Long term storage of bauxite residue materials requires a capping stratum which will limit erosion while stabilizing slopes, limit deep infiltration of water into storage piles, and be aesthetically acceptable to the surrounding community. A diverse native vegetative community capable of surviving seasonal drought, low plant available water and nutrient constraints has the best potential of satisfying most, if not all of these requirements. Current and past rehabilitation of residue disposal areas (RDAs) using species native to southwest Western Australia has exhibited varying success. Current practices at Alcoa World Alumina Australia’s (Alcoa) Western Australia refineries have bauxite residue fines (< 150 ìm) stored within impoundments, in which the outer embankments are constructed with bauxite residue sands (> 150 ìm). The residue sands are also used as the growth media in the capping stratum for vegetation establishment on the disposal sites. Despite the inherently hostile properties of residue sand (pH > 10, EC(1:5) > 4 dS m-1, and ESP > 50), reductions in alkalinity (pH), salinity (EC) and sodicity (ESP) are corrected, through freshwater leaching, to a greater extent than is possible with residue fines. Although leaching can reduce the hostile character of residue sand, additions of phosphogypsum are typically added to expedite the removal of Na and alkalinity, and inorganic fertilizers are incorporated to improve the nutrient status of the growth media. However, due to the inconsistencies in vegetation establishment, which are attributed to poor water retention, inherent nutrient deficiencies and rapid loss of nutrients within residue sands (because of high hydraulic conductivity), further amendments are required. The aim of this study was to determine if amending the residue sand capping layer with residue fines would enhance its overall growth potential for vegetation establishment. Additions of fines to residue sands were predicted to increase water retention, add nutrients and increase the ability of the growth media to retain nutrients. Comparisons were made between the treated residue fines (seawater washed, carbonated, or unaltered) at a series of fines additions (1 - 20 % w/w) and a control(residue sand) amended with 2% (w/w) phosphogypsum and inorganic fertilizer. Comparisons were to determine the differences in 1) water retention, 2) nutrient concentrations and nutrient retention, and 3) plant growth responses and plant biomass nutrient concentrations between the growth media treatments. Four experiments were set up to measure differences in these variables which included: a glasshouse study involving the growth of Acacia saligna; a germination and emergence study (A.saligna); a two year field study in Western Australia; and a glasshouse column leaching study. Water retention increased with increasing percentage of residue fines addition. Plant available water (PAW) increased up to 110 %, with a 20 % increase in fines, representing an increase of 0.026 m3 PAW m-3 residue growth media, when compared to the residue sand only. This increase in PAW was attributed to changes in pore space distributions, due to the increasing fines contents altering the sandy texture to loamy sand texture class. However, initially much of this increase in PAW may not be realized, due to estimated temporary increases in osmotic potential associated with the high salt contents of residue sand and fines. Fines materials have much greater salt contents, and thus need to be leached to a greater extent than sands to remove the associated osmotic potential effects. Essential plant nutrients (P, K, S, Ca, Mg, and B) were increased with additions of residue fines in the glasshouse studies, although many nutrients (Mg, Zn, Mn and B) were still marginal for sustainable plant growth and development. Seawater treated residue fines additions produced the greatest increases in growth media nutrients with substantial increases in soluble (> 7 mg L-1) and exchangeable (> 0.10 cmolc kg-1) Mg, being up to 400 % greater than all other treatments. Along with these necessary nutrients, concentrations of Na were also increased in all fines additions treatments. Added Na may offset the benefits of fines additions, at least in the short term, due to inhibitions of cation uptake from Na competition. However, in the column leaching study soluble and exchangeable Na was lost rapidly from the profile, due to Ca and K displacement of Na from exchange sites during leaching. Soluble Na was removed from the profile to < 5 % of initial concentrations, after only three pore volumes of leaching, and exchangeable Na was removed from charge sites to less than 25 % of the initial concentration. Fines additions did increase concentrations of Mg and K on exchange sites, thus reflecting increased nutrient retention capacity relative to that in residue sand only. Plant growth responses and plant biomass nutrient concentrations were altered with the additions of residue fines to residue sands. The germination and emergence study demonstrated that the emergence of native seedlings was affected by additions of fines, due to the increased salinity and sodicity of the materials. Acacia saligna seedling emergence was inhibited by EC(1:5) > 2 dS m-1, which was highly correlated with a Na/Ca ratio of > 40, for all treatments, except the seawater fines additions. Seeds sown in seawater treatments emerged from growth media with EC(1:5) as high as 3.33 dS m-1 and appeared to be better correlated with Ca/Mg ratios than any other variable. Native vegetation growth responses showed mixed results in fines treated residues in the field. In the greenhouse study, plant growth tended to decrease with fines additions. Poor plant growth with increasing fines additions occurred despite the increased water retention and increased nutrients. This was attributed to the addition of Na associated with the residue fines, as increases in Na, EC and ESP in fines treatments all appear to have limited growth of Acacia saligna in the glasshouse over three months. Seawater fines additions had elevated Mg and B concentrations in plant biomass, and performed better than the carbonated or unaltered fines treatments, but still had reduced growth compared to the residue sand, which contained lower Na concentrations. Additional plant growth limitations may have occurred, due to possible plant nutrient deficiencies including: Mg, Zn, Mn and B and Na toxicity. Incorporation of residue fines into residue sands did increase water retention, nutrient concentrations and the nutrient retention capacity, but did not enhance the overall growth potential for vegetation, at least in the short term. Reductions in germination and emergence of seedlings and reduced plant growth were attributed to increases in Na concentrations introduced from the fines. Seawater washed residue fines had lower ESP and greater concentrations of nutrients, thus reducing the negative impacts from the additional Na introduced, and showed the greatest promise as a fines amendment. As leaching occurs over the first few initial months of rehabilitation, it is expected that the majority of the Na will be removed, from a system with an addition of 5 to 10 % fines, and the positive benefits of the fines additions will than be realized. Findings also illustrate that delaying the planting of vegetation on RDAs, until adequate leaching has occurred to reduce the Na concentrations, will substantially increase vegetation emergence and establishment.

A lama vermelha é o resíduo gerado pela Indústria do Alumínio. Assim como outros resíduos industriais apresenta características complexas com inúmeras dificuldades de manipulação, além de ser um material perigoso pela sua baixa granulometria e alcalinidade. É um resíduo com potencial poluidor alto, agravado pela forma de disposição vulnerável geralmente adotada, sendo esta a disposição do resíduo em lagoas projetadas para esta finalidade. O estudo e desenvolvimento de alternativas sustentáveis para a utilização da lama vermelha devidamente tratada como matérias-primas de outros processos são tendências importantes e necessárias no contexto mundial de preservação do meio ambiente. O objetivo deste estudo é compreender o comportamento da lama vermelha sob a influência de diferentes temperaturas de tratamento térmico. Baseados nos efeitos de redução de área e transformações de fases, característicos dos processos térmicos, adotou-se um foco de análise voltado para a redução pH e dos íons livres. A identificação dos pHs adequados de análise da concentração de íons solúveis foi feita com base nas curvas de mobilidade eletroforética e condutividade. Os resultados obtidos para as amostras calcinadas mostraram queda do pH inicial das dispersões e da concentração dos íons solubilizados. Esse efeito pode ser atribuído a redução de área e a incorporação de íons à estrutura, o que assegura ao resíduo menor reatividade. / Red mud is the waste generated by Aluminium Industry, like other industrial wastes, has complex features with several difficulties in handling, as well as being a hazardous material because of its low particle size, alkalinity and high amount generated. It is a waste with high pollution potential, compounded by the vulnerability of the disposition generally adopted, usually in lagoons designed for this purpose. The study and development of sustainable alternatives for the use of properly treated red mud, as raw material of other processes, are important tendencies and necessaries in the global context of environmental preservation. However, this work deals the thermal treatment as method to modify the characteristics of the waste, suggesting the reduction of alkalinity with the lower leaching of alkaline ions. This approach can be a discarding alternative most reliable and safe for the environment. The objective of this study is understand the red muds behavior using thermal treatment. Based on the reduction effects of the area and phase transformations characteristic of thermal process, the analysis was taken observing the reduction of free ions and pH. Identification of correct pH of analyse of soluble ions concentration was based at mobility electrophoretic and conductivity graphics. The results of calcined samples showed reduction of initial pH and the concentration of soluble ions. This effect could be assigned to the area reduction and ions incorporation at structure, which ensures the residue lower reactivity.

The desire of the minerals industry to be more sustainable has led towards the increasing development of by-products. One such industry is the production of Alumina. The Alumina industry in Australia is the major producer of alumina in the western world with over 25 million tonnes of Bauxite Residue per annum. Alcoa World Alumina (Alcoa) has three refineries in Western Australia producing approximately 20,000 tonnes of Mud and a similar level of Red Sand each day. These as yet unutilised potential resources are being stockpiled, occupying a significant footprint. It is widely recognised within industry that there would be economic, environment and social benefits if a sustainable use for these materials were found. One such potential by-product is the production of coarse bauxite residue (Red Sand), neutralised and washed low in salt. The main purpose of this research was to establish a potential market for this material, through scientific evaluation of Red Sand as a replacement of natural fine aggregate (Natural Yellow Sand) in concrete mixes. For this research, the mixed stream of Bauxite Residue (fine and coarse) obtained in the Bayer process was neutralized by a process of carbonation then washed using cyclones and counter current wash towers to a value added byproduct. The coarse particles (Washed and Carbonated Sand-WCS) of the stream were separated by Wet High Intensity Magnetic Separation technique (WHIMS) so that different segments such as High Iron Sand (HIS) and Low Iron Sand (LIS) were formed. Physical, chemical and mineralogical properties of these materials have been tested and compared with that of natural sand. Several mixes of concrete were then designed using Red Sand as a fine aggregate in order to verify their effects on strength and durability indicators of concrete. / The comparative analysis between normal mix proportions and the mix proportions utilizing Red Sand was also achieved. In addition, the impact of marine environment on concrete mix design and properties of manufactured concrete were evaluated with a series of standard laboratory tests. The findings were promising in terms of both mechanical properties and durability and suggested that Red Sand, in particular Low Iron Sand is likely to be effective in place of fine aggregates and can be used within marine grade concrete with no major differences when compared to normal concrete. From the results obtained, it can be deduced that this material can be used in a wide range of concrete applications in Civil Engineering and Construction.

A lama vermelha é o resíduo gerado pela Indústria do Alumínio. Assim como outros resíduos industriais apresenta características complexas com inúmeras dificuldades de manipulação, além de ser um material perigoso pela sua baixa granulometria e alcalinidade. É um resíduo com potencial poluidor alto, agravado pela forma de disposição vulnerável geralmente adotada, sendo esta a disposição do resíduo em lagoas projetadas para esta finalidade. O estudo e desenvolvimento de alternativas sustentáveis para a utilização da lama vermelha devidamente tratada como matérias-primas de outros processos são tendências importantes e necessárias no contexto mundial de preservação do meio ambiente. O objetivo deste estudo é compreender o comportamento da lama vermelha sob a influência de diferentes temperaturas de tratamento térmico. Baseados nos efeitos de redução de área e transformações de fases, característicos dos processos térmicos, adotou-se um foco de análise voltado para a redução pH e dos íons livres. A identificação dos pHs adequados de análise da concentração de íons solúveis foi feita com base nas curvas de mobilidade eletroforética e condutividade. Os resultados obtidos para as amostras calcinadas mostraram queda do pH inicial das dispersões e da concentração dos íons solubilizados. Esse efeito pode ser atribuído a redução de área e a incorporação de íons à estrutura, o que assegura ao resíduo menor reatividade. / Red mud is the waste generated by Aluminium Industry, like other industrial wastes, has complex features with several difficulties in handling, as well as being a hazardous material because of its low particle size, alkalinity and high amount generated. It is a waste with high pollution potential, compounded by the vulnerability of the disposition generally adopted, usually in lagoons designed for this purpose. The study and development of sustainable alternatives for the use of properly treated red mud, as raw material of other processes, are important tendencies and necessaries in the global context of environmental preservation. However, this work deals the thermal treatment as method to modify the characteristics of the waste, suggesting the reduction of alkalinity with the lower leaching of alkaline ions. This approach can be a discarding alternative most reliable and safe for the environment. The objective of this study is understand the red muds behavior using thermal treatment. Based on the reduction effects of the area and phase transformations characteristic of thermal process, the analysis was taken observing the reduction of free ions and pH. Identification of correct pH of analyse of soluble ions concentration was based at mobility electrophoretic and conductivity graphics. The results of calcined samples showed reduction of initial pH and the concentration of soluble ions. This effect could be assigned to the area reduction and ions incorporation at structure, which ensures the residue lower reactivity.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A técnica de deposição de resíduos de processamento de bauxita prevê uma operação inicial de lançamento de resíduos, por via úmida, no interior de reservatórios artificiais. Nesta fase de deposição, os resíduos são lançados em forma de polpa, sofrendo processos de sedimentação e adensamento por peso próprio. A vida útil dos reservatórios depende fundamentalmente do comportamento geotécnico do resíduo, cujas propriedades variam ao longo do tempo e da profundidade. A presente dissertação tem como objetivo a análise do comportamento de uma área de resíduos de bauxita durante a operação de enchimento do reservatório. Para tanto, foi utilizado o programa Plaxis, que executa análises tensão-deformação pelo método dos elementos finitos. Os parâmetros geotécnicos do resíduo foram definidos com base em ensaios de adensamento e piezocone, executados em amostras representativas da polpa de resíduos. Para calibração do modelo, a batimetria executada no reservatório foi confrontada com as cotas de enchimento previstas numericamente. Finalmente, a distribuição dos parâmetros geotécnicos (peso específico, índice de vazios, permeabilidade) com a profundidade prevista numericamente foi confrontada com os valores medidos no campo, ao final da etapa de enchimento. O conhecimento da variação dos parâmetros geotécnicos com a profundidade ao final do enchimento é importante para avaliar o comportamento do reservatório na etapa de operação de alteamento, e para a estimativa do ganho de vida útil do reservatório. Os resultados permitiram avaliar o funcionamento da drenagem de fundo, a distribuição complexa dos excessos de poropressão ao final do enchimento, os perfis dos índices físicos com a profundidade e o ganho de vida útil. As análises mostraram que o programa foi capaz de reproduzir os processos simultâneos de sedimentação e adensamento por peso próprio, em análises de enchimento de reservatórios de resíduos. / The technique of disposing of waste bauxite processing provides an initial launch of operation, the wet disposal, within artificial reservoirs. In this phase of deposition, the waste is released in the form of pulp, suffering processes of sedimentation and consolidation by self-weight. The useful life of the reservoirs depends crucially on the Geotechnical behavior of the residue, whose properties vary over time and depth. The present dissertation aims to behavior analysis of a bauxite waste area during the operation of filling the tank. To this end, we used the program Plaxis, which performs stress-strain analyses by the finite element method. The Geotechnical parameters of residue were defined based on piezocone, consolidation and tests carried out on representative samples of waste pulp. For calibration of the bathymetry model executed in the reservoir was faced with filling quotas provided for numerically. Finally, the distribution of geotechnical parameters (specific weight, void ratio, permeability) with the depth expected numerically was confronted with the values measured in the field, at the end of the filling stage. Knowledge of geotechnical parameters variation with depth at the end of the filling is important to evaluate the behavior of the reservoir in heightening operation step, and for the estimation of the useful life of the reservoir. The results made it possible to assess the functioning of the Fund drainage, the complex distribution of excess pore pressure dissipations at the end of the filling, the profiles of physical indexes with the depth and the gain of life. The analysis showed that the program was able to reproduce the simultaneous processes of sedimentation and consolidation by selfweight, in analyses of reservoir filling of waste.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A técnica de deposição de resíduos de processamento de bauxita prevê uma operação inicial de lançamento de resíduos, por via úmida, no interior de reservatórios artificiais. Nesta fase de deposição, os resíduos são lançados em forma de polpa, sofrendo processos de sedimentação e adensamento por peso próprio. A vida útil dos reservatórios depende fundamentalmente do comportamento geotécnico do resíduo, cujas propriedades variam ao longo do tempo e da profundidade. A presente dissertação tem como objetivo a análise do comportamento de uma área de resíduos de bauxita durante a operação de enchimento do reservatório. Para tanto, foi utilizado o programa Plaxis, que executa análises tensão-deformação pelo método dos elementos finitos. Os parâmetros geotécnicos do resíduo foram definidos com base em ensaios de adensamento e piezocone, executados em amostras representativas da polpa de resíduos. Para calibração do modelo, a batimetria executada no reservatório foi confrontada com as cotas de enchimento previstas numericamente. Finalmente, a distribuição dos parâmetros geotécnicos (peso específico, índice de vazios, permeabilidade) com a profundidade prevista numericamente foi confrontada com os valores medidos no campo, ao final da etapa de enchimento. O conhecimento da variação dos parâmetros geotécnicos com a profundidade ao final do enchimento é importante para avaliar o comportamento do reservatório na etapa de operação de alteamento, e para a estimativa do ganho de vida útil do reservatório. Os resultados permitiram avaliar o funcionamento da drenagem de fundo, a distribuição complexa dos excessos de poropressão ao final do enchimento, os perfis dos índices físicos com a profundidade e o ganho de vida útil. As análises mostraram que o programa foi capaz de reproduzir os processos simultâneos de sedimentação e adensamento por peso próprio, em análises de enchimento de reservatórios de resíduos. / The technique of disposing of waste bauxite processing provides an initial launch of operation, the wet disposal, within artificial reservoirs. In this phase of deposition, the waste is released in the form of pulp, suffering processes of sedimentation and consolidation by self-weight. The useful life of the reservoirs depends crucially on the Geotechnical behavior of the residue, whose properties vary over time and depth. The present dissertation aims to behavior analysis of a bauxite waste area during the operation of filling the tank. To this end, we used the program Plaxis, which performs stress-strain analyses by the finite element method. The Geotechnical parameters of residue were defined based on piezocone, consolidation and tests carried out on representative samples of waste pulp. For calibration of the bathymetry model executed in the reservoir was faced with filling quotas provided for numerically. Finally, the distribution of geotechnical parameters (specific weight, void ratio, permeability) with the depth expected numerically was confronted with the values measured in the field, at the end of the filling stage. Knowledge of geotechnical parameters variation with depth at the end of the filling is important to evaluate the behavior of the reservoir in heightening operation step, and for the estimation of the useful life of the reservoir. The results made it possible to assess the functioning of the Fund drainage, the complex distribution of excess pore pressure dissipations at the end of the filling, the profiles of physical indexes with the depth and the gain of life. The analysis showed that the program was able to reproduce the simultaneous processes of sedimentation and consolidation by selfweight, in analyses of reservoir filling of waste.

Bayer processing of bauxite employed for production of alumina yield a residue red-mud. The worldwide annual-rate of red-mud generation is approximately 120 million tons, and most of this is stockpiled. Red mud is rich in elements like aluminum, titanium and rare earths, in addition to the major iron-bearing constituents. The objective of this research is to explore such a strategy to extract Iron as fine particulate magnetite. Pyrometallurgical reduction experiments using carbon mixtures and a novel hydrometallurgical route are experimented. Reduction experiments performed with petroleum coke as a reductant resulted in incomplete reduction. The ‘optimal conditionsÂ’ for gaseous state reduction are determined to be: a processing temperature of 540oC ± 10oC, partial pressures CO (g) and CO2 (g) each of 0.070atm (bar) ± 0.001atm.(bar)/ inert diluent-gas: N2 (g), for a conversion-time of 30min. A mathematical-model was developed on the basis of unidirectional-diffusion of CO2 (g) within the CO2 (g)–CO (g)–N2 (g) gas-phase of the porous product-layer. Magnetic separation applied to the optimally reduced sample in: obtaining a magnetic portion with high iron and non-magnetic portion containing nonferrous (Al, Ti) is not successful. This finding was subsequently attributed to the nanometer length-scales crystallites of the predominant iron-containing phase, hydrated ferric-oxide(s) as determined by STEM micrographs. In addition, the presence of substitution for Fe3+ by Al3+ and Ti3+/4+ are determined with the help of MÖssbauer spectrograms. A hydrometallurgical route involving selective leaching and precipitation of iron in red-mud is tried. Red-mud is leached in oxalic acid at: 95˚C, 15 % Pulp density, 2.5 h leaching time, 1.5 pH. Kinetic studies yielded the leaching mechanism to be predominantly fluid film control. Ferric oxalate in the leach liquor is reduced to insoluble ferrous oxalate selectively using Iron powder. The ferrous oxalate formed is ~98 % pure. The precipitated ferrous oxalate is magnetically separated and reduced in Nitrogen atmosphere to form fine particulate magnetite. Additionally an economic feasibility study was conducted for the hydro and pyro alternatives to produce magnetite using Monte Carlo Simulations by imparting uncertainties in various input cost components. A traditional process was also compared to the proposed approaches for Total Capital Investment (TCI), Total Product Cost (TPC), Net Present Value (NPV) and sensitivity analysis. ~52 % reduction in Total product cost, 46 % reduction in Total Capital Investment was achieved for the hydrometallurgical process when compared to the traditional approach.

Στην παρούσα Διατριβή παρουσιάζεται η μελέτη της δυνατότητας αξιοποίησης της ερυθράς ιλύος, ΕΙ, η οποία παράγεται κατά τη διαδικασία παραγωγής της αλουμίνας με τη διεργασία Bayer, για την παραγωγή δομικών παραδοσιακών κεραμικών, κύρια τούβλων και κεραμιδιών. Μελετήθηκαν αργιλούχα μίγματα με ΕΙ για ποσοστά ΕΙ από 10%κβ έως και 100%κβ.Επιγραμματικά, για την ΕΙ, πραγματοποιήθηκε χαρακτηρισμός και μελέτη της θερμικής συμπεριφοράς της. Για τα μίγματα της ΕΙ με αργιλούχες Α' ύλες, πραγματοποιήθηκε θεωρητικός σχεδιασμός τους, ενώ μελετήθηκε η επίδραση των σταδίων ανάμιξης και λειοτρίβησης, η επίδραση της ΕΙ στην πλαστικότητα, η θερμική συμπεριφορά, οι φυσικομηχανικές ιδιότητες των τελικών κεραμικών, η επίδραση της θερμοκρασίας και ατμόσφαιρας όπτησης καθώς και η περιβαλλοντική τους συμπεριφορά. Πραγματοποιήθηκαν επιπρόσθετα πιλοτικές δοκιμές παραγωγής τούβλων και κεραμιδιών. Τα αποτελέσματα της διατριβής, οδήγησαν στην ανάπτυξη μιας βέλτιστης διεργασίας παραγωγής κεραμικών με ΕΙ, η οποία αφορά στο σχεδιασμό του μίγματος με ΕΙ και την όπτησή του σε αναγωγικές συνθήκες. / In the present thesis, Bayer's process red mud, RM, is being studied as an additive and raw material for the production of heavy clay ceramics, mainly bricks and roofing tiles. A number of clay mixtures with RM were studied, for a RM content ranging from 10wt% to 100wt%. In summary, RM was characterised and studied for its thermal behaviour whereas, for the clay mixtures with RM, their design is provided, and the effect of comminution steps, the effect of RM on plasticity, their thermal behaviour, the influence of firing temperature and atmosphere, the physicomechanical properties of the end bodies, as well as their environmental behaviour are studied. In addition, pilot plan scale experiments were performed for the production of bricks and roofing tiles. The results of this thesis, led to the development of an optimised process for the production of ceramics with RM, which emphasises on the design of the body mixture as well as on the firing in reducing conditions.

[Truncated abstract] Industrial processing to refine alumina from bauxite ore produces millions of tonnes of refining residue each year in Australia. Revegetation of bauxite residue sand (BRS) is problematic for a number of reasons. Harsh chemical conditions caused by residual NaOH from ore digestion mean plants must overcome extremely high pH (initially >12), saline and sodic conditions. At such high pH, manganese (Mn) is rapidly oxidised from Mn2+ to Mn4+. Plants can take up only Mn2+. Thus, Mn deficiency is common in plants used for direct BRS revegetation, and broadcast Mn fertilisers have low residual value. Added to this, physical conditions of low water-holding capacity and a highly compactable structure make BRS unfavourable for productive plant growth without constant and large inputs of water as well as Mn. However, environmental regulations stipulate that the residue disposal area at Pinjarra, Western Australia, be revegetated to conform with surrounding land uses. The major land use of the area is pasture for grazing stock. Hence, pasture revegetation with minimum requirement for fertiliser and water application is desirable. This thesis investigates a number of avenues with potential for maintaining a productive pasture system on BRS whilst reducing the current level of Mn fertiliser and irrigation input. Emphasis was placed on elucidation of chemical and physical factors affecting Mn availability to plants in BRS