This study was focused to assess major and trace elements in bauxitic duricrusts from Ngaoundal and its surroundings in order to establish their mining interest. To this end, fieldworks, mineralogical and geochemical ...This study was focused to assess major and trace elements in bauxitic duricrusts from Ngaoundal and its surroundings in order to establish their mining interest. To this end, fieldworks, mineralogical and geochemical analyses were carried out. Four facies of duricrust were identified and characterized from the summit to the top of the slope of the Ngaoundal mountain: scoriaceous, pisolitic, nodular and massive. Mineralogical and geochemical analyses performed on 16 samples, revealed a significant concentration of Al<sub>2</sub>O<sub>3</sub> mainly in the scoriaceous facies (over 45% in grade), moderate in Fe<sub>2</sub>O<sub>3</sub> (averaging 23.69%) and SiO<sub>2</sub> (averaging 21.7%). Trace elements were generally low, excluding Cr (421 ppm on average), Zr (327 ppm on average and V (213 ppm on average). In addition, the limited quantities of alkalis (Na<sub>2</sub>O, K<sub>2</sub>O) and alkaline earths metals (MgO, CaO) coupled with the very high values of Chemical Index of Alteration (CIA) and Mineralogical Index of Alteration (MIA), (more than 99%) attest to the intense weathering of the studied materials. Allitization and monosiallitization constituted the crystallochemical phenomena that have led to the development of bauxitic minerals. More than 90% of gibbsite in scoriaceous facies, 52.21% - 76.01% of kaolinite in pisolitic facies and more than 40% of hematite in nodular facies were quantified. The relationships between the constitutive components indicated their interdependency during the bauxitization phenomenon. The mineralogical and geochemical properties highlighted the mining interest of the studied duricrusts to be valorized.展开更多
The differences in the competitive reactions of hydrogarnet and quicklime when reacting with titaniumcontaining and silicon-containing minerals during the Bayer digestion process were investigated.Thermodynamic analys...The differences in the competitive reactions of hydrogarnet and quicklime when reacting with titaniumcontaining and silicon-containing minerals during the Bayer digestion process were investigated.Thermodynamic analysis,artificial mineral experiments,and an evaluation of the digestion effect of natural diasporic bauxite were conducted.The results indicate that hydrogarnet shows a preferential reaction with anatase,and this preference becomes more pronounced as the silicon saturation coefficient increases.In contrast,quicklime participates in non-selective reactions with both anatase and desilication products(DSP).The preference of hydrogarnet for anatase significantly enhances the utilization efficiency of CaO in the high-temperature Bayer digestion process.展开更多
A new manufactured soil product (Turba) was produced using acidified bauxite residue into which 10% green waste compost had been incorporated. A laboratory/greenhouse experiment was carried out to determine if sand co...A new manufactured soil product (Turba) was produced using acidified bauxite residue into which 10% green waste compost had been incorporated. A laboratory/greenhouse experiment was carried out to determine if sand could be used as an ingredient or an amendment for Turba. Sand was added at rates of 0%, 5%, 10%, 25, 50% and 75% (w/w) in two different ways 1) by incorporating it into the Turba during its manufacture (IN) or 2) by mixing it with Turba aggregates after their manufacture (OUT). Incorporation of sand into Turba aggregates (IN) decreased the percentage of sample present as large aggregates (2 - 4 mm dia.) after crushing and sieving (<4 mm) and also reduced the stability of 2 - 4 mm dia. formed aggregates (to dry/wet sieving) and are therefore not recommended. In a 16-week greenhouse study, ryegrass shoot yields were greater in Turba than in sand [and decreased with increasing sand additions (OUT)] while root dry matter showed the opposite trend. The greater grass growth in Turba than sand was attributed to incipit water stress in plants grown in sand and this may have promoted greater allocation of assimilates to roots resulting in a greater root-to-top mass ratio. The much lower macroporosity in Turba coupled with the solid cemented nature of Turba aggregates resulted in production of thinner roots and therefore greater root length than in sand. Turba (manufactured from bauxite residue and compost added at 10% w/w) is a suitable medium for plant growth and there is no advantage in incorporating sand into, or with, the Turba aggregates.展开更多
As a pyrometallurgical process,circulating fluidized bed(CFB) roasting has good potential for application in desulfurization of high-sulfur bauxite.The gas-solid distribution and reaction during CFB roasting of high-s...As a pyrometallurgical process,circulating fluidized bed(CFB) roasting has good potential for application in desulfurization of high-sulfur bauxite.The gas-solid distribution and reaction during CFB roasting of high-sulfur bauxite were simulated using the computational particle fluid dynamics(CPFD) method.The effect of primary air flow velocity on particle velocity,particle volume distribution,furnace temperature distribution and pressure distribution were investigated.Under the condition of the same total flow of natural gas,the impact of the number of inlets on the desulfurization efficiency,atmosphere mass fraction distribution and temperature distribution in the furnace was further investigated.展开更多
To accurately identify the factors affecting the formation of stable aggregates in bauxite residue during the soil formation process,the comprehensive effects of a combined chemical-biological amelioration strategy in...To accurately identify the factors affecting the formation of stable aggregates in bauxite residue during the soil formation process,the comprehensive effects of a combined chemical-biological amelioration strategy including solid wastes and a functional microorganism on aggregate size distribution and its stability in bauxite residue were investigated during a 365-d simulation experiment.The results showed that the combined amelioration effectively reduced the saline alkalinity of bauxite residue,and markedly changed the contents of aggregate-associated chemical binding agents.Desulfurization gypsum and maize straw-Penicillium oxalicum(P.oxalicum)differentiated the formation of aggregates within different sizes.Maize straw-P.oxalicum stimulated the formation of water-stable macroaggregates with more durable erosion resistance by the wet-sieving and laser dynamic diffraction analysis.The Pearson correlation analysis showed that exchangeable polyvalent metal ions,pyrophosphate extractable Fe oxide,and organic carbon exhibited positive correlations with aggregate stability during the 365-d incubation.The findings in this study may provide data support and engineering practical reference for ecological restoration in the disposal areas.展开更多
Investment casting shell moulds are widely applied to cast alloys, but how to efficiently form a hierarchical porous structure inside the wall is an innovation and challenge. In this research, porous shell moulds with...Investment casting shell moulds are widely applied to cast alloys, but how to efficiently form a hierarchical porous structure inside the wall is an innovation and challenge. In this research, porous shell moulds with three infill patterns(rectilinear, grid, and honeycomb) were prepared using bauxite slurry and slurry extrusionbased additive manufacturing technology, and the effects of infill patterns on the properties were evaluated. The hierarchical pores inside the wall are composed of the macropores formed by infills and the micropores among bauxite particles. Different infill patterns result in changes in distribution and shape of pores, thereby affecting the properties of the shell moulds. The honeycomb pattern has more comprehensive advantages compared to the other two infill patterns. The samples prepared with the honeycomb pattern exhibit the highest bending strength(11.62 MPa) and porosity(41.6%), as well as good heat-transfer ability, with an average shrinkage rate within 2.0%. This work provides an attractive feasibility for fabricating shell moulds with hierarchical porous walls.展开更多
Bauxite mining will bring huge economic benefit,but it also faces the risk of environmental pollution.Metal pollution problem has been widely concerned in bauxite tailing areas.Biodiversity indices,metal concentration...Bauxite mining will bring huge economic benefit,but it also faces the risk of environmental pollution.Metal pollution problem has been widely concerned in bauxite tailing areas.Biodiversity indices,metal concentrations of moss crusts,and soil contamination indices in Wachangping bauxite tailing areas in Guizhou Province,China were measured and analyzed.In a total of 40 species belonging to 19 genera and 12 families of moss in the study areas,Ditrichum flexicaule(Schwaegr.)Hamp.(DF),Oxystegus cylindricus(Brid.)Hilp.(OC),and Ditrichum brevidens Nog.(DB)are the dominant moss crusts.Moss species diversity in different habitats has a certain regularity:waste residues area<waste rocks area<ore stockpile area<slope shrub area<shrub area by gutter<slope shrub herbaceous area.Sorenson diversity index(β)of moss species is influenced by microenvironment and substrate.Concentrations of Al,Mg,Ca,Fe,K,and Ti are the largest in DB(2,990 to 73,210 mg kg^(-1)),followed by those in DF(2,900 to 61,890 mg kg^(-1)),and are the smallest in OC(690 to 32,240 mg kg^(-1)),which show that the three moss crusts have different bioaccumulation capacities.Metal contents in underlying soils of moss crusts are higher than the background levels.Bioaccumulation factor(BAF)of Al,Mg,Ca,Fe,and K in three moss crusts are decreased in the following order:DB>DF>OC.Single factor pollution index(Ps)and Nemero comprehensive pollution index(Pc)of six metal are much greater than 3,and the index of geoaccumulation(Igeo)(1geo<5)reveals that the soil environment is at moderately to seriously contaminated levels.Principal components analysis(PCA)shows that there is no significant correlation between p H value,and metal contents(Al,Mg,Fe,K and Ti),soil temperature(ST)and metal contents(Al,Mg,Fe,K and Ti).Soil humidity(SH)is negatively correlated with metal contents(Al,Mg,Fe,K and Ti).These three environmental factors have little effect on the distribution of metal.Result also reflects that DB moss is readily able to both tolerate and accumulate metal,which makes it a suitable bioindicator of multiple metal contamination in Wachangping bauxite tailing areas.展开更多
Bauxite tailing(BT)slurry has been generated and accumulated in large quantities,posing a threat to the green and sustainable development of the alumina industry.The regression equation between the actual water conten...Bauxite tailing(BT)slurry has been generated and accumulated in large quantities,posing a threat to the green and sustainable development of the alumina industry.The regression equation between the actual water content and mud water separation rate was established to achieve efficient resource utilization,and the feasibility of foam lightweight soil(FLS)prepared from BT was investigated.The effects of industrial waste residues(fly ash and slag powder)on the properties of FLS were studied.Meanwhile,the micro-mechanisms were revealed by XRD,SEM-EDS,and TG-DSC.The results revealed that fly ash reduced the workability and compressive strength of FLS.Slag powder can significantly enhance the compressive strength of FLS,which increased by 18.60%-23.26%,17.07%-58.54% and 12.12%-52.12%,respectively.Besides,slag powder can improve the long-term water stability performance and enhance carbonation resistance.XRD and thermal analyses showed that adding fly ash decreased the hydration degree of FLS,leading to a decrease in the hydration products.Slag powder improved the pore structure and compacted the skeleton structure of FLS.This study would provide an effective way to realize the resource utilization of BT,fly ash,and slag powder,with certain socio-economic and environmental benefits.展开更多
The“upper coal and lower bauxite”resource distribution pattern is widespread in China,where mining of the overlying coal seam significantly alters the stress environment of the underlying bauxite layer.This study in...The“upper coal and lower bauxite”resource distribution pattern is widespread in China,where mining of the overlying coal seam significantly alters the stress environment of the underlying bauxite layer.This study investigates the stability of inclined bauxite pillars under the influence of stress redistribution caused by coal seam extraction.A theoretical model is developed to calculate the direction and magnitude of principal stresses in the inclined floor strata,and a pillar stability analysis model is established that considers the effect of principal stress rotation.The research employs a combination of theoretical analysis,physical modeling,numerical simulation,and field observation.Findings indicate that stress rotation is most pronounced at both ends of the coal seam goaf,with the maximum clockwise and counterclockwise rotation angles of 19°and-40°,respectively,observed in the bauxite layer.Inclined bauxite pillars are subjected to combined compressive and shear loading.Under such conditions,clockwise rotation of principal stress increases the shear-to-normal stress ratio,thereby reducing pillar stability.Pillars located beneath the coal wall are the first to fail due to stress concentration and principal stress rotation,which can trigger a cascade of instability among the adjacent pillars.The findings provide a theoretical basis and practical guidance for ensuring the safe co-mining of coal seams and bauxite resources.展开更多
Reaction behaviors of sulfur and iron compounds in sodium aluminate solutions were investigated. The results show that iron compounds can remarkably remove the S2 but cannot get rid of S2Oc2-, SO^2- and SO4^-2 in sodi...Reaction behaviors of sulfur and iron compounds in sodium aluminate solutions were investigated. The results show that iron compounds can remarkably remove the S2 but cannot get rid of S2Oc2-, SO^2- and SO4^-2 in sodium aluminate solutions. The removal efficiency of S^2- using ferrous compound and ferric compound can reach 86.10% and 92.70% respectively when the iron compounds were added with a molar ratio of 2：1 compared with the sulfur in liquors at 100℃. Moreover, several same compounds are formed in those two desulfurization processes with ferrous or ferric compounds, including erdite, hematite, amorphous ferrous sulfide, polymerized sulfur-iron compounds and ferric sulfate. The major difference between these two processes is that the erdite generated from ferrous compounds at the initial reaction stage will convert to a sodium-free product FeS2 at the subsequent stage.展开更多
The flotation of diaspore and three kinds of silicate minerals, including kaolinite, illite and pyrophyllite, using an organosilicon cationic surfactant (TAS101) as collector and starch as depressant was investigated....The flotation of diaspore and three kinds of silicate minerals, including kaolinite, illite and pyrophyllite, using an organosilicon cationic surfactant (TAS101) as collector and starch as depressant was investigated. The results show that both diaspore and aluminosilicate minerals float readily with organosilicon cationic collector TAS101 at pH values of 4 to 10. Starch has a strong depression effect for diaspore in the alkaline pH region but has little influence on the flotation of aluminosilicate minerals. It is possible to separate diaspore from aluminosilicate minerals using the organosilicon cationic collector and starch depressant. Further studies of bauxite ore flotation were also conducted, and the reverse flotation separation process was adopted. The concentrates with the mass ratio of Al2O3 to SiO2 of 9.58 and Al2O3 recovery of 83.34% are obtained from natural bauxite ore with the mass ratio of Al2O3 to SiO2 of 6.1 at pH value of 11 using the organosilicon cationic collector and starch depressant.展开更多
For the low-grade gibbsitic bauxite,the leaching rate of alumina is very low during the Bayer process.The acid leaching method is attracting more attention,and the hydrochloric acid leaching was developed rapidly.The ...For the low-grade gibbsitic bauxite,the leaching rate of alumina is very low during the Bayer process.The acid leaching method is attracting more attention,and the hydrochloric acid leaching was developed rapidly.The mineral composition and chemical composition were investigated by X-ray diffraction analysis and semi-quantitative analysis.The thermodynamics of leaching process was analyzed.The results show that the major minerals in the bauxite are gibbsite,secondly goethite and quartz,anatase and so on.The acid leaching reactions of the bauxite would be thermodynamically easy and completed.Under the conditions that ore granularity is less than-55 μm,the L/S ratio is 100：7,and the leaching temperature is 373-383 K,the leaching time is 120 min and the concentration of HCl is 10%,both the leaching rates of Al and Fe are over 95%.The main composition of leaching slag is SiO2 which is easy for comprehensive utilization.展开更多
The sulfur phase in high sulfur-containing bauxite was studied by an X-ray diffraction analysis and a chemistry quantitative analysis.The methods for the removal of different shaped sulfur were also discussed.The resu...The sulfur phase in high sulfur-containing bauxite was studied by an X-ray diffraction analysis and a chemistry quantitative analysis.The methods for the removal of different shaped sulfur were also discussed.The results show that sulfur phases in high sulfur-containing bauxites exist in the main form of sulfide sulfur （pyrite） or sulfate sulfur,and the main sulfur forms of bauxites from different regions are not the same.Through a combination of an X-ray diffraction analysis and a chemistry quantitative analysis,the sulfur phases of high sulfur-containing bauxite could be accurately investigated.Deciding the main sulfur form of high sulfur-containing bauxite could provide theoretical instruction for choosing methods for the removal of sulfur from bauxite,and an oxidizing-roasting process is an effective way to remove sulfide sulfur from high sulfur-containing bauxite,the content of S^2-in crude ore in the digestion liquor is above 1.7 g/L,but in the roasted ore digestion liquor,it is below 0.18 g/L.Using the sodium carbonate solution washing technology to wash bauxite can effectively remove sulfate sulfur,the content of the total sulfur in ore is lowered to below 0.2% and can meet the production requirements for the sulfur content.展开更多
Acoupled biharmonic spline and linear interpolation algorithm was proposed to create a three-dimensional smooth deposit model with minimal curvature containing grade and position data. To obtain the optimal technical ...Acoupled biharmonic spline and linear interpolation algorithm was proposed to create a three-dimensional smooth deposit model with minimal curvature containing grade and position data. To obtain the optimal technical parameters, such as cuttingheight and drum diameter, a virtual longwall mining procedure was modelled by simulating the actual fully mechanized longwall mining process. Based on the above work, a bauxite deposit in a longwall mining panel was modelled by scattered grade data from ores sampled on the entry wall. The deposit was then demarcated by industrial indexes and sliced according to the virtual longwallmining procedure. The results show that the proposed interpolation algorithm can depict the stratiform structure of bauxite depositsand that the uncovered bauxite deposit has high proportions of high-grade and rich ore. The ranges of optimal cutting height and drum diameters are 1.72-2.84 m and 1.42-1.72 m, respectively. Finally, an intellectualized longwall mining procedure was designed to guide the mining process with the lowest dilution and loss rates.展开更多
The effect of electrolyte on settling behavior of kaolinite was studied. Effects of hard water on selective flocculation of diasporic bauxite was tested and the measures were taken to eliminate the effects of Ca2＋ an...The effect of electrolyte on settling behavior of kaolinite was studied. Effects of hard water on selective flocculation of diasporic bauxite was tested and the measures were taken to eliminate the effects of Ca2＋ and Mg2＋ in hard water. The results indicated that, not only the concentration of electrolyte ions but also the ionic valence of the electrolyte ions affects the settling behavior of kaolinite; hard water significantly affects its selective flocculation owing to Ca2＋ and Mg2＋; general dispersants could not eliminate the effects of Ca2＋ and Mg2＋. Self-made softening agent in our lab could weaken or eliminate the effects of hard water on flocculation processes. The results of molecular dynamics simulation show that softening agent molecules could restrict Ca2＋ and prevent them from playing their roles, so as to eliminate the effects. The continuous pilot experiment results of bauxite flocculation were even better than those obtained in laboratory.展开更多
The Lower Carboniferous Jiujialu Formation bauxite deposits of northern Guizhou Province,China,are a Kazakhstan subtype of karst bauxite deposits.The provenance of the Jiujialu Formation has long been debated,with unc...The Lower Carboniferous Jiujialu Formation bauxite deposits of northern Guizhou Province,China,are a Kazakhstan subtype of karst bauxite deposits.The provenance of the Jiujialu Formation has long been debated,with uncertainty about the formation of the bauxite deposits.Here we report new geochemical data that indicate the affinity between the Lower-Middle Ordovician clastic rocks and argillaceous dolostones and the overlying Carboniferous bauxite deposits,all of which are characterized by high Al_(2)0_(3),K2_(O),and∑REE contents,flat post-Archean Australian shale(PAAS)-normalized REE patterns,and uniform immobile element ratios(TiO2/Al_(2)0_(3),Nb/TiO2,and Zr/TiO2).Their similar detrital zircon age distributions further indicate the link between the bauxite deposits and the clastic rocks and argillaceous dolostones.Zircon age spectra of clastic rocks of the Lower Silurian Hanchiatien Formation in northern Guizhou match those of the bauxite deposits,with a maximum age peak at-980 Ma and other secondary age peaks,suggesting these clastic rocks may represent the provenance of the bauxite deposits.The youngest detrital zircons(-445 Ma)occur only in the bauxite deposits and are probably sourced from K-bentonite beds of the Ordovician-Silurian tran-sition.Our analyses indicate that the source materials of the bauxite deposits in the Jiujialu Formation are of mixed provenance:Lower-Middle Ordovician aluminosilicate rocks and argillaceous dolostones of the underlying strata,and Lower Silurian clastic rocks and K-bentonite from adjacent areas.A comparison of Early Carboniferous bauxitic provenances in northern and central Guizhou indicates that paleotopography was the major factor controlling the provenance of these bauxite deposits.展开更多
To lower the cost of bauxite electrolysis desulfurization using NaOH solution as the supporting electrolyte, effects of electrolyte recycling on bauxite electrolysis desulfurization were investigated. The results in...To lower the cost of bauxite electrolysis desulfurization using NaOH solution as the supporting electrolyte, effects of electrolyte recycling on bauxite electrolysis desulfurization were investigated. The results indicate that electrode corrosion, cell voltage, the desulfurization rate and the pH value of the electrolyte have no obvious changes with the increase of cycle times. Additionally, there were some transitive valence S-containing ions in electrolyte after the electrolysis, such as SO3^2-,S2O3^2- . However, most of the sulfur in bauxite was eventually oxidized into SO4^2- into the electrolyte, and these S-containing ions did not affect the recycling utilization for electrolyte.展开更多
Reduction of the high alkalinity of bauxite residue is a key problem to solve to make it suitable for plant growth and comprehensive utilization. In this study, phosphogypsum, a waste product from the phosphate fertil...Reduction of the high alkalinity of bauxite residue is a key problem to solve to make it suitable for plant growth and comprehensive utilization. In this study, phosphogypsum, a waste product from the phosphate fertilizer industry, was used to drive the alkaline transformation of the bauxite residue. Under optimal water washing conditions(liquid/solid ratio of 2 mL/g, 30°C, 24 hr), the impact of quantity added, reaction time and reaction mechanism during phosphogypsum application were investigated. Phosphogypsum addition effectively lowered p H levels and reduced the soluble alkalinity by 92.2%. It was found that the concentration of soluble Na and Ca ions in the supernatant increased gradually, whilst the exchangeable Na+and Ca^(2+)in solid phase changed 112 mg/kg and 259 mg/kg, respectively. Ca^(2+)became the dominant element in the solid phase(phosphogypsum addition of 2%, liquid/solid ratio of 2 mL/g, 30°C, 12 hr). X-ray diffraction data indicated that cancrinite and hydrogarnet were the primary alkaline minerals. SEM images suggested that phosphogypsum could promote the formation of stable macroaggregates, whilst the content of Ca^(2+)increased from 5.6% to 18.2% and Na reduced from 6.8% to 2.4%. Treatment with phosphogypsum could significantly promote the transformation of alkalinity cations by neutralization, precipitation and replacement reactions.This research provided a feasible method to promote soil formation of bauxite residue by phosphogypsum amendment.展开更多
Bauxite residue is a highly alkaline byproduct which is routinely discarded at residue disposal areas. Improving soil formation process to revegetate the special degraded lands is a promising strategy for sustainable ...Bauxite residue is a highly alkaline byproduct which is routinely discarded at residue disposal areas. Improving soil formation process to revegetate the special degraded lands is a promising strategy for sustainable management of the refining industry. A laboratory incubation experiment was used to evaluate the effects of gypsum and vermicompost on stable aggregate formation of bauxite residue. Aggregate size distribution was quantified by fractal theory, whilst residue microstructure was determined by scanning electron microscopy and synchrotron-based X-ray micro-computed tomography. Amendments addition increased the content of macro-aggregates(> 250 μm) and enhanced aggregate stability of bauxite residue. Following gypsum and vermicompost addition, fractal dimension decreased from 2.84 to 2.77, which indicated a more homogeneous distribution of aggregate particles. Images from scanning electron microscopy and three-dimensional microstructure demonstrated that amendments stimulate the formation of improved structure in residue aggregates. Pore parameters including porosity, pore throat surface area, path length, and path tortuosity increased under amendment additions. Changes in aggregate size distribution and microstructure of bauxite residue indicated that additions of gypsum and vermicompost were beneficial to physical condition of bauxite residue which may enhance the ease of vegetation.展开更多
Bauxite residue is a highly alkaline material generated from the production of alumina in which bauxite is dissolved in caustic soda.Approximately 4.4 billion tons of bauxite residues are either stockpiled or landfill...Bauxite residue is a highly alkaline material generated from the production of alumina in which bauxite is dissolved in caustic soda.Approximately 4.4 billion tons of bauxite residues are either stockpiled or landfilled,creating environmental risks either from the generation of dust or migration of filtrates.High alkalinity is the critical factor restricting complete utilization of bauxite residues,whilst the application of alkaline regulation agents is costly and difficult to apply widely.For now,current industrial wastes,such as waste acid,ammonia nitrogen wastewater,waste gypsum and biomass,have become major problems restricting the development of the social economy.Regulation of bauxite residues alkalinity by industrial waste was proposed to achieve‘waste control by waste’with good economic and ecological benefits.This review will focus on the origin and transformation of alkalinity in bauxite residues using typical industrial waste.It will propose key research directions with an emphasis on alkaline regulation by industrial waste,whilst also providing a scientific reference point for their potential use as amendments to enhance soil formation and establish vegetation on bauxite residue disposal areas(BRDAs)following large-scale disposal.展开更多
文摘This study was focused to assess major and trace elements in bauxitic duricrusts from Ngaoundal and its surroundings in order to establish their mining interest. To this end, fieldworks, mineralogical and geochemical analyses were carried out. Four facies of duricrust were identified and characterized from the summit to the top of the slope of the Ngaoundal mountain: scoriaceous, pisolitic, nodular and massive. Mineralogical and geochemical analyses performed on 16 samples, revealed a significant concentration of Al<sub>2</sub>O<sub>3</sub> mainly in the scoriaceous facies (over 45% in grade), moderate in Fe<sub>2</sub>O<sub>3</sub> (averaging 23.69%) and SiO<sub>2</sub> (averaging 21.7%). Trace elements were generally low, excluding Cr (421 ppm on average), Zr (327 ppm on average and V (213 ppm on average). In addition, the limited quantities of alkalis (Na<sub>2</sub>O, K<sub>2</sub>O) and alkaline earths metals (MgO, CaO) coupled with the very high values of Chemical Index of Alteration (CIA) and Mineralogical Index of Alteration (MIA), (more than 99%) attest to the intense weathering of the studied materials. Allitization and monosiallitization constituted the crystallochemical phenomena that have led to the development of bauxitic minerals. More than 90% of gibbsite in scoriaceous facies, 52.21% - 76.01% of kaolinite in pisolitic facies and more than 40% of hematite in nodular facies were quantified. The relationships between the constitutive components indicated their interdependency during the bauxitization phenomenon. The mineralogical and geochemical properties highlighted the mining interest of the studied duricrusts to be valorized.
基金the financial support from the Natural Science Foundation of Hunan Province,China(No.2022JJ40616)。
文摘The differences in the competitive reactions of hydrogarnet and quicklime when reacting with titaniumcontaining and silicon-containing minerals during the Bayer digestion process were investigated.Thermodynamic analysis,artificial mineral experiments,and an evaluation of the digestion effect of natural diasporic bauxite were conducted.The results indicate that hydrogarnet shows a preferential reaction with anatase,and this preference becomes more pronounced as the silicon saturation coefficient increases.In contrast,quicklime participates in non-selective reactions with both anatase and desilication products(DSP).The preference of hydrogarnet for anatase significantly enhances the utilization efficiency of CaO in the high-temperature Bayer digestion process.
文摘A new manufactured soil product (Turba) was produced using acidified bauxite residue into which 10% green waste compost had been incorporated. A laboratory/greenhouse experiment was carried out to determine if sand could be used as an ingredient or an amendment for Turba. Sand was added at rates of 0%, 5%, 10%, 25, 50% and 75% (w/w) in two different ways 1) by incorporating it into the Turba during its manufacture (IN) or 2) by mixing it with Turba aggregates after their manufacture (OUT). Incorporation of sand into Turba aggregates (IN) decreased the percentage of sample present as large aggregates (2 - 4 mm dia.) after crushing and sieving (<4 mm) and also reduced the stability of 2 - 4 mm dia. formed aggregates (to dry/wet sieving) and are therefore not recommended. In a 16-week greenhouse study, ryegrass shoot yields were greater in Turba than in sand [and decreased with increasing sand additions (OUT)] while root dry matter showed the opposite trend. The greater grass growth in Turba than sand was attributed to incipit water stress in plants grown in sand and this may have promoted greater allocation of assimilates to roots resulting in a greater root-to-top mass ratio. The much lower macroporosity in Turba coupled with the solid cemented nature of Turba aggregates resulted in production of thinner roots and therefore greater root length than in sand. Turba (manufactured from bauxite residue and compost added at 10% w/w) is a suitable medium for plant growth and there is no advantage in incorporating sand into, or with, the Turba aggregates.
基金supported by the National Key Research and Development Program of China(2022YFC2904400)Guangxi Science and Technology Major Project(Gui Ke AA23023033)。
文摘As a pyrometallurgical process,circulating fluidized bed(CFB) roasting has good potential for application in desulfurization of high-sulfur bauxite.The gas-solid distribution and reaction during CFB roasting of high-sulfur bauxite were simulated using the computational particle fluid dynamics(CPFD) method.The effect of primary air flow velocity on particle velocity,particle volume distribution,furnace temperature distribution and pressure distribution were investigated.Under the condition of the same total flow of natural gas,the impact of the number of inlets on the desulfurization efficiency,atmosphere mass fraction distribution and temperature distribution in the furnace was further investigated.
基金Projects(42177391,42477437)supported by the National Natural Science Foundation of ChinaProject(2024RC3041)supported by the Science and Technology Innovation Program of Hunan Province,China+1 种基金Project(2023CXQD064)supported by the Innovation-Driven Research Programme of Central South University,ChinaProject(242102321124)supported by the Henan Provincal Science and Technology Research Project,China。
文摘To accurately identify the factors affecting the formation of stable aggregates in bauxite residue during the soil formation process,the comprehensive effects of a combined chemical-biological amelioration strategy including solid wastes and a functional microorganism on aggregate size distribution and its stability in bauxite residue were investigated during a 365-d simulation experiment.The results showed that the combined amelioration effectively reduced the saline alkalinity of bauxite residue,and markedly changed the contents of aggregate-associated chemical binding agents.Desulfurization gypsum and maize straw-Penicillium oxalicum(P.oxalicum)differentiated the formation of aggregates within different sizes.Maize straw-P.oxalicum stimulated the formation of water-stable macroaggregates with more durable erosion resistance by the wet-sieving and laser dynamic diffraction analysis.The Pearson correlation analysis showed that exchangeable polyvalent metal ions,pyrophosphate extractable Fe oxide,and organic carbon exhibited positive correlations with aggregate stability during the 365-d incubation.The findings in this study may provide data support and engineering practical reference for ecological restoration in the disposal areas.
基金financially supported by the National Natural Science Foundation of China (No. 52062029)the Key Science and Technology Project of Gansu Province (No. 18YF1GA064)the Natural Science Foundation of Gansu Provence (No. 25JRRA094)。
文摘Investment casting shell moulds are widely applied to cast alloys, but how to efficiently form a hierarchical porous structure inside the wall is an innovation and challenge. In this research, porous shell moulds with three infill patterns(rectilinear, grid, and honeycomb) were prepared using bauxite slurry and slurry extrusionbased additive manufacturing technology, and the effects of infill patterns on the properties were evaluated. The hierarchical pores inside the wall are composed of the macropores formed by infills and the micropores among bauxite particles. Different infill patterns result in changes in distribution and shape of pores, thereby affecting the properties of the shell moulds. The honeycomb pattern has more comprehensive advantages compared to the other two infill patterns. The samples prepared with the honeycomb pattern exhibit the highest bending strength(11.62 MPa) and porosity(41.6%), as well as good heat-transfer ability, with an average shrinkage rate within 2.0%. This work provides an attractive feasibility for fabricating shell moulds with hierarchical porous walls.
基金the National Natural Science Foundation of China(NSFC No.32360309)。
文摘Bauxite mining will bring huge economic benefit,but it also faces the risk of environmental pollution.Metal pollution problem has been widely concerned in bauxite tailing areas.Biodiversity indices,metal concentrations of moss crusts,and soil contamination indices in Wachangping bauxite tailing areas in Guizhou Province,China were measured and analyzed.In a total of 40 species belonging to 19 genera and 12 families of moss in the study areas,Ditrichum flexicaule(Schwaegr.)Hamp.(DF),Oxystegus cylindricus(Brid.)Hilp.(OC),and Ditrichum brevidens Nog.(DB)are the dominant moss crusts.Moss species diversity in different habitats has a certain regularity:waste residues area<waste rocks area<ore stockpile area<slope shrub area<shrub area by gutter<slope shrub herbaceous area.Sorenson diversity index(β)of moss species is influenced by microenvironment and substrate.Concentrations of Al,Mg,Ca,Fe,K,and Ti are the largest in DB(2,990 to 73,210 mg kg^(-1)),followed by those in DF(2,900 to 61,890 mg kg^(-1)),and are the smallest in OC(690 to 32,240 mg kg^(-1)),which show that the three moss crusts have different bioaccumulation capacities.Metal contents in underlying soils of moss crusts are higher than the background levels.Bioaccumulation factor(BAF)of Al,Mg,Ca,Fe,and K in three moss crusts are decreased in the following order:DB>DF>OC.Single factor pollution index(Ps)and Nemero comprehensive pollution index(Pc)of six metal are much greater than 3,and the index of geoaccumulation(Igeo)(1geo<5)reveals that the soil environment is at moderately to seriously contaminated levels.Principal components analysis(PCA)shows that there is no significant correlation between p H value,and metal contents(Al,Mg,Fe,K and Ti),soil temperature(ST)and metal contents(Al,Mg,Fe,K and Ti).Soil humidity(SH)is negatively correlated with metal contents(Al,Mg,Fe,K and Ti).These three environmental factors have little effect on the distribution of metal.Result also reflects that DB moss is readily able to both tolerate and accumulate metal,which makes it a suitable bioindicator of multiple metal contamination in Wachangping bauxite tailing areas.
基金Project(5206800)supported by the National Natural Science Foundation of ChinaProject(2024JJA160096)supported by the Natural Science Foundation of Guangxi Province,China。
文摘Bauxite tailing(BT)slurry has been generated and accumulated in large quantities,posing a threat to the green and sustainable development of the alumina industry.The regression equation between the actual water content and mud water separation rate was established to achieve efficient resource utilization,and the feasibility of foam lightweight soil(FLS)prepared from BT was investigated.The effects of industrial waste residues(fly ash and slag powder)on the properties of FLS were studied.Meanwhile,the micro-mechanisms were revealed by XRD,SEM-EDS,and TG-DSC.The results revealed that fly ash reduced the workability and compressive strength of FLS.Slag powder can significantly enhance the compressive strength of FLS,which increased by 18.60%-23.26%,17.07%-58.54% and 12.12%-52.12%,respectively.Besides,slag powder can improve the long-term water stability performance and enhance carbonation resistance.XRD and thermal analyses showed that adding fly ash decreased the hydration degree of FLS,leading to a decrease in the hydration products.Slag powder improved the pore structure and compacted the skeleton structure of FLS.This study would provide an effective way to realize the resource utilization of BT,fly ash,and slag powder,with certain socio-economic and environmental benefits.
基金Project(2021YFC2902101)supported by the National Key Research and Development Program of ChinaProjects(42271139,52174135)supported by the National Natural Science Foundation of China。
文摘The“upper coal and lower bauxite”resource distribution pattern is widespread in China,where mining of the overlying coal seam significantly alters the stress environment of the underlying bauxite layer.This study investigates the stability of inclined bauxite pillars under the influence of stress redistribution caused by coal seam extraction.A theoretical model is developed to calculate the direction and magnitude of principal stresses in the inclined floor strata,and a pillar stability analysis model is established that considers the effect of principal stress rotation.The research employs a combination of theoretical analysis,physical modeling,numerical simulation,and field observation.Findings indicate that stress rotation is most pronounced at both ends of the coal seam goaf,with the maximum clockwise and counterclockwise rotation angles of 19°and-40°,respectively,observed in the bauxite layer.Inclined bauxite pillars are subjected to combined compressive and shear loading.Under such conditions,clockwise rotation of principal stress increases the shear-to-normal stress ratio,thereby reducing pillar stability.Pillars located beneath the coal wall are the first to fail due to stress concentration and principal stress rotation,which can trigger a cascade of instability among the adjacent pillars.The findings provide a theoretical basis and practical guidance for ensuring the safe co-mining of coal seams and bauxite resources.
基金Project(51374239)supported by the National Natural Science Foundation of China
文摘Reaction behaviors of sulfur and iron compounds in sodium aluminate solutions were investigated. The results show that iron compounds can remarkably remove the S2 but cannot get rid of S2Oc2-, SO^2- and SO4^-2 in sodium aluminate solutions. The removal efficiency of S^2- using ferrous compound and ferric compound can reach 86.10% and 92.70% respectively when the iron compounds were added with a molar ratio of 2：1 compared with the sulfur in liquors at 100℃. Moreover, several same compounds are formed in those two desulfurization processes with ferrous or ferric compounds, including erdite, hematite, amorphous ferrous sulfide, polymerized sulfur-iron compounds and ferric sulfate. The major difference between these two processes is that the erdite generated from ferrous compounds at the initial reaction stage will convert to a sodium-free product FeS2 at the subsequent stage.
基金Project(51304085)supported by the National Natural Science Foundation of ChinaProject(GJJ12363)supported by the Education Department of Jiangxi Province,ChinaProject(20142BAB216021)supported by the Natural Science Foundation of Jiangxi Province,China
文摘The flotation of diaspore and three kinds of silicate minerals, including kaolinite, illite and pyrophyllite, using an organosilicon cationic surfactant (TAS101) as collector and starch as depressant was investigated. The results show that both diaspore and aluminosilicate minerals float readily with organosilicon cationic collector TAS101 at pH values of 4 to 10. Starch has a strong depression effect for diaspore in the alkaline pH region but has little influence on the flotation of aluminosilicate minerals. It is possible to separate diaspore from aluminosilicate minerals using the organosilicon cationic collector and starch depressant. Further studies of bauxite ore flotation were also conducted, and the reverse flotation separation process was adopted. The concentrates with the mass ratio of Al2O3 to SiO2 of 9.58 and Al2O3 recovery of 83.34% are obtained from natural bauxite ore with the mass ratio of Al2O3 to SiO2 of 6.1 at pH value of 11 using the organosilicon cationic collector and starch depressant.
基金Projects(50974035,51074047,51004033) supported by the National Natural Science Foundation of ChinaProject(2008BAB34B01) supported by the National Science and Technology Pillar Program of China during the Eleventh Five-Year Plan Period+1 种基金Project (N100302005) supported by the National Higher-education Institution General Research and Development Funding,ChinaProject (2010AA03A405) supported by the Hi-tech Research and Development Program of China
文摘For the low-grade gibbsitic bauxite,the leaching rate of alumina is very low during the Bayer process.The acid leaching method is attracting more attention,and the hydrochloric acid leaching was developed rapidly.The mineral composition and chemical composition were investigated by X-ray diffraction analysis and semi-quantitative analysis.The thermodynamics of leaching process was analyzed.The results show that the major minerals in the bauxite are gibbsite,secondly goethite and quartz,anatase and so on.The acid leaching reactions of the bauxite would be thermodynamically easy and completed.Under the conditions that ore granularity is less than-55 μm,the L/S ratio is 100：7,and the leaching temperature is 373-383 K,the leaching time is 120 min and the concentration of HCl is 10%,both the leaching rates of Al and Fe are over 95%.The main composition of leaching slag is SiO2 which is easy for comprehensive utilization.
基金Project(20971041) supported by the National Natural Science Foundation of ChinaProject(09B032) supported by Scientific Research Fund of Hunan Provincial Education Department,China
文摘The sulfur phase in high sulfur-containing bauxite was studied by an X-ray diffraction analysis and a chemistry quantitative analysis.The methods for the removal of different shaped sulfur were also discussed.The results show that sulfur phases in high sulfur-containing bauxites exist in the main form of sulfide sulfur （pyrite） or sulfate sulfur,and the main sulfur forms of bauxites from different regions are not the same.Through a combination of an X-ray diffraction analysis and a chemistry quantitative analysis,the sulfur phases of high sulfur-containing bauxite could be accurately investigated.Deciding the main sulfur form of high sulfur-containing bauxite could provide theoretical instruction for choosing methods for the removal of sulfur from bauxite,and an oxidizing-roasting process is an effective way to remove sulfide sulfur from high sulfur-containing bauxite,the content of S^2-in crude ore in the digestion liquor is above 1.7 g/L,but in the roasted ore digestion liquor,it is below 0.18 g/L.Using the sodium carbonate solution washing technology to wash bauxite can effectively remove sulfate sulfur,the content of the total sulfur in ore is lowered to below 0.2% and can meet the production requirements for the sulfur content.
基金Project(11472311)supported by the National Natural Science Foundation of ChinaProject(2015CX005)supported by the Innovation Driven Plan of Central South University of ChinaProject(2015zzts083)supported by the Fundamental Research Funds for the Central Universities of Central South University,China
文摘Acoupled biharmonic spline and linear interpolation algorithm was proposed to create a three-dimensional smooth deposit model with minimal curvature containing grade and position data. To obtain the optimal technical parameters, such as cuttingheight and drum diameter, a virtual longwall mining procedure was modelled by simulating the actual fully mechanized longwall mining process. Based on the above work, a bauxite deposit in a longwall mining panel was modelled by scattered grade data from ores sampled on the entry wall. The deposit was then demarcated by industrial indexes and sliced according to the virtual longwallmining procedure. The results show that the proposed interpolation algorithm can depict the stratiform structure of bauxite depositsand that the uncovered bauxite deposit has high proportions of high-grade and rich ore. The ranges of optimal cutting height and drum diameters are 1.72-2.84 m and 1.42-1.72 m, respectively. Finally, an intellectualized longwall mining procedure was designed to guide the mining process with the lowest dilution and loss rates.
基金Project (2005CB623701) supported by the National Basic Research Program of China
文摘The effect of electrolyte on settling behavior of kaolinite was studied. Effects of hard water on selective flocculation of diasporic bauxite was tested and the measures were taken to eliminate the effects of Ca2＋ and Mg2＋ in hard water. The results indicated that, not only the concentration of electrolyte ions but also the ionic valence of the electrolyte ions affects the settling behavior of kaolinite; hard water significantly affects its selective flocculation owing to Ca2＋ and Mg2＋; general dispersants could not eliminate the effects of Ca2＋ and Mg2＋. Self-made softening agent in our lab could weaken or eliminate the effects of hard water on flocculation processes. The results of molecular dynamics simulation show that softening agent molecules could restrict Ca2＋ and prevent them from playing their roles, so as to eliminate the effects. The continuous pilot experiment results of bauxite flocculation were even better than those obtained in laboratory.
基金This study was supported by the Natural Science Foundation of China(Nos.U1812402,41802116)Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(Nos.CUG170684,CUGQY1908).
文摘The Lower Carboniferous Jiujialu Formation bauxite deposits of northern Guizhou Province,China,are a Kazakhstan subtype of karst bauxite deposits.The provenance of the Jiujialu Formation has long been debated,with uncertainty about the formation of the bauxite deposits.Here we report new geochemical data that indicate the affinity between the Lower-Middle Ordovician clastic rocks and argillaceous dolostones and the overlying Carboniferous bauxite deposits,all of which are characterized by high Al_(2)0_(3),K2_(O),and∑REE contents,flat post-Archean Australian shale(PAAS)-normalized REE patterns,and uniform immobile element ratios(TiO2/Al_(2)0_(3),Nb/TiO2,and Zr/TiO2).Their similar detrital zircon age distributions further indicate the link between the bauxite deposits and the clastic rocks and argillaceous dolostones.Zircon age spectra of clastic rocks of the Lower Silurian Hanchiatien Formation in northern Guizhou match those of the bauxite deposits,with a maximum age peak at-980 Ma and other secondary age peaks,suggesting these clastic rocks may represent the provenance of the bauxite deposits.The youngest detrital zircons(-445 Ma)occur only in the bauxite deposits and are probably sourced from K-bentonite beds of the Ordovician-Silurian tran-sition.Our analyses indicate that the source materials of the bauxite deposits in the Jiujialu Formation are of mixed provenance:Lower-Middle Ordovician aluminosilicate rocks and argillaceous dolostones of the underlying strata,and Lower Silurian clastic rocks and K-bentonite from adjacent areas.A comparison of Early Carboniferous bauxitic provenances in northern and central Guizhou indicates that paleotopography was the major factor controlling the provenance of these bauxite deposits.
基金Projects(51004090,51474198)supported by the National Natural Science Foundation of ChinaProject(KF13-03)supported by State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingProject(2015036)supported by Youth Innovation Promotion Association,Chinese Academy of Sciences
文摘To lower the cost of bauxite electrolysis desulfurization using NaOH solution as the supporting electrolyte, effects of electrolyte recycling on bauxite electrolysis desulfurization were investigated. The results indicate that electrode corrosion, cell voltage, the desulfurization rate and the pH value of the electrolyte have no obvious changes with the increase of cycle times. Additionally, there were some transitive valence S-containing ions in electrolyte after the electrolysis, such as SO3^2-,S2O3^2- . However, most of the sulfur in bauxite was eventually oxidized into SO4^2- into the electrolyte, and these S-containing ions did not affect the recycling utilization for electrolyte.
基金supported by the National Natural Science Foundation of China(Nos.41701587 and 41371475)the Environmental Protection's Special Scientific Research for Chinese Public Welfare Industry(No.201509048)
文摘Reduction of the high alkalinity of bauxite residue is a key problem to solve to make it suitable for plant growth and comprehensive utilization. In this study, phosphogypsum, a waste product from the phosphate fertilizer industry, was used to drive the alkaline transformation of the bauxite residue. Under optimal water washing conditions(liquid/solid ratio of 2 mL/g, 30°C, 24 hr), the impact of quantity added, reaction time and reaction mechanism during phosphogypsum application were investigated. Phosphogypsum addition effectively lowered p H levels and reduced the soluble alkalinity by 92.2%. It was found that the concentration of soluble Na and Ca ions in the supernatant increased gradually, whilst the exchangeable Na+and Ca^(2+)in solid phase changed 112 mg/kg and 259 mg/kg, respectively. Ca^(2+)became the dominant element in the solid phase(phosphogypsum addition of 2%, liquid/solid ratio of 2 mL/g, 30°C, 12 hr). X-ray diffraction data indicated that cancrinite and hydrogarnet were the primary alkaline minerals. SEM images suggested that phosphogypsum could promote the formation of stable macroaggregates, whilst the content of Ca^(2+)increased from 5.6% to 18.2% and Na reduced from 6.8% to 2.4%. Treatment with phosphogypsum could significantly promote the transformation of alkalinity cations by neutralization, precipitation and replacement reactions.This research provided a feasible method to promote soil formation of bauxite residue by phosphogypsum amendment.
基金supported by the National Natural Science Foundation of China (No. 41701587)
文摘Bauxite residue is a highly alkaline byproduct which is routinely discarded at residue disposal areas. Improving soil formation process to revegetate the special degraded lands is a promising strategy for sustainable management of the refining industry. A laboratory incubation experiment was used to evaluate the effects of gypsum and vermicompost on stable aggregate formation of bauxite residue. Aggregate size distribution was quantified by fractal theory, whilst residue microstructure was determined by scanning electron microscopy and synchrotron-based X-ray micro-computed tomography. Amendments addition increased the content of macro-aggregates(> 250 μm) and enhanced aggregate stability of bauxite residue. Following gypsum and vermicompost addition, fractal dimension decreased from 2.84 to 2.77, which indicated a more homogeneous distribution of aggregate particles. Images from scanning electron microscopy and three-dimensional microstructure demonstrated that amendments stimulate the formation of improved structure in residue aggregates. Pore parameters including porosity, pore throat surface area, path length, and path tortuosity increased under amendment additions. Changes in aggregate size distribution and microstructure of bauxite residue indicated that additions of gypsum and vermicompost were beneficial to physical condition of bauxite residue which may enhance the ease of vegetation.
基金Projects(41877551,41842020)supported by the National Natural Science Foundation of ChinaProject(201509048)supported by the Environmental Protection’s Special Scientific Research for Chinese Public Welfare Industry
文摘Bauxite residue is a highly alkaline material generated from the production of alumina in which bauxite is dissolved in caustic soda.Approximately 4.4 billion tons of bauxite residues are either stockpiled or landfilled,creating environmental risks either from the generation of dust or migration of filtrates.High alkalinity is the critical factor restricting complete utilization of bauxite residues,whilst the application of alkaline regulation agents is costly and difficult to apply widely.For now,current industrial wastes,such as waste acid,ammonia nitrogen wastewater,waste gypsum and biomass,have become major problems restricting the development of the social economy.Regulation of bauxite residues alkalinity by industrial waste was proposed to achieve‘waste control by waste’with good economic and ecological benefits.This review will focus on the origin and transformation of alkalinity in bauxite residues using typical industrial waste.It will propose key research directions with an emphasis on alkaline regulation by industrial waste,whilst also providing a scientific reference point for their potential use as amendments to enhance soil formation and establish vegetation on bauxite residue disposal areas(BRDAs)following large-scale disposal.
