Bauxite Processing Research Articles

The Middle-Late Permian Yakshawa and Late Cretaceous Daresard bauxite deposits, western Iran: Elemental deportment, parental affinities and genesis of REY minerals

The Middle-Late Permian Yakshawa bauxite deposit in the Sanandaj-Sirjan Zone and the Late Cretaceous Daresard bauxite deposit in the Zagros Fold-Thrust Belt have bauxite ores with different textures and mineralogical compositions. The presence of detrital and authigenic REY-phosphates, fluorocarbonates of the bastnasite group, and cerianite with diverse generations reflect an intricate formation process of the REY-bearing minerals in these two deposits. This clearly shows that the studied deposits have a multi-stage evolution including diagenetic and/or low-grade metamorphic, in situ fluid-assisted dissolution–reprecipitation reactions, and later bauxitization. The high abundance of monazite, textural relationships, and its LREE pattern indicate this mineral is the main LREE reservoir in the studied bauxite ores whereas xenotime, both authigenic and detrital, is the main host for HREE. The R-mode factor analyses indicates that the bauxitization process induces, at large, similar interelemental relationships in the studied deposits involving the attitude of Al oxyhydroxides, Ti oxides, and Fe oxyhydroxides to concentrate critical metals and the capability of REY-phosphate of being the main reservoir of REE + Y. As for provenance, the Eu/Eu*, Sm/Nd, and Nb/Ta proxies suggest that the bauxite ores of the Yakshawa deposit have a genetic relationship with Middle-Late Permian mafic volcanic rocks, whereas the ores of the Daresard deposit show parental affinity with the underlying fine-grained clayey limestone of the Sarvak Formation.

Manufactured soil: A new use for bauxite residue

Bauxite processing residue produced at an Alumina refinery was used to produce manufactured soil. The residue was first acidified and then leached to remove excess salts. Green waste compost was added at rates of 5 and 10 % w/w, with or without the addition of 20 % w/w dune sand. The products were dried, crushed and sieved and the chemical, physical and microbial properties of the materials characterized. Products had an electrical conductivity and pH of 1.0–1.1 dS m−1 and 8.0–8.1 respectively in 1:5 soil:water extracts and corresponding values in saturation paste extracts were 5.4–5.7 dS m−1 and 7.4–7.5. The effective cation exchange capacity was 202–351 mmolc kg−1, exchangeable Na percentage was 41–46 %, Colwell-extractable P was 108–119 mg kg−1 and the Toxicity Characteristic Leaching Procedure showed that extractable metal concentrations were an order of magnitude below regulatory limits so the material can be considered as non-hazardous. Diethylenetriaminepentaacetic acid-extractable Cu, Zn and Mn were below reported critical levels. Addition of compost lowered concentrations of extractable Cr, As and V and drying the material further reduced extractable levels. When the material was dried it shrunk and solidified and the aggregates produced had a low macroporosity and high microporosity and water holding capacity compared with dune sand. Aggregates were very stable as measured by wet sieving. Compost addition increased organic C content, and the size (microbial biomass C) and activity (basal respiration and the activity of enzymes involved in C, N, S and P mineralization) of the soil microbial community. It was concluded that the materials produced had soil-like chemical, physical and microbial properties and could potentially be used as a soil substitute.

The mid-Cretaceous bauxites of SE France: Geochemistry, U-Pb zircon dating and their implications for the paleogeography at the junction between Alpine Tethys and Pyrenean Rift

Karst bauxites mark episodic exhumation of carbonate platforms, thus providing key information for basin analysis and paleoclimate processes at the regional to continental scale. Most karst bauxite deposits of SE France lie between Jurassic platform carbonates in the footwall and Upper Cretaceous marine to continental sediments in the hanging wall. These deposits delineate a stratigraphic gap coeval with the Durance extensional tectonics, which led to the separation of the Vocontian and South Provence Basins, and shaped the junction between the Alpine Tethys and the Pyrenean Rift.Our new mineralogical and geochemical data show that SE France karst bauxites were affected by in-situ weathering and alteration in conjunction to sedimentary reworking. Statistical analysis of geochemical data indicates that bauxite deposits have a similar chemical footprint, likely pointing to a common and long-lasting bauxitization process. New U-Pb zircon data from the Provence deposits confirm that the source material for the SE France bauxites is to be primarily found in the Hercynian basement. The data suggest the presence of an additional exotic zircon source deriving either from Avalonia and/or Baltica. The comparison of the new U-Pb zircon data with those on coeval bauxites evidences a marked difference between the SE France and the Sardinian deposits. This difference indicates diversification in the detritus provenance of the two areas since the Lower Cretaceous, setting the bauxites of SE France and Sardinia in lateral continuity with the bauxites occurring on the two opposite margins of the Pyrenean Rift, and supporting the development of these deposits on the shoulders of the rift-related basin formed at the eastern termination of the Pyrenean Rift.

Study on sedimentation of tailings sludge from bauxite processing plant of TKV's Aluminum Companies by lamella thickener

Study on sedimentation of tailings sludge from bauxite processing plant of TKV's Aluminum Companies by lamella thickener

Co-Extraction of Aluminum and Silicon and Kinetics Analysis in Carbochlorination Process of Low-Grade Bauxite.

Addressing the issue that the Bayer process is not suitable for low-grade bauxite, carbochlorination was proposed to recover aluminum and silicon from low-grade bauxite. This study focused on the behavior of aluminum and silicon during the carbochlorination process of low-grade bauxite. The impact of various process parameters on the chlorination efficiency was investigated, and the chlorination mechanism and kinetics of aluminum and silicon chlorination in bauxite were analyzed and discussed. Under optimal experimental conditions, the chlorination efficiency of Al2O3 and SiO2 reached 94.93% and 86.32%, respectively. The carbochlorination of aluminum and silicon in bauxite adhered to a shrinking, unreacted core model governed by gas diffusion within the product layer. This process can be bifurcated into two stages. Additionally, calculations were conducted to determine the apparent activation energy and reaction order of the chlorination processes involving Al2O3 and SiO2. Examining the chlorination mechanism revealed that the bauxite carbochlorination encompasses transformations among various minerals. Notably, the aluminum component prefers to participate in the carbothermal chlorination reaction over silicon.

A STATE OF ART AND PROSPECTS OF RED MUD MANAGEMENT

The basic data on the global volumes and composition of red mud, which is a highly alkaline waste of the aluminum industry, namely the Bayer process – technology for the extraction and purification of alumina (aluminum oxide) from bauxite are presented. The analysis of the current state of red mud management allows to distinguish the following main directions: physical-mechanical, physical-chemical, biological and combined methods of handling it, which are used in agriculture (chemical land reclamation (increasing soil pH), use as fertilizers); building materials industry (cement, construction mortar, expanded clay, fireclay, bricks, building blocks, ceramic tiles, concrete alkali-acid-resistant products, refractories); road construction (soil strengthening for the lower layers of the road surface, asphalt); production of other materials (sorbents, catalysts, flocculants, pigments, caustic soda, filler for polymer composites); ferrous and non-ferrous metallurgy. Currently, the most common methods of red mud utilization are its direct use, use in the construction materials industry, as well as pyrometallurgical technologies, as a result of which iron or its alloys are obtained, as well as slag, from which alumina, titanium, rare earth metals can be extracted or which is processed into various building materials. The most expedient method of red mud disposal is either direct use of red mud with minimal changes in its properties, or complex processing with maximum yield of target components and minimization of new waste generation. At the same time, one of the promising ways of red mud management can be its biological processing with the help of plants and microbes, which will help reduce the dangerous man-made load from red mud in the territory adjacent to bauxite processing plants. Bibl. 113, Fig. 2.

Study on preparation and properties of supported compound desulfurizer for Bayer dissolution

In view of the serious harm caused by sulfur ion to alumina production and the high cost of desulfurization in Bayer dissolution process of high sulfur bauxite leaching at high temperature and high pressure, the supported compound desulfurizer was prepared by melt infiltration method to realize simultaneous desulfurization in Bayer dissolution process. In this paper, Zn(NO3)2·6H2O and Cu(NO3)2·3H2O as the main components, kaolin, sepiolite, activated alumina as the active carrier, the supported compound desulfurizer was prepared. The active carrier was optimized and the optimum preparation parameters were determined by means of DSC, IR, TG, SEM and XRD. The results show that kaolin is more suitable as the active carrier of compound desulfurizer. The best melting temperature of the precursor is 100 °C, the best calcination temperature is 400 °C, and the best calcination time is 2 h. The supported compound desulfurizer mainly consists of ZnO, CuO, AlOOH, SiO2 and Mullite. The results provide a basis for the active preparation of the supported compound desulfurizer.

Influence of red mud as a catalyst in the thermocatalytic reforming process

AbstractThis work studies red mud, a residue from the processing of bauxite, as a support catalyst in the thermocatalytic reforming (TCR) process, using wood, digestate, and straw as case studies. Thermocatalytic reforming is a thermochemical process for the conversion of biomass into biofuels, combining intermediate pyrolysis and catalytic reforming and resulting in high‐quality biofuels. The quantity and quality of the catalyst in the postreformer is vital as it influences the reactions taking place in it. Normally, nonreactive components of the char produced in the process act as the catalyst in the postreformer but adding a support catalyst may improve the products. In this work, red mud is introduced in the process by mixing it with the feedstock in a ratio of 1:3. The results, in comparison with normal TCR experiments on the same feedstock materials, show that the introduction of red mud into the process generally reduces the biochar yield and generally increases the biogas and product water yields, and the bio‐oil yield remains constant. Its introduction also increases the hydrogen fraction of the gas and tends to reduce the nitrogen and sulfur content of the products, thus improving their quality. These observations are consistent across feedstock materials and postreformer temperatures. The results therefore suggest that red mud is a good support catalyst for increasing the gas yield, increasing the hydrogen fraction of the gas, and improving the quality of the products from the TCR process.

Study of the corrosion resistance of high chromium white cast iron welds in the presence of NaOH (30% w/w)

– In the mining industry, specifically in bauxite processing, adverse working conditions demand high mechanical and chemical resistance. For such conditions, the choice of potentially resistant materials, such as high chromium white cast iron (HCr-CWI), is necessary. However, presently, there is no effective recovery of equipment made with HCr-CWI, primarily due to the machining difficulties encountered during the repair process. An alternative recovery method is being developed by the Laboratory of Metallic Materials Characterization at UFPA – LCAM, using electric arc welding with two filler metals: the ER307L stainless steel wire andsa high Mn value wire. Within this context, this study aims to investigate the corrosion resistance of the welded joint obtained with these two filler metals. The base metal (HCr-CWI) was analysed as a reference, alongside the metals generated by the welded joints, ER307L and high Mn. The samples underwent tests involving optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and electrochemical tests for corrosion potential, polarization, and impedance. It was observed that the samples exhibited a similar matrix-carbide structure but with different organization and volumes. However, the electrochemical behaviour in terms of corrosion potential, polarization, and impedance was similar, with very close resultant values: 50 V; 3.53 μA; 0.18 kOhms, respectively. This was supported by the corrosion rate of 0.4mmpy and explained by calculations of Cr and Ni volume, which showed inverse concentration magnitudes among the samples.

Sorption Extraction of Gallium from Alumina-Alkaline Solutions

AbstractThe possibility of sorption concentration of gallium from alumina-alkaline solutions resulting by leaching of recycled soda with sludge water during alumina production—which are middlings of alumina production—has been studied. During bauxite processing, soda is accumulated in recycled alkali solutions, extracted by evaporation and used in sintering. The sludge water is formed during storage of wastes pumped in the form of slurry to the settling tank and can be used in production as wash water. Sorption processes with application of ion exchange resins with high capacity and selectivity, presented in the world market in a large assortment, seem to be a promising direction of gallium concentration from alumina-alkaline solutions. On the basis of the analysis carried out, anion exchangers AN-31 and D-403 OH form were selected for sorption concentration of gallium from alumina-alkaline solutions. A comparative analysis of the sorption properties showed that the D-403 anion exchange resin exhibited better selectivity and a higher dynamic exchange capacity for gallium. The high capacity for gallium absorption with the D-403 anion exchanger resulted from its greater basicity, since the oxyhydryl groups at the β-, γ- and δ-positions in the resin matrix exert a greater negative inductive effect on the tertiary nitrogen atom, which has a lone electron pair, compared to the oxyhydryl and hydroxy groups in the β- and γ-positions relative to the secondary nitrogen atom of the anion exchange resin AN- 31. Due to the unshared electron pair of the nitrogen atom, an additional covalent effect arose, causing stronger chemical bonding between the gallium ions and the D-403 anion exchange matrix. Studies were carried out to determine the optimal conditions for the desorption of gallium with a 2 N sodium hydroxide solution. The gallium content in the alkaline eluates was suitable for electrolytic production of metallic gallium.

The mineralogy and geochemistry of the Pirashkaft bauxite, Zagros belt, Iran: New inferences on the paleo-climate at the time of formation and on the nature of the parent rock

The Pirashkaft karst type bauxite is located in north of the Paskuhak anticline, Pirashkaft region, in the Fars province (Iran). The deposit is composed of six bauxite horizons, occurring between upper Cretaceous Sarvak and Gurpy Formations, and formed in the late Turonian. Mineralogical composition includes boehmite, hematite, diaspore, kaolinite, goethite, anatase and minor minerals like, gibbsite, spinel, rutile, and kaolinite. The major oxides in the bauxite horizons mainly comprise Al2O3 (46.93–61.34 wt%), SiO2 (5.78–14.60 wt%), Fe2O3 (11.22–28.00 wt%), and TiO2 (1.66–3.03 wt%). The bauxite has a pisolitic–oolitic texture. Pisoids are mainly composed of large Al-bearing hematite cores, surrounded by layers of gibbsite or boehmite. This structure suggests that bauxite formed under a humid climatic regime, punctuated by periodic arid periods. In the Pirashkaft deposit, LREEs vary between 136.49 ppm and 928.56 ppm, whilst HREEs range from 16.48 ppm to 59.5 ppm. Positive anomalies of Ce (Ce/Ce* between 1.08 and 2.36) indicate dominant oxidizing conditions during the bauxitization process. The Eu/Eu* anomalies of the bauxite samples vary between 0.44 and 0.92, this suggesting that parent material likely derived from two geochemically distinct source rocks. Stratigraphical, mineralogical, and geochemical evidences, such as the REE distribution between the bauxitic horizons and the Sarvak marly limestone, suggest that the underlying marly carbonates were one of the sources of the Pirashkaft bauxite.

REE and trace element mobility during the transformation of basalt to laterite and bauxite, Payas Province, Türkiye

The bauxites of the Payas area in the eastern Mediterranean region of Turkey occur as a stratigraphically continuous layer between Early and Late Cretaceous shallow marine carbonates. The laterites represent an in situ formation and mark a key stratigraphic layer in the region. Bauxite pockets are also present in the laterites, formed from the reworking of the laterites and accumulated in depressions in the karst terrain. Therefore, bauxite occurrences are found locally in this stratigraphic layer. The parental rock was a Ti-rich basalt that is compositionally similar to Hawaiian basalts, as indicated by petrographic features and distinctive trace element composition (Zr/TiO2 and Nb/Y). The behavior of elements during the lateritization and bauxitization processes was interpreted using the composition of the Hawaiian basalts with the iron laterite and Ti-rich bauxites of the Payas Region. During lateritization, Fe, Al, Ti, Cr, Nb, and Ta, were largely immobilie while REE and other trace elements, except for Rb, Ni, Co, and Pb were significantly removed. Approximately 75 % of the REE were removed at the end of the bauxitization and/or transportation of the lateritic soil into the karstic depressions. REE were not equally mobile with La to Ce and Lu to Yb having a relatively lower mobility than highly mobile middle REE. During the transformation of laterite to bauxite, low mobility elements such as Ti, Nb, Th, Cr, Hf, and Sn were enriched in the bauxite phase. In comparison to other elements, Rb, As, Pb, Mo, and Ni were strongly removed from the lateritic material during the bauxitization processes. The transfer of MREE during lateritization and bauxitization would have resulted in the enrichment of both light and heavy REE (concave pattern) in contemporaneous seawater. In other words, silicate weathering periods on land should be marked by a concave REE pattern with positive Eu anomaly in marine sediments throughout the geological period.

Mobility of Major and Trace Elements during the Bauxitization Processes in Ngaoundal Area (Adamawa Cameroon): Implication on Mining Perspectives

Mobility of Major and Trace Elements during the Bauxitization Processes in Ngaoundal Area (Adamawa Cameroon): Implication on Mining Perspectives

Red mud application as filler in asphalt mixtures production

Red mud is the solid waste from bauxite processing during aluminium production. Its inadequate disposal causes social, economic and environmental prejudices. The industrial solid waste insertion evaluation in the production chain is beneficial and necessary. This work aims to evaluate the mechanical performance of asphalt mixtures produced with red mud as filling material. Asphalt mixtures with 5% and 7% red mud were produced, and permanent deformation and moisture-induced damage tests were carried out. A mixture without red mud addition (control) was produced for comparison. The results showed that the mixtures with red mud presented permanent deformation resistance greater than the control one, with more than 40% reduction in rutting deformation. The moisture damage did not significantly affect the mixtures tested. The red mud application as a filler in asphalt mixtures is viable and can be an alternative to reduce the damage such a waste can cause to the environment.

Process Flow Charts and Recommendations for Processing of Bauxite with Increased Contents of Iron and Fine Particles of Valuable Components

Process Flow Charts and Recommendations for Processing of Bauxite with Increased Contents of Iron and Fine Particles of Valuable Components

Alumina production: Historical development, issues, and solutions. Part 1

This study focuses on documenting the historical stages of aluminium and alumina production prior to the transition to a modern industry structure, involving the Hall-Héroult electrometallurgical process, and their technical significance for the contemporary metallurgical complex. It highlights the significance of these stages in the development of scientific knowledge related to alumina, aluminium, and their production technology when using chemical methods for obtaining metallic aluminium. The analysis includes aspects, such as classification, technical evaluation of the processes, and the raw material base. It is shown that the formation of scientific knowledge regarding alumina and aluminium is mainly associated with the practical need for using alum and, to some extent, clay minerals. Since the commencement of deliberate research into methods for aluminium production in its elemental state and virtually until the 1890s, aluminium was primarily produced using the metallothermal methods pioneered by Henri St. Clair Deville and his colleagues due to the high thermodynamic stability of aluminium compounds and the absence of affordable energy sources. It was found that from 1854 to 1890, the production of aluminium by chemical method was associated with the use of sodium aluminium chloride (NaCl·AlCl3), natural cryolite, or synthesised fluoride salts. Available technical reagents (aluminium sulphate, ammonia alum, and aluminium hydroxide), along with natural raw materials (cryolite, bauxite, and clay), were used as source materials in this period. The extraction and processing of bauxite were primarily associated with the production of alum and aluminium sulphate consumed by light industry. Although the demand for pure aluminium oxide was limited during the metallothermic production of aluminium, the driving force behind the advancement of modern technologies for alumina production was the demand for chemical products. This demand led to the development of technology for processing bauxite, which forms the foundation of the metallurgical complex in aluminium production using the Hall-Héroult electrometallurgical method.

Research of the production of iron ore sinter from bauxite processing waste

This article presents the results of a study of the agglomeration of waste alumina ferrous sands and the use of sinter as a substitute for metal charge in steelmaking. At this time, in the process of processing bauxite, JSC "Aluminium of Kazakhstan" produces a large number of fines, which is of great interest to ferrous metallurgy. Wastes from alumina production include a variety of waste sludge, including red, gray sludge, and ferrous sands. According to the chemical composition, ferrous sands can be attributed to iron ore material with a high content of alumina. Most of these problems are eliminated by preliminary agglomeration of fines. In this work, agglomeration studies made it possible to establish the optimal parameters for sintering ferrous sands. When using 10% fuel, the best sintering performance is achieved. The optimal parameters for sintering ferrous sands mixed with other metallurgical wastes are such as productivity - 0.92 t / m2 h, mechanical strength - 80.0%, sintering speed - 19.3 mm/min, yield - 82.0%, the maximum temperature in the layer is 1340 °С. The results of laboratory melt carried out in an induction melting furnace indicate the possibility of using a sinter as a substitute for metal charge in iron and steel smelting. The conducted melting confirms the fundamental possibility of using a sinter, made from waste products of alumina production of ferrous sands, is a man-made charge material that is suitable for use as a 5% additive to the metal charge in the smelting of iron-carbon alloys similar in composition to cast irons.

Assessing the Life Cycle Performance in the Metallurgical Sector: A Case Study in Italy

This study compared two types of sheets: one made of steel and one made of aluminum, using Life Cycle Assessment (LCA), Life Cycle Costing (LCC), and Social Life Cycle Assessment (S-LCA). The LCA results show that the aluminum sheet had a greater environmental impact than the steel one in 11 out of 18 impact categories, such as a 5% higher Global Warming Potential, 3% higher Stratospheric Ozone Depletion, and 72% higher Ionizing Radiation. The main contributing factors were energy-intensive processes and bauxite processing associated with aluminum production. The LCC results also supported the findings of the LCA, demonstrating that the raw material, electricity, and labor costs for aluminum sheets were higher compared to steel ones, with the aluminum sheets costing €163 and the steel ones costing €19. However, the S-LCA results presented a contrasting perspective. They indicated that steel sheets exhibited poorer social performance compared to aluminum ones, particularly regarding child labor and discrimination, primarily due to the harsh working conditions in Ghana, the primary source of iron used in steel production. Overall, this study highlights the environmental superiority of steel screens over aluminum ones but also underscores the social challenges associated with steel production.

Utilization of Extraction Procedures for Evaluating Environmental Risk from Waste Materials.

Several procedures for extracting content from different waste materials types were investigated, with the aim of evaluating their environmental impact. The waste materials consisted of wastes from bauxite ore processing by means of the Bayer process (red mud, Ajka, Hungary), bauxite ore using the sintering process followed by the Bayer process (brown-red mud, Žiar nad Hronom, Banská Bystrica region, Slovakia) and sulphide ores (metal-rich post-flotation tailing, Lintich, Slovakia). The extraction procedures were carried out with the aim of isolating "mobilizable" fractions using 0.05 M ethylenediaminetetraacetic acid (EDTA) and 0.43 M acetic acid (AA) (representing environmental risk during changes in normal environmental conditions) and "maximum potentially mobilizable" fractions using 2 M HNO3 (representing the total environmental risk). The content of chosen toxic heavy metals (THMs) (Cd, Cr, Cu, Pb, Ni, Zn) and Fe, Mn as metals creating Fe/Mn oxides in the extracts and solutions after microwave digestion was determined using high-resolution continuum source flame atomic absorption spectrometry (HR CS FAAS). On the basis of the results obtained in this study, it is possible to state that different origin of waste materials is reflected in different mobility of toxic heavy metals into the surrounding environment. From the point of view of toxic heavy metals mobility, disposal site of wastes after bauxite processing are much less of a threat to the environment than disposal site of flotation sludge after processing sulphide ores. The single extraction of 0.43 M AA is more effective than the extraction of 0.05 M EDTA for the purposes of determining the content of metals in the mobilizable fraction of tailing waste materials. The mobility of the studied toxic heavy metals in the Lintich tailing decreases in the direction from the lagoon to the dam, which may indicate the fact that the dam serves to a certain extent to inhibit the mobility of metals into the surrounding ecosystem.

Flotation Decarbonization and Desulfurization of a High-Sulfur Bauxite in China

A high sulfur content is one of the challenges in the processing of refractory bauxites in China. The high carbon content of bauxite makes it more difficult to deal with. Desulfurization and decarbonization are the critical issues in the efficient exploitation of high-sulfur bauxite resources. An experimental study on the removal of sulfur and carbon in high-sulfur bauxite is proposed. The sulfur and carbon phases in high-sulfur bauxite were studied via X-ray diffraction and chemistry quantitative analyses. The results show that the sulfur phases in the high-sulfur bauxite mainly exist in the form of sulfide sulfur (pyrite), and the carbon phases in the sample mainly exist in the form of elementary substance carbon. The morphological features of pyrite in the high-sulfur bauxite were analyzed using a microscopic analysis and a scanning electron microscope (SEM). The pyrite exists in minerals in the forms of euhedral, semi-euhedral and other crystalline structures, with a particle size varying from several hundred microns to only a few microns. The raw ore, with a sulfur content of 4.78%, a sulfide sulfur content of 4.20%, a carbon content of 3.10% and an elementary substance carbon content of 2.46% goes through the “one roughing, one cleaning, two scavenging” process after a pre-decarburization, obtaining the total desulfurization recovery of 96.20% with a desulfurization tailing sulfur content of 0.38%, a carbon content of 0.27% and an alumina content of 71.85%, respectively. This work provides technical support for the efficient utilization of high-sulfur and high-carbon bauxite.