Sands Tailings Research Articles

Strength and microstructural development in concrete pavements by blended copper tailings powder and copper tailings sand

This study investigated the effects of replacing cement with copper tailings powder on pavement concrete performance. Concrete pavements were prepared by substituting 5 %, 10 %, and 15 % of the cement with copper tailings powder. Additionally, 70 % of the river sand (0.6–0.15 mm) was replaced with copper tailings sand of a fixed particle size. The study aimed to understand how this combined replacement affected the mechanical and microstructural properties of the concrete. Tests revealed that two hours of mechanical milling was optimal for activating the copper tailings powder, resulting in a Pozzolanic activity index of 82 %. Concrete specimens with 5 % copper tailings powder achieved the highest flexural strength (6.21 MPa) and compressive strength (52.8 MPa). Furthermore, this replacement level resulted in the lowest porosity and highest resistivity. Scanning electron microscope images revealed that increasing the amount of tailing powder reduced the degree of hydration within the microstructures. However, the specimens with both tailings powder and sand exhibited better compactness and homogeneity in their internal pore structures compared to those with only tailings sand. It suggests a beneficial microfilling effect from the tailings powder.

Evaluation of state parameter interpretation methods using CPT calibration chamber data

The cone penetration test (CPT) is widely used to determine the in situ state parameter of soils because it provides continuous data and excellent repeatability at a relatively low cost. Accurate interpretation of the state parameter from CPT is the basis for evaluating the strength of granular soils, including assessing liquefaction susceptibility in important structures such as tailings storage facilities. A few interpretation methods are used in practice. They use two different overburden stress normalisation schemes on tip resistance. These methods vary in how much information they utilise to differentiate among soils. This paper evaluates these methods by applying them to an extensive database of calibration chamber tests. Then, the state parameter interpreted by each method is compared with that determined from laboratory data. The database includes manufactured sands, natural sands, and clean sand tailings. The soils were selected such that both calibration chamber testing and triaxial compression data were available from the literature. This evaluation serves as a minimum requirement for applying these methods in engineering projects, especially those dealing with challenging soils such as fines-rich tailings. This study suggests that methods that account for soil properties and in situ horizontal stresses perform better than those that do not.

Strategies for Hydrocarbon Removal and Bioleaching-Driven Metal Recovery from Oil Sand Tailings

Oil sand tailings from bitumen extraction contain various contaminants, including polycyclic aromatic hydrocarbons, BTEX, and naphthenic acids, which can leak into surrounding environments, threatening aquatic ecosystems and human health. These tailings also contribute to environmental issues such as habitat disruption and greenhouse gas emissions. Despite these challenges, oil sand tailings hold significant potential for waste-to-resource recovery as they contain valuable minerals like rare earth elements (REEs), titanium, nickel, and vanadium. Traditional metal extraction methods are environmentally damaging, requiring high energy inputs and generating dust and harmful emissions. Furthermore, the coating of hydrocarbons on mineral surfaces presents an additional challenge, as it can inhibit the efficiency of metal extraction processes by blocking access to the minerals. This highlights the need for alternative, eco-friendly approaches. Bioleaching, which uses microorganisms to extract metals, emerges as a sustainable solution to unlock the valuable metals within oil sand tailings. This review discusses the minerals found in oil sand tailings, the challenges associated with their extraction, methods from hydrocarbon removal from minerals, and bioleaching as a potential metal recovery method.

Short‐term survival and growth of 32 native boreal plants on treated oil sands tailings

AbstractThe consolidation of oil sands tailings is a cost‐ and time‐consuming process that requires treatment via active (e.g., centrifugation) and passive (e.g., self‐weight consolidation) methods. The use of plants to dewater tailings is a promising concept and has previously been evaluated using agronomic grass species in greenhouse studies. This greenhouse study evaluated the short‐term survivorship and growth of 32 upland and lowland native plant species (12 forbs, 14 graminoids, and six woody plants) in centrifuged tailings and benchmarked their performance against reclamation soil and undisturbed forest soil. All plant species were propagated from seed and transplanted as seedlings into containers filled with one of the three substrates. After 42 days, the height (woody species only) and total aboveground biomass were determined for all living plants. As expected, the mortality of seedlings in tailings was higher than plants grown in the other two substrates. Graminoid species, regardless of species community type (wetland or upland), had higher survival probabilities and growth compared to forb or woody species across all substrates. Of forbs and woody species evaluated, Geum aleppicum and Populus tremuloides showed the most promise amongst the upland species, and Rumex occidentalis was the wetland equivalent.

Exploring Soil–Water Characteristic Curves in Transitional Oil Sands Tailings

Soil–water characteristics curves (SWCC) have proved useful in estimating parameters used in modeling unsaturated geotechnical properties of soils including permeability and strength. Either saturation, gravimetric, and instantaneous and initial volumetric water content designation can be used to develop SWCCs. Studies have shown that any of the designations will give good estimates for soils that do not undergo volume change with suction change whereas, for soils that undergo substantial volume change, only saturation and instantaneous volumetric water content designation obtained by incorporating shrinkage curves can give correct estimates. Transition oil sands tailings have fines content that cannot be categorized as sandy or fine materials, and research on volume change with suction change in these materials is limited. In this study, HyProps, Tempe cells, and a chilled-mirror water potential meter were used to measure suction and corresponding water contents for samples that were prepared by mixing coarse sand and Fluid Tailing by ratios that mimic transition zone tailings. Shrinkage tests were also performed to observe the extent of volume change with suction increase. Air Entry Values (AEV) estimated from SWCCs based on gravimetric water content were found to be lower than those estimated from saturation-based SWCCs due to substantial volume changes in these materials with suction increase. The use of saturation water content designation is recommended in estimating AEV for transitional oil sands tailings. This is useful information in predicting the long term unsaturated geotechnical behavior of these materials for environmental management and safety purposes.

Eccentric compression behaviors of iron tailings and recycled aggregate concrete-filled steel tube columns

This paper presents a sustainable method for using iron ore tailings (IOTs) sand and recycled coarse aggregate (RCA) in concrete and concrete-filled steel tube (CFT) columns. The study first examines the impact of RCA replacement ratios (0 %, 50 %, 100 %) on concrete's mechanical properties, finding that both compressive and tensile strengths decrease with higher RCA content due to the negative effects of old interfacial transition zones and adhered cement in RCA. Then, twelve iron tailing and recycled aggregate concrete-filled steel tube (ITRAC-CFT) columns were tested under eccentric compression to assess the effects of varying RCA replacement ratios, eccentricity ratios (0.3, 0.5), and slenderness ratios (12.12, 19.05). Results indicate that RCA ratios have minimal impact on failure modes, ultimate bearing capacity, and stiffness, although ductility increases with higher RCA content. As slenderness ratios increase, the ultimate bearing capacity decreases by 5.3 % and 6.8 % for eccentricities of 0.3 and 0.5, respectively. The study further validates these findings through the finite element method (FEM), showing strong agreement between experimental and predicted results, average value, standard deviation, and coefficient of variation of Nu/NFE were 1.02 %, 0.04, and 3.92 %, respectively. Finally, a comparison with existing design codes (EC4, AISC 360, and GB 50396) reveals that AISC 360 provides the most accurate predictions of the ultimate bearing capacity of ITRAC-CFT columns. The research concludes that the comprehensive use of IOTs sand and RCA in CFT structural concrete is a highly viable and eco-friendly solution, offering potential benefits for sustainable construction practices.

Enhancing Sustainable Subgrade Engineering Using Soil Tuff for Modifying Iron Tailings Sand: A Comprehensive Engineering Performance and Sustainability Analysis

Soil tuff, an industrial solid waste, can serve as a sustainable alternative to cement for modifying iron tailings sand (ITS). To substantiate this claim, the physical properties, durability and microstructure of soil tuff and cement-modified ITSs were analyzed at different modifier dosages, compaction degrees and maintenance ages, with a comprehensive comparison in the perspective of sustainable built environments. The results indicate that the physical properties of soil tuff-modified ITS (STM-ITS) were significantly enhanced in subgrade engineering applications compared with cement-modified ITS (CM-ITS). In addition, compared with CM-ITS, the hydration products of STM-ITS possessed a smaller amount of Ca(OH)2 and were cemented with surrounding binding products, which resulted in fewer cracks. STM-ITS featured a more stable C–S–H gel than CM-ITS due to a lower Ca/Si ratio, contributing to its higher corrosion resistance. Notably, a sustainability analysis demonstrated that incorporating STM-ITS has physical properties comparable to those of CM-ITS and can be obtained at a significantly lower cost, CO2 emission, and energy consumption. Therefore, this study highlights the potential of soil tuff as a promising eco-friendly option for subgrade engineering, promoting waste usage, improving built environments, and contributing to carbon-neutrality goals. These findings have significant implications for the construction industry and the pursuit of sustainable development.

Effects of pressure on the biogeochemical and geotechnical behavior of treated oil sands tailings in a pit lake scenario

Reclamation options for oil sands fluid fine tailings (FFT) are limited due to its challenging geotechnical properties, which include high water and clay contents and low shear strength. A feasible reclamation option for tailings with these properties is water capped FFT deposits (pit lakes). A relatively new proposal is to deposit FFT that has been treated with alum and polyacrylamide in pit lakes. Though over 65 Mm3 of alum/polyacrylamide treated FFT has been deposited to date, there is limited publicly available information on the biogeochemical and geotechnical behavior of this treated FFT. Further, the effects of pressure from overlying tailings on microbial activity and biogeochemical cycling in oil sands tailings has not been previously investigated. Twelve 5.5 L columns were designed to mimic alum/polyacrylamide treated FFT deposited beneath a water cap. A 2x2 factorial design was used to apply pressure and hydrocarbon amendments to the tailings. Pressure (0.3–5.1 kPa) was applied incrementally and columns were monitored for 360 d. Pressure significantly enhanced consolidation and microbial activity in treated FFT. Columns with pressure generated significantly more CH4(g) and CO2(g) and had significant increases in dissolved organic carbon and chemical oxygen demand in the FFT and water caps. The enhanced microbial activity in columns with pressure indicates that pressure increased the solubility of microbial substrates and metabolites in the tailings, thereby increasing the bioavailability of these compounds. Ammonium generation was significantly higher in columns with pressure, suggesting that microorganisms utilized polyacrylamide and/or N2 fixation as a nitrogen source to meet enhanced nutrient demands. Pressure also impacted microbial community structure, shifting methanogenic communities from hydrogenotrophic methanogens to predominately acetoclastic methanogens. This study also revealed the importance of sulfur cycling in treated FFT. Extensive sulfate reduction occurred in all columns, generating dissolved sulfides and H2S(g), and this was accelerated by hydrocarbon amendments.

Characterization of Seismic Dynamic Response of Uranium Tailings Dams Based on Discrete Element Method

Tailings dams play a critical role in ensuring the safety of mining operations. However, earthquakes can cause breaches in these dams, resulting in significant casualties and property damage. This study investigates the dynamic response characteristics of uranium tailings dams subjected to seismic loading, employing the discrete element method. It specifically analyzes how seismic wave amplitude, frequency, and the friction angle of tailings sand affect the dams’ dynamic response. The results reveal that the peak ground acceleration ratio (PGAR) exhibits an increasing–decreasing–increasing pattern with elevation. When the friction angle of the tailings sand exceeds 35°, the overall stability of the dam improves. Conversely, a friction angle below 25° significantly increases the risk of dam failure. Additionally, the dam shows a reduced dynamic response to seismic waves with frequencies exceeding 15 Hz. At lower frequencies, deformation and damage are primarily concentrated on the slope face, while at higher frequencies, damage is predominantly located at the bottom of the model. These findings provide a theoretical foundation and reference for the safe operation of tailings dams, highlighting their practical significance.

Study on impact resistance performance of MSWIFA-based low-carbon fiber-reinforced concrete

The accumulation of carbide slag (CS), red mud (RM), and municipal solid waste incineration fly ash (MSWIFA) has led to significant environmental pollution issues, necessitating urgent resource utilization. Building upon the previously developed CS-MSWIFA synergistic activation RM-slag cementitious system, this study aims to further incorporate iron tailings sand and polypropylene fibers to prepare fiber-reinforced concrete. The systematic investigation focuses on the influence of cementitious material types, aggregate types, fiber shapes, lengths, and dosages on the impact resistance of concrete. Furthermore, an impact damage evolution equation and life prediction model were developed based on the two-parameter Weibull distribution. Results indicate that the type of cementitious material and aggregate has minimal influence on the impact resistance of concrete, while the addition of fibers significantly enhances its impact resistance, shifting the failure mode from brittle to ductile. Mesh polypropylene fibers with a length of 12 mm and a volume dosage of 1.0 % demonstrate excellent impact resistance, with initial and final crack numbers reaching 78 and 105, respectively. This represents an increase of 136.4 % and 200.0 % compared to the control concrete without fibers. The findings of this study offer new avenues for the resource utilization of solid waste and provide theoretical foundations and technical support for the potential application of solid waste based fiber-reinforced concrete in structural engineering.

Synergistic solidification of heavy metal tailings by polyethylene glycol (PEG) and microorganisms

A significant amount of tailings rich in heavy metals is left behind after mining, causing environmental pollution due to long-term storage. In recent years, microbial-induced carbonate precipitation (MICP) has shown potential to solidify and stabilize heavy metal-contaminated soils. However, high concentrations and complex mixtures of heavy metals have toxic effects on microorganisms, resulting in decreased carbonate yield. Additionally, tailings sand often has a small particle size and poor permeability, which significantly reduces the solidification uniformity when using traditional grouting methods. To address these challenges, a low pH treatment method using PEG-MICP was proposed. This method increased the unconfined compressive strength (UCS) of tailings sand by 2.5 times and significantly improved soil uniformity while substantially reducing exchangeable heavy metal ions. Microscopic analysis showed that the introduction of PEG modifies the morphology of calcium carbonate, transforming calcite from a mineral to sheet-like and faceted forms, thus enhancing solidification efficiency. This study suggests that PEG-MICP has broad application prospects for solidifying heavy metal-contaminated tailings sand.

Flexural performance of reinforced concrete beams repaired with BFRP grid-TSUHDC

Due to the influence of time, load, and external environmental factors, many reinforced concrete beams have been damaged and require repair. Tailings are waste generated during mineral production, resulting in substantial environmental pollution and economic losses due to the excessive generation of tailings and low comprehensive utilization. In the UHDC, tailings replaced quartz sand, while BFRP grids itself is an environmentally friendly material. Two repair methods were evaluated in this study, Tailings Sand Ultra-High Ductile Concrete (TSUHDC) and Basalt Fiber Reinforced Polymer (BFRP) grid-TSUHDC, grounded in the principles of green and sustainable development. Five reinforced concrete beam specimens were designed and fabricated for bending performance tests and finite element simulations. The effects of different repair methods and levels of damage on the flexural performance of reinforced concrete beams were investigated. The results reveal that, compared to untreated reinforced concrete beams, both TSUHDC and BFRP grid-TSUHDC repair methods enhanced bending load-bearing capacity. However, the stiffness of specimens repaired with TSUHDC decreased when subjected to 80 % of the pre-applied failure load. When the pre-applied failure load is less than 80 %, the recommended repair approach is the use of TSUHDC for repair. For cases where the pre-applied failure load exceeds 80 %, BFRP grid-TSUHDC is the preferable option. The flexural bearing capacity formula for this type of repair method was derived by improving existing formulas, yielding prediction results in close alignment with the experimental results.

Evaluation of accurate measurement methods for radon exhalation rate with advection effect and application in field

In decommissioning of a uranium tailings pond, radon exhalation rates on a beach surface should meet regulatory standards. Accurate measurements of the radon exhalation rate are demanded. However, current studies fail to consider the impact of advection under temperature variations or pressure gradients caused by gas movement on measurements using an accumulation chamber. Two proposed methods were therefore evaluated to accurately measure radon exhalation rates on the loose medium surface under advective conditions. Repeated experiments were conducted on a laboratory experimental platform filled with uranium tailings sand under advective flow rates of 0.03 and 0.3 L/min to validate the stability and reliability. Deviations between measured and true values were 0.1–6.1 % and 6.3–29.2 % for the two methods, respectively. Subsequently, numerical simulation was used to analyze defects of traditional methods and mechanisms of the new methods. In a field study, all methods were compared, and a predictive map of radon exhalation rates was created using interpolated data from 20 random sites using the new method. Results from the proposed methods, compared with traditional ones, were closer to true values under advective conditions, and accurate assessment of beach surface treatment was expected.

A new approach for improving the properties of tailings sand autoclaved aerated concrete - From a mineralogical perspective

This study proposed a new method to improve the performance of tailings sand autoclaved aerated concrete (SAAC). Firstly, high silicon iron tailings from the Anqian area and low silicon molybdenum tailings from the Weinan area were selected, and the mineral composition of these two tailings was analyzed. Then, the single mineral in the two tailings were used instead of siliceous raw materials to prepare mineral autoclaved concrete (MAC). The autoclaved reactivities of these minerals were analyzed through compressive strength, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG-DTG), and scanning electron microscopy (SEM), and which minerals were beneficial for the preparation of SAAC were determined. On this basis, magnetic separation and gravity-magnetic separation processes were used to pretreat Anqian iron tailings and Weinan molybdenum tailings, respectively. Finally, the effectiveness of this method was verified by preparing SAAC made with tailings before and after pretreated. The tested results showed that the autoclaved activities of siliceous minerals were in the following order: quartz hornblende, feldspar, chlorite, while the montmorillonite and biotite, and the metal mine (hematite and pyrite) did not have autoclaved reactivities. The main crystalline phase of hydration products in MAC made with single mineral without autoclaved reactivities were C-S-H, Ca(OH)2, CaCO3, and hibschite, and that in MAC made with quartz, hornblende, feldspar, and chlorite were C-S-H, tobermorite, Ca(OH)2, CaCO3, and hibschite (except quartz). After 1.3 T strong magnetic separation treatment, the content of Fe2O3 in iron tailings decreased from 11.11 % to 4.16 %, and the compressive strength of SAAC made with iron tailings with magnetic separation pretreated increased by 11.43 % comparted to that of SAAC made with original iron tailings. After gravity separation and 1.1 T strong magnetic separation pretreated, the content of SiO2 in molybdenum tailings increased from 63.97 % to 84.03 %, and the mineral content of biotite decreased from 40.5 % to 11.2 %. The compressive strength of SAAC made with molybdenum tailings with gravity-magnetic separation pretreated increased by 24.09 % comparted to that of SAAC made with original molybdenum tailings.

Experimental study on the road performance of molybdenum tailings sand stabilized with cement and fly ash

The large accumulation of molybdenum tailings (MoT) has resulted in a series of hazards, including environmental pollution, damage to water resources, and increased risk of geological disasters. This study employs ordinary Portland cement (OPC) and fly ash (FA) stabilization of MoT sand and seeks the optimal mix ratio through experimentation. The strength properties of MoT sand stabilized with different proportions of OPC and FA are studied and analyzed through unconfined compressive strength tests, splitting tensile strength tests, and splitting rebound modulus tests. Additionally, the microstructure of MoT sand stabilized with OPC and FA is analyzed using scanning electron microscopy (SEM). The results indicate that with an increase in OPC content, the compressive strength, splitting tensile strength, and splitting rebound modulus all increase. With an increase in FA content, the compressive strength gradually increases, while the splitting tensile strength and splitting rebound modulus show a trend of initially increasing and then decreasing. The results show that the optimal mix proportion for OPC and FA-stabilized MoT sand is 7 % OPC content and 15 % FA content. This mixture is suitable for a heavy traffic base of expressways and class I highways, as well as for an extra heavy traffic base of class II and below highways. The research results can provide reference for using OPC and FA stabilized MoT sand as roadbed material.

Pertumbuhan dan Hasil Kedelai Edamame (Glycine max (L) Merill) Terhadap Pemberian Kombinasi Legin dan Kompos di Media Tailing Pasir Pasca Tambang Timah

Post tin mining land in Bangka Belitung can still be utilized as agricultural land with the application of various soil amandment including the combination of compost and legin. The compost provide organic matter for the soil and legin provide rhizobium to maximize nitrogen fixation in the soil. Post tin mining land improved with compost and legin combination can be used potentially for the development of edamame soybean commodities which are widely known as adaptive plant on suboptimal land. The purpose of this study was to determine the type of compost, legin dose and the best combination of both compost and legin on the growth and the yield of edamame soybeans in sand tailing media. This research had been conducted in February-August 2023 at the Experimental and Research Station, Faculty of Agriculture, Fisheries and Marine, Universitas Bangka Belitung. This study used a field experimental method with a Factorial Randomized Group Design with the first factor was the dose of legin, consists of 3 treatment levels, namely: L0: No treatment (Control), L1: 10 g legin, L2: 12 g legin. The second factor was the type of compost consisting of 3 treatment levels, namely: P1: Cow dung compost, P2: rice husk compost, P3: Commercial compost. There were 9 treatment combinations that were replicated 4 times. Each experimental unit had 6 plants so that 216 plant populations were obtained and 144 plants were obtained as samples. The results showed that the dose of 12 g legin had the highest effect on edamame growth and 10 g legin treatment had the highest effect on edamame yield. Commercial compost treatment had the best effect to edamame growth, while rice husk compost had the best effect to edamame yield. The combination of rice husk compost and 10 g legin was the treatment combination that showed the best growth and yield of edamame soybean plants in sand tailing media of post tin mining. Keywords: Edamame, rice husk, compost, legin, sand tailings

Comparative study on the effect of SRB and Sporosarcina pasteurii on the MICP cementation and solidification of lead–zinc tailings

The production of tailings sand due to mining and smelting activities is one of the reasons for the accelerated environmental pollution caused by heavy metals, drawing social attention to the management of tailings sand. Microbially induced carbonate precipitation (MICP) is an environmentally friendly soil remediation technique that is gradually becoming the preferred method for soil stabilisation and heavy metal pollution control. To address the issues of heavy metal pollution release and the loose particle structure of lead–zinc tailings sand (LZTS), this study employs a layered MICP approach. The solidification effects of two typical mineralising bacteria, sulfate-reducing bacteria (SRB) and Sporosarcina pasteurii, on LZTS, were compared for the first time. The results show that the maximum unconfined compressive strength (UCS) of SRB cemented solidified lead–zinc tailings sand (SRB-CS-LZTS) specimens is 0.22 MPa, while that of S. pasteurii cemented solidified lead–zinc tailings sand (SP-CS-LZTS) specimens is 0.95 MPa. Compared with the UCS of SRB-CS-LZTS, the UCS of SP-CS-LZTS increased by 3.32 times. The effect of S. pasteurii on the improvement of UCS and immobilisation of heavy metal ions was greater than that of SRB. The immobilisation effect of SRB on SO42- in the LZTS was better than that of S. pasteurii. Compared with SRB, the biological CaCO3 formed by S. pasteurii exhibited stronger adhesion and was more suitable for the cementation and solidification of LZTS. This study uses MICP technology to treat LZTS, aligning with the green environmental concept and providing a reference for the bioremediation of multiple heavy metals in tailing areas.

Experimental study on fiber-reinforced cement tailings sand-based grouting material preparation and factors influencing the grouting effect

To address the problem of permeation of tailings pond initial dams rockfill dams, fiber-reinforced cement tailings sand-based grouting (FRCTG) material, which can be used for rockfill dam reinforcement, was prepared by selecting ordinary portland cement (OPC), iron tailings sand (ITS), basalt fiber (BF), fly ash (FA) and water as the raw materials. Orthogonal tests were used to investigate the effects of the water-binder ratio (w/b) and material mass fraction on the rheological and mechanical properties of FRCTG and determine the optimum mixing ratio. Comparative analyses were performed of the grouting effect of FRCTG and pure OPC grouting materials based on concrete self-compacting tests and COMSOL simulations. Combined X-ray diffraction (XRD) and scanning electron microscopy-energy spectroscopy (SEM-EDS) microstructural characterization were used to reveal the factors influencing FRCTG mechanical properties. The results showed that when the water-binder ratio (w/b) was 0.5, ITS substitution percentage for OPC was 10 %, BF dosage was 0.2 %, BF length was 6 mm, and FA substitution percentage for OPC was 8 %, FRCTG had better rheological properties and flexural strength than pure OPC grouting materials. In addition, FRCTG self-compacting concrete also had stronger compressive strength and splitting strength. FRCTG showed a better filling capacity and diffusion effect, which preliminarily verified the feasibility of rockfill dam grouting. ITS inhibited the hydration reaction of the cementitious material and prolonged the setting time of the slurry. The interlocking structure formed by FA and hydration products indirectly enhanced the flexural strength of the grouting material. BF not only provided FRCTG reinforcement but also acted as the hydration product skeleton. FRCTG demonstrated better economic and environmental performance than traditional cement material while effectively utilizing ITS and FA solid waste.

The Effect of Copper Tailings Sand on the Workability and Mechanical Properties of Concrete

The Effect of Copper Tailings Sand on the Workability and Mechanical Properties of Concrete

Effects of size and composition of bitumen drops on intra-oil diffusion and dissolution of hydrocarbon solvents in froth treatment tailings ponds

The rate of mass transfer of lower molecular weight hydrocarbons (naphtha) from bitumen drops in mature fine tailings of oil sand tailings ponds (OSTPs) may control their bioavailability and the associated rate of GHG production. Experiments were conducted using bitumen drops spiked with o-xylene and 1-methylnaphthalene to determine the mass transfer rate of these naphtha components from bitumen drops. The results were compared to simulations using a multi-component numerical model that accounted for transport in the drop and across the oil-water interface. The results demonstrate rate-limited mass transfer, with aqueous concentrations after 60 days of dissolution that were different than those in equilibrium with the initial drop composition (less for o-xylene and greater for 1-methylnaphthalene). The simulations suggest that mole fractions were unchanged at the center of the drop, resulting in concentration gradients out to the oil-water interface. Numerical simulations conducted using different drop sizes and bitumen viscosities also suggest the potential for persistent naphtha dissolution, where the time required to deplete 80% of the o-xylene and 1-methylnaphthalene mass from an oil drop was estimated to be on the order of months to years for mm-sized drops, and years to decades for cm-sized drops assuming instantaneous biodegradation in the aqueous phase surrounding the bitumen.