Bayer Liquor Research Articles

Extraction and Removal of Lithium by Adsorption onto Resin Amberlyst35 from Bayer Liquor Before Seed Decomposition

Extraction and Removal of Lithium by Adsorption onto Resin Amberlyst35 from Bayer Liquor Before Seed Decomposition

Adsorption of Lithium onto Resin Retardion11A8 from Bayer Liquor before Seed Decomposition

Adsorption of Lithium onto Resin Retardion11A8 from Bayer Liquor before Seed Decomposition

Utilization of desilication products as efficient adsorbents for the removal of basic fuchsine

Desilication products (DSPs) are one of the main components of bauxite residue, which is currently discharged without further usage. The present study reports on the use of DSPs as adsorbents for basic fuchsine dye. Using artificial spent liquor, we synthesized not only neat DSP but also solids in the presence of various organics, to account for their likely occurrence during the Bayer process. The physico-chemical properties of all DSPs are similar, except for the specific surface area (SSA), which decreases as the organic content in the final product increases. Further, we compared the adsorption characteristics of DSP to those of Y-type faujasite (FAUY). Strikingly, both time-dependent adsorption measurements and adsorption isotherms showed that DSP, despite its 28-fold smaller SSA, binds 4–5 times more dye molecules. Computational modelling for sodalite (as a model for DSP) and FAUY indicates not only more favourable adsorbent-adsorbate interactions, but also more available free Si-OH sites for binding of fuchsine in the case of sodalite. Finally, we find that organic impurities present in the Bayer liquor do not alter the adsorption capacity of neat DSP to any significant degree; therefore, this adsorbent tolerates numerous organic contaminants without decreasing its affinity to the binding of fuchsine.

Ultrasonic-induced crystallization for efficient extraction of hazardous sodium oxalate with ultra-low alkali loss in alumina industry: From laboratory-scale to continuous pilot-scale

Since sodium oxalate (Na2C2O4) in Bayer liquor seriously threatens the sustainable development of the alumina (Al2O3) industry, efficient extraction of Na2C2O4 and reduction of alkali loss have received widespread attention. A new process for extracting Na2C2O4 from mother aluminate liquor by ultrasonic-induced crystallization (UIC) is established at laboratory scale. Due to the controlled sound field and cavitation effect, compared with conventional crystallization (CC) process, the UIC process increases the Na2C2O4 extraction rate from 61 % to 70 %, and reduces the alkali loss rate from 41 % to 19 %. Numerical simulation and sonochemiluminescence confirm that the cavitation effect is mainly concentrated near the axis and at the tip of the titanium alloy horn, and the average life of the cavitation bubble is maintained at 0.9 ms. Density functional theory (DFT) calculations, crystal structure observations and simulations show that the UIC process successfully promotes the development of Na2C2O4 from long strips to lamellar forms, maintaining the safety of Al2O3 production. Additionally, UIC process operates stably on continuous pilot-scale (CPSC) system, with the Na2C2O4 extraction rate and TOC emission rate remaining at around 50 % and 85 % respectively. The UIC method for extracting Na2C2O4 is expected to generate annual profits of $ 267.3 million for China, while also providing support for the innovation and application of ultra-low alkali loss in Al2O3 industry.

Cost-efficient removal of organics from Bayer liquor by tricalcium aluminate hexahydrate: Insights into the organic micelle and multilayer adsorption

The existence state and effective removal of organics from Bayer liquor have troubled the alumina industry for six decades. This study delved into the aggregation behavior and micellization of organics in Bayer liquor. Tricalcium aluminate hexahydrate (3CaO·Al2O3·6H2O, TCA) was then employed as a cost-effective adsorbent to remove organics by regulating the aggregation behavior of organics. Sodium dodecylsulfate (SDS), acting as a research object of organics, aggregated into inhomogeneous and large micelles (>3080.00 nm) with an extremely low critical micelle concentration (CMC) of 0.14 mmol·L−1 in the sodium aluminate solution (CNa2O = 2.42 mol·L−1, αK = 3.0, I ≥ 4.84 mol·L−1) at 298 K. Decreasing temperature facilitated the formation of these large micelles and the micellar size reached 2.20 μm in length. The solvated Ca2+ (Ca(OH)+) of TCA, acting as counterions with a content exceeding 11.97 wt%, initially induced the formation of micelles and then enlarged their size. Furthermore, these large micelles exhibited a preferential aggregation at the active concave of TCA. As a result, the interaction among inhomogeneous micelles, solvated Ca2+ (Ca(OH)+), and special active concave collectively contributed to the maximum organic carbon adsorption capacity of 32.46 mg·g−1 (equivalent to 64.92 mg·g−1 of SDS) at 298 K. These results open up new perspectives for understanding the existence state of the anionic organics in sodium aluminate solutions, as well as a cost-effective and eco-friendly approach to removing organics from Bayer liquor.

Application of clean oxidation technology using H2O2 for simultaneous removal of sulfur and organic substances in the Bayer process

The harmful effects of sulfur and organic substances pose constraints on the green and sustainable development of the Bayer process for alumina production. This research aims to develop a method that utilizes H2O2 to remove sulfur and organic substances during the digestion stage of bauxite, based on the mineralogical investigation of sulfur and organic substance. The extent of removal of S2− and total organic carbon reached 95.6% and 68.0%, respectively, under most suitable conditions of 12% H2O2 dosage, temperature of 533 K, and duration of 80 min. Based on thermodynamic calculations, it is suggested that S2− is oxidized to SO42−. Additionally, the free radical reaction mechanism of organic substances in H2O2 wet oxidation of Bayer liquor is proposed. The results confirm that this method does not introduce any impurities and does not have any impact on the digestion efficiency of alumina and the Bayer process.

A Review on the Zone Refining Process Technology toward Ultra‐Purification of Gallium for GaAs/GaN‐based Optoelectronic Device Applications

AbstractUltrapure gallium up to 99.9999%/ 99.99999% (6N/7N) purity level is a highly demanding material needed for the growth of gallium‐based group III–V semiconductor compounds and optoelectronic devices. However, general extraction of gallium from Bayer liquor contains high impurity content and ultra‐purification of the same cannot be accomplished by a single step. Thus, the purpose of this review is to assess various purification processes for the production of ultra‐pure gallium and to critically examine its applications in the optoelectronics industry. Through this research survey, it is found that zone refining of the zone melting process stands tall over other methods in purifying materials even up to 13N. Hence, scientists are adopting detailed mathematical models and simulation tools for designing unique zone refining systems for material purification. Current‐day technology even adopts intelligence methods such as machine learning, which sheds light on the importance of different zone refining parameters that influence the purification process. Here, the practical aspects of zone refining and how the feedback from the theoretical models or performance prediction through intelligence methods can be effectively incorporated into practice have also been emphasized

A Review of the Current State of Research on Gallium Recovery from Bayer Liquor

A Review of the Current State of Research on Gallium Recovery from Bayer Liquor

Zeolite–resin magnetic nanocomposite as an efficient adsorbent for separation of vanadium from industrial Bayer liquor

Zeolite–resin magnetic nanocomposite as an efficient adsorbent for separation of vanadium from industrial Bayer liquor

Combining ozone and ultrasound technology to remove S2− in Bayer liquor

High content sulfur (S2−) in Bayer liquor can increase alkali consumption, accelerate equipment corrosion, especially seriously affect alumina production. The removal of S2− in Bayer liquor is studied using ultrasonic enhanced ozone method, which significantly improves the removal efficiency. Results indicate that the best removal efficiency of 93.83 % is obtained with reaction duration of 20 min, oxygen flow rate of 80 L/h, ultrasonic power of 60 W and reaction temperature of 60 °C. The comparative analysis shows that the removal efficiency of S2− is 25.34 % higher than that of ozone (O3) system after introducing ultrasound (US), indicating that US accelerates the mass transfer process of O3 and increases the hydroxyl radicals (OH) content. For further explanation of the mechanism of US/O3 system, EPR and XPS spectra are applied to analyze the content of free radical and the form of sulfur in Bayer liquor, indicating that the content of free radical in US/O3 system is more than US and O3 systems, and all sulfur is converted to SO42− after full oxidation.

Enhancement of the precipitation extent of Al(OH)3 crystals in the Bayer process within a down-scaled tank

Depending on the size of the precipitation circuit equipment compared with other parts of the Bayer process and its long residence time, the precipitation stage could be the most significant step for producing alumina and directly influence the overall production efficiency. In the present study, a 1/100 downscaled precipitation tank of a real industrial Bayer tank has been constructed, and different experimental scenarios have been evaluated to find the optimal conditions for maximizing the precipitation extent of aluminum hydroxide. Since each of the considered parameters significantly affects precipitation extent, determining the most appropriate limit of each input parameter under examination constitutes optimal conditions for this investigation. The actual Bayer liquor from an Iranian bauxite mine has been used to mimic the industrial conditions. Some preliminary scenarios, including changes in stirring rate, seed concentration, and tank temperature have been tested and more effective strategies have been identified. According to the proposed optimal condition of the response surface method (RSM), controlling the condition at T = 50 °C, a stirring rate of 230 rpm, and a seed concentration of 327 g/L leads to an increase in the extent of precipitation between 46% and 53%.

Comparative study of artificial intelligence based multi‐modelling approach and optimization of photoreactor

AbstractThis study presents a generic methodology for modelling and optimizing a reactor with complex and poorly understood kinetics. Here, a photoreactor is considered which performs photodegradation of sodium oxalate salt in spent Bayer liquor. Multiple data‐driven modelling methods, including artificial neural networks (ANN), genetic programming (GP), hybrid genetic programming‐grey wolf optimization (GP‐GWO), and multi‐gene genetic programming (MGGP), were used to model the reactor's performance based on experimental data. The input parameters considered for modelling were initial solution pH, power of the lamp, total organic carbon, and catalyst loading. The models were evaluated based on their predictability, explainability, complexity, and adherence to the reactor's phenomenology. The MGGP model was found to be the most effective and was used to generate surface plots showing the parity between experimental results and model predictions. Additionally, the MGGP model was optimized using GWO to determine the process conditions that maximize the reaction rate.

New perspectives for bio-technical treatment of oxalate-containing waste streams from bauxite processing

Alumina is typically produced from bauxite ore using the Bayer process, in which the ore is mixed with alkaline liquor under elevated temperatures. Australian bauxite ore contains a wide range of organics, which detrimentally affect the Bayer process. Therefore, the removal of organic compounds from the alkaline Bayer process liquor is critical in maintaining process efficiency and alumina quality. Oxalate (C2O42−) is a key organic impurity in the Bayer process liquors that requires removal as it increases in concentration in the processing circuit as the Bayer liquor is continually recycled. Compared to conventional physiochemical or physical methods (e.g., chemical precipitation, wet-oxidation, liquor burning), microbial bioreactor treatment processes have the potential to be more economical and environmentally sustainable for oxalate removal. Some Australian alumina refineries have implemented full-scale bioreactors such as moving bed biofilm reactors (MBBRs) and aerobic suspended growth bioreactors (ASGB). While these bioreactors are robust and effective in removing oxalate, they have some limitations, such as the need for pre-acidification of influent and the loss of ammonia (nutrient) through volatilization. Therefore, this study aimed to provide an overview of the fundamentals and recent advances in biotechnical processes for the treatment of alkaline oxalate-containing liquor. Laboratory-scale studies on promising new biotreatment concepts, such as the use of bioelectrochemical systems to facilitate concurrent oxalate degradation and caustics recovery, as well as the utilization of nitrogen-fixing microorganisms to obviate the requirement for external nutrient dosage, are discussed. Perspectives for further research on oxalate-containing waste streams are also proposed.

Control of Sodium Oxalate Precipitation by Ammonium/Quaternary Ammonium Compounds in the Gibbsite Precipitation Stage of Bayer Liquor

Control of Sodium Oxalate Precipitation by Ammonium/Quaternary Ammonium Compounds in the Gibbsite Precipitation Stage of Bayer Liquor

The influence of sodium sulphate on sodium aluminosilicate solubility in Bayer liquor aiding the desilication process

The influence of Na2SO4 at chemical equilibrium in the NaOH-Al2O3-SiO2-Na2SO4-H2O system were studied in synthetic Bayer liquors. Sodium aluminosilicate, otherwise referred to as desilication product (DSP) in the alumina industry, was synthesised hydrothermally from kaolin used in a rotating bomb heater. Experiments spanned several days to reach equilibrium at 90 °C, 150 °C and 250 °C and employed Na2SO4 concentration ranging from 0 to 0.4 M. The SO42− incorporation into DSP was best modelled by the mathematical form of Langmuir-type isotherms, and reached maximum occupancy of 85%, primarily displacing OH−, and Al(OH)4− to a lesser degree. The presence of Na2SO4 enhanced desilication (measured by solution SiO2 concentration) by up to 80% compared to sulphate-free tests, with diminishing relative effect with increasing SO42− concentration. Approximate maximum sulphate cage occupancy and effect on desilication were achieved at a Na2SO4 concentration of 0.1 M. Solid residues contained Bayer (alumina)-type cancrinite, sulphate-type cancrinite (vishnevite), hydroxycancrinite, hydroxysodalite and amorphous material as determined by X-ray diffraction. The presence of sulphate led to different transformation pathways for DSP precipitated from kaolin. Sulphate-bearing DSPs exhibited rod-like morphology and presented enhanced thermal stability over their hydroxy counterparts. Valuable new data on the relationship between sulphate ion uptake, and the composition, structure and solubility of DSP are presented, and the results are suitable for the development of kinetic and thermodynamic models describing zeolite equilibria in alumina processing.

Investigating the formation of zeolitic compounds from dissolution of clays through vibrational spectroscopy

The dissolution of clays in alkaline media is one of the important pathways in the hydrothermal formation of zeolites; despite this it is not fully understood. In this work we investigate the dissolution of kaolinite, halloysite and metakaolin and the subsequent re-precipitation of zeolites via infrared spectroscopy. Specifically, the behaviour in Bayer synthetic liquor was focused on. It was found that the appearance of a broad H-bonding absorbance suggests dissolution for all these clays begins by ingress of OH− into the interlayer region. In addition, the calcined kaolinite (metakaolin) appears to reform surface or accessible Al-OH species as shown by the sharp peaks observed at ∼3620 and ∼3680 cm−1. All clay dissolution leads to observable silicate species in the solution at early times and water dominates at later times. The rate at which the clays dissolve was found to be in the order kaolinite < halloysite = calcined kaolinite. The dissolution of halloysite and kaolinite showed no subsequent zeolite Linde-type A (LTA) formation but dissolution of calcined kaolinite showed that desilication product formation followed an LTA > sodalite transformation pathway in caustic while this was not observed in Bayer liquor. Finally, infrared can be used to monitor the silicate in solution (provided samples have not aged and an appropriate control is used) as well as monitoring the solids formed through a peak ratio method. Having said this, LTA is harder to monitor than sodalite where other supporting evidence was required.

Removal of organic compounds from Bayer liquor by oxidation with sodium nitrate

Large amounts of organic-containing bauxite ores are used during alumina production. Here, based on sulfur removal by NaNO3 oxidation during actual production, we propose a method involving NaNO3 wet oxidation to remove organic matter during bauxite dissolution. The effects of different dosages of NaNO3, oxidation temperatures, and oxidation times on the organic carbon removal efficiency, sodium oxalate concentration, and sodium humate concentration were studied. The organic carbon removal efficiency was 85.2% under the most suitable conditions (5% NaNO3 and 13% CaO relative to the mass of bauxite; oxidation temperature of 260 °C; oxidation time of 60 min). The oxidation and removal of sodium humate were high, but those of sodium oxalate were poor. The red mud obtained under the optimal conditions was analyzed.

Use of O3 and O3/H2O2 for degradation of organic matter from Bayer liquor towards new resource management: Kinetic and mechanism

AbstractSince the quality of bauxite resources has decreased and the organic carbon content has increased, different approaches are explored to remove the organic matter in alumina production. Advanced oxidative processes (AOPs) represent a possibility since they are widely used as an alternative for treating wastewaters to degrade organic pollutant molecules and in hydrometallurgy processes. For this reason, the goal of the project was the ozonation of Bayer liquor for organic matter removal. The ozone concentration was evaluated over time, as well as the H2O2 concentration and temperature. Results showed that the total organic carbon (TOC) removal achieved 19% in the most optimized condition with a kinetic rate of 0.0157 h−1 –21.9 mg/L O3, 0.05 mol/L H2O2 at 80°C. The colour of the liquor changed from dark brown to white‐yellow, indicating that the size of the organic compounds had decreased. Also, 95.4% of degraded TOC formed CO2, and almost 50% of the organic matter was oxalate compounds. The energy required for ozone production versus removed organic matter demonstrated that the technique proposed might be technically and economically feasible to be applied in the Bayer process. The study demonstrates the application of AOP in an extremely alkaline condition.

Multilayer adsorption improving the organic removal by foam flotation from sodium aluminate solutions

Effective enrichment of organics by foam flotation will notably contribute to the removal of organics from the Bayer liquor. The present study shows that the removal efficiency increased with increasing concentration of sodium laurate (SL) and sodium stearate (SS). Over 29% SS removal with a concentration ratio of 2.92 was obtained from the Bayer liquor. The surface pressure increased with increasing spreading concentration, while the mean molecular area decreased. From the remarkable difference in the π-A isotherms of SS on the surface of sodium aluminate solution and water, a minimum molecular area of 2.39 Å2 occurred in the sodium aluminate solution, which was notably lower than 24.6 Å2 in water. Adding sodium palmitate (SP) into SS increased the minimum molecular area, while the addition of sodium oleate (SO) raised the maximum surface pressure. From Langmuir-Blodgett films, the micellar size of SS and SL increased with increasing spreading concentration. Adding SP and SO into SS enlarged the micellar size owing to the synergistic interaction between organics. As a result, the complicated interfacial structure, multilayer adsorption of micelles at the air/solution interface, and precipitation of aluminum hydroxide synergistically promoted the removal efficiency of organics from the sodium aluminate soluion.

Enhanced conversion mechanism of Al-goethite in gibbsitic bauxite under reductive Bayer digestion process

The conversion mechanism of Al-goethite under the action of different additives (lime or reductant for typical or reductive Bayer digestion) was investigated by thermodynamic calculation, XRD, and SEM−EDS. The results show that the formation of Fe-substituted hydrocalumite is crucial to converting Al-goethite to hematite during Bayer digestion by adding lime. However, the conversion proceeds more easily under the action of reductant due to the rapid formation of magnetite. Additionally, Bayer liquor composition significantly affects the product composition and also the conversion rate of Al-goethite. Compared to typical Bayer digestion with Al-goethite containing gibbsitic bauxite as raw material, the red mud yield of reductive Bayer digestion decreases from 39.02% to 31.19%, and the grade of TFe in red mud increases from 41.66% to 53.80%.