Bauxite Research Papers - Academia.edu (original) (raw)

Infrared emission spectroscopy has been used to study the dehydroxylation behavior over the temperature range from 200 to 750 degrees Celsius of three major Al-minerals in bauxite: gibbsite (synthetic and natural), boehmite (synthetic and natural) and diaspore. A good agreement is found with the thermal analysis and differential thermal analysis curves of these minerals. Loss in intensity of especially the hydroxyl-stretching modes of gibbsite, boehmite and diaspore as function of temperature correspond well with the observed changes in the TGA/DTA patterns. The DTA pattern of gibbsite clearly indicates the formation of boehmite as an intermediate shown by a endotherm around 500 degrees Celsius. Dehydroxylation of gibbsite is followed by a loss of intensity of the 3620 and 3351 cm-1 OH-stretching bands and the corresponding deformation band around 1024 cm-1. Dehydroxylation starts around 220 degrees Celsius and is complete around 350 degrees Celsius. Similar observations were made for boehmite and diaspore. For boehmite dehydroxylation was observed to commence around 250 degrees Celsius and could be followed by especially the loss in intensity of the bands around 3319 and 3129 cm-1. The DTA pattern of diaspore is more complex with overlapping endotherms around 622 and 650 degrees Celsius. The dehydroxylation can be followed by the decrease in intensity of the OH-stretching bands around 3667, 3215 and 2972 cm-1. Above 550 degrees Celsius only a single band is observed that disappears after heating above 600 degrees Celsius corresponding to the two endotherms around 622 and 650 degrees Celsius in the DTA

- by
- •
- Engineering, Materials Science, Decomposition, Minerals

Post-mining land reclamation aims to improve the condition of land that has been damaged by mining activities so as to restore the level of fertility and productivity of the land. The success rate of this reclamation activity can be seen from the quality of growth of the types of plants that planted on the land. The higher the success rate of reclamation activities, the greater the potential for carbon sequestration from the land. This paper reviews the results of bauxite mine reclamation research, with the aim of predicting the carbon potential stored in each post-mining revegetation stand structure

- by IAEME Publication
- •
- Bauxite, Post-Mining Land Use, Iaeme, Ijaret, Reclamation Land
- by Ken Evans
- •
- Environmental Sustainability, Alumina, Bauxite, Red Mud

Abompe is the current bauxite beadmaking site in Ghana and the hills of the Kwahu Plateau above the village are pocked with hundreds, perhaps thousands, of pits dug in search of the raw material. To determine the age of the beadmaking industry in the region, people in Abompe and other villages were interviewed and related stories that suggest the first beadmakers were following the example of people in or around Bepong, a village on the plateau above Abompe. Three areas of bauxite pits on the Kwahu Plateau were investigated to see if there was physical evidence of ancient mining; those currently used by Abompe people and those previously dug by Bepong and Adasowase people. Four boulders with polished upper surfaces were found in the Abompe mining area and are believed to represent large-scale bead polishing. Caves where miners occasionally stay overnight were explored and evidence of bead production in the form of chipping waste was found. Pit counts by transect at Odumparara Bepo, the Abompe mining area, suggest the presence of possibly as many as 4,700 pits. These appear to have been created in the past 100 years.

- by Karlis Karklins
- •
- Beads, Bauxite, Stone beads, African Trade Beads

Near-infrared (IR) spectroscopy has been used to distinguish between alumina oxo and hydroxy phases. Two near-IR spectral regions are identified for this function: (1) the high-frequency region between 6400 and 7400 cm−1, attributed to the first overtone of the hydroxyl stretching mode, and (2) the 4000–4800 cm−1 region attributed to the combination of the stretching and deformation modes of the AlOH units. Near-IR spectroscopy allows the study and differentiation of the hydroxy and oxo(hydroxy) alumina phases, since each phase has its own characteristic spectrum. The spectrum of bayerite resembles that of gibbsite, whereas the spectrum of boehmite is similar to that of diaspore. Bayerite has four characteristic near-IR bands at 7218, 7128, 6996, and 6895 cm−1. Gibbsite shows five major bands at 7151, 7052, 6958, 6898, and 6845 cm−1. Boehmite displays three near-IR bands at 7152, 7065, and 6960 cm−1. Diaspore shows a prominent band at around 7176 cm−1. The use of near-IR reflectance spectroscopy to study alumina surfaces has a wide application, particularly with thin films and surfaces. The technique is rapid and accurate. Near-IR, because of its sensitivity, can be used in reflectance mode for the on-line processing of bauxitic minerals.

- by J. THEO KLOPROGGE
- •
- Optics, Analytical Chemistry, Minerals, Vibrational Spectroscopy

Red mud is highly alkaline (pH 13), saline and can contain elevated concentrations of several potentially toxic elements (e.g. Al, As, Mo and V). Release of up to 1 million m3 of bauxite residue (red mud) suspension from the Ajka repository, western Hungary, caused large scale contamination of downstream rivers and floodplains. There is now concern about the potential leaching of toxic metal(loid)s from the red mud as some have enhanced solubility at high pH. This study investigated the impact of red mud addition to three different Hungarian soils with respect to trace element solubility and soil geochemistry. The effectiveness of gypsum amendment for the rehabilitation of red mud-contaminated soils was also examined. Red mud addition to soils caused a pH increase, proportional to red mud addition, of up to 4 pH units (e.g. pH 7  11). Increasing red mud addition also led to significant increases in salinity, dissolved organic carbon (DOC) and aqueous trace element concentrations. However, the response was highly soil specific and one of the soils tested buffered pH to around pH 8.5 even with the highest red mud loading tested (33% w/w); experiments using this soil also had much lower aqueous Al, As, and V concentrations. Gypsum addition to soil / red mud mixtures, even at relatively low concentrations (1% w/w) was sufficient to buffer experimental pH to 7.5-8.5. This effect was attributed to the reaction of Ca2+ supplied by the gypsum with OH- and carbonate from the red mud to precipitate calcite. The lowered pH enhanced trace element sorption and largely inhibited the release of Al, As and V. Mo concentrations, however, were largely unaffected by gypsum induced pH buffering due to the greater solubility of Mo (as molybdate) at circumneutral pH. Gypsum addition also leads to significantly higher porewater salinities and column experiments demonstrated that this increase in total dissolved solids persisted even after 25 pore volume replacements. Gypsum addition could therefore provide a cheaper alternative to recovery (dig and dump) for treatment of red mud affected soils. The observed inhibition of trace metal release within red mud affected soils was relatively insensitive to either the percentage of red mud or gypsum present, making the treatment easy to apply. However, there is risk that over-application of gypsum could lead to detrimental long term increases in soil salinity.

- by Dr. Arup Kumar Mandal and +1
- •
- Environmental Engineering, Plasma Physics, Waste recycling, Plasma

For decades land, forests, water and other natural resources are not free from public debates and academic discourses due to several reasons. In India this debate has taken different forms in different places based on the specific character of the locality. There has been, particularly in the neo-liberalisation era, a noticeable shift both in the tenor and the content of the debate. While looking at the history of Adivasi land alienation, there has been several interconnections between the multiple characteristics of post independent neo-capitalistic economics and the pre-independent colonial imperialism – both only aimed at taking away the land from the community with the consolidation of power centres or 'eminent domain,' at the cost of the community itself. This ethnographic paper gradually discusses the sociology of land debate from pre-colonial period to present. It builds the argument that why land reforms failed in India at large and specifically in the context of Adivasi land rights. To understand the issue of Adivasi land alienation, the case of Mainpat hills in Surguja district of Chhattisgarh is taken to study in detail, where Vedanta Resources Plc is currently engaged in mining bauxite at the cost of the communities. In this paper, I discuss how the State initiated public hearing is applied as a strategic tool to construct 'consent' by flouting laws and dismissing people's dissent. The last two sections of the paper capture the larger impact of land acquisition, land alienation and the socio-ethnic polity of Adivasi depeasantisation. In these Adivasi hotbeds, people have lost their faith in State and it's democratic systems, due to excessive focus on alien patterns of development. Here land alienation and depeasantisation are interconnected aspects which in itself is a gross violation of human rights of Adivasi people not only in Mainpat but at large across the length and breadth of the state. It has changed the socio-cultural, economic and political dynamics of the community itself.

- by JOURNAL OF PEOPLE'S STUDIES
- •
- Sociology, Rehabilitation, Mining, Alienation

The Bolkardağı bauxite province is located in the Tauride Belt of southern Turkey. The region hosts many
lateritic- and karstic-type bauxite deposits within the Bolkardağı Unit (BU), the Namrun Tectonic Unit
(NTU) and the Aladağ Unit (AU). The lateritic-type deposits occur on the Upper Triassic sericite-chlorite
schist of the BU, on the Lower Triassic slates, and on the Upper Triassic phyllites of the NTU. The gradual
transition from the protolith to saprolite and, eventually, to bauxite is observed in the lateritic-type deposits
in the field. The karstic-type deposits occur in the carbonates of the BU, the NTU and the AU and were
accumulated by clastic transportation from the lateritic material. The deposits within the BU and the NTU
are metamorphosed and consist mainly of diasporite, haematite, pyrophyllite, chlorite, chamosite, and
anatase; the deposits within the AU are not metamorphosed and consist mainly of boehmite and kaolinite,
haematite, goethite, chlorite and anatase.
The mean compositions of the deposits are 53% Al2O3, 19% Fe2O3, 12% SiO2, and 3% TiO2. The lateritic-type
deposits have higher silica content (e.g., Camızalanı Bauxite Zone; mean 21% SiO2) than the karstic-type,
indicating higher mobilisation of silica in the karstic-type deposits because of alkaline pH conditions. The
ΣREE content varies between 273 ppm and 1693 ppm, and the ΣREE content increases with an increase in
the content of La, Ce and Nd. The mass change calculations according to the Ti index element show that
Rb, K, Ba, Ce, Si, Y, Sr, P, Ca, Mg and U were mobile during the bauxitisation processes. The Zr, Ta, Nb and
Hf elements are relatively immobile in the first stage of bauxitisation in the saprolite zone but were slightly
mobile at a later stage of bauxitisation. Fe, V, Pb, Ni, and Cr are the elements that were gained in the bauxite
zone.
From field evidence and geochemical data, it is concluded that the first stages of bauxitisation in the
Bolkardağı Bauxite Province started during the post-Upper Triassic by the formation of a kaolinite-rich
bauxitic soil via chemical weathering of the Lower Triassic pelitic rocks and Upper Triassic shales under acidic
conditions. The kaolinite-rich bauxitic soil was transformed to boehmite during low water activity in hot and
humid climatic conditions. The Aalenian–Bajocian transgression submerged the bauxite, causing burial
diagenesis. At the time of the closure of the Tethyan Ocean during the Upper Cretaceous, ophiolite obductions
over the continent gave rise to imbrication and further burial of the bauxite-bearing units. During this time, the
bauxite deposits and their host units underwent a very low grade metamorphism in relation to their burial
depths and thrusting. Thus, kaolinite was transformed to dickite, nacrite and pyrophyllite at 240–260 °C in
the saprolite zone, and boehmitic bauxite was transformed to diasporite in the deeply buried BU and the
NTU. The boehmite was preserved as a primary bauxite mineral in the deposit which avoided burial metamorphism
in the uppermost tectonic unit, the AU.

- by Wenchao Yu
- •
- Earth Sciences, Geology, Bauxite
- by Chemistry International
- •
- Solvent Extraction, Bauxite, Aluminum Hydroxide

Karst-bauxite deposits form as a result of the accumulation of residual clay minerals in depressions on a karst limestone surface, and their subsequent lateritic weathering. Rare earth elements (REE) become concentrated in the bauxite deposits due to crystallisation of authigenic REE-bearing minerals, accumulation of residual phases and the adsorption of ions on clays and other mineral surfaces. REE are concentrated in the red mud waste generated by alumina production from bauxite through the Bayer process. Red muds thus contain on average 900 ppm REE compared with typical values of <100 ppm to ~500 ppm REE in the bauxites. Extraction of REE from red mud has been shown to be feasible although it is challenging due to the heterogeneous spatial distribution of REE in the bauxites and the need for development of appropriate processing methods. With annual European extraction of bauxite estimated to be approximately 3.5 million tonnes per annum, resulting in approximately 1.4 million tonnes of red mud from the production of alumina, understanding the REE resource potential of bauxites is integral to the assessment of European REE resources.

- by Eimear Deady and +1
- •
- Rare Earth Elements, Ore deposits, Bauxite, Red Mud

The Parnassus-Giona karst bauxite deposits contain significant concentrations of rare earth elements (400-500 ppm). Preliminary results from a pilot leaching study show that between 19 and 47% of rare earth elements in the bauxite are... more

- by Evangelos Mouchos and +1
- •
- Leaching, Rare Earth Elements, Bauxite
- by Ali Rıza Söğüt
- •
- Geochemistry, Turkey, Petrography, Laterite

This research investigates the possibility of produce refractory mortar which can withstand at high temperatures in the industrial furnaces for different industries. The raw materials used represented by (Grog Bauxite, Attapulgite, CaO, White Cement and Gum Arabic). In this study, we used Gum Arabic liquid for the first time instead of solution of sodium silicate as adhesive material to improve cold bonding strength. Many types of mixtures are prepared with different ratios of the materials. The mortar mixtures were prepared by adding water to dry components, some mixtures prepared by adding gum Arabic liquid with weight ratio 40% of dry content. The samples of mortar were sintered at (1350, 1400, 1450) C°. Experimental study was carried out to evaluate physical and mechanical properties of mortar based on (sieve analysis, refractoriness, bonding strength, bulk density, and linear firing shrinkage). The results show that two types of refractory mortars that prepared by adding gum Arabic liquid have properties conform to the requirements of standard ASTM C64 with cold bonding strength more than 1.38MPa, the first type has accepted refractoriness at sintering temperature 1400 C°, the second one has accepted refractoriness at sintering temperature 1350C°.

- by IAEME Publication
- •
- Gum Arabic, Bauxite, CaO, Attapulgite

During the Early Cretaceous, successive tectonic phases and several sea level fallsbrought up the exondation of the main part of Western Europe and the development of thick "lateritic" weathering. This long period of continental evolution ended with the UpperCretaceous transgressions. During this period, the exposed lands displayed a mosaic of diverse morphologies and weathered landscapes.The bauxitesare the most spectacular paleoweathering features, known for long insouthern France. Recently, new residual outcrops have been identified, trapped in the karsticdepressions of the Grands Causses. Other bauxitic formations, containing gibbsite, have alsobeen recognised coming with the Clay-with-Jurassic-cherts in the southeastern border of theParis Basin. These bauxitic formations overlay Jurassic limestone and are buried beneathUpper Cretaceous marine deposits. The recognition of bauxites up North to the southern ParisBasin significantly widens the extension of the Lower Cretaceous bauxitic paleolandscapes.On the Hercynian basementsoccur thick kaolinitic weathering mantles, which havebeen classically ascribed to the Tertiary. The first datings of thesein situpaleosoils, by meanof paleomagnetism and/or radiogenic isotopes, record especially Early Cretaceous ages. Thisis the case for the "Siderolithic" formations on the edges of the French Massif Central, butalso for the kaolinitic profiles on the Belgian Ardenne. In the Flanders, the Brabant basementis deeply kaolinised beneath the Upper Cretaceous cover. These paleosoils show polygeneticevolutions. The relief of these basement paleolandscapes may have been significant. Therewhere probably high scarps (often of tectonic origin) reaching 100 m in elevation or beyond,as well as wide surfaces with inselbergs, as in the present day landscapes of tropical Africaand South America.On the Jurassic limestone platformsare found diverse kaolinitic and ferruginousweathering products. Around the Paris Basin they show various facies, going from kaoliniticsaprolites to ferricretes. Due to the lack of sedimentary cover, the age of these ferruginous andkaolinitic weathering products has been debated for long, most often allocated to theSiderolithicsensu lato(Eocene-Oligocene). The recent datings, using paleomagnetism, havealso allowed to date them (Borne de Fer in eastern Paris Basin) back to the Early Cretaceous(130 ± 10 Ma). These wide limestone plateaus show karstified paleolandforms, such as vastclosed depressions with flat bottom broken by conic buttes, but also deep sinkholes in thehigher areas of the plateaus and piedmonts. The depth of the karst hollows may be indicativeof the range of relative paleoelevations. The dissolution features show few contemporaneous karst filling, thus implying that the karstland had not a thick weathering cover or that thiscover had been stripped off before or by the Late Cretaceous transgression. Nevertheless,some areas, especially above chert-bearing Jurassic limestone or marl, show weatheringproducts trapped in the karst features or as a thick weathering mantle.In the Paris Basin, the Wealden gutter looked like a wide floodplain in which fluvio-deltaic sands and clays deposited and on which paleosoils developed during time of non-deposition. The edges of the gutter were shaped as piedmonts linked up with the upstreambasement areas. The rivers flowing down to the plain deposited lobes of coarse fluvial sandsand conglomerates. The intensity of the weathering, the thickness of the profiles and theirmaturation are directly dependent on the duration of the emersion and the topographiclocation relative to the gutter. Near the axis of the gutter, where emersion was of limitedduration, the paleoweathering features are restricted to rubefaction and argillization of theLower Cretaceous marine formations. On the other hand, on the borders of the basin and onthe Hercynian basement, where emersion was of longer duration, the weathering profiles arethicker and more intensively weathered.The inventoryof the Lower Cretaceous paleoweathering features shows the complexityof the continental history of this period. Moreover, the preserved weathering products are onlya part of this long lasting period, all the aspects relative to erosion phases are still moredifficult to prove and to quantify. In this domain, the Apatite Fission TracksThermochronology (AFTT) can be helpfull to estimate the order of magnitude of thedenudation. Residual testimonies and subsequent transgressions may allow to estimaterelative elevations, but in return, we presently have not any reliable tool to estimate theabsolute paleoelevations. In the work presented here, the inventory allowed to draw acontinental paleogeographic map showing the nature of the weathering mantles and thepaleolandscape features, just as paleoenvironments and paleobathymetry presently appear onthe marine paleogeographic maps. For the future, the challenge is to make progress in datingthe paleoweathering profiles and especially in the resolution of these datings, in order tocorrelate precisely the continental records with the different events which trigger them(eustatism, climate, regional and global geodynamics). The final goal will be to build up astratigraphic scale of the "continental geodynamic and climatic events" facing the "sequentialstratigraphy" in the marine realm.

- by Medard Thiry and +1
- •
- Geology, Geomorphology, Soil Science, Climate Change

The Lower Carboniferous Jiujialu Formation bauxite deposits at Zunyi, northern Guizhou are distinguished by their great thickness (to 110 m) and cyclic alternation of bauxite ore and bauxitic claystone layers. These features are typical of the Kazakhstan subtype of karst bauxite deposits, although the genesis of this type of deposit is poorly understood. Here, we undertook a petrological, mineralogical, and geochemical study of the Zunyi deposit in drillcore ZK5600 to gain insights into its formation history. The Zunyi proﬁle contains seven bauxite cycles, as recorded by petrological, mineralogical and geochemical features, indicating a multistage formation history. Each cycle is composed of a lower bauxitic claystone layer and an upper bauxite ore layer. The bauxite ore is characterized by high Al 2 O 3 , high Al-mineral (diaspore), and low SiO 2 content. Positive Ce anomalies, high CIA values (> 90), and strong depletion of major elements indicate that the bauxite ore formed through intense chemical weathering and leaching in a well-drained soil environment. The bauxitic claystone is characterized by
relatively lower Al 2 O 3 and higher SiO 2 and clay mineral (mostly illite) content. This lithology exhibits both negative and positive Ce anomalies, moderate CIA values (70–80), and enrichment of some elements (e.g., Fe, K), indicating formation through moderate chemical weathering in a poorly drained soil environment. Secular variations in chemical weathering intensity and soil drainage conditions were linked to regional hydrologic changes. During the early Carboniferous, the Zunyi area was located in a karstiﬁed coastal upland setting, and its hydrologic system was aﬀected by glacio-eustatic ﬂuctuations. High groundwater table elevations during eustatic highstands led to formation of bauxitic claystone layers, whereas low groundwater table elevations during
eustatic lowstands led to formation of bauxite ore layers.

- by Wenchao Yu
- •
- Paleoclimate, Carboniferous, Bauxite

Abstract
The late Paleozoic Era was an interval of major tectonic and climatic changes,
including formation of the supercontinent Pangea and the ~60-Myr-long Late
Paleozoic Ice Age (LPIA). Although bauxite formation declined globally from the
Carboniferous to the Permian in conjunction with global cooling, it was an interval of
widespread bauxite formation in China. In South China, (1) the Jiujialu Formation
bauxite deposits in central and northern Guizhou (Zunyi area) are of early-middle
Visean age; (2) the Dazhuyaun Formation bauxite deposits in northern Guizhou
(Wuchuan–Zheng’an–Daozheng area) to southern Chongqing (Nanchuan area) and
southeastern Guizhou (Fuquan–Kaili area) are of Late Pennsylvanian–Early Permian
age; and (3) the Heshan Formation bauxite deposits in western Guangxi to Yunnan are
of Middle–Late Permian age. In North China, the Benxi Formation bauxite deposits
are of Late Mississippian–Middle Pennsylvanian age. The contrasting trends in
bauxite metallogenesis between China and the rest of the world imply different
climatic patterns in the eastern Tethys (high annual humidity with seasonal dryness)
and Pangea (aridification). This hypothesis is further supported by differences in the
chemical index of alteration, or CIA (>80 in the eastern Tethys vs. ~50 in western
Pangea), and in paleotemperatures (mean annual temperature, or MAT = ~20 °C in the
eastern Tethys vs. ~4 °C in western Pangea) determined from Permo-Carboniferous
siliciclastic deposits. Permo-Carboniferous bauxite deposits in South China formed in
coastal plain and coastal karstic depression environments, in which the position of the
groundwater table was related to sea-level changes. During the late Paleozoic,
high-frequency eustatic fluctuations caused by waxing and waning of Gondwana
icesheets controlled sedimentation in these coastal depositional systems, leading to
cyclic accumulation of coal and bauxite deposits and cycles of vadose- and
phreatic-type bauxite formation. The results of the present study show that, during
interglacial stages, lateritization resulted from high pCO2, high sea-level and
groundwater-table elevations, low precipitation, and limited vegetation cover, whereas
during glacial stages, bauxitization of these ferralitic weathering products was
promoted by low pCO2, low sea-level and groundwater-table elevations, high precipitation, and more extensive vegetation cover. Thus, a unique combination of
geographic, climatic, and eustatic factors accounted for widespread formation of
bauxite in South China during the LPIA.

Bauxite is an ore that consists of aluminum hydroxide minerals and impurities which are mainly composed by silicates, iron oxides (goethite and hematite), titanium oxides, alumino silicates, among others. The studied bauxite ore is intended to the refractory industry, whose market specifications request for an iron content lesser than 2.5%. The objective of this study was to investigate the applicability of direct flotation route so as to concentrate bauxite ore from Barro Alto-GO. The sample was initially comminuted and characterized. After that, it were accomplished flotation experiments in order to investigate the influence of collector (Hidroxamate-Cytec) dosage, flotation pH (8.5, 9.5, 10.5) and milling time (6, 8 e 10 min) on the reduction of the iron content. It was observed that the increase of collector dosage conducted to the increase in metallurgic recovery of alumina (Al2O3), and consequent decrease in its grade besides a rise in the Fe2O3 content. With the same collector dosage (395 g/t), it was found that the pH which yielded the greater performance of concentration by flotation was 9.5. The study of the influence of milling time revealed that the major milling time (10 min) produced more efficient results of Al2O3 recovery, and content of both alumina and contaminants. The experiment which conducted to more appropriated results was those carried out with 395 g/t of collector, pH 9.5 and 10 min of milling. The result was a concentrated with 3.74% of Fe2O3, 60.00% of Al2O3 and metallurgic recovery of 40.87%.

- by Mauricio Bergerman
- •
- Mineral Processing, Bauxite, Bauxite Mining

- by IAEME Publication
- •
- Bauxite, Post-Mining Land Use, Reclamation Land, Store Carbon

Red mud is described as a major industrial waste produced by the Bayer process for the extraction of alumina from bauxite ores. The Red mud was collected from Bukit Goh and it physical, chemical and mineralogical composition were investigated in terms of it environmental effects. Because red mud has a lot of hazardous effect on man and his environment, it intrinsic properties are characterised by high alkaline, extremely saline, sodic and high heavy metals content. The pH, EC, Heavy Metals and Mineral contents were analysed using pH meter, EC meter, ICPOES and XRD respectively. The results show that, pH, EC and Heavy metals concentration of red mud decreased with increasing storage time and Fe, Cd, As and Pb concentration were determined. In general, the newly collected red mud retained more heavy metals than the old red muds. The mineralogical composition of Calcite, Gibbsite, Boehmite, Hematite, Siderite and Calcium aluminate decreased with increasing storage time with a large percentage of Calcite presence. Boehmite Mineral composition was completely removed from the 50days and 100days. It is fascinating to know that Goethite, Magnetite, Sodium titanate and Sodalites increased with increasing storage time.

Gandhamardan hill stands as a testimony to the first victory of the people's movement, in Odisha, against mining. But, with more and more mining companies are eying on the bauxite reserved in it, Gandhamardan's existence is threatened.... more

- by Basudev Mahapatra
- •
- Ecology, Mining, Aluminum, Protest Movements

The Taurides region of Turkey is host to a number of important bauxite, Al-rich laterite, and Mn deposits.
The most important bauxite deposits, Dog˘ankuzu and Mortas¸, are karst-related, unconformity-type deposits in
Upper Cretaceous limestone. The bottom contact of the bauxite ore is undulatory, and bauxite fills depressions
and sinkholes in the footwall limestone, whereas its top surface is concordant with the hanging-wall limestone.
The thickness of the bauxite varies from 1 to 40 m and consists of böhmite, hematite, pyrite, marcasite, anatase,
diaspore, gypsum, kaolinite, and smectite. The strata-bound, sulfide- and sulfate-bearing, low-grade lower part
of the bauxite ore bed contains pyrite pseudomorphs after hematite and is deep red in outcrop owing to supergene
oxidation. The lower part of the bauxite body contains local intercalations of calcareous conglomerate
that formed in fault-controlled depressions and sinkholes. Bauxite ore is overlain by fine-grained Fe sulfidebearing
and calcareous claystone and argillaceous limestone, which are in turn overlain by massive, compact
limestone of Santonian age. That 50-m-thick limestone is in turn overlain by well-bedded bioclastic limestone
of Campanian or Maastrichtian age, rich with rudist fossils. Fracture fillings in the bauxite orebody are up to 1
m thick and consist of bluish-gray-green pyrite and marcasite (20%) with böhmite, diaspore, and anatase. These
sulfide veins crosscut and offset the strata-bound sulfide zones. Sulfur for the sulfides was derived from the
bacterial reduction of seawater sulfate, and Fe was derived from alteration of oxides in the bauxite. Iron sulfides
do not occur within either the immediately underlying or overlying limestone.
The platform limestone and shale that host the bauxite deposits formed at a passive margin of the Tethys
Ocean. Extensive vegetation developed on land as the result of a humid climate, thereby creating thick and
acidic soils and enhancing the transport of large amounts of organic matter to the ocean. Alteration of the organic
matter provided CO2 that contributed to formation of a relatively 12C-rich marine footwall limestone.
Relative sea-level fall resulted from strike-slip faulting associated with closure of the ocean and local uplift of
the passive margin. That uplift resulted in karstification and bauxite formation in topographic lows, as represented
by the Dog˘ankuzu and Mortas¸ deposits. During stage 1 of bauxite formation, Al, Fe, Mn, and Ti were
mobilized from deeply weathered aluminosilicate parent rock under acidic conditions and accumulated as hydroxides
at the limestone surface owing to an increase in pH. During stage 2, Al, Fe, and Ti oxides and clays
from the incipient bauxite (bauxitic soil) were transported as detrital phases and accumulated in the fault-controlled
depressions and sinkholes. During stage 3, the bauxitic material was concentrated by repeated desilicification,
which resulted in the transport of Si and Mn to the ocean through a well-developed karst drainage system.
The transported Mn was deposited in offshore muds as Mn carbonates. The sulfides also formed in stage
3 during early diagenesis. Transgression into the foreland basin resulted from shortening of the ocean basin and
nappe emplacement during the latest Cretaceous. During that time bioclastic limestone was deposited on the
nappe ramp, which overlapped bauxite accumulation.

- by P A Azeez
- •
- Botany, Landscape Ecology, Soil Science, Conservation Biology

- by IAEME Publication
- •
- Gum Arabic, Bauxite, CaO, Attapulgite

Arundhati Roy highlights the relationship between the indian government and the mass-media, she shows a lack of political transparency as cause of part of the social and political situation. The journalist describes her travel with the tribal people Adivasis, also called “the biggest internal security challenge ever faced” by the governements. Against this distorted and altered definition of them, the author takes the reader with her through the discovery of the truth about the Operation “Green Hunt”, launched in 2009 against the Naxal-Maoist insurgency. The governmental offensive to keep the regions away from the Adivasis is, of course, exactly upon the territories richest in mineral resources, as the bauxite.
This book describes the adivasist resistance against that economic system which accelerates the resources depletion and brings devastation in those few and tiny parts of the world that are still free from the capitalistic and economical development, or depletion.

- by CRISTINA GARDENGHI
- •
- Political Ideology, Adivasi Studies, Maoism, Arundhati Roy
- by Emmanuel Igonor
- •
- Business, Entrepreneurship, Marketing, Economic Growth

Aluminium within bauxite residue represents one of the major losses in Bayer process. The proposed process development of recovering aluminium from bauxite residue involved pyro-, hydro- and iono-metallurgical routes. In this paper, iono-metallurgical route is used to investigate the identification of the appropriate aluminium salt that can be dissolved in pyrrolidinium ionic liquid (BMPTFSI, 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide). The characterisation of the resultant solution and electrowinnning of aluminium on copper cathode were also investigated. It was found that Al(OTf)3 salt was able to be dissolved relatively easily in the ionic liquid, creating a solution of 0.09 mol/L concentration. Following that, the solution density, viscosity and conductivity were measured and FTIR spectra of solution was characterised. The cyclic voltammetry in the Al(OTf)3 solution indicated a visible cathodic peak at -2.8V vs Ag/Ag+ in Acetonitrile. The solution was then s...

- by Dimitrios Panias
- •
- Materials Science, Bauxite, Aluminium

— Kaolin and bauxite were used as alumina and silica sources to synthesize zeolites hydrothermally. The source materials as well as the synthesized zeolites were characterized by X-ray diffraction (XRD) scanning electron microscopy (SEM), energy dispersive x-ray analysis (EDX) and Fourier transformed infrared spectroscopy (FTIR). XRD spectra of the bauxite showed Gibbsite phase whereas that of kaolin gave 32.4 % quartz and 67.6 %. The main phases of zeolites obtained after hydrothermal crystallizations were zeolite types LTA, analcime and zeolite X. Longer crystallization time resulted in phase change of the zeolites into sodalite. Hence, natural raw materials such as bauxite and kaolin have the attractive features of providing the staring reagents for the synthesis of ultrapure synthetic zeolites.

- by Isaac Nkrumah
- •
- TIME, Zeolites, Characterization, Bauxite
- by Slobodan Miko
- •
- Mercury Pollution, Bauxite

High‐quality Raman spectra were used for the characterization of alumina phases of gibbsite, bayerite, diaspore and boehmite. The Raman spectrum of gibbsite shows four strong, sharp bands at 3617, 3522, 3433 and 3364 cm−1 in the hydroxyl stretching region. The spectrum of bayerite shows seven bands at 3664, 3652, 3552, 3542, 3450, 3438 and 3420 cm−1. Five broad bands at 3445, 3363, 3226, 3119 and 2936 cm−1 and four broad and weak bands at 3371, 3220, 3085 and 2989 cm−1 are present in the Raman spectrum of the hydroxyl stretching region of diaspore and boehmite. The hydroxyl stretching bands are related to the surface structure of the minerals. The Raman spectra of bayerite, gibbsite and diaspore are complex whereas the Raman spectrum of boehmite shows only four bands in the low‐wavenumber region. These bands are assigned to deformation and translational modes of the alumina phases. A comparison of the Raman spectrum of bauxite with those of boehmite and gibbsite showed the possibility of using Raman spectroscopy for on‐line processing of bauxites that contain a mixture of alumina phases.

- by J. THEO KLOPROGGE
- •
- Geology, Condensed Matter Physics, Raman Spectroscopy, Minerals
- by Doug Stewart
- •
- Environmental Science, Geochemistry, Environmental Studies, Arsenic

Companhia Brasileira de Alumínio (CBA) has a preparation plant at Itamarati de Minas, MG. This plant washes two different kinds of bauxite ore, one originating from the laterization of gnaisses and another from amphybolites. Both ores have the same behavior in the coarser size fractions but behave differently under 0.355 mm (42# Tyler). In these small sizes, gneissic ores are rich in quartz and amphybolitic ores are rich in iron and titanium bearing ores. The unit operations are: scrubbing of the feed in drum scrubbers, desliming in cyclones, and screening of the scrubbed bauxite in high frequency screens (0.355 mm) - the +0.355 mm product is a final concentrate. The -0.355 mm fraction is desliming in two stage cyclones and goes to a fines gravity concentration circuit of Reichert spirals complemented by magnetic separation of the light product from the spirals. The research work, including mineralogy, process development, batch tests and pilot plant tests, is described and compared...

- by Nilson Tadeu Ramos Nunes
- •
- Mineral Processing, Bauxite

Far-infrared spectroscopy (FIR) has been used to distinguish alumina phases boehmite, diaspore, gibbsite and bayerite. The pellets of samples were prepared by mixing alumina phases with polyethylene at a ratio of 1:50, and the spectra were recorded between 50 and 400 cm−1. The spectrum of boehmite resembles that of diaspore in the 300–400 cm−1 region. Boehmite has two characteristic FIR bands at 366 and 323 cm−1, while diaspore has five at 354, 331, 250, 199 and 158 cm−1. The spectrum of gibbsite resembles that of bayerite in the 230–300 cm−1 region. Gibbsite shows three characteristic FIR bands at 371, 279 and 246 cm−1, whereas bayerite shows six at 383, 345, 326, 296, 252 and 62 cm−1. The overlapping bands were resolved, and the spectra were manipulated appropriately using band analysis techniques. The FIR spectra are in harmony with the FT-Raman spectra. Far-infrared spectroscopy allows the study and differentiation of the stretching of AlO4 units to characterize these four alumina phases. Far-IR spectroscopy complements the mid-IR and near-IR for distinguishing alumina phases in bauxites.

- by J. THEO KLOPROGGE
- •
- Raman Spectroscopy, Minerals, Vibrational Spectroscopy, Alumina

Red mud is highly alkaline (pH 13), saline and can contain elevated concentrations of several potentially toxic elements (e.g. Al, As, Mo and V). Release of up to 1 million m(3) of bauxite residue (red mud) suspension from the Ajka repository, western Hungary, caused large-scale contamination of downstream rivers and floodplains. There is now concern about the potential leaching of toxic metal(loid)s from the red mud as some have enhanced solubility at high pH. This study investigated the impact of red mud addition to three different Hungarian soils with respect to trace element solubility and soil geochemistry. The effectiveness of gypsum amendment for the rehabilitation of red mud-contaminated soils was also examined. Red mud addition to soils caused a pH increase, proportional to red mud addition, of up to 4 pH units (e.g. pH 7 → 11). Increasing red mud addition also led to significant increases in salinity, dissolved organic carbon and aqueous trace element concentrations. However, the response was highly soil specific and one of the soils tested buffered pH to around pH 8.5 even with the highest red mud loading tested (33 % w/w); experiments using this soil also had much lower aqueous Al, As and V concentrations. Gypsum addition to soil/red mud mixtures, even at relatively low concentrations (1 % w/w), was sufficient to buffer experimental pH to 7.5-8.5. This effect was attributed to the reaction of Ca(2+) supplied by the gypsum with OH(-) and carbonate from the red mud to precipitate calcite. The lowered pH enhanced trace element sorption and largely inhibited the release of Al, As and V. Mo concentrations, however, were largely unaffected by gypsum induced pH buffering due to the greater solubility of Mo (as molybdate) at circumneutral pH. Gypsum addition also leads to significantly higher porewater salinities, and column experiments demonstrated that this increase in total dissolved solids persisted even after 25 pore volume replacements. Gypsum addition could therefore provide a cheaper alternative to recovery (dig and dump) for the treatment of red mud-affected soils. The observed inhibition of trace metal release within red mud-affected soils was relatively insensitive to either the percentage of red mud or gypsum present, making the treatment easy to apply. However, there is risk that over-application of gypsum could lead to detrimental long-term increases in soil salinity.

- by Doug Stewart and +1
- •
- Earth Sciences, Environmental Science, Geochemistry, Arsenic
- by Syamsul Rusdi
- •
- Social Sciences, Community Resilience, Community Development, Indonesia

The tailings dam breach at the Ajka alumina plant, western Hungary in 2010 introduced 1 million m3 of
red mud suspension into the surrounding area. Red mud (fine fraction bauxite residue) has a characteristically
alkaline pH and contains several potentially toxic elements, including arsenic. Aerobic and anaerobic
batch experiments were prepared using soils from near Ajka in order to investigate the effects of red
mud addition on soil biogeochemistry and arsenic mobility in soil–water experiments representative of
land affected by the red mud spill. XAS analysis showed that As was present in the red mud as As(V) in
the form of arsenate. The remobilisation of red mud associated arsenate was highly pH dependent and
the addition of phosphate to red mud suspensions greatly enhanced As release to solution. In aerobic
batch experiments, where red mud was mixed with soils, As release to solution was highly dependent
on pH. Carbonation of these alkaline solutions by dissolution of atmospheric CO2 reduced pH, which
resulted in a decrease of aqueous As concentrations over time. However, this did not result in complete
removal of aqueous As in any of the experiments. Carbonation did not occur in anaerobic experiments
and pH remained high. Aqueous As concentrations initially increased in all the anaerobic red mud
amended experiments, and then remained relatively constant as the systems became more reducing,
both XANES and HPLC–ICP-MS showed that no As reduction processes occurred and that only As(V)
species were present. These experiments show that there is the potential for increased As mobility in
soil–water systems affected by red mud addition under both aerobic and anaerobic conditions.

- by Doug Stewart and +3
- •
- Environmental Science, Environmental Studies, Environmental Geochemistry (Environmental Studies), Arsenic

Bauxite residue is an important by-product of the alumina industry, and current management practices do not allow their full valorisation, especially with regard to the recovery of critical metals. This work aims to test the efficiency of ion exchange resins for vanadium (V) removal and recovery from bauxite residue leachates at alkaline pH (11.5 and 13). As an environmental pollutant, removal of V from leachates may be an obligation of bauxite residue disposal areas (BRDA) long-term management requirements. Vanadium removal from the leachate can be coupled with the recovery, and potentially can be used to offset long-term legacy treatment costs in legacy sites. Kinetics studies were performed to understand the adsorption process. The rate kinetics for the V adsorption was consistent with the pseudo-first-order kinetic model, with a higher adsorption rate for pH 11.5 (1.2 min(-1)). Adsorption isotherm data fitted better to Freundlich equations than to the Langmuir model. The maximum...

- by Helena I. Gomes
- •
- Chemistry, Kinetics, Environmental Pollution, Medicine
- by Caroline Peacock
- •
- Environmental Science, Geology, Geochemistry, Chemistry
- by Anjan Prusty
- •
- Botany, Landscape Ecology, Soil Science, Conservation Biology
- by Frank Gnanam
- •
- Environmental Science, Geochemistry, Chemistry, Bauxite
- by J. Hein
- •
- Geology, Geochemistry, Economic Geology, Stable Isotope Geochemistry

- by Jocelyn BARBARAND
- •
- Geology, Geomorphology, Soil Science, Climate Change
- by H. Papaefthymiou
- •
- Radioprotection, Bauxite, Natural Radionuclides

Hexagonal ferrites can be employed in a multitude of applications, the most common hexaferrites are the M ferrites such as BaFe12O19 (barium hexaferrite, BaM). It is known that if Fe3+ is substituted with a combination of Ti4+/Co2+ the coercivity of BaM can be reduced to produce soft M ferrites with easily switchable magnetisation. They can be utilised as powders, films or bulk ceramics, and can be manufactured from a wide variety of synthesis methods. The production of hexaferrites usually requires commercial raw materials, but if an industrial waste can be utilised, this will help to ease waste disposal and storage costs, valorise a waste material and encourage circular economy. In this study, bauxite residue (red mud) from the production of alumina was used to synthesise M-type hexaferrites, using a simple ceramic process. BaCO3, or BaCO3+Co3O4, were added to the red mud, blended and heated at 1000 °C to produce the M-type hexaferrites. Without cobalt addition up to 81.1 wt% M ferrite was produced, and with Co addition up to 74.3 wt% M ferrite was formed. Without cobalt, the M ferrite phase closely resembled BaFe9Al3O19, and was a hard ferrite with a magnetisation of 12–19 A m2/kg for the whole powder (up to 23.6 A m2/kg for the M ferrite phase) and a coercivity of ~290 kA/m. When cobalt was added, secondary titanate phases vanished, and Ti4+/Co2+ partially substituted very soft M ferrite was formed with a low coercivity of ~16 kA/m but a higher magnetisation of 24.5 A m2/kg for the whole powder (up to 34.9 A m2/kg for the M ferrite phase). Therefore, not only can good quality magnetic materials be easily produced from this common waste material, but its magnetic properties can be tuned by varying the 2 + ions added during the process.

- by Robert C Pullar
- •
- Magnetic Materials, Waste Materials and Composites, Bauxite, Red Mud
- by PA Azeez and +2
- •
- Botany, Landscape Ecology, Conservation Biology, Biology
- by semiha ilhan
- •
- Turkey, Bauxite