The low grade bauxite utilization and red mud treatment become to the key problems of Bayer process caused by the balance phase of sodium aluminosilicate. To solve these problems, ¡°Calcification-Carbonation Method¡± was put forward by Northeastern University. The main purpose of this method is to change the balance phase of red mud into 2CaO•SiO2 and CaCO3 with a low energy consumption hydrometallurgical process. Through treatment by ¡°Calcification-Carbonation Method¡±, A/S of the new structure red mud lowered below to 0.5 and the Na content lowered below to 0.3%, the red mud could be used in cement industry directly or planting soil preparation. This paper mainly introduced the technological idea and principle of new method, thermodynamic analysis and typical experiment results are given as well.

With the continuous consumption of high quality bauxite, the high-iron and high-titanium bauxite which is more difficult to dispose has to be used for alumina production gradually. Iron and titanium are both disadvantageous factors in the Bayer process which may have some impact on the alumina production in the calcification-carbonization process, especially in the calcification process. In this paper, the calcified transformation of iron and titanium in the calcification-carbonization process was investigated separately. The experimental results show that the additive Fe(OH)3 converts to Fe-containing hydrogarnet with the increase of temperature. Fe(OH)3 reacts more readily than Fe2O3 and promote the conversion of Fe-containing hydrogarnet. The additive TiO2 firstly transform to Ca3TiSi2(Al2Si0.5Ti0.5)O14 and then CaTiO3 with the elevated temperatures.

China has abundant Fe-Al associated resources, the comprehensive utilization of which plays a great role in easing the shortage of bauxite and iron ores nowadays. A new and innovative technology to economically extract both iron and alumina from Fe-Al associated core basing on the coal-based direct reduction has been proposed in this paper. The Fe-Al associated core is firstly pre-reduced at a lower temperature in a rotary hearth furnace, then molten reduced at a higher temperature to separate the iron and calcium aluminate slag, and finally extracted alumina from the calcium aluminate slag. The results show that the iron metallization rate during the pre-reduction process is above 60%, and the main minerals in the pre-reduced ore are Fe, 12CaO¡¤7Al2O3, 3CaO¡¤Al2O3, 2CaO¡¤Al2O3¡¤SiO2 and 2CaO¡¤SiO2. The separation property of molten iron and calcium aluminate slag is very good, and the iron recovery rate can reach over 95%. The minerals of calcium aluminate slag are mainly comprised of 12CaO¡¤7Al2O3, CaO¡¤Al2O3 and 2CaO¡¤SiO2, which have a good alumina leaching efficiency as high as over 85%.

The characteristic of dispersoids in the semi-continuous casting ingot of 7475 aluminum alloy and the evolution of their distribution during rolling have been investigated by means of optical microscopy (OM) and transmission electron microscopy (TEM). The size, shape and distribution of dispersoids are controlled by pre-treatment before homogenization of semi-continuous casting ingot of 7475 aluminum alloy. The results show that there are many coarse triangular, irregular block and spindly rod-like dispersoids which contain some of Cr and Mg and a little of Cu and Zn in the 7475 aluminum alloy which subject to conventional one-step homogenization treatment at 470¡æ for 24h. The size and the distribution of the Cr-containing dispersoids is not uniform. The width of the coarse dispersoids is close to 1 um and the length of the spindly rod-like dispersoids is more than 4 um. There is no dispersoids in the center of the dendritic grains, but the nonuniform distribution of dispersoids is completely eliminated when the hot rolling reduction exceed 80%. The dispersoids in the semi-continuous casting ingot of 7475 aluminum alloy can be significantly refined and homogenously distributed by pre-treated at 240¡æ~340¡æ before the conventional one-step homogenized at 470¡æ for 24h. The pre-treatment can stimulate the nucleation of Cr-containing dispersoids, increase their density and narrow down the dispersoids free zone. The size of the dispersiods in semi-continuous casting ingot of 7475 aluminum alloy ingot is dramatically reduced by pre-treated at 240 ¡æ for 48h before the conventional homogenization at 470¡æ for 24h, and the width of the coarse dispersoids and length of the spindly rod-like ones are less than 0.3 um and 1 um, respectively, so that the dispersiods are hardly observed in the etched sample by OM.

Aluminum electrolysis with ultrasound was carried out in cryolite-alumina melt at 950 C in a laboratory cell. The power ultrasound was introduced into the anode-melt interface through a stainless steel of anode rod. The effects of ultrasound on current efficiency were investigated with varying current density as well as other parameters. The results obtained and the potential benefits will be discussed.

NEUI has successfully eliminated a great many technical bottlenecks hindering the development of high amperage aluminum reduction technologies, such as high amperage pot MHD stability technology, 3D thermal-electric field simulation technology, dynamics simulation technology of pot gas flow, etc., and has also developed the world¡¯s first 400kA aluminum reduction potline technology package, which has already been put into extensive use. On that basis, with the same development method and technical standards, NEUI constantly takes advantage of the latest development breakthroughs and developed NEUI500, NEUI600 technologies. NEUI600kA reduction potline has been put into commercial operation in Dec. 2014 in China. At the present time, the operating amperage of the potline is 602kA, and more excellent techno-economic indices have achieved such as average pot working voltage less than 4.0V, DC energy consumption less than 12500kWh/t-Al, anode effect frequency less than 0.01effects/pot¡¤day

Aluminum and aluminum-magnesium alloys were prepared by direct current electrodeposition and pulse electrodeposition in AlCl3-LiAlH4-benzene-tetrahydrofuran (THF) system. Electrochemistry experiment was conducted by three electrode system and the cyclic voltammetry and chronamperometric graphs were studied. The surface morphology, composition, and content of the aluminum and the aluminum- magnesium alloys were studied by using scanning electron microscope (SEM) and energy spectrum (EDS). Results show that the coating of aluminum and the aluminum magnesium are superior when the pulse duration ratio (ton:toff) is 0.08s:0.02s. The coatings are best when DC deposition current density is 14.89mA/cm2. SEM shows that the grains size is thick and the surface is rough by DC deposition. But the coatings obtained by pulse electrodeposition are more uniform and thinner than the coatings obtained by DC deposition and the surface is flatter.

A roadmap and direction for energy saving and emission reduction in aluminum electrolysis were suggested. There is large room for saving energy and raw materials in the aluminum reduction process. The potential of energy saving and emission reduction is significant. A new cell, named full closed reduction cell was suggested in this paper. In addition, insulation materials with the high fraction of alumina can be reused as alumina raw material after reduction pot failure, which enables clean Hall-Heroult process.

The high-alumina fly ash containing more than 40 wt% alumina is mainly distributed in midwest Inner Mongolia and north Shanxi province of China, which is the solid waste of high-aluminum coal during combustion. The prospective reserves of high-alumina fly ash are estimated to be 15 billion tons in the form of alumina. The processing technologies and the characteristics of the main products, as well as the by-products in the alkaline processes and the acid processes to extract alumina from high-alumina fly ash, were discussed in this paper based on both the experimental results and the engineering applications. The key points and prospects during the engineering processes were also pointed out. The application of alumina extraction from the high-alumina fly ash can not only expand the reserves of alumina-containing resources and reduce the covers of solid wastes, but also possess great economic value in special areas of China, which has a positive and profound influence on the sustainable development of the aluminum industry.

Chinese aluminum reduction industry has developed rapidly in the decades. It has made a great contribution to the development of national economy and people¡¯s living, yet produced a lot of waste as well. The spent cathode of aluminum reduction is the largest amount of solid waste when the cell shutting and relining, and it contains some dangerous substances such as fluoride and cyanide which may cause serious environmental and safe problems, so harmless treatment on spent cathode has become an urgent and serious problem for Chinese aluminum refiners. Yet from the perspectives of resource, there are also a lot of value materials such as graphite, cryolite and alumina in the spent cathode, so it is also very important to recovery valuable substances from spent cathode of aluminum reduction. In this paper, current processing methods of harmless treatment and resource recovery for spent cathode of aluminum reduction were reviewed, and future development trend was also predicted. The main problem to be resolved for harmless treatment is to decrease the cost of industrial application. For hydrometallurgical treatments such as leaching and flotation, the key is to improve the recovery ratio and grade of recovered carbon powder and cryolite for further usage. It is a promising method and worth exploring further for adding a certain amount of spent cathode into the sintering process of alumina production, of which sodium and aluminum can be recovered together, graphite acts as a reductant of high ignition point and fuel, and fluoride becomes an improving agent of the sintering process.

In this paper, a new method for saving DC consumption in aluminum electrolysis was described. After ordering the importance of many process parameters to energy consumption, cell voltage and current efficiency, and find the root cause of problems due to management or process control, the potential of decreasing DC energy consumption can be continually improved based on the principle of aluminum electrolysis and data analysis. The practice and its results of the method in the industry were also introduced in this paper.

Physical-chemical properties of the molten salt system Na3AlF6-ExAlF3-5wt%Al2O3-CaF2-KF-LiF for aluminum electrolysis were investigated in this paper. The combined effects of ExAlF3, KF and LiF on the liquidus temperatures, alumina dissolution, aluminum solubility, electrical conductivity were discussed. A regression equation describing liquidus temperatures was derived. The effects of lithium fluoride and potassium fluoride on bath chemistry analysis were also discussed.

A test was conducted to product activated alumina with aluminum chloride solution as feedstock. The reaction mechanism and suitable conditions of activated alumina production by spray pyrolysis had been analyzed. The calculation results showed that the standard Gibbs free energy of the pyrolysis reaction was far less than zero; through the analysis of AlCl3, H2O, HCl partial pressure, reaction degree could be controlled by the partial pressure of the gas phase. The physical characterization of Al2O3 was studied by XRD and SEM for different AlCl3 precursor concentration and reaction time on the reaction and optimized the synthesis conditions of activated alumina. It is therefore suggested that the combination of 15min and 15% was the best for activated alumina production, products mainly existed as ¦A- Al2O3 and particle size distribution was average£¬the maximum specific surface area of the product surface area was 97.52m2/g.

The aluminum or magnesium liquid obtained by fused salt electrolysis was usually casted into ingots in the past. Nowadays, the aluminum liquid has been used to fabricate its alloys and even its ultimate products directly. In this paper, the method to prepare aluminum or magnesium foam by liquid route will be introduced, i.e. the industrial aluminum or magnesium liquid will be used as primary material to manufacture a kind of foamed materials holding multiple functional characteristics. The structural and functional properties, as well as potential applications of these materials, will be also discussed in the paper.
Keywords: aluminum foam; magnesium foam; liquid route

(NH4)2SO4 roasting technology was used for extract alumina from fly ash which is located in Shandong Zibo power plant. The roasting temperature, the molar ratio of (NH4)2SO4/Al2O3 and roasting time on the effect of the extract rate of alumina was studied. The optimal roasting technology condition is 380¡aC for 120min with a molar ratio of (NH4)2SO4/Al2O3 to 6:1. Under the optimal roasting condition, the alumina extraction rate can reach 83% and a new phase NH4Al(SO4)2 was formed in the clinker. NH4Al(SO4)2 in clinker was leached by distilled water and separated from clinker by filtration. Fe in leached liquid was removed by NH4Fe3(SO4)2(OH)6 formation. Results showed that Fe precipitation of 95% and Al precipitation less than 5% could be achieved with pH value keeping from 1.5 to 2.0 for 2h at 95¡æ and a final pH value keeping at 3.0. NH4Al(OH)2CO3 was prepared by adding (NH)4HCO3 in leached liquid. Ultrafine ¦A-Al2O3 powder was prepared by calcining NH4Al(OH)2CO3 in 1100¡æ for 120min, which was characterized by XRD and SEM.

Synthesis and decomposition of hydrogarnet are the main reactions of "Calcification-Carbonization Method", and the saturation coefficient of Si affects the alumina recovery efficiency significantly. This research mainly focuses on the phase transformation performance in the new method. The experiment results indicated that: Al, Si transformed into hydrogarnet with a different saturated coefficient at 180¡æ and 245¡æ through calcification treatment, and silicon phase changed into 2CaO•SiO2 through carbonization treatment. The effect of saturation coefficient of Si in hydrogarnet product on the "Calcification-Carbonization" process is discussed with thermodynamic analysis and experiment as well.

Because of severe experimental hindrances, the knowledge on molten fluoride salts chemistry has long remained limited to few experimental approaches. Molten fluorides mixtures can be strongly organized at unusually long distances due to the predominance of coulombic interactions and described by the formation of an intermediate range ordering. The description of free fluorine content evolution is also of primary importance for a better understanding of their properties. NMR spectroscopy is one of the techniques able to provide such information. Nevertheless, these systems cumulate high temperatures (from 500 K to 1800 K), corrosive properties towards most of the materials and sensitivity to moisture and oxygen making the NMR experiment a real challenge. We have already shown that thanks to the specific design of the sample container and of the heating system it was possible to obtain NMR spectra in the melt and to follow the evolution of the local structure with temperature and composition up to 1500°C. The signal position, or the isotropic chemical shift, is the weighted averaged chemical shift of the different components in the melt. Knowing the chemical shift of the individual species, it is possible to define their proportions depending on the composition, except when the number of individual species becomes too high compare with the equilibrium equations. We are now able to calculate directly the chemical shifts corresponding to the system, thanks to the coupling between molecular dynamic calculations and theoretical approach of the NMR chemical shifts calculations. This new step towards a better description of the speciation in such molten salts will provide a new capability to determine the physical and chemical properties of molten fluorides .

Hall-Heroult process for primary aluminum production is energy intensive. The energy efficiency of the process is less than 50%, which can be increased by the spent heat recovery technology. A new type of aluminum electrolysis cell was designed for this special purpose and installed at Northeastern University. A 3000A laboratory scale test was carried out. This paper presents some results for this technology.

The production of primary aluminium in January 2016 was 4726000 tons, corresponding to about 57 million tons a year. The latest expansions have been in the Middle East and above all in China which now is responsible for 52% of the world production. The newest smelters are either high amperage, +600 kamp or low energy, less than 11 kWh/kg Al. The used cathode materials are getting more graphitic and SiC sidewalls are used extensively. Strong shells are needed, while the refractory and insulation materials remain the same. The off gas of fluorides to air is very satisfactory, less than 0,2 kg F/tAl, but spent potlining is still a problem. Only amperage and voltage can be measured continuously, but proprietary computer programs have led to very good management of the cell technology. No radical innovations are in sight, but the following actions which will be discussed are promising: The Chinese protruding cathodes, use of slotted anodes, flow adapted feeding, 25% increase of amperage within the same shell, use of copper collector bars, improved analytic sensors as the Alcoa and Heraeus probes. No new demonstrations of inert cathodes or anodes have been reported.

Three-layer liquid electrolytic purifying is the main method for producing refined aluminum and the NaF-AlF3-CaF2-BaF2 system is widely used as the electrolyte in that process. In this paper, Raman spectra of NaF-AlF3 with the composition of practical aluminum refining electrolyte are recorded and the melts structure was investigated, firstly, with the help of the quantum chemical calculation. On that basis, the effect of CaF2 addition to the ionic structure of NaF-AlF3 was then studied. The results have indicated that AlF4- tetrahedron and entities containing two or more AlF4- tetrahedron connected by ¡°bridge fluoride¡± were in NaF-AlF3 binary melts. CaF2 was added as a fluoride donor, when the ratio between NaF and AlF3(CR) and the content of CaF2/BaF2 are relatively low, the only kind of Al-F complex in the melts is AlF4- tetrahedron and the net or chain structure containing two or more AlF4- tetrahedrons connected by ¡°bridge fluoride¡±. With the increasing CR and content of CaF2, AlF52- appears in the melts and when continuing to increase CR and content of CaF2, AlF63- will appear. The temperature has little effect on the relative content of the complexes. The relationship between molar percent of the three complexes and CR has been obtained. At last, a dissolved model of CaF2 in NaF-AlF3 was discussed.

Basic properties (crystallization temperatures, electrical conductivity, oxides solubility) and structure of electrolytes composed of potassium (KF-AlF3), sodium (NaF-AlF3) cryolites or their mixtures with additions of scandia and alumina have been studied in order to determine the admissible concentration and temperature ranges for the production of aluminum-scandium alloys. The scandia in cryolite melts behaves similarly to the alumina: reduces the liquidus temperature and decreases the electrical conductivity. The solubility values of scandia and alumina in the sodium-cryolite-based melts are close. These facts indicate that the Sc2O3 interacts with cryolite melts forming Al2O3. However, in contrast to alumina, the scandia solubility in potassium cryolite (KF-AlF3) with the molar ratio of KF/AlF3<1.5 is rather low. Based on the Raman spectroscopy and solubility data it was assumed that a mechanism of the Sc2O3 dissolution in the KF-AlF3 and NaF-AlF3 melts is different. The scandia dissolves in the NaF-AlF3 with subsequent formation of the ScF63- and Sc2OF62- ions, whereas in the KF-AlF3 at temperatures of 650-800 °C the dissolution process is obstructed by a K3ScF6, highly melted and poorly soluble substance.

The treatment of Waste Electrical and Electronic Equipment (WEEE) includes several subsequent steps. The aim of this paper is to obtain a new ecological route for recycling of different metals (Al, Zn, Pb, Ag, and Au) from WEEE by using deep eutectic solvents (DES). DES is a form of ionic liquids that are mixtures of salts such as choline chloride with hydrogen-bond donors such as urea. DESs are environmentally benign, yet chemically stable and, furthermore, the components are already produced in large quantities at comparable costs to conventional reagents. The dissolution of different metals or of the multicomponent alloy obtained by pyro metallurgical technology from WEEE was found to be soluble in Choline chloride-X (X=Urea, Ethylene glycol, Malonic acid, 0,2MCuCl2&#61655;2H2O +30% ChCl) through an oxidative/non-oxidative leach at 45–80&#61616;C. A remarkable difference between genuine DES and ILs with the solutions used in this paper is the addition of rather large quantities of water, which was shown to have a lot of advantages on the leaching of metals, while the properties typical for DES still remain. The dissolution of some metals was studied with or without oxidizing agents. In the experiments on ChCl-(CuCl2&#61655;2H2O+ChCl) it was observed that Al dissolved fast at 80ºC, while at room temperature the leaching stopped after 10 minutes presumably because of a protective layer formed on the Al surface. For Zn and Pb this is ascribed to the impossibility of forming a protective layer at a higher temperature. For Au and Ag this solution was not efficient. It seems that the presence of water is not advantageous in this case, but good results were obtained in ChCl-X (X=Urea, Ethylene glycol). Metals were electrodeposited on Cu/Pt from the studied ionic liquids and submitted to XRD and SEM experiments. Finally, the metals electrodeposition mechanism was studied by cyclic voltammetry and a two steps mechanism was found for Al, Pb and one step for Zn, Ag, Au.

Keywords: metals recovery from WEEE, ionic liquids, electrodeposition, cyclic voltammetry

Electrodeposition of aluminium (Al) from chloroaluminium ionic liquids (ILs) has been studied extensively. However, Al coatings obtained from these ILs lack metallic luster. In order to get coatings with a good surface, it is always necessary to add additives to the ILs electrolyte as that of aqueous solutions. There is little additives for ILs systems. We have chosen some pyridine derivatives (nicotinic acid, methyl nicotinate, nicotinamide and 3- methyl pyridine) to study the effect of them on the morphologies of Al coatings obtained from chloroaluminium ILs. It has been summarized from series of research results that pyridine derivatives with electron-withdrawing groups (nicotinic acid, methyl nicotinate and nicotinamide) have stronger adsorption ability on the cathode and they are effective brighteners. By contrast, the pyridine derivative with an electron-donating group(3-methylpyridine) has a weak adsorption ability and cannot be used as a brightener. Furthermore, the research results have proved that the brighteners refine the grain size, orient the Al(200) plane, and level the deposits; thus, Al coatings with highly uniform and smooth surface are obtained.
Acknowledgment: The authors gratefully acknowledge the financial support from the General Program Youth of National Natural Science Foundation of China (51404230), National Basic Research Program of China (2013CB632606), and National Natural Scientific Fund of China (21476234).

Aluminum is the second most produced metals, only below iron. China is the top producer of primary aluminum with a production capacity of 38000 kt and output of 32000 kt in 2015. A large amount of spent pot lining (SPL) was produced after electrolytic pot failure. SPL is consisted of spent refractory materials and spent carbon cathode, which contains fluorides, alkali metals and oxides. SPL is considered as a hazardous material because it contains significant concentrations of toxic and leachable cyanides and fluorides. Nowadays, no economical and satisfactory process for the treatment of SPL has been developed in the world. Land filling of SPL, which was adopted by most Chinese smelters, not only pollutes the environment, but also wastes secondary resources. A new method, named Vacuum Distillation Process (VDP), was developed to separate effectively carbon from alkali metals and aluminum electrolyte in the spent carbon cathode. VDP can also be used to recycle the spent insulating materials by the addition of aluminum dust from the foundry shop. Aluminum reacts with alkali metal oxides to produce alkali metals. During the step of distillation cryolite-based electrolyte and alkali metals are removed from the insulating materials, which can be used again in prebaked cells. VDP technology can recycle SPL at very low cost. This paper presents you some important data on VDP.

In the automobile industry, zinc is often used as anti-corrosive coatings on steel surfaces. Conventionally, 80% of the world¡¯s zinc production is produced via the electrolysis of zinc oxide in a sulfuric acid electrolyte. However, this method inevitably involves hydrogen evolution on an electrode, which degrades current efficiency and causes massive hydrogen embrittlement in zinc coatings. This is a serious drawback for some substrate materials, especially for high-grade steels.
Hence, in this study, we developed a new electrolyte to replace sulfuric acid and investigated the effect of temperature on the electrochemical behavior of zinc coatings in the electroplating process.
The electrochemical behavior of zinc was recorded in a three-electrode cell by cyclic voltammetry and chronoamperometry techniques using a potentiostat/galvanostat. Electrodeposition experiments were conducted on a tungsten substrate and products were characterized by XRD, SEM and EDS.
Zinc coating was deposited electrochemically using ZnO as precursors instead of ZnCl2 and the effect of temperature on the electrochemical behavior of zinc coatings and surface morphologies of coatings in the zinc oxide-urea-1-ethyl-3-methylimidazolium chloride system were investigated. Cyclic voltammetry illustrated that the diffusion coefficients of zinc are rising as the temperature increases. Chronoamperometric experiments show that the zinc reduction process followed a three-dimensional instantaneous nucleation with a diffusion-controlled growth model. The Coatings electrodeposited on a tungsten substrate were pure zinc metal characterized by XRD and EDS. SEM analysis shows that the particles of zinc coatings became clusters when temperature increases from 333 K to 363 K

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