Bauxite Mining Research Articles

A Statistical Model for Estimating Shear Undrained Strength in Bauxite Mining Tailings Based on in situ Tests

A Statistical Model for Estimating Shear Undrained Strength in Bauxite Mining Tailings Based on in situ Tests

Isolation and characterization of potential indigenous bacteria from the former bauxite mining area for heavy metal reduction

Abstract. Amelia T, Liliasari, Kusnadi, Aditiawati P. 2023. Isolation and characterization of potential indigenous bacteria from the former bauxite mining area for heavy metal reduction. Biodiversitas 24: 5096-5104. This study aimed to isolate, identify, and characterize some indigenous bacterial strains from the former bauxite mining area of Tanjungpinang, Bintan Island, Indonesia. Furthermore, this study focused on evaluating the potential of these bacteria for reducing the heavy metals lead (Pb) and chromium (Cr). The measurements of heavy metal concentrations at four sampling points, collection of soil samples as a bacteria source, and laboratory assessments for bio-removal capabilities were all conducted. Screening experiments were performed to identify bacterial strains resistant to heavy metal, using basic growth media such as Nutrient Agar (NA) and Nutrient Broth (NB) enriched with 100 ppm Pb and Cr metals. The reduction of heavy metal was analyzed with atomic absorption spectrophotometry (AAS), while the bacteria species were determined using MALDI TOF-MS. A modified version of the Kirby Bauer method was employed for toxicity reduction testing. Two bacterial strains were identified as Pb and Cr reducers and demonstrated resistance to both metals. Based on a 99.9% similarity value, the isolates were identified as Bacillus altitudinis (Isolate A) and Klebsiella pneumoniae (Isolate B), reducing Pb by approximately 72.7% and 34.5%, and Cr by 87.4% and 86.2%, respectively. The results indicated reduced toxicity in the metal-enriched media, with bacterial growth following three hours of incubation but no toxicity after 21 hours.

Viability of Bauxite Deposits from Catalonia (Spain) for Ceramic Applications

This study provides a characterization of materials from wastes and outcrops of two inactive bauxite mines located close to Sant Joan de Mediona and Peramola, Spain. Mineralogy was determined via powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Thermal properties were measured via differential thermal analysis–thermogravimetry (DTA-TG) and gresification tests. The crystalline phases are medium-high crystalline kaolinite and variable amounts of illite, quartz, calcite, boehmite, hematite and rutile/anatase. DTA show two endothermic peaks produced by the dehydroxylation of minerals: the first peak, at 530–538 °C, belongs to boehmite; the second peak, at 535–568 °C, corresponds to kaolinite. An exothermic peak at 950–978 °C is associated with mullite crystallization. The optimal sintering temperatures obtained from the gresification curves (firing shrinkage and water absorption) were 970 °C for carbonate-poor, illite-rich clays; 1100 °C for illite- and carbonate-poor samples; and near 1190 °C for carbonate-rich materials. The carbonate-poor samples fired at 1300 °C contain sillimanite and mullite, and the carbonate-rich materials are rich in gehlenite, anorthite, and hedenbergite. The mineralogy of these materials is sufficient to obtain ceramic materials with suitable properties, but not their low plasticity. They could be used in the formulation of bricks or as part of mixtures to produce refractory ceramics.

Assessment of plant ecological variability and heavy metal accumulation potential in naturally growing plant species of Pakhar bauxite mine site, Jharkhand, India

Abandoned bauxite mine (ABM) soil generally contains an unacceptable number of heavy metals (HMs), causing several ecological and environmental issues. The present study was conducted with a similar objective to assess the HM accumulation potential of the naturally growing plant species from Pakhar ABM site. Vegetation communities were studied using quadrat methods for plant species at both ABM and the control site (near the ABM site). A total of 21 (9 at the ABM site and 12 at the control site) plant species were recorded in the present study belonging to 10 families. Vegetation study revealed that the dominant plant species were Ammophila arenaria and Lantana camara at ABM site and Lantana camara at the control site. The concentration of HMs in soil at the ABM site, were 66180.00 mg kg−1 Al, 62.20 mg kg−1 Cr, 22.60 mg kg−1 Cu, 346800.00 mg kg−1 Fe, 780.80 mg kg−1 Mn, and 39.80 mg kg−1 Zn while in the soil of site located nearby taken as the control showed 56500.00 mg kg−1 Al, 4.40 mg kg−1 Cu, 51120.00 mg kg−1 Fe, 58.20 mg kg−1 Mn, 13.00 mg kg−1 Zn. Ammophila arenaria, Miscanthus sinensis, Acacia drepanolobium and Rumex pulcher exhibited the highest metal accumulation at the ABM site, while Ocimum campechianum, Lantana camara, Panicum virgatum L., Euphorbia hirta and Holcus lanatus, Cerastium glomeratum thuill and Shorea robusta exhibited the highest metal accumulation at control site. Plant Lantana camara showed considerable TF values for Pb, Al and Fe, from the ABM soil while Shorea robusta showed high TF values for Al, Cu, Zn, and Fe from the control soil. The BAF for Cu, Mn and Zn from ABM soil were observed in Acacia drepanolobium whereas Cerastium glomeratum thuill exhibited maximum BAF values for Zn and Cu from control soil.

Investigation of Elemental Deposition in Lamdong Province (Vietnam) by the Moss Biomonitoring Method and Neutron Activation Analysis

The results of an investigation of heavy metal air pollution in Lamdong province (Vietnam) using the moss biomonitoring method are presented in this paper. Barbula Indica moss samples were collected at 30 different locations in Dalat and Baoloc, two major cities of Lamdong province. The concentrations of 10 heavy metal and metalloid elements, Sc, V, Cr, Mn, Fe, Co, Zn, As, Hf, and Ta in the collected moss samples, were determined by the neutron activation analysis method using the nuclear reactor at the Nuclear Research Institute in Dalat. The results show that the air in Lamdong province may be polluted by Mn and is moderately polluted by Sc, V, Cr, Fe, Co, Zn, As, Hf and Ta. The main sources of heavy metal pollution in the Lamdong atmosphere may be soil dust, traffic emissions, industry, bauxite mining and refining, chemical fertilizers and pesticides, and combustion of coal and oil. By comparing heavy element concentrations in the moss from Lamdong with that of Hanoi, Thainguyen, and several European countries, it is found that heavy metal air pollution in Lamdong is much lower than in Hanoi and Thainguyen and much higher than in the European countries.

Reaction Behavior of Kaolinite in Sulfur-Bearing Sodium Aluminate Solution under the Simulated Bayer Process

Over a billion tons of high-sulfur bauxite has not been utilized effectively currently in China, because the pyrite existing in the bauxite poses a range of hazards during the Bayer process. A novel idea was proposed to remove sulfur by the silicon-containing minerals in bauxite reacting with sulfur species in sodium aluminate solution to form sulfur-bearing desilication products (SDSP) for discharge with the red mud in the Bayer process. This study investigated the reaction behavior between kaolinite and different sulfur-containing ions under the simulated Bayer process conditions, elucidating the desulfurization rate variation and formation mechanism of SDSPs. The thermodynamic calculations suggest that the reaction between kaolinite and sulfur-bearing sodium aluminate solution to form SDSPs can occur spontaneously. The experimental results demonstrated that various SDSPs can be produced through the reaction of kaolinite and sulfur-containing ions in sodium aluminate solution during the simulated Bayer process, resulting in various desulfurization efficiencies, while the desulfurization process will not result in additional alkali consumption. Increasing the kaolinite dosage, extending the reaction time, and elevating the reaction temperature all contribute positively to enhancing desulfurization efficiency. Kaolinite reacted with S2O32− in sodium aluminate solution to generate Na8Al6Si6O24S2O3·2H2O, achieving a desulfurization rate exceeding 90% under optimized conditions. Under the simulated Bayer digestion process conditions at elevated temperature, the desulfurization rates of kaolinite ranked in ascending order as S2− < SO32− < SO42− < S2O32−. Kaolinite reacted with SO42− and S2O32− to form cancrinite type SDSPs, and a superior desulfurization rate can be achieved. This work can provide a theoretical foundation and technological support for the efficient utilization of high-sulfur bauxite by the Bayer process.

Impact assessment of Guinea mining on air pollution in bauxite mining

Impact assessment of Guinea mining on air pollution in bauxite mining

Contribution to the Study of Water Pollution in the Nunez River estuary, (Republic of Guinea)

Bauxite mining offers an important livelihood strategy, a source of economic and social development relevant to countries with this natural wealth. It emerges, from the observations and extensive bibliographical reviews, that this exploitation has direct impacts on estuarine ecosystems through the establishment of ports and mining industries, hence our research theme "Contribution to the study of the impacts of industrial activities on the estuarine ecosystem of the Nunez River" In addition, the observation on the ground tells us that despite the efforts made by the authorities through the competent institutions and the investors, reducing the environmental impacts generated by this mining operation often has problems and insufficient capacity to deal with them, as revealed by our study conducted on the Nunez estuary. The hypothesis of this theme can be summarized as follows: The negative effects of the major pollutants of the Nunez River estuary due to the installation of industrial units, associated with the impacts related to climate change in the locality contribute to the dysfunction of the estuary, in turn to the reduction of opportunities and ecosystem services offered by the Nunez River. Nevertheless, given the high variability of the recorded values of the physicochemical parameters of the estuarine waters (temperature, pH, electrical conductivity, turbidity, salinity, dissolved oxygen, nitrate, nitrite, dissolved solids, suspended solids and phosphate) it seemed necessary to study them. Eleven sampling sites served as a study framework, the CERE/UGANC laboratory, as an analytical framework. Keywords: Industrial activities, estuarine ecosystems, environmental impacts, pollution.

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%.

Extraction of lithium as lithium phosphate from bauxite mine tailings via mixed acid leaching and chemical precipitation

Phosphate can be used to facilitate the concentration and precipitation of lithium from low-concentration solutions. In this study, a novel process has been developed to extract lithium as lithium phosphate from bauxite mine tailings, which includes: 1) leaching with mixed acid (H3PO4 + H2SO4), 2) leachate neutralization, and 3) Li3PO4 preparation. Mixed acid was used to effectively leach lithium (Li) without roasting pretreatment, the Li leaching rate can be up to 96.67%. Subsequently, NH3·H2O and H2O2 were used to separate Al and Fe from the leachate by chemical precipitation. After investigating the effects of the temperature, NH3·H2O concentration, and the dilution ratios of leachate and gel solution on the Li loss rate, we propose that the optimal conditions are: zero leachate dilution ratio, 45℃ temperature, 6 mol·L-1 NH3·H2O concentration, and a gel solution dilution ratio of one, which gives a 28.22% Li loss rate. In our experiment, lithium in the mother liquor was precipitated as Li3PO4 with Na2CO3. Our results provide a simple and effective route to extract lithium from low-Li resources.

Assessing impacts of mining on provisioning ecosystem services in a culturally diverse landscape of Western Cape York, Australia

ContextMitigating the impacts of mining on biodiversity and ecosystem services (ES) is critical for maintaining human wellbeing in mineral-rich landscapes. Environmental assessments and mitigation plans almost always consider impacts on biodiversity, yet few extend to the individual ES valued by local communities. As a result, mine site management, rehabilitation, and compensation activities may fail to prevent the loss of some ES, particularly those valued by remote Indigenous communities.ObjectivesWe seek to understand: (1) which ecosystems contain culturally significant plant species and where they are located in respect to mining areas; (2) whether areas containing large numbers of culturally significant plant species are protected under current environmental management plans focused on addressing biodiversity impacts, and; (3) which ES will be lost due to planned (and approved) future mining operations.MethodsWe consider a region rich in both natural capital and Indigenous culture–western Cape York Peninsula in northern Australia. We identify and map the distribution of ES that are both valued by local Indigenous communities and threatened by current and future bauxite mining including plants that have significant cultural value (e.g., for food and medicine), and compare them to areas currently protected from mining due to their biodiversity value.ResultsWe find that open woodlands contain the highest number of culturally significant plant species (32 species) compared to other vegetation types in the region. However, despite this, open woodlands are the least protected vegetation type from mining operations under current management plans and regulatory requirements.ConclusionsOur results illustrate the benefits ES provide for local Indigenous people, and that the areas set aside for biodiversity management will not compensate for expected ES losses. We discuss the need for a collaborative approach between industry, government, and Traditional Owners to capture and manage ES for local people throughout and beyond the mining lifecycle.

“Our People Can’t Hold the Line!”

A protracted movement emerged in Kashipur in Southern Odisha in 1993 that stalled a bauxite mining project for over 18 years. It went through fragmentations and eventually petered out by the early 2010s. This paper aims to understand how and why the processes of capital accumulation through dispossession cause fragmentation of social movements and their eventual petering out. I analyse the collective strikes that the villagers engaged in during 2008–2010, paralyzing the company’s incipient construction work over a tumultuous nine months. Critically engaging with David Harvey’s concept of “accumulation by dispossession” (ABD) and Kalyan Sanyal’s concept of “jobless growth”, I argue that ABD processes entail protracted interaction of extractive capital, bureaucratic structures, ecology, and the movements of subaltern communities with existing divisions. Dispossession processes generate new fissures in which ownership of land or lack of it due to land acquisition becomes the central axis of cleavage, shaping the politics and outcomes of dispossession. I further reveal that ‘jobless growth’ is unachievable for a company that can push ahead only through the provision of precarious employment and such promises...

Creep Characteristics of a Strongly Weathered Argillaceous Sandstone Sliding Zone and the Disaster Evolution Mechanism of the Huaipa Landslide, China

The creep characteristics of sliding zones strongly influence slope deformation and long-term stability, as well as the occurrence of landslide catastrophes. In this paper, large-scale triaxial creep tests were performed on the strongly weathered argillaceous sandstone sliding zone of the Huaipa landslide in the Henan Province, China, to study its creep characteristics and long-term strength in natural and saturated states. Three-dimensional numerical simulations were conducted to analyze the deformation creep law and catastrophic evolution mechanism of the slope after excavation and rainfall. The results show that the sliding zone underwent appreciable creep deformation prior to failure, and that the progression of specimen damage with an increasing stress level followed decay creep → steady creep → accelerated creep. The stress level played a decisive role in the creep deformation, with higher stress levels resulting in higher instantaneous displacement, creep displacement, and longer times required to reach steady creep. The stress level also determined the specimen’s creep stage. When the stress level was low, the adjustment of the specimen’s internal structure was dominated by air space compression and particle movement, whereas particle fragmentation mostly occurred at high stress levels. The long-term rock strength was approximately 62–66% of the instantaneous strength, the internal friction angle decreased by approximately 8° relative to the instantaneous strength, and the cohesion decreased by approximately 30%. The slope foot unloaded and deformed owing to the excavation of a bauxite mine at its front edge, after which the slope deformed via creep. The landslide disaster occurred when the deformation was significantly accelerated and the slope started to slide as a whole once the sliding zone became water saturated owing to continuous rainfall. The simulation results indicate that the landslide can be divided into a front edge bulging zone, central sliding zone, and trailing edge tension zone, which provides valuable insight on the creep deformation evolution process and the disaster mechanism of the landslide under the action of front edge excavation and rainfall.

The Characteristics of Doğanşehir (Malatya-Turkey) Bauxite Mineralization in the Eastern Taurus Orogenic Belt Using Scanning Electron Microscopy (SEM)

The Taurus Orogenic Belt in Turkey is a prominent tectonic zone where significant occurrences of bauxite mineralization are observed. The bauxite deposits in Doğanşehir, located in Malatya, Turkey, are found as extensive bodies and lenses within the carbonate rocks of the Permian-Triassic Malatya Metamorphics, situated in the Eastern Taurus Orogenic Belt. The geological foundation of this region consists primarily of lithologies attributed to the Malatya Metamorphics. This unit mainly comprises schists, calc-schists, and marble, overlain by the Berit Metaophiolite of the Late Cretaceous-Eocene, the Maden Complex of the Eocene, the Doğanşehir Granitoid of the Early-Middle Eocene, and the Plio-Quaternary cover sedimentary units. Bauxite mineralization of oolitic and pisolitic nature is present within the Permian-Triassic carbonate rocks of the Malatya Metamorphics. These mineralizations occur in carbonate rocks containing fossils and are observed in the form of lens-shaped bodies. The bauxite lenses are covered by relatively thin, intermediate layers of Permian-Triassic carbonate rocks of the Malatya Metamorphics. With the advancement of technology, Scanning Electron Microscopy (SEM) has been utilized to analyze bauxite ores and determine the presence of elements within their crystal lattice structure. The point analysis and mapping technique were employed to identify the elements that might be present within the crystal lattice structure of the bauxite ores. SEM analysis of the samples using the mapping method revealed the distribution of elements such as Fe, Ti, Si, Al, and O, both before and after activation. The images indicate that bauxite exhibits a wide grain distribution, both below and above 50 µm. The elemental spectrum diagram demonstrates the presence of O, Al, and Si in the sample, and the detection of Fe, Ti, C, K, and Mg as well. By employing SEM analysis and the mapping method on the same samples, the distribution of Fe, Ti, Si, Al, and O elements within the structure was examined before and after activation. The images reveal that the elements Al, O, and Si display high density in specific regions before activation but show a more uniform distribution and similar structures after activation. Fe, Mg, and K exhibit a similar distribution pattern, while Ti and C exhibit different characteristics.

Kapadokya’daki Post-Bizans (XIX yüzyıl) Kilisesindeki Duvar Resimlerindeki Pigmentlerin Arkeometrik Teknikler ile Araştırılması

Cappadocia region, rock churches, monasteries, houses, underground settlements, valleys and historical and geological formations have unique beauty. The region, which is rich with its cultural assets belongs to Christian culture in Anatolia, is generally known with its rock churches, and is a subject to researches. The purpose of this study is; to understand the wall painting technology of the 19th century church, and to make a comparison with the wall painting materials of the rock churches. The study material is composed of pigments in the wall paintings of the Church of St. Theodoros Trion, which is from the 19th century, and located in Nevşehir. Scanning Electron Microscope and Energy Distributed Spectrometer (SEM-EDX), X-Ray Diffraction Spectrometry (XRD) and Fourier Transformed Infrared Spectrophotometer (FTIR) are used to determine material characterization of pigments. X-Ray Fluorescence Spectrometer (XRF) analysis method was used in the analysis of the soil structure. As a result of analysis of the wall painting, it has been found that the ultramarine pigment is obtained from the lapis lazuli mineral and the covellite mineral of the covellite blue. In red, the red ochre and the caput mortuum pigment in purple color has been found. In the mineral of different pigment species, bauxite mineral belongs to the region have been detected. Green color, it has been determined that it is obtained from the glauconite and celadonite mineral in the region. According to the research carried out in the region in green color, it has been detected that only this pigment species has been used from the 6th century to the 19th century.

Mining Machines for Comprehensive Mechanized Mining of Bauxite

The mining machine for bauxite is the key equipment for the mechanized mining of underground bauxite ore. The mining machines for shearing and loading bauxite ore have been studied in this paper from three aspects: the determination of key technical parameters, the in-situ tests, optimization, and improvement. Mechanical and physical parameters of bauxite ore, such as high tensile strength, no-cleavage, and abrasion properties, have a great impact on the determination of key technical parameters of the mining machine. The conventional conical picks which are widely used in mining equipment drums for soft rock, such as coal mines, are not suitable for bauxite and other high-abrasion ore rocks. The chisel pick is theoretically a better choice. The main faults of the mining machine for bauxite during the in-situ tests are closely related to the high abrasion of bauxite rock, especially for the abrasion of conical picks and the walking actuator of the traction part. So the second-generation mining machine should be optimized from the selection of types, linear speed, and cutting depth of picks, from selecting wear-resistance material for the walking actuator of the traction part and designing a more suitable structure for the walking actuator of the traction part. The research results have important theoretical significance for the design of mining machines for bauxite.

GEOLOGICAL CHARACTERISTICS OF BOLKARDAĞI BAUXITE DEPOSITS IN AYRANCI, THE TAURUS MOUNTAIN, TURKEY

The aim of this study is to determine the stratigraphic position of the bauxite deposits in the Ayrancı region, where the most important bauxite mineralization of the Bolkardağı region is located. In this context, the age of bauxite will be determined by determining the erosion surface associated with stratigraphic features during the formation of bauxite and the age of bauxite according to its side rocks. In the region, there are Permian-Cretaceous aged rocks belonging to the Bolkardağı Union, one of the main tectonic units forming the Central Taurus Mountains. Miocene units covering these rocks are surfaced in the study area. Karamanoglu ophiolite and older units are uncomfortably covered by Miocene aged Mazı and Divlek formations. Bauxite deposits are clearly seen in the Upper Permian aged Dedeköy formation. According to the field studies, the bauxites were formed in the Late Triassic - Early Jurassic interval, on the Upper Permian aged carbonate rocks and Lower Triassic aged shale - sandstone - limestone units and then deposited in caves and dolines within the carbonate rocks. The fact that bauxites are located above dolomites and below, within and above limestones is thought to be due to the different behavior of carbonate rocks.

Assessing the potential of red mud and dehydrated mineral mud mixtures as soil matrix for revegetation

The disposal of red mud (RM) and dehydrated mineral mud (DM) presents a significant challenge for the global alumina industry. This study proposes a novel disposal method for RM and DM, which uses mixtures of RM and DM as a soil matrix for revegetation in the mining area. RM mixed with DM effectively alleviated its salinity and alkalinity. X-ray diffraction analysis indicated that reduction of salinity and alkalinity may be due to the release of chemical alkali from sodalite and cancrinite. Applications of ferric chloride (FeCl3), gypsum, and organic fertilizer (OF) improved the physicochemical properties of the RM–DM mixtures. FeCl3 significantly reduced available Cd, As, Cr, and Pb content in the RM–DM, while OF significantly increased the cation exchange capacity, microbial carbon and nitrogen, and aggregate stability (p < 0.05). Micro-computed tomography and nuclear magnetic resonance analysis showed that amendment with OF and FeCl3 increased the porosity, pore diameter, and hydraulic conductivity in the RM–DM mixture. The RM-DM mixtures had low leaching of toxic elements, indicating low environmental risk. Ryegrass grew well in the RM–DM mixture at a ratio of 1:3. OF and FeCl3 significantly increased the ryegrass biomass (p < 0.05). These results suggested that RM–DM amended with OF and FeCl3 has a potential application in the revegetation of areas after bauxite mining.

N fertilization did not raise soil greenhouse gas emissions in a reforested reclaimed-mine site over a short-term study

Bauxite mining is a human activity that can have drastic effects on the soil environment, altering its physical, chemical, and biological properties. To improve water and nutrient retention, microbiological activity, and environmental service, it is essential to recover and maintain soil organic carbon stocks. Reforesting reclaimed mine sites and fertilization are two strategies that can be used to eliminate nutrient limitation and accelerate biomass production and soil C sequestration. In this study, we investigated the secondary impacts of nitrogen (N) fertilization on greenhouse gas emissions, microbial community, and total phospholipid fatty acid analysis over a 17-day period at a reclaimed mine site in Brazil. Three forest species compositions were tested: only Eucalyptus, only Anadenanthera peregrina, and a mixture of 16 native forest species collected in fragments of Atlantic Forest. Our short-term observation did not reveal any significant effects of short-term N fertilization on greenhouse gas (GHG) emissions, total phospholipid fatty acid analysis, or the relative abundance of the microbial community. These initial short-term results were favorable for acceptance of the N fertilization recommendation for stimulating biomass regeneration in reclaimed mine sites because there were no negative impacts on environmental quality indexes, such as GHG fluxes. However, longer-term experiments are necessary to better understand the environmental costs and benefits of long-term N fertilization practices associated with reclaimed sites and confirm its recommendation.

Effect of pH value on effectiveness of biopolymer-based treatment of bauxite mine slurry

Effective dehydration and flocculation of mine slurries or sludge is important for nonferrous metal industries and environmental engineering. However, the mechanisms for the flocculation of slurry remain largely unclear. This paper presents the results of a series of flocculation tests, which was conducted on the slurry suspensions treated by xanthan gum (flocculant) at different pH values. It is shown that the settlement rate of mine slurry particles can be accelerated by adding xanthan gum, and the maximum sedimentation rate was obtained at a pH value of 5.9, and the final volume of flocs is significantly increased due to the addition of the flocculant. In addition, the settlement rates of xanthan gum-treated slurry suspensions at the pH values of 3, 5 and 7 decrease slightly compared with the reference slurry suspensions with pH=5.9, and the slurries remained stable as suspensions at the pH value of 9 and 11. The zeta potential measurement and SEM image analysis show that flocculation occurs primarily due to electrostatic attraction between slurry particles and the flocculants, and the bridging effect between the carboxylic groups in the side chains of xanthan gum molecule and the suspension particles.