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In this work, vanadium is extracted from TiCl4 refining tailings by a clean metallurgical process and FeVO4 is prepared by adjusting the pH of acid leaching solution. The main factors affecting the leaching of vanadium from tailings are leaching temperature, solid-to-liquid ratio, hydrochloric acid concentration and type of oxidant. Under the optimal leaching conditions, when the leaching temperature is 30°C, the solid-liquid ratio is 1 : 4, the hydrochloric acid concentration is 400 g/L, and the oxidant is H2O2, the leaching rate of V can reach 97.1% after 60 min of reaction. The main factors affecting the precipitation of FeVO4 are the precipitation temperature, the initial vanadium concentration, the pH endpoint value of acid leaching solution and the addition amount of H2O2 oxidant. Under the optimal precipitation conditions, when the precipitation temperature is 40°C, the initial vanadium concentration is 5 g/L, the pH endpoint value of the acid leaching solution is 1.4, the addition amount of H2O2 oxidant is 6%, the precipitation rate of V can reach 95.4% after 60 min. By adjusting the pH value of precipitation filtrate, metal ions such as Fe, Al, Ca and Mg precipitate to form neutralization slag. The neutralization filtrate can be prepared NaCl crystals by evaporation crystallization, and the mother liquor of evaporation crystallization is returned to acid leaching for use. Acid leaching residue (TiO2 content is 55.42%) can be recycled as high-titanium raw material. This study can properly deal with the environmental pollution caused by the stacking of TiCl4 refining tailings.

When bauxite and alumina resources are limited, high-alumina fly ash becomes a potential aluminum resource. The comprehensive utilization of high value-added elements in high-alumina fly ash is of great significance to resource circulation. In order to solve the difficult comprehensive utilization of valuable components in high-alumina ash problem, the existing traditional research methods of high-alumina ash are firstly summarized and compared in this paper. Following the review, a new method for the treatment of high-alumina fly ash by electrotransformation is proposed. This new method can realize reduction in slag volumes, with no waste acid, no alkali input required. It can be concluded that this new method can effectively treat high-alumina fly ash and realize the comprehensive utilization of valuable components of high-alumina fly ash.

A green process that uses the spray pyrolysis method to prepare activated alumina is proposed in this research. The effects of spray temperature, carrier gas pressure, and AlCl3 solution concentration are experimentally investigated using pure reagents. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and specific surface area (BET) analyses. The results indicate that the spray temperature is the most important factor on the conversion ratio of alumina during the spray pyrolysis process. The conversion ratio of alumina achieved over 99% at the following optimal conditions: temperature of 1000°C, pressure of 0.3 MPa, and AlCl3 solution concentration of 10 wt%. The activated alumina with 8–20 nm particle size (γ-Al2O3+α-Al2O3) was prepared using the same process, which well met the requirement of the catalyst carrier. The green utilization of high-alumina fly ash and acid recycling can be achieved by using this process.

The highly-alkaline red mud, which is the Bayer process residue generated from the alumina industry, is a severe environmental problem. In this study, a new calcification–carbonation process was proposed for red mud disposal. Red mud was processed by lime to convert the aqueous silicon phase into hydrogarnet, which was then decomposed by CO2 to recover alumina. In the direct carbonation process, the NaOH-containing solution after calcification was directly carbonated without prior liquid–solid separation. The discrete and direct carbonation processes had alumina recovery rates of 34.9 and 35.5%, respectively, with 0.15 and 0.21 wt % Na2O in the final red muds, respectively. The optimum NaOH concentration in the calcification liquor was 30 g/L. Under these conditions, alumina recovery was increased to 44.5% and the Na2O concentration in the processed red mud was reduced to

The kinetics of oxygen pressure acid leaching marmatite with high indium content was studied. The effects of particle size, agitation rate, temperature, H2SO4 concentration, and oxygen partial pressure on leaching rate of indium were investigated. The results show that when the agitation rate is above 600 r·min−1, its influence on indium leaching rate is insignificant. It is determined that the leaching rates increase with the increase in sulfuric acid concentration, temperature, partial oxygen pressure, and the decrease in particle size. Moreover, the results demonstrate that the process of indium leaching is controlled by interface chemical reaction, with apparent activation energy of 65.7 kJ·mol−1. The apparent reaction orders of sulfuric acid and oxygen partial pressure are determined to be 0.749 and 1.260, respectively. The leaching reaction process follows shrinking unreacted core model. And finally, the kinetics model equation is established for indium.

The disposal of red mud, which is a solid waste that is generated during the extraction of alumina from bauxite, is one of major problems faced by the aluminum industry. Alkali in red mud seeping under the soil may pollute land and water. The Northeastern University, China, has proposed a calcification–carbonation method to deal with low-grade bauxite or red mud. Its main purpose is to change the equilibrium phase of red mud to 2CaO·SiO2 and CaCO3 hydrometallurgically, so that recomposed alkali-free red mud can be widely used. We conducted calcification transformation experiments using diasporic bauxite sampled from Wenshan, and investigated the effects of parameters such as diasporic bauxite grain size, temperature and treatment time on the calcification transformation digestion rate, which is also termed the calcification transformation rate (CTR). The main phase in the calcification transformation slag (CTS) is hydrogarnet with different grain sizes. The CTR increases with decrease in diasporic bauxite grain size, or increase in temperature or reaction time. The CTR reaches a maximum of 87% after 120 min reaction at 240°C. The Na2O/Al2O3 ratio decreases with increase in temperature and reaches 1.5. The sodium content in the CTS decreases with increasing reaction time and is lower than that in the red mud treated using the Bayer process (4–12%).

Titanium has a great effect on the digestion of bauxite in the Bayer process because it reacts readily at high temperatures in alkaline sodium aluminate solution. Under this consideration, the hydrothermal conversion of Ti-containing minerals in the system of Na2O–Al2O3–SiO2–CaO–TiO2–H2O with increased temperatures was studied based on the thermodynamic analysis and systematic experiments. The results show that anatase converts to Al4Ti2SiO12 at low temperatures (60–120 °C), which is similar to anatase in crystal structure. As the temperature continues to rise, Al4Ti2SiO12 decomposes gradually and converts to Ca3TiSi2(Al2Si0.5Ti0.5)O14 at 200 °C. When the temperature reaches 260 °C, CaTiO3 forms as the most stable titanate species for its hexagonal closest packing with O2− and Ca2+. The findings enhance the understanding of titanate scaling in the Bayer process and clarify the mechanism of how additive lime improves the digestion of diaspore.

Fly ash, generated during the combustion of coal for energy production, is an industrial by-product which is recognized as an environmental pollutant. In this paper, thermodynamic calculations and experiments in a tubular furnace reactor were conducted to investigate the process of pelletizing chlorination of fly ash. The thermodynamic calculations indicated that with the increase of the chlorination temperature, the Gibbs free energy of the chlorination reaction is negative, and this demonstrates the thermodynamics feasibility of pelletizing chlorination process. Experiments results show that the alumina chlorination efficiency was up to 70% when the pellet diameter was 8 mm and the C/Al was 3:1 at 1050 °C for 30 min. The effect of alumina chlorination efficiency in pelletizing chlorination process mainly depended on the temperature, chlorination time and pellet diameter. These findings provide useful information for understanding the pelletizing chlorination process, facilitating the development of pelletizing chlorination metallurgy in efficient clean utilization of fly ash.

Processes of chemical alumina preparation of high alumina content fly ash raw materials are put forward in order to solve the problems of bauxite resource shortage in China and high value application of fly ash. High white aluminum hydroxide and Pseudoboehmite can be obtained by sintering process with the precipitation and carbonate decomposition. 4A zeolite is prepared through the pre-roasting and synthesis process, and activated aluminium oxide is prepared through the acid leaching and pyrolysis method. Typical experiments for preparing different kind of chemical alumina products are presented as well. Whiteness, porosity, pore volume, crystalline and other key parameters of chemical alumina products determined by XRD and ASAP match the industry requirements well.

Molten MgCl2 generally sold as a kind of waste at low price after cooling, which caused the waste of resource and energy. In order to solve the problem, a new method named “situ pyrolysis of molten magnesium chloride” was proposed. The molten MgCl2 produced by vacuum distillation in magnesium thermal reduction process was treated by the direct oxidation thermal decomposition method to produce super fine MgO with high purity. The magnesium produced by thermal reduction of MgO could be returned to the boiling chlorination of high titanium slag. The new cycle of magnesium and chloride in titanium sponge production was achieved. Based on the thermodynamic analysis of the reaction between O2 and MgCl2, the single factor experiments had been done. The optimal reaction condition was determined and the impact of each factor in the pyrolysis process was studied.

A novel method was developed to prepare aluminium via fluidizing chlorination with untraditional aluminum resources as raw materials. The main steps in this method were: alumina transformed into aluminium chloride through fluidizing chlorination; aluminium chloride reacted with NaOH solution for aluminium hydroxide and NaCl; NaOH and Cl2 were recycled from NaCl solution by electrolytic process. The new process for preparing aluminium resources by fluidizing chlorination method was proposed to realize efficient separation of the valuable components in non-traditional aluminum resources such as fly ash or low grade bauxite, silicon in untraditional aluminum changed into SiCl4 in fluidizing chlorination which could be used as raw materials for high purity Si products. Furthermore, the tailings emission of this process was quite lower than that of Bayer process. This paper mainly introduce the principle of this new process, the thermodynamics of fluidizing chlorination is analysis as well.

The novel calcification-carbonation method was proposed to process the diasporic red mud discharged from Bayer process alumina plant. In this study, Batch experiments were performed to evaluate the potential effects of important parameters such as temperature, amount of CaO added, CO2 partial pressure and carbonation cycles on the recovery of alkali and alumina. The results showed that 78.74% alumina was recovered from the diasporic red mud with decreases in the mass ratios of Al2O3 to SiO2 (A/S) from 1.27 to 0.27. The Na2O content in the processed red mud was less than 0.3 wt%, and it can be used as a construction material.

A novel method was developed to prepare activated alumina via spray pyrolysis of aluminum chloride solution. In this paper, activated alumina was obtained by spray pyrolysis in tube furnace with aluminum chloride solution as raw materials in different temperatures. X-ray diffraction (XRD), scanning electron microscope(SEM) and the specific surface area analysis were used to characterize the spray pyrolysis products, respectively. XRD results showed that the crystal phase composition of activated alumina can be controlled through adjusting pyrolysis temperature. The crystal structure of γ-Al2O3 in the products conformed to the requirements of the index of activated alumina. Most of pyrolysis products were porous structure which the particle size was around 5 μm under scanning electron microscope. With the activated alumina were examined by specific surface area analysis, the products existed as inkbottle-shaped and parallel-plate pores. Pyrolysis products more conformed to the requirements of activated alumina after examined by XRD, SEM, and the specific surface area.

A new type of high-temperature jet spray pyrolysis (SP) reactor is investigated in this article as part of studies on the preparation of rare earth oxides at Northeastern University (NEU), Shenyang, China. The jet spray reactor examined here is a horizontal, tubular reactor conveying the hot products of the combustion of methane and oxygen with a converging–diverging jet section in an arrangement that provides for inspiration of LaCl3 solution to pyrolyze to La2O3 with the hot gas. The present article is concerned with a computer simulation using a computational fluid dynamic model to develop the velocity, temperature, and pressure profiles in the jet reactor since direct measurement is difficult. The article includes brief comments on a room-temperature model designed to examine the flow characteristics of the jet SP reactor. It was found that the velocity decreased at first, and then it increased near the jet throat. The highest velocity occurred at the throat of jet SP reactor where the LaCl3 enters the unit. Along the reactor axis, the temperature decreases with distance from the gas inlet. The lowest temperature zone was near the wall before the throat of the reactor due to wall heat losses. The temperature was estimated to be close to 1700 K at the throat of the reactor, and it was about 1300 K toward the exit of the reactor. It was shown that a reaction would take place mainly in the throat and in the vicinity of first contact between gas and induced spray. A negative pressure was produced as gas passes through the converging–diverging throat of the jet SP reactor that causes the LaCl3 solution to enter the throat of the reactor. While the investigations of this type of reactor are at an early stage, the results look promising. NEU continues to investigate this approach for the preparation of La2O3 based on high-temperature testwork and physical modeling techniques.