Ultrafine Clay Research Articles

Efficient utilization of waste shield slurry and CDW fines to prepare eco-friendly controlled low-strength material

Shield slurry has not been effectively utilized due to its ultrafine clay particles and high water content. Controlled low-strength filling material (CLSM) provides a promising approach for efficient, large-scale utilization of shield slurry and construction & demolition waste (CDW) fines owing to its low requirement for raw materials However, incorporating shield slurry into CLSM brings challenges such as prolonged setting time, reduced flowability and mechanical performance. This study utilized waste shield slurry to adjust the yield stress and viscosity of CLSM, thereby increasing its flowability while reducing segregation and bleeding risks. Additionally, sodium lignosulfonate and recycled gypsum powder were introduced to disperse the ultrafine clay particles and reduce water demand, further accelerating setting and hardening and increased both early and later strengths. A series of shield slurry-CDW fines-based CLSMs with superior workability, low bleeding ratio, and adjustable strength was prepared. The maximum slurry substitution ratio reached 50 wt% of the CLSM. Furthermore, mix proportion design principles correlating CLSM workability and rheology were proposed. Compared to CLSMs utilizing industrial solid wastes, shield slurry-CDW based CLSM has a >50% reduction in cost and 80–86% reduction in natural resource consumption, offering significant economic and environmental benefits.

PHYSICAL PROPERTIES OF ULTRAFINE CLAY-WOOD DUST HYBRID REINFORCED RECYCLED POLYETHYLENE TEREPHTHALATE MATRIX COMPOSITE FOR SEMI-STRUCTURAL APPLICATIONS

This research involves the production of polymer matrix composites as a combination of ultrafine clay, wood dust and recycled Polyethylene Terephthalate (PET) where the matrix is recycled Polyethylene Terephthalate, and the dispersed phase (hybrid fillers) are ultrafine clay and wood dust. The proportion of recycled PET used for composite production varied from 97 wt% - 99 wt%, while that of wood dust varied from 0.5 wt% - 2 wt% and ultrafine clay from 0.5 wt% - 2 wt%. Physical tests including porosity, water absorption and flammability tests were also carried out on the developed samples. Results obtained from physical tests revealed that the densities of ultrafine clay-wood dust hybrid reinforced recycled PET composites (1.051 - 1.209 g/cm3) were relatively higher than those of ultrafine clay reinforced recycled PET composites and wood dust reinforced recycled PET composite. The WD2 composite sample has the least experimental density value of 0.793 g/cm3. The percentage water absorption rate of the wood dust reinforced recycled PET composites were relatively higher than the ultrafine clay reinforced recycled PET composites. The percentage water absorption rate of the hybrid reinforced recycled PET composites were in between those of the wood dust reinforced and ultrafine clay reinforced fillers. The UFC0.5 composite sample (0.5 wt% ultrafine clay, 0 wt% wood dust reinforced 99.5 wt% recycled PET composite sample) has the least percentage water absorption value of 0.12846535 when compared to other samples. The porosity of the hybrid reinforced recycled PET composite samples were relatively lower than the control sample and separately reinforced samples with ultrafine clay and wood dust. However, HB1 composite sample has the least % porosity value of 1.1563. UFC2 has the least flame propagation rate of value of 0.05482456 mm/s.
 Keywords: Ultrafine Clay, Recycled Polyethylene Terephthalate, Polymer Matrix Composite, Wood Dust.

Ultrafine Kaolinite Removal in Recycled Water from the Overflow of Thickener Using Electroflotation: A Novel Application of Saline Water Splitting in Mineral Processing.

The presence of ultrafine clay particles that are difficult to remove by conventional filtration creates many operational problems in mining processing systems. In this work, the removal of clay suspensions has been investigated using an electroflotation (EF) process with titanium electrodes. The results show that EF is a viable and novel alternative for removing ultrafine particles of kaolinite-type clay present in sedimentation tank overflows with low salt concentrations (<0.1 mol/L) in copper mining facilities based on the saline water splitting concept. Maximum suspended solid removal values of 91.4 and 83.2% in NaCl and KCl solutions, respectively, were obtained under the experimental conditions of the constant applied potential of 20 V/SHE, salinity concentration of 0.1 mol/L, and electroflotation time of 10 and 20 min in NaCl and KCl solutions, respectively. Furthermore, the visual evidence of particle aggregation by flocculation during the experiments indicates a synergy between EF and electrocoagulation (EC) that enhances the removal of ultrafine particles of kaolinite.

MECHANICAL PROPERTIES AND WEAR BEHAVIOUR OF KAOLINITE CLAY PARTICLES REINFORCED EPOXY MATRIX COMPOSITES

Epoxy matrix composites reinforced with clay particles were developed by hand lay-up open mould casting technique. The clay used in this study was pulverized and processed into ultrafine particles through the sedimentation process. The composites were developed by blending the epoxy matrix and hardener with various weight fractions of the ultrafine clay particles (2, 4, 6, 8 and 10 wt%) in open test moulds. In order to accomplish a homogeneous blend of the constituents; manual mixing of the blend was carried out for 3 min. The test specimens were left to cure for 24 hours in the moulds and for additional 27 days at room temperature of 27 ± 2 °C and were thereafter detached from the moulds. The developed composites test specimens were subjected to mechanical tests (flexural, tensile and impact) in accordance with ASTM standards and performed at room temperature. Structural characteristics of the clay particles were determined with the aid of an X-ray diffractometer (XRD). The morphologies of the composites were determined using a scanning electron microscope (SEM). There was a progressive enhancement in the mechanical properties of epoxy composites containing 2-6 wt.% ultrafine clay particles while a drastic decrease in the mechanical properties was noticed in the epoxy/clay composites reinforced with 8-10 wt.% ultrafine clay particles. The SEM images revealed homogeneous particles distributions within the epoxy matrix at lower ultrafine clay particles weight fractions (2 wt. % and 6 wt.%).

A Study on Removal of Clay Minerals from Barbil Region Iron Ore; Effect of Scrubbing Followed by Pelletization

The presence of appreciable quantity of clay mineral in Indian hematite ore needs an attrition technique using screw scrubber in the beneficiation circuit to remove the ultrafine clays and avoid downstream operational problems. Spectroscopic analysis revealed that iron ore samples obtained from the Barbil region of Odisha contain a high amount of silica and alumina in the form of clay minerals (e.g., kaolinite) contributed as a loss on ignition (LOI) in the iron-making process. Iron ore fines of below 10 mm size were subjected to a laboratory-scale screw scrubber, and the effectiveness of scrubbing as well as the pelletization of the scrubbed product was investigated. The screw scrubber in the beneficiation circuit helps to remove the clay minerals, causes an increase in iron values from 63.65% Fe(T) to 66.18% Fe(T), with improved physical (CCS of 325 kg/pellet) and metallurgical (RDI of 2.24%) pellet properties.

Microstructural evolution and deformation mechanisms of Khao Kho Fault, Thailand

Lithologies and microstructures of fault rocks from the Khao Kho Fault in Thailand are investigated to understand fault behavior and underlying deformation mechanisms. Fault gouges in the shear zone are mainly composed of kaolinite, illite-mica, and illite-smectite and exhibit weak preferred orientation, ranging from 1.2 to 2.3 m.r.d. These fault cores are characterized by high localized strain and intense deformation due to cataclasis and frictional granular flow mechanisms, which produce transgranular fractures, rounded quartz grains, and an ultrafine clay matrix. In contrast, wall rocks show stronger clay preferred orientation, up to 3.9 m.r.d., despite having less clay content than the fault gouges. Much larger fault-related bent and sheared clay grains are present in the wall rocks, suggesting less severe deformation. The discrepancy between fault cores and wall rocks indicate that the development of fabrics is related to faulting and authigenic processes. Weak fabrics in the slip zone are attributed to the comminution of grains and neomineralization, allowing clay platelets to grow and rotate in many directions. In addition, the abundance of metal oxides indicates extensive, multiple fluid alteration processes, which further influence microstructures and fault properties.

Determination of ultratrace (

There is on-going concern regarding fugitive emissions of trace elements from mining and upgrading of the Athabasca Bituminous Sands (ABS) in northern Alberta, Canada, but remarkably few quantitative elemental data about the resource itself exists. By exploring advances in analytical techniques, an inductively coupled plasma sector field mass spectrometry (ICP-SFMS) method was developed for the determination of trace and ultratrace amounts (<0.1mg/kg) of several elements of environmental concern (Ag, As, Be, Bi, Cd, Pb, Sb and Tl) in bulk ABS and respective bitumen and mineral fractions as separated materials. Samples (n=7) averaged 86±4% mineral matter and 12±3% bitumen. High pressure microwave digestion employing HNO3-HBF4 yielded good recoveries (100±20%) for Ag, As, Be, Bi, Cd, Mo, Ni, Pb, Re, Sb, Tl and V in certified reference materials (NIST 1635, NIST 2711). The distribution of elements within the ABS was dichotomous, with V, Ni, Mo and Re predominantly found in the organic fraction (bitumen) and Ag, As, Be, Bi, Cd, Pb, Sb, and Tl predominantly found in the mineral residue. Trace amounts of As and Pb (0.1–2.0mg/kg), plus ultratrace amounts of Ag, Bi, Cd, Sb and Tl (<0.1mg/kg) were found in the bitumen. Despite filtration (<0.45µm), the bitumen fraction also contained trace amounts of lithophile elements (Be, Co, Ga, Sc, Y, Sm, Dy, Th), which suggested that the occurrence of Ag, As, Be, Bi, Cd, Pb, Sb, and Tl in bitumen was associated with ultrafine clays. Our demonstration of a distinct separation of the ABS trace elements into organic (V, Ni, Mo, Re) and mineral fractions (effectively all other trace elements) may have profound consequences regarding emissions of trace elements to the environment from the industrial development of this resource in northern Alberta.

Study and Practice of Fine Sand Recovery and Wastewater Cleaning System for Xinkaiyuan Crushed Stones Company

Water must be sprayed on the screens to wash off the intermixed clay materials and the fines generated while crushing, so slurry were produced and should be treated to adapt to the requirement of clean production and sustainable development. Based on the slurry natures of the stone-crushing and sand-making process, we presented a novel process comprising hydro-cyclone separation, fines screening，clarification and filtration technologies to recover fine sands and clean the wastewater for recycle. The commercial system were established and run for 3 months. It shows that the +0.045mm fine sands and -0.045mm ultrafine clay materials in the slurry are separated and recovered respectively. Fine sands which was lost and wasted originally are recovered now. The ratio of the water cleaned and reused is up to 95%.

A novel wastewater cleaning system for the stone-crushing and sand-making process

The nature of the slurry from the stone-crushing and sand-making processes is analyzed to develop a novel separation process. The process comprises hydro-cyclone separation followed by screening of the fines, clarification, and filtration. Recovering fine sand and clean wastewater for recycle is demonstrated. The +0.045mm fine sand fraction and −0.045mm ultra-fine clay in the slurry are separated and recovered. Fine sand that was previously lost and wasted is now recoverable. The cleaned and reused water is as much as 94% of the total.

Saline lake diagenesis as revealed by coupled mineralogy and geochemistry of multiple ultrafine clay phases: Pliocene Olduvai Gorge, Tanzania

Mineralogical and geochemical analyses of ultrafine (<0.1μm) extracts of Pliocene clays from Olduvai Gorge reveal the complexities of clay diagenesis in saline, alkaline paleo-waters. Multiple authigenic phases are routinely present; these may be distinguished and quantified by decomposition of XRD (060) peaks coupled with geochemical (microprobe, HRTEM-AEM) and crystallographic (IR) investigation. By assigning geochemistry based on XRD results, we identify three principal phases by octahedral composition: dioctahedral Al-rich, dioctahedral relatively Fe-rich, and Mg-rich with a trioctahedral component. Average octahedral formulae are Al 1.30 Fe 0.57 Mg 0.13 (Al-rich), Al 0.56 Fe 0.80 Mg 0.62 (Fe-rich), and Al 0.09 Fe 0.23 Mg 2.09 (Mg-rich) per half formula unit. IR analyses support these octahedral structures. The Mg-rich phase either has coexisting dioctahedral and trioctahedral domains within individual sheets, or a homogeneous octahedral sheet of intermediate composition. This is, to our knowledge, the first report of an intermediate octahedral occupancy in a 2:1 phyllosilicate. HRTEM observations indicate both solid state octahedral and illitization reactions and dissolution-precipitation. Layer charge and interlayer cations suggest that during illitization, layer charge increase was due to interaction with Na-rich brines, but later K uptake may have been with either saline or fresher fluids with higher K/Na ratios. All three phases occur throughout the basin; relative proportions and octahedral compositions vary. Total Mg content of bulk <0.1μm clay fractions, (a paleochemical indicator in this and other basins) is the product of both the relative abundance and the Mg content of the Mg-rich phase. In addition to shedding light on the crystal chemistry of authigenic 2:1 phyllosilicates, these results demonstrate the paleolimnologic importance of discriminating the presence of multiple authigenic clay phases in lacustrine deposits.

05/02421 Recovery of bitumen from oilsands: gelation of ultra-fine clay in the primary separation vessel

05/02421 Recovery of bitumen from oilsands: gelation of ultra-fine clay in the primary separation vessel

Recovery of bitumen from oilsands: gelation of ultra-fine clay in the primary separation vessel

The bulk of bitumen recovery from oilsands takes place via a flotation/settling process in the primary separation vessel (PSV). Under certain conditions, some oilsands slurries become non-segregating, i.e. both fines and coarse solids remain in suspension and little or no bitumen froth is generated. An ultra-fine (<0.3 μm) component of the oilsands fines fraction (<44 μm) is identified as having the potential to be the major contributor to the thickening (gelation), or sludging, phenomenon observed in some ores. In this work we determined the amounts of ultra-fines in oilsands from different depositional environments. Although a generally linear correlation exists between ultra-fines and fines or clay contents, some samples were found to have a disproportionately high ultra-fines contribution relative to other oilsands. Waste units, in particular, were found to be extremely rich in the ultra-fines and clay-sized fractions. We used a 2H NMR method to measure both the rate and degree of gelation of ultra-fines suspensions separated from oilsands. Sludging conditions are reached when the ultra-fines concentration is between about 1.5 and 2.0 w/w%. Measurement of ultra-fines gelation times showed them to be of the same order as slurry residence time in the PSV. Laboratory jar tests have demonstrated that poor segregation of oilsands components can be correlated with the gelation conditions determined by NMR measurements.

Authigenic clays in East Africa: Regional trends and paleolimnology at the Plio–Pleistocene boundary, Olduvai Gorge, Tanzania

Ultrafine clays ( 4 (saline, alkaline lake deposits). The association of Mg-rich clays with saline, alkaline conditions provides a paleochemical proxy in sedimentary contexts. The octahedral chemistry of central-basin clays from paleolake Olduvai (∼1.79 Ma) records two lake expansions, with an intervening lake contraction, over ∼18,000 years. The initial lake expansion correlates well with the marine record of increased African humidity, but the subsequent drying episode does not, suggesting that some high-frequency environmental oscillations in East Africa may occur independent of obliquity and precession control. The clay record correlates well with the fossiliferous and archaeologically rich stratigraphy of the lake margin, and suggests that fossils and artifacts accumulated on the exposed lake margin over <4000 years. The chemistry of clays is a potentially powerful tool to add to multi-proxy studies in basins with alkaline waters, particularly in stratigraphic intervals that lack pollen, calcareous, or siliceous microfossils.

Athabasca oil sands: effect of organic coated solids on bitumen recovery and quality

The Canadian oil sands deposits in northern Alberta contain about 1.3 trillion barrels of crude oil equivalent. The largest of the four major formations is found in the Athabasca region where bitumen is heterogeneously distributed throughout an unconsolidated mineral matrix. About one-tenth of the oil sands in this deposit is economically recoverable by conventional surface mining techniques. The Hot Water Extraction Process (HWEP) is used commercially to recover bitumen from surface mined oil sands ore. The viability of this process relies on the existence of a thin water film around each solid particle in the ore matrix. However, a completely water-wet mineral condition is not generally the case for oil reservoirs, including oil sands deposits. In the latter case, it has been shown that certain solid fractions are associated with significant amounts of toluene insoluble organic matter (TIOM), physically or chemically adsorbed onto particle surfaces. These fractions are generically described as ‘organic rich solids’ (ORS). In bitumen separation processes, the organic matter associated with various ORS fractions represents an impediment to optimum bitumen separation and upgrading. In this sense, these solids are considered to be ‘active’ relative to the ‘inactive’ water wetted quartz particles comprising the bulk of the oil sands ore. Preliminary results indicate that the ORS content of an ore appears to be a better predictor for ore processability than the traditional use of bitumen or fines (−44 μm) contents. Two types of ORS have received particular attention. The first is a coarser fraction, usually less than 44 μm but also occurring as particles greater than 100 μm in diameter. This material typically occurs as aggregates of smaller particles bound together by humic matter and precipitated minerals. During the bitumen separation process, these heavy aggregates carry any associated bitumen into the aqueous tailings, thus reducing overall bitumen recovery. The second important fraction comprises very thin, ultra-fine clay particles with a major dimension of <0.3 μm. These ultra-fine clays, with a surface coating of organic matter, remain with bitumen during the separation process. In bitumen upgrading, these solids may be entrained with volatile overheads and cause problems in downstream operations. This paper summarises the protocols developed to separate and characterise these intractable components from HWEP process streams and discusses their role in determining bitumen recovery and quality.

Effect of heat treatment on the dispersity of Sn(IV)—Sb—O powders and the porosity of thick-film gas sensors based on them

A study is made of how the granulometric composition and porosity of powders of solid solutions in the system Sn(IV)−Sb−O is affected by the conditions of precipitation of mixtures of tin hydroxide and antimony hydroxide and the heat-treatment temperature. Powders of tin and antimony hydroxides have a microporous structure and a high (≥200 m2/g) specific surface. Heat treatment above 870 K forms Sn1−xSbxO2 solid solutions, this being accompanied by an increase in the size of the particles and transformation of the microporous structure to a mesoporous structure. An increase in the antimony content of the solid solutions helps form finer powders. A examination is made of the parameters of the pore structure of bulk specimens of semiconductor gas sensors obtained by heat-treating mixtures of powders of solid solutions and ultrafine clay.

Effect of particle size on the flocculation behaviour of ultra-fine clays in salt solutions

AbstractThe Athabasca oil sands deposit in Alberta contains ~5 x 109 m3 of bitumen accessible by surface mining. During bitumen separation from the mined ore, ultra-fine (&lt;300 nm) aluminosilicate clays only a few layers thick (U/F) are mobilized and become dispersed in the process water. In this water containing dissolved salts from natural deposits, U/F are capable of forming thixotropic gels. The consequence of this is the production of large volumes of mature fine tailings (MFT) with a high water holding capacity. For mine planning purposes, the objective of predicting and possibly mitigating MFT formation requires an understanding of the colloidal behaviour of U/F particles in salt solutions. In this work, photon correlation spectroscopy and the deuterium NMR method are used to provide an insight into the U/F floc formation process. These results are correlated with conventional analysis of settling data.

DISTRIBUTION AND TYPES OF SOLIDS ASSOCIATED WITH BITUMEN

ABSTRACT In the conventional Hot Water Extraction Process bitumen is separated as a froth that is then diluted with naphtha and subjected to two stages of centrifugation. The resulting bitumen solution still contains residual water, dissolved salts and mineral solids. Before upgrading the solvent and other volatile components are removed by topping at 524°C. The salts and mineral solids remain with topped bitumen; their presence can lead to serious operational problems in the bitumen upgrading process. In the present work the solids associated with bitumen (BS) have been identified as mainly ultra-fine (nano sized) aluminosilicate clays coated with strongly bound toluene insoluble organic material having “asphaitene characteristics”. It is proposed that these ultra-fine clays with their strong tendency to collect at oil-water interfaces, are the key component responsible for the presence of intractable water and associated salts in bitumen froth.

Effect of Particle Size on the Flocculation Behaviour of Ultra-Fine Clays in Salt Solutions

Effect of Particle Size on the Flocculation Behaviour of Ultra-Fine Clays in Salt Solutions

Rb-Sr Ages of Diagenesis of Mg-rich Clay in Permian Sediments, Palo Duro Basin, Texas Panhandle, U.S.A.

ABSTRACT Mid- to upper Permian sedimentary rocks in the shallow (< 3 km), intracratonic Palo Duro Basin, Texas Panhandle, occur in multicyclic carbonate-evaporite-redbed sequences, interpreted to be hypersaline shelf depositional assemblages. Certain marker horizons can be traced continuously over the entire basin. Clay minerals include distinctive varieties of Mg-rich smectite, chlorite, or mixed-layer species resulting from diagenesis in an evaporitic environment. Discrete particle-size fractions of clay were separated from core recovered from the Tubb (Leonardian), San Andres Unit #4 (lower Guadalupian), upper Seven Rivers (upper Guadalupian), and Salado-Tansill (Guadalupian-Ochoan) Formations to determine the times of mineral genesis. Rb-Sr isotopic data, for aliquots of a clay sample that has been leached by diverse ion exchange reagents, plot as a linear array in a Rb-Sr isochron diagram. For ultra-fine clay (< 0.05 µm), interpreted to be diagenetic, the slope of the data array corresponds to the time of diagenesis. Ages of clay diagenesis in the four sampled stratigraphic units agree generally with ages of deposition according to the geologic time scale, signifying that diagenesis was penecontemporaneous with deposition. Analyses of coarser clay fractions (0.2-0.5 µm and 2-4 µm) indicate the presence of a detrital component. In most instances, initial 87Sr/86Sr in diagenetic clay is higher than the Sr isotope ratio measured directly in associated anhydrite. Introduction of radiogenic Sr from occasional stream influx or from concurrent diagenetic dissolution of silicate detritus could have elevated 87Sr/86Sr in the ambient brine that mediated clay diagenesis.

Biwetted ultrafine solids and structure formation in oil sands fine tailings

A high water holding capacity of oil sands fine tailing has been attributed to the presence of ultrafine (<0.2 μm) clay fractions. On the basis of hydrophobic character two major types of ultrafines are recognized: biwetted, associated with a significant coverage or organic matter and preferentially hydrophilic solids. The effect of biwetted solids on the colloidal stability of ultrafine clays in aqueous suspensions has been studied by dynamic light scattering and 2H n.m.r. methods. The organic matter associates with the surfaces of the biwetted solids is believed to be responsible for their accelerating effect on aggregation. The results indicate that prevention, or reduction, of the amount of biwetted solids entering the tailings pond could be beneficial.