a critical intermediate step. Here, we report a study of gibbsite solubility in highly alkaline solutions using deuterium substitution to probe equilibrium and kinetic factors that could affect oligomeric intermediate formation, including the reactivity and the diffusivity of aluminate ions. When substituting sodium hydroxide with sodium deuteroxide, solution analysis shows a nearly 40% and 50% increase in gibbsite solubility in 2.4 and 3.3 mol·kg–1 total sodium solutions, respectively. Raman spectroscopy indicated that monomeric aluminate ions are the predominant species in solution irrespective of deuteration. However, both 27Al and 23Na nuclear magnetic resonance (NMR) spectroscopy revealed significant differences in chemical shifts in deuterated solutions, and analysis of 1H, 23Na, and 27Al diffusion coefficients with pulsed-field gradient, stimulated echo NMR spectroscopy shows a decrease in ion diffusivity with increasing total deuterium in solution, consistent with the notion of increasing strength in the hydrogen/deuterium bonding network. Because the relative change in 1H diffusion coefficients are commensurate with the difference in apparent solubility constants, there is evidence for an oligomeric intermediate whose steady-state concentration is maintained by the collision frequency of aluminate ions.

Термическое разложение химически осажденного нанопорошка гидроксида алюминия

In this study, the phase formation of aluminum oxide nanopowder during thermal heating of chemically precipitated aluminum hydroxide was discussed. Nanopowders of aluminum oxide and hydroxide were characterized by X-ray diffraction and thermogravimetric analysis, electron microscopy, energy dispersive X-ray spectroscopy analysis. XRD analysis detected a complex phase composition consisting of different modifications of aluminum hydroxide. It was shown that the precipitated aluminum hydroxide has a flake morphology with an average particle diameter of 5.5 nm. The differential thermal analysis showed that as-deposited aluminum hydroxide undergoes a multiple stage phase transformation. The deconvolution of the experimental differential curve by the Gaussian function and comparison of the temperature intervals of mass change with the literature data revealed that the precipitated aluminum hydroxide powder consists of bayerite α-Al(OH)3 and aluminum oxyhydroxide AlOH. It was found that bayerite is transformed to boehmite in the temperature range of 100 – 400 °C. After that γ-Аl2O3 is formed during the thermal decomposition of boehmite in the temperature range of 400 – 530 °C. The second hydroxide phase formed during the chemically precipitated method has a single stage phase transformation from AlO(OH) to γ-Аl2O3 in the temperature range of 260 – 500 °C. The nanopowder of γ-Аl2O3 formed at the temperature of higher than 600 °C has an equiaxed particle shape and an average size of 7 nm.

MODELLING OF THE PRECIPITATION PROCESS OF ALUMINIUM HYDROXIDE FROM ALUMINATE SOLUTIONS BASED ON FUZZY LOGIC THEORY

The article deals with the application of the fuzzy logic approach to the stage of precipitation of aluminum hydroxide from sodium aluminate solutions obtained from the alkaline solution of raw alunite by hydrogen peroxide as an eco-friendly reagent. Factors influencing the precipitation of aluminum hydroxide in the presence of H2O2 from poor aluminate solutions include the concentration of hydrogen peroxide, the volume of hydrogen peroxide, and other parameters. The application of fuzzy logic to this process allows calculating the probabilities that the parameters can occur not only in one value but in a wide range as well, to find the optimal conditions for obtaining high-yield aluminum hydroxide. Based on the results of the experiments, it is possible to precipitate aluminum hydroxide with a yield of 92% using 15.5 ml of 17% hydrogen peroxide at 25 °C using fuzzy sets suitable for low, medium and high levels, and this figure can be increased or decreased by changing the parameters. The simulation of process control through a fuzzy logic controller is compiled using membership functions in Matlab.

Precipitation of Aluminium Hydroxide by Hydrogen Peroxide from Natrium Aluminate Solutions

Precipitation of Aluminium Hydroxide by Hydrogen Peroxide from Natrium Aluminate Solutions

Indicators and regularities of hydrolytic decomposition of metastable aluminate solutions in the Na2O – K2O – Al2O3 – H2O system

Target processing of aluminum ores with increased potassium content is well known in the world practice and at different stages of development of alumina production technology was associated with the use of the most available and preferable raw materials, including leucites, alunites, nepheline syenites and close to them urtite minerals. Currently, we can talk about a renaissance of interest in potassium-containing raw materials due to the gradual depletion of reserves and the impoverishment of traditional aluminum-containing raw materials against the high demand for and cost of the soda-potash products, potassium fertilizers, aluminum hydroxide, alumina, and materials based on them. This study used theoretical and experimental methods of research, including calculations of the equilibrium composition of aluminate solutions in the Na2O – K2O – Al2O3 – H2O system based on the additivity principle and experimental study of indicators and regularities of hydrolysis of aluminate solutions on aluminum hydroxide seed (decomposition), depending on the mole fraction of K2O in alkaline aluminate solution. It was found that the degree of decomposition of aluminate solutions in the Na2O – K2O – Al2O3 – H2O system has a violation in the monotonicity of its change with the appearance of a special point at the mole fraction of K2O equal to 0.33, the presence of which can be explained by a change in the process mechanism due to a change in the ionic composition of the aluminate solution. The correlation between the degree of decomposition of aluminate solutions and the value of the average median particle diameter of the resulting aluminum hydroxide precipitate was shown, indicating a close relationship between the growth processes of crystallization and the hydrolytic decomposition mechanism in general, as well as their dependence on the ionic composition of aluminate solutions. The effect of transition of supersaturated (metastable) aluminate solutions into the area of unsaturated compositions has been established, which is of theoretical significance for understanding the mechanism of decomposition of potassium-bearing aluminate solutions and of practical importance for creating an effective technological cycle for the processing of aluminum-bearing raw materials based on the Na2O – K2O – Al2O3 – H2O system. The work was carried out with the financial support of the Russian Science Foundation under the Agreement No. 18-19-00577-П of April 28 2021 of grant for fundamental scientific research and exploratory scientific research.

Extracting lithium from the H2SO4 leaching solution of bauxitic claystone via co-precipitation methods without addition of Al source

Newly mined bauxitic claystone resources have received attention due to the rapidly growing demand for lithium. However, existing methods for extracting lithium from bauxitic claystone are still difficult and costly. This study proposed a novel aluminum hydroxide precipitation method to improve the extraction rate of Li by cleverly utilizing Al from bauxitic claystone. First, the ball-milled and calcined bauxitic claystone samples were leached by sulfuric acid to obtain a leaching solution with a high concentration of Al3+. Then, a NaOH solution was added to form amorphous aluminum hydroxide to adsorb Li+. The precipitation rate of Li+ reached 97.2% under the suitable precipitation conditions. Lastly, the precipitate was calcined and leached with deionized water to extract lithium. Li+ reached a water-leaching rate of 86.13%. According to the X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) results, the prepared precipitate was mainly amorphous aluminum hydroxide and part was composed of a gibbsite phase. The elution experiment showed that the amorphous aluminum hydroxide had good adsorption selectivity for Li+. In addition, Al2O3 could be recovered from the solid phase after water-leaching, which can significantly reduce the cost.

Processing of Hydro-Mineral Lithium Raw Material of Kazakhstan Using Inorganic Sorbents

The article presents the results of studies on recovery of lithium from reservoir brines using both commercial and synthesized aluminum hydroxide and hydrated manganese oxide as sorbents. The research results showed that, when using commercial aluminum hydroxide and synthesized hydrated manganese oxide as sorbents, lithium recovery from brine was 21.8 and 20.1%, respectively. Studies were conducted on lithium chemisorption on freshly precipitated aluminum hydroxide, which was obtained by adding aluminum chloride solution and tri-calcium hydro-aluminate to the brine. Chemisorption of lithium was carried out under the following conditions: T = 50 °C; AlCl3 solution concentration - 120 g/dm3; molar ratio Li/Al = 7; pH equal = 8.0-8.8; holding time with stirring 1 h. The degree of lithium extraction from brine was 71%; lithium capacity of freshly precipitated Al (OH)3 was 5.9 mg/g. During calcareous leaching of lithium-aluminum precipitate, lithium was extracted into a solution by 74.7%.

A new bioleaching strategy for the selective recovery of aluminum from multi-layer beverage cans

Used beverage cans (UBĆs) represent one of the largest sources for secondary aluminum production worldwide. Beverage cans are one of the most frequently produced multi-layer packaging materials made of aluminum with an inner epoxy resin coating to prevent direct contact of food and aluminum surface. In the common way of UBĆs recycling, the whole can is re-melted, resulting in the burning and loss of the inner epoxy coating. The use of acidophilic bacteria for the biological leaching of metals has already been well studied, but until now their applications for the selective separation of metal-containing multilayer materials has not been investigated. In this study, the three bioleaching bacteria: A. ferrooxidans, A. thiooxidans and A. caldus were explored to selectively leach the aluminum from the epoxy layer, resulting in leaching efficiencies of around 92% after three weeks of incubation. Surface characterization of the epoxy layer after bioleaching application revealed that the nature of the epoxy resin was unchanged, which could allow for recycling. The dissolved aluminum was afterwards selectively precipitated from the lixiviants at pH = 6.5, resulting in aluminum hydroxide precipitation efficiencies of almost 100%. The high leaching efficiencies and the selective precipitation shows the significant potential of acidophilic bacteria in the separation and recycling of multi-layer materials.

Al-doped yttrium iron garnets Y3AlFe4O12: Synthesis and properties

A method to synthesize nanosize particles of Y3AlFe4O12 garnet ferrite by precipitation in aqueous solutions at constant pH during the synthesis has been demonstrated. The effect of the sequence of the metal hydroxides precipitation on the filtration coefficient is studied. The filtration coefficient is found to be three times greater in the case of simultaneous precipitation of iron and aluminum hydroxides compared to the one observed for the case of simultaneous precipitation of all hydroxides. Synthesized precipitates are established to be amorphous and crystalline nanoparticles are formed in one stage after the treatment at 800 °C. The average particles size is around 60–70 nm. The ceramics obtained after a proper heat treatment of the nanoparticles is shown to be characterized by the high density and good electrophysical properties.

Influences of New Synthesized Active Seeds and Industrial Seed on the Aluminum Hydroxide Precipitation from Sodium Aluminate Solution

The aluminum hydroxide precipitation process from sodium aluminate solution was studied by adding the new synthesized active seeds and industrial seed separately. The results show that the precipitation rate reached 47, 81, and 68% at 60 h by adding industrial seed, seed A, and seed B (active seeds), respectively. Specific surface area, composition, morphology, and particle size distribution of seeds/precipitated products from supersaturated sodium aluminate solutions were investigated by Brunauer, Emmett, and Teller (BET) analysis, X-ray crystallography (XRD) analysis, Scanning electron microscope (SEM) images, and Power-spectral-density (PSD) analysis. Also, to study and understand the functional groups on the surface of seed/precipitated products and precipitation mechanisms, Fourier-transform infrared spectroscopy (FTIR) analysis was recorded. The result showed that the precipitation rate of the active seeds is higher than that of the industrial seed owing to the higher surface area, more active sites, crystal defects, and finer particle size that cause rise to nucleation for gibbsite. Also, improved precipitation of aluminum hydroxide from sodium aluminate solution may be due to the predominant phase crystallized of bayerite in the composition of active seeds. The FTIR analysis shows that the decline of the precipitation process in the presence of industrial seed may be due to oxalate–Al bonds and the impurity of carbonate.

The effect of exposure conditions on performance evaluation of post-treated anodic oxides on an aerospace aluminium alloy: Comparison between salt spray and immersion testing

In this work, the effect of the corrosion testing methodology on the degradation of anodized and post-treated AA-2024T3 specimens is considered. Two post-treatments are selected for the anodized layers, namely hydrothermal sealing and cerium-based post treatment. The two post-treatments are selected such that in one case corrosion protection mainly arises from a barrier effect (hydrothermal sealing) and in the other it arises from active inhibition (cerium-based treatment). It is found that salt spray and immersion testing provide similar results for the hydrothermally sealed oxides, but differ substantially for the cerium-treated oxides. The discrepancy is due to the fact that the continuously refreshing electrolyte layer during salt-spray testing promotes film dissolution and hinders precipitation of aluminium hydroxide and cerium compounds, unlike in stagnant bulk electrolyte. Hence, salt-spray testing is likely to be more aggressive than immersion testing for those systems that rely on active inhibition.

Effect of reaction conditions on agglomeration of aluminum hydroxide in the recovery of waste aluminum-catalyst

Water-soluble waste salts, especially those contain harmful ions, are a great threat to soil, water, air, and human health. NaAlCl4 waste salt, containing harmful Al3+ ion, is massively by-produced in the manufacture of dichlorophenylphosphine (DCPP) and remains a big issue to both industry and environment. In this work, we intensively investigated the aluminum hydroxide precipitation process during the recovery of NaAlCl4 waste salt via acid-base reaction. The aluminum hydroxide crystallized under different conditions was monitored and characterized using XRD, TG, SEM, and Zeta potential. The effect of precipitation pH and temperature on crystal form, gel content, agglomerate size distribution, and moisture content of filter cake were studied. Precipitation pH was found to influence both gel-precipitation conversion and agglomerate state, but its effect varied under different temperature, indicating complex gelation and agglomeration processes. Temperature, however, has similar effect at different pH conditions that low gel content and hardened agglomerate can be achieved with increasing temperature due to intensified particle movement and collision. In addition, NaCl has little effect on the crystal form of aluminum hydroxide even though some initial NaCl exists in the solution. Then, the precipitation mechanism was proposed, in which agglomerate void filling process was discovered and verified via porosity analysis. Furthermore, the precipitation process was optimized and a drop of 25.16% in filter cake moisture content was achieved which can lead to a better separation of Al3+ and Na+ and a higher efficient recovery of the waste salts.

Mineral Formation under the Influence of Mine Waters (The Kizel Coal Basin, Russia)

The development of coal deposits is accompanied by negative environmental changes. In the territory of the Kizel coal basin (Perm Region, Russia), the problem of contamination of water sources by acid mine waters and runoff from rock dumps is particularly acute. Mine waters are acidic (pH 2–3), with high mineralization (up to 25 g/L) and significant content of sulfate ions, iron, aluminum, manganese, toxic trace elements (As, Co, Ni, Pb and Zn). They are formed as a result of the interaction of underground waters from flooded mines of the Kizel basin with coal and rocks of dumps with high sulfur content (15%). Uncontrolled inflow of mine water into rivers (about 22 million m3 annually) leads to significant amounts of iron and aluminum hydroxide precipitation. These precipitations are in active interaction with river water, polluting the rivers tens of kilometers downstream and are entering the Kama reservoir. Studies of alluvial precipitation can be considered as a method of control and predictors of technogenic water pollution. The mineral composition of river sediments was studied with the application of different methods, including studies of sand-gravel and silty-clayey sediments. The sandy-gravel grains in the bottom load are mainly composed by natural minerals and are represented by a significant number of particles of coal dumps, slags and magnetic spherules. The silty-clayey material, mixed with natural minerals, contains a significant number of amorphous phases with a predominance of iron-rich substances, which may actively concentrate toxic elements. The presence of jarosite, goethite, basaluminite, lepidorocite and copiapite in silty-clayey sediments are indicators of the influence of mine waters.