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Controlled low-strength material (CLSM) is a self-leveling and self-compacting pozzolan backfill material made from various industrial by-products. The ingredients such as Fly ash, Red mud (RM), GGBS, etc can be used in different combinations to obtain the required CLSM mix. RM is a granular by-product of the Bayer process, which manufactures alumina from bauxite. Every year, India produces approximately 4-5 million tonnes of red mud. It is currently stored or disposed of near alumina factories on land or in the oceans. It has excessive alkalinity, on the other hand, poses a threat to water, land, and air pollution. India is the largest producer of alumina. Due to variances in ore types used in the production procedures, there are some changes in mineralogical composition between leftovers from India and other nations. This review study investigates the applications and benefits of CLSM including a variety of industrial by-products. The flowability, UCS, and microstructural characteristics of CLSM are reviewed. [ABSTRACT FROM AUTHOR]

Nanofluid is a candidate for replacing conventional cooling fluid. The nanofluids can be applied as a cooling fluid for some equipment such as automotive and nuclear reactors. In this work, we prepared nanofluids using the synthesized Al2O3 nanoparticles. The synthesis was done as follows; precursor of Al(OH)3 was extracted from local bauxite using the Bayer process then calcined at 1000°C for 2 hours. The nanoparticles were characterized using X-ray diffraction, and the specific surface area was measured using a surface area meter. Nanofluids were prepared by dispersing the Al2O3 nanoparticles into water and ultrasonicated the mixture in an ultrasonic bath. The nanofluids were added with a dispersant of polyacrylic acid (PAA) with concentrations of 0, 0.01, 0.02, 0.03, 0.04, and 0.05 g. We identified that the Al2O3 nanoparticles had two phases or structures, alpha with crystallite size of 80 nm and gamma with crystallite size of 5 nm, and lattice constant (a= 4.76 nm, c=12.73 nm) for alpha and 7.89 nm for gamma. According to surface area data, the Al2O3 nanoparticles had a specific surface area of 56.7 m2/gr with BET particles size of 28.2 nm. The zeta potential data showed that the prepared nanofluids were stable with -47.7 to -57.8 mV zeta potential. This data showed that the nanofluids had the potential to be applied as cooling fluids. [ABSTRACT FROM AUTHOR]

Bauxite Metallurgical Residue (BR) is a highly alkaline and very fine-grained by-product of the Bayer process for alumina production. Its huge global annual production has resulted in increasing accumulation of BR, causing deposition problems and serious environmental issues. RM contains oxides and salts of the main elements Fe, Al, Ca, Na, Si, Ti, and rare earths—REEs (Sc, Nd, Y, La, Ce, Ds)—many of which have been categorised by EU as critical metals (CMs). The valorisation of BR as a low-cost secondary raw material and metal resource could be a route for its reduction, introducing the waste into the economic cycle. REEScue constitutes a research project that aims to instigate the efficient exploitation of European bauxite residues, resulting from alumina production from Greece (MYTILINEOS SA), Turkey (ETI Aluminium), and Romania (ALUM SA), containing appreciable concentrations of scandium and REEs, through the development of a number of innovative extraction and separation technologies that can efficiently address the drawbacks of the existing solution. The consortium consists of three alumina producers from Greece (MYTILINEOS SA), Turkey (ETI Aluminium), and Romania (ALUM SA) and two academic partners from Greece (National Technical University of Athens) and Turkey (Necmettin Erbacan University). We present preliminary characterization results of three different BR samples that originate from the three aluminium industries, in respect of bulk chemical analysis (XRF, ICP), mineralogical investigation (XRD), and morphological observation through microscopy. [ABSTRACT FROM AUTHOR]

The Pedersen Process was developed at the beginning of the 20th century as an alternative process to the Bayer route for producing alumina Al2O3. A successful operation in an industrial environment took place in Norway from 1925 to 1969. It ended due to economic reasons. Having a smaller environmental footprint (no bauxite residue) and the ability to handle alternative raw materials makes the approach promising for grappling with future challenges in Europe. This paper shows the status of the ongoing European Commission-funded work and the outline of a first industrial process concept. [ABSTRACT FROM AUTHOR]

The worldwide olive oil sector is a strategic sector for olive oil producing countries due to olive oil nutrition and health benefits. With what is being produced of olive oil, it continues to produce wastewater with a significant environmental impact due to the high organic load and the biochemical composition of this wastewater, particularly, the presence of microbial growth inhibiting compounds such as phenolic compounds, which makes its biological treatment difficult. On other way, red mud, the main leaching residue resulting from the alkaline treatment of bauxite (Bayer process), can be used as catalyst in chemical processing. Bayer red mud reveals high alkalinity, strong water absorption, and a large content of iron. The presence of metals in the composition of the red mud, such as iron dioxide (hematite), titanium dioxide, etc. allows its use as a catalyst in advanced oxidation processes. In this work, red mud has been revalued as a catalyst in the treatment of olive mill wastewater (OMW) by Fenton reaction. All experiments were carried out at laboratory scale in reactor with capacity of 500 cm³. Experiments have been carried out at different concentrations of red mud 0.05, 0.10, 0.5, 1.0, 2.0, 4.0, 5.0, 20, and 30 g/L. In parallel, three control experiments were carried out using only hydrogen peroxide or hydrochloric acid or red mud without pH adjustment (adsorption experiment). Experimental results have determined that the introduction of red mud as a catalyst in the like Fenton reaction (H2O2/red mud) with concentrations higher than 0.05 g/L has allowed the increase of the degradation percentages until reaching stable values at red mud concentrations higher than 5 g/L. The removal percentages at 0.5 g/L of red mud were COD = 47.1 %, total organic carbon (TOC) = 58.1 %, total carbon (TC) = 66.8 %, total nitrogen = 44.1 %, and total phenolic compounds (TPCs) = 63.5 % versus 57.2 % for COD, 74.4 % for TOC, 79.9 % for TC, 70.7 % for TN, and 66.0 % for TPCs in Fenton like reaction with 5 g/L of red mud. The common operating conditions were initial COD of OMW = 6171.9 mg O2/L, initial TOC of OMW = 3253.7 mg/L, pH = 3, magnetic agitation speed = 460 rpm, environment temperature, and the H2O2 at 10 % (w/v) added to the OMW according to the stoichiometry of the reaction. Given these results, it can be concluded that red mud can be a promising catalyst in oxidation systems based on the Fenton reaction allowing the incorporation of wastes into new green processes leading to the achievement of circular economy in industrial processes. [ABSTRACT FROM AUTHOR]

The application of bauxite enrichment in the Bayer process before leaching for bauxites from Guinea and Sierra Leone is due to the loss of alumina or alkali in the red mud. In this article we have attempted to resolve this issue by performing preprocessing before proceeding with leaching operations. Three types of bauxite were used, two are mined by the Compagnie des Bauxites de Guinée (Sangaredi) and the third one by Vimetco in Sierra Leone. These three types of bauxite present some different mineralogical characteristics. Type 1 identified as bauxite Sierra Leone (BSL) is the one which contains a little more kaolinite greater than 8% therefore a slightly higher silica content. Type 2 'Low Mono Grade' (LMG) contains some mono (isomorphic of boehmite and aluminous goethite) and type 3 with more mono greater than 3% and is difficult to process due to the presence of ore such as aluminous goethite. The results obtained at the end of experiments give us an advantage of leaching yield for the fractions grouped together after washing, the particle size of which is greater than 0.045 mm. [ABSTRACT FROM AUTHOR]

This paper is one of a study that implements reverse flotation methods as an alternative beneficiation on bauxite processing. This study is aimed at decrease silica content and increase alumina content in bauxite so its qualified as feed of Bayer Process. The experiments were carried out in a 1375 mL of flotation cell tank. Dodecylamine (DDA) and AERO 3000C were used as the collector, starch as the depressant, and Dowfroth 1012 as frother. The overall experiments were conducted on solid content to solution 25% w/w. Alumina content and silica content as results of flotation were analyzed by XRF. The results of XRF of flotation products show that increasing of alumina content and decreasing of silica content. The optimum pH range of bauxite flotation using DDA and AERO 3000C as collectors can be achieved at pH 4 – 10. From the results, flotation performance using DDA is better than AERO 3000C because get higher Al2O3 content, 61.4%. The increasing of collector dosage at pH 10 gives a good result on Al2O3 content is 62% and SiO2 is 29.4% with 50.44% recovery of Al2O3 obtained at dosage of collector at 500 g/ton. The Al2O3 ontent which is higher in conditions without the addition of depressant is 66.8% while SiO2 in 23.5%. While for the size fraction variation, it shows that separation is better in the finer particle which gives an increasing of alumina and decreasing of silica as a result. The best condition in this study was achieved by 400 g/ton of DDA dosage, 400 g/ton of depressant dosage and size fraction of particle in -325 mesh at pH 10 with increasing alumina to 79.1% and decreasing silica to 8.89%. [ABSTRACT FROM AUTHOR]

Amorphous silica can be prepared from industrial waste, such as wet magnetic separation tailings of titanium magnetite ore beneficiation and red mud from the Bayer processing of bauxite into alumina, with silicon content of 10 to 50% in them. We considered fluoridation of polycomponent technogenic materials by solid-phase synthesis with the change of process temperature and a hydrochemical synthesis by NH4HF2 solution. The variation of the sintering process temperature range allows obtaining the ammonium fluorometallates or simple fluorides. It was found that nanosized silica obtained from waste has a high purity (≥99%), specific surface area (240-300 m2/g), pore volume (0.25-0.28 cm3/g). The experiments demonstrated that to produce amorphous silicon dioxide from waste, a solution should be with an ammonium hexafluorosilicate concentration 80-100 g/l and the process of ammonia hydrolysis should be carried out at 40-80 °C. An efficient method for extraction of SiO2 with a small particle size and high hydrophobic properties from waste is proposed, which currently does not have an appropriate application and is stored on disposal area. Such amorphous silica can be used in the production of catalysts, ceramics, heat- and fire-resistant rubber, and silicon fluoride complexes. [ABSTRACT FROM AUTHOR]

The paper presents the establishment of a pathway to progressively integrate solar thermal (CST) energy technologies into the current energy-intensive Bayer Process that produces calcined alumina from bauxite. This four-and- a-half-year program has developed three classes of CST technologies, low temperature steam production, solar syngas production and direct use of solar energy in the calciner, to enable a 29% to 45% solar share. In doing so, we ensure that continuous operation can be maintained, and that only minimal changes would need to be made to the refinery process, hence minimising the risk that industry takes on when introducing a new technology like this. In the present study, we have developed three process models for the low-temperature and high temperature processes using packages, such as the System Advisor Model (SAM), UNISIM, and Microsoft Excel, of the Bayer process to assess the impact of storage hour and solar resource variability on solar share or annual fuel saving and CO2 reduction for CST technologies relative to the conventional Bayer process. [ABSTRACT FROM AUTHOR]

Red Mud is a dust-like and high alkalinity waste material produced during the production of alumina from Bauxite ore by Bayer Process. Nearly 1 – 2.5 tons of Red mud, which consists of various oxides are produced per ton of alumina. The current practice is the disposal into long-term-storage sites, which is a major environmental problem throughout the world. Now the question comes: why to throw this valuable material as industrial waste and create environmental pollution instead of reusing it. This paper examines various possibilities of exploitation and utilization of Red Mud. [ABSTRACT FROM AUTHOR]

This paper reports a study that implements reverse flotation method to separate silica from West Kalimantan bauxite ores. The study is aimed to find the good process condition to obtain low-silica bauxite as the feed for the Bayer process. The experiments were carried out in a 1 L of flotation cell tank. Dodecylamine was used as the collector, starch as the depressant, and MIBC as the frother. The varied parameters were solid content to solution (15-30% w/w), and pH (6 - 10). The results of XRF of products show that in all reverse flotation experiments, the ratio of alumina to silica (Al/Si) are increased from 7 up to 14. The increase of solid percentage in the flotation gives a good result for Al/Si ratio as well as alumina and silica recovery in concentrate, with 30% w/w solid percentage to solution increases Al/Si ratio to 14.38, with silica recovery of 20%. The good separation with variation of depressants is obtained with depressant concentration of 400 g/ton bauxite, with Al/Si ratio in concentrate 15 and ratio in tailing 7. For the pH variation, the good condition is obtained at pH 8, while for collector concentration, the good condition is obtained at 200 g/ton bauxite. XRD analysis of the feed indicates that bauxite ore consists of gibbsite, diaspore, kaolinite, halloysite, quartz, boehmite, hematite and rutile. It is found that the concentrate has similar minerals, but halloysite became very minor or classified as a trace.eng [ABSTRACT FROM AUTHOR]

The bauxite is not processed through the usual processes of ore enrichment because of the mineralogical composition and structure, the intergrowths of minerals being very fine. Mineralogical characterization is very important to choose the method of extracting alumina from bauxite. This paper presents the mineralogical study of a hydrargyllitic bauxite from Sierra Leone and of the red mud resulted after extraction of alumina by Bayer method. The mineralogical characterization of red mud is needed to choose the method of neutralization of red mud dumps and recovery of by-products. The present study was made by chemical and physical methods - X-ray diffraction, differential scanning calorimetry and optical microscopy in polarized light. The physico-chemical characterization was performed in the National Institute of Research and Development for Non-ferrous and Rare Metals. [ABSTRACT FROM AUTHOR]

The hydrometallurgical process for obtaining alumina by Bayer process bauxite is getting significant amounts of red mud (0.8 - 2 t / t Al2O2). It is deposited in dumps which can cause danger for environment mainly due to the alkali content ( pH = 8-13) and small dimensisons of particles (less than 60 microns). Chemical and mineralogical composition of red mud bauxite is closely related to type of the bauxite used as raw material and processing conditions determined by some peculiarities of applied technology (pressure, temperature, etc.). In Romania, a producer of alumina and aluminum tradition for over 50 years, have been processed in time many varieties of bauxite of internal origin and imported bauxites. Red mud is stored entirely in dump type deposits. This paper presents the results of the mineralogical study (x-ray diffraction, scanning electronic microscopy, optical microscopy) and chemical analysis of different sorts of red mud. [ABSTRACT FROM AUTHOR]

This paper presents the results of multi-performance optimization model of the Bayer bauxite leaching process in aluminum production. Data was collected under the industrial conditions from alumina plant "Biroč" in Zvornik, Bosnia and Herzegovina. The leaching paramethers (temperature of leaching, leaching time and CaO supplement) were analzyed as influencing factors in multi-response optimization of process outputs (Al2O3 losses, Al2O3 overall losses, Na2O losses in autoclave sludge, as well as the utilization of Al2O3 from the leaching of the sludge). The Taguchi orthogonal array (L16'), the signal-tonoise ratio (S/N), and ANOVA are used in this study to optimize the considered process inputs in regard to four measured process outputs. Furthermore, all S/N values in optimization model were fuzzified to obtain single universal output measure, which was than tested by ANOVA to determine the optimal set of input factors that could lead to the better efficiency of disscused process. [ABSTRACT FROM AUTHOR]