Low-grade Aluminum Research Articles

Development of Wet Treatment Process for Volume Reduction, Detoxification and Recycling of Low-grade Aluminum Dross

For the purpose of volume reduction and detoxification of the low-grade aluminum dross (abbreviated as L-dross) with low content of metallic Al, the leaching behavior of two kinds of L-dross was investigated using 2 mol/dm3 H2SO4 and 2 mol/dm3 NaOH with or without heating operation. Ettringite with an anion removal ability was synthesized from the L-dross leachate generated after the volume reduction and detoxification treatment. A series of wet treatment process composed of L-dross leaching and ettringite synthesis was tried to develop in this study.

ПЕРСПЕКТИВЫ ИСПОЛЬЗОВАНИЯ РОССИЙСКОГО ВЫСОКРЕМНИСТОГО АЛЮМОСОДЕРЖАЩЕГО СЫРЬЯ В ГЛИНОЗЕМНОМ ПРОИЗВОДСТВЕ

Актуальность исследования обусловлена ограниченными запасами в нашей стране низкокремнистого алюмосодержащего сырья для производства металлургического глинозема по способу Байера. Поэтому руководство глиноземных комбинатов закупает данное сырье за рубежом (Гвинея, Бразилия, Ямайка). Стоимость транспортировки данного сырья с каждым годом становится все дороже и дороже, что повышает себестоимость металлургического глинозема. Также не стоит забывать о политических рисках, что еще больше усугубляет данную проблему. Следовательно, необходим переход на использование отечественного высококремнистого алюмосодержащего сырья, менее качественного, однако его запасы, находящиеся в непосредственной близости от глиноземных комбинатов, составляют сотни миллиардов тонн. Цель: исследование отечественной рудной базы высококремнистого алюминий содержащего сырья, определение первоочередных сырьевых источников и их месторождений, изучение характеристик сырья для оценки возможности его использования для производства металлургического глинозема. Объект: высококремнистые алюмосодержащие каолиновые глины сибирских месторождений. Проведенные исследования. Выполнен химический, фазовый, гранулометрический, микроструктурный, микрорентгеноспектральный и термогравиметрический анализы каолиновой глины Трошковского месторождения. Результаты. Анализ отечественной рудной базы позволил выявить наиболее крупные месторождения высококремнистого алюминиевого сырья, пригодного для получения металлургического глинозема. Установлено, что наиболее перспективным является Трошковское месторождение. Преимуществами данного месторождения являются огромные запасы высококремнистого алюмосодержащего сырья, высокая степень изученности месторождения и благоприятные инженерно-геологические условия. Проведенные исследования каолиновой глины Трошковского месторождения позволили сделать вывод, что глина данного месторождения может быть использована для получения металлургического глинозема по кислотно-щелочной технологии.

Studying the Efficiency of Lime-Soda Sinter Process to Extract Alumina from Colored Kaolinite Ores Using Factorial Technique of Design of Experiments

As the increasing demand for alumina in recent years with the result diminishing reserve of bauxite, the need to secure a domestic raw material base is driving research in new technologies to process low grade ores into alumina, with the intention that these technologies will lead to a significant reduction of bauxite and alumina transportation costs, allow the extraction of more valuable components from the ore and reduce environmental impact. Clays are types of the low-grade aluminum ores, they're also well abundant which make them a potential substitutes for Bauxite. In this work, lime soda sinter process was adopted for extracting alumina from kaolinitic claystone from Al-Ga'ara formation (Duekhla) quarry in western Iraq. The operation efficiency of sintering was studied in which the whole process has been done with three stages: the sintering process for the raw materials, leaching and carbonizing processes to precipitate and separate the alumina from the leach pregnant solution . Factorial technique of Design of Experiments (DOE) module in Minitab was used as a principal methodology to examine the sintering efficiency over alumina extraction. The results obtained showed that the optimum parameters for the sintering operation were CaO/SiO2 molar ratio of 2.2, Na2O/Al2O3 molar ratio of 1.2, sintering temperature at 1213 °C for 90 min. The sintered materials were leached with sodium carbonate solution, and sodium aluminate solution was obtained. By bubbling carbon dioxide gas into this extract solution aluminum hydroxide [Al(OH)3] has been precipitated and on calcination at 1200 °C for 2 hrs, alpha alumina (α-Al2O3) was obtained with purity of 98.5 %.

Nanoporous Anodic Aluminum Oxide (AAO) Thin Film Fabrication with Low-Grade Aluminium

Anodic aluminum oxide (AAO) is well known for its nanoscopic structures and its applications in microfluidics, sensors and nanoelectronics. The pore density, the pore diameter, and the interpore distance of an AAO substrate can be controlled by varying anodization process conditions. In this research, the self-organized two-step anodization is carried out with a low-grade (Al6061) aluminium substrate using a 40V voltage at the temperature of 2 to 5 °C. Three experiments are done with the anodization time of 24 hours, 48 hours and 72 hours. The structural features of AAO are characterized by a field emission electron microscope (FE-SEM). The data from FE-SEM show that the average pore diameter increases with the anodization time, and that the Al6061 aluminium substrate can be used to fabricate a nanoporous AAO film with an average pore diameter smaller than 17 nanometers.

A Low-Cost Mechanically Rechargeable Aluminum–Air Cell for Energy Conversion Using Low-Grade Aluminum Foil

The performance of a mechanically rechargeable aluminum (Al)–air cell, fabricated with low-cost materials including low-grade aluminum foil and carbon paper electrodes, was evaluated. The design adopted a free gravity flow for the electrolyte to eliminate the use of an external pump. A tank for storing waste electrolyte was designed with a dedicated channel for the collection of hydrogen gas generated during the cell discharge. The cell achieved a high utilization efficiency of aluminum. Considering both the electricity and hydrogen generated, an overall utilization efficiency of around 90% or even higher could be achieved under different working voltages. Results of repeated recharging/discharging showed that the performances of the cell could be maintained for repeated refilling.

Management of Social and Ethical Impacts from the Product Life Cycle of High End Wrought Aluminium Products

There is a growing interest to use recycled low-grade aluminium wrought alloys in high end structural components in the automotive industry. High energy consumption in extraction and production of virgin aluminium makes it environmentally favorable to increase the use of recycled post-consumer wrought alloys. Such use of low-grade wrought alloy aluminium, however, introduces new actors to a previously known and familiar product system, and belonging new and unfamiliar social and ethical aspects. The objective of the article is to present a simplified method for social life cycle assessment (SLCA) for such products tailored for original equipment manufacturers in the automotive industry. By using the method, an overview of social and ethical impacts from all life cycle stage will be provided, including an aggregated display for all life cycle stages together. The results can be used to compare different design alternatives and value chain actors, or to identify options for reducing potential negative impacts through manufacturing in global value chains through risk management. Comparative studies can be made for materials (various alloys, degrees of recycled alloys), production, or end of life alternatives for social responsible companies. Using a front lower control arm for personal vehicles as test case, the article will present the social impacts from different material alternatives over the product's life cycle, and how they can be managed. The proposed method may also be used in other settings to provide actionable insights.

The Sensitivity of Overall Collapse of Damaged Submarine Pressure Hulls to Material Strength

Budget and schedule restrictions sometimes require naval submarines to be operated with unrepaired corrosion damage to the pressure hull. It is important to understand the effects of corrosion wastage on the structural capacity of the hull, so that appropriate diving depth restrictions can be imposed if necessary. The current paper presents an experimental study of the interaction of material behavior with corrosion defects, especially with respect to their effect on overall elasto-plastic collapse of pressure hulls. Twenty ring-stiffened cylinders, representative of submarine pressure hulls failing by overall collapse, were machined from high- and low-grade aluminum alloy tubes. Artificial general corrosion damage was introduced in selected specimens by machining away material from the outside of the cylinder shell in rectangular patches of uniform depth. The cylinders were monotonically loaded to collapse under external hydrostatic pressure. One corroded cylinder was repeatedly loaded past the yield limit before the collapse test in order to study the effect of cyclic plastic loading on its ultimate collapse strength. Overall collapse pressures for corroded cylinders with a variety of patch sizes and depths and material strengths were reduced by, on average, 0.85 times the depth of thinning divided by the original shell thickness. The collapse strength of corroded cylinders was found to be more sensitive to the shape of the stress-strain curve than for intact specimens. Higher levels of strain hardening and ductility were found to improve the performance of damaged cylinders. Permanent deformations in the cyclically loaded cylinder, as measured with strain gauges, grew with each constant-amplitude load cycle; however, the additional deformations tended towards zero with increasing number of cycles, and a subsequent collapse test indicated that the cyclic loading did not affect the collapse pressure. The sensitivity of overall collapse to material strength is related to not only the yield stress, but also the plastic reserve of the material; higher levels of strain hardening and ductility increase overall collapse strength of hulls, especially those with general corrosion damage. The effect of a given level of corrosion thinning is less severe for cylinders with relatively greater levels of strain hardening. It is unlikely that cyclic plastic loading of corroded hulls will lead to premature collapse at a load level below the monotonic collapse pressure.

An Industrial Method for Determining the Amount of Organics in Representative Samples of Aluminum Scrap

In recycling plants, especially those specializing in the recycling of low-grade aluminum scrap for wrought aluminum alloys, timely and accurate information about the amount of organics and other impurities in the incoming scrap is an important parameter in achieving both economic benefits and standard metallurgical quality of the recycled metal. To use aluminum scrap combined with organics as a source of aluminum for producing wrought aluminum alloys of standard quality, its metallurgical composition and the content of organic and other impurities should be quickly and cost-effectively analyzed on representative samples. In this work, an industrial thermogravimetric/differential thermal analysis of representative scrap samples was developed as an efficient analytical methodology for analyzing the humidity and organic impurities in incoming scrap. When performed in continuous mode, under a flowing atmosphere of argon with 1 wt.% of oxygen, this methodology enables a routine measurement of the humidity, the quantity of organics, and the carbon content in representative samples of incoming scrap in less than 15 min within an accuracy of ±0.5%.

No association between the aluminium content of trabecular bone and bone density, mass or size of the proximal femur in elderly men and women

BackgroundAluminium is considered a bone toxic metal since poisoning can lead to aluminium-induced bone disease in patients with chronic renal failure. Healthy subjects with normal renal function retain 4% of the aluminium consumed. They might thus also accumulate aluminium and eventually be at risk of long-term low-grade aluminium intoxication that can affect bone health.MethodsWe therefore examined 62 patients with femoral neck fractures or osteoarthritis of the hip (age range 38–93), with the aim of examining whether aluminium in bone is associated with bone-mineral density (BMD), content (BMC) or width of the femoral neck measured by dual-energy X-ray absorptiometry (DXA). During operations bone biopsies were taken from the trabecular bone of the proximal femur. The samples were measured for their content of aluminium using a mass spectrometer.ResultsNo significant association between the aluminium content in bone and femoral neck BMD, BMC or width could be found after multivariate adjustment.ConclusionOur results indicate that the accumulated aluminium content in bone during life does not substantially influence the extent of osteoporosis.

The aluminum content of bone increases with age, but is not higher in hip fracture cases with and without dementia compared to controls

Aluminum is considered a potentially toxic metal, and aluminum poisoning may lead to three types of disorders: aluminum-induced bone disease, microcytic anemia and encephalopathy. This is well known in patients with chronic renal failure, but since healthy subjects with normal renal function retain 4% of the aluminum consumed, they are also at risk of long-term low-grade aluminum intoxication. Included in this study were a total of 172 patients (age range 16-98 years) with the aim of examining whether aluminum accumulates in bone with increasing age. Additionally, we aimed to investigate whether the aluminum content of bone differs between controls and hip fracture cases with and without dementia, in particular in those with Alzheimer's disease. During operations for all cases, bone biopsies were taken with an aluminum-free instrument from the trabecular bone. The samples were measured for their content of aluminum using an inductively coupled mass spectrometer. We found an exponential increase in aluminum content of bone with age. The average aluminum values, adjusted for age, were similar in men and women (P=0.46). No significant differences in sex- and age-adjusted mean aluminum values between the controls and the hip fracture cases with (P=0.72) and without (P=0.33) dementia could be detected. The average aluminum concentration among cases with Alzheimer's disease was also similar to the values of hip fracture patients with other types of dementia (P=0.47). Odds ratios of hip fracture for each quartile of aluminum content in bone were also estimated to detect non-linear effects, but we did not find any statistically significant association remaining after age and sex adjustment. Thus, our results indicate that we accumulate aluminum in bone over our life span, but this does not seem to be of major pathogenetic significance for the occurrence of hip fracture or dementia.

Aluminum, Alzheimer's disease and bone fragility.

The incidence of fragility fractures has increased epidemically. Especially patients with senile dementia (including Alzheimer's disease) have a greatly increased risk of fragility fractures. Aluminum inhibits bone mineralization; the greater the aluminium exposure, the higher the risk of an early fracture. Aluminium is neurotoxic and may, in addition to genetic factors, play a role in the development of Alzheimer's disease by contributing to the formation of the characteristic beta-amyloid and neurofibrillary tangles. Thus, a common denominator between Alzheimer's disease and bone fragility may be a chronic low-grade aluminum intoxication. The epidemic of fragility fractures may be caused by increased aluminium exposure--due to the use of aluminum cooking pots or the pollution acidification of our environment. In our pilot study of 26 hip-fracture patients (13 patients with Alzheimer's disease and 13 individually age- and gender-matched non-demented patients), the aluminum content, determined mass-spectro-metrically, was higher in trabecular bone biopsies from the patients with Alzheimer's disease than from the non-demented patients (p = 0.005). The aluminum content was also higher in the younger of the 26 patients (p = 0.02). Our findings agree with the hypothesis that aluminum plays a role in the development of Alzheimer's disease and bone fragility.

Thermogravimetric and infrared spectroscopic investigations on the interactions between mordenites and phosgene

By analogy to chlorination technologies for processing low-grade aluminium ores, an attempt was made to remove aluminium from zeolitic frameworks (dealumination) using phosgene. The more or less separated individual steps of interaction of phosgene with exchange and framework ions were followed by changes of the mass of the sample specimen using a sensitive Mettler balance. The reaction products identified permitted the setup of a reasonable sequence of steps and stoichiometry for the interactions. The rate-determining step of dealumination could be traced back to the slow release of the AlCl 3 (or decomposition of NaAlCl 4) product. The bulky molecules of Al 2Cl 6 and NaAlCl 4 block the narrow pores of mordenite, thereby causing transport hindrance in both directions. “Complete” dealumination can, therefore, be achieved only by repetition of the dealumination cycles.

アルミニウムへの電着における素材の純度の影響について

As base metals 3 kinds of aluminium plates of different composition (99.9% Al, commercial aluminium, and 52S) are used in the experiments.Specimens are made by plating the anodized and plate mentioned above. The examination of the adhesive property of these specimens shows that the low grade aluminium has the best adhesive property.The cause of the difference in the adhesive properties is investigated, and the following results are obtained:i) The electron-microscopic observation of the oxide film shows that the inherent pores are slightly larger for the higher purity aluminium than the lower one. When the phosphoric acid bath is used, no relation exists between the adhesive property and pore size. The cell structure of the oxide film is more uniform and continuous in the high purity aluminium, while the low grade aluminium has many defects in the oxide film.ii) The anodized surface of low grade aluminium macro or micro-scopically rough.iii) The nucleation during initial plating is selective as a rule, and the higher the purity of aluminium is, the higher is the selectivity.iv) In the case of nickel bath, the lower the grade is, the higher is the electric potential, and the easier is the plating operation. This agrees with the well known fact that the nobler the metal is, the easier is the plating operation. The potential rises due to the anodizing, and the highest possible potential becomes almost as high as that obtained by using iron plates.