Clay Deposits Research Articles

Nesting habits of Baya Weaver Ploceus philippinus (Linnaeus, 1766) on power and television cables in the agricultural landscape of Kallakurichi district, Tamil Nadu, India

The nesting habits of Baya Weaver Ploceus philippinus with nesting site (e.g., power and television cables), source of nest materials, various developmental stages of nests, abnormal nests, number of individuals and their association with other bird species, and threats to their nests were studied between March and September 2021 in the agrarian landscapes of 42 villages in Kallakurichi District, Tamil Nadu. A total of 155 nest colonies containing 1,725 nests of various developmental stages and 1,993 adult birds were counted on power/television cables. The number of nests per colony found varied from one to 57. The average number of nests per colony was eleven. Baya Weaver had preferred power/television cables as nesting sites in the study area in spite of availability of potential nest-supporting trees, such as Cocos nucifera and Borassus flabellifer within 500 m radii from cables bearing nests. Birds used fibres of sugarcane leaves (Saccharum officinarum) for the construction of nests. Out of 778 helmet stage nests observed, 90% (n = 716) helmet stage nests had clay deposits on their inner walls and no clay deposits were found in the remaining 10% (n = 62) helmet stage nests. Eleven types of abnormal nests constituted 17% (n = 286) of the total nests. Sixteen other bird species (e.g., birds of order: Passeriformes, Coraciiformes, Piciformes, Cuculiformes and Columbiformes) were found associated with the individuals of Baya Weaver. These bird species strictly shared similar roosting and foraging grounds. The avian predators such as House Crow Corvus splendens, Large-billed Crow Corvus macrorhynchos, Black Drongo Dicrurus macrocercus, Rufous Treepie Dendrocitta vagabunda, Coucal Centropus senegalensis, and Shikra Accipiter badius had damaged the nests, eggs and chicks. The study revealed that about 1.1% nests (n = 197) were probably damaged by these avian predators. Power cables in the study sites had provided suitable nesting sites for Baya Weavers. The causes for utilization of power cables as nesting sites in larger geographical areas require further studies.

Deciphering Mineralogical Composition and Clay Diagenesis in Exposed Shales of Jaintiapur, Surma Basin: Unveiling Insights into Burial Diagenesis

Mineralogical analysis of exposed shale samples in the Jaintiapur region was conducted utilizing X-ray diffraction (XRD) techniques. The studied shales are characterized by illite, chlorite, illite/ smectite mixed layer clay, and kaolinite as the predominant clay minerals, with a relatively lower proportion of smectite. Additionally, the non-clay fraction consists mainly of quartz, feldspar, dolomite, and trace amounts of pyrite. Notably, illite and chlorite exhibit prominent abundance within the clay portion, while quartz is the prevailing non-clay mineral. Furthermore, the investigation reveals a notable enrichment of illite and chlorite with the advancement from younger to older stratigraphic formations in the studied shale samples, indicating greater intensity in clay mineral diagenesis in deeper stratigraphic formations. The transition from smectite to illite minerals can release Si, Ca, Fe, and Mg ions, potentially entering nearby sandstones and leading to cementation with quartz, chlorite, and calcite. This process aids in retaining pore water in shales. In this context, overpressure development influenced by clay diagenesis is not primarily due to cementation while undergoing smectite to illite conversion but due to illite packet formation within smectite, reducing shale permeability. During this conversion, interlayer water shifts to free water, causing volume reduction compounded by the low permeability of shale, trapping fluids in the pores. This expansion of pore water, reduced velocity, and increased pore pressure suggest that mineral transformation with burial depth might contribute to overpressure development. However, the observed decline in smectite clays in sediments transitioning from younger to older, culminating in their absence in older shale-dominated formations, explains the presence of diagenetic illite and chlorite. This study underscores the progressive diagenetic transformation in clay mineralogical composition with progressive burial across the sedimentary succession. The Dhaka University Journal of Earth and Environmental Sciences, Vol. 12(2), 2023, P 69-82

Insight into hemostatic performance and mechanism of natural mixed-dimensional Attapulgite clay

Clay minerals have attracted wide attention as biomedical materials due to the unique crystal structure, abundant morphology and good biocompatibility. However, the relevant studies on the abundant natural mixed clay deposits were scarcely reported. Herein, the hemostatic performance of natural mixed-dimensional attapulgite clay (MDAPT) composed of one-dimensional attapulgite and multiple two-dimensional clay were systematically investigated based on the structural evolution using oxalic acid for different time. The results of hemostatic evaluation showed that MDAPT leached by oxalic acid with 1 h presented the shortest clotting time (134 ± 12.17 s), a 15.09 % and 41.74 % reduction of relative hemoglobin absorbance at 180 s and 120 s when compared with the control group, respectively, and an increase of 19.45 % of the blood clotting index in vitro, as well as MDAPT obtained the shortest bleeding time (158.5 ± 6.9 s), nearly 66 % and 31 % reduction blood loss as compared to the blank group and the YNBY group in vivo. This improvement was primarily ascribed to the synergistic effect of lamellar non-expandable illite, and nano rod-like attapulgite. Furthermore, the rapid hemostasis of MDAPT was also due to the joint effect of superhydrophobic property toward blood, minimizing blood loss, surface negative charge, metal ions from MDAPT structural skeleton, promoting an average increase of 21 % for platelet activation. The results suggested that MDAPT could be served as a promising efficient inorganic hemostatic materials, which provided a feasible strategy to realize the high-valued utilization of natural mixed clay resources.

Seismic response of offshore tetrapod piled jacket foundations subjected to environmental loads in soft-over-stiff clay deposit

Under the combined action of environmental and seismic loadings, offshore wind turbines supported by tetrapod piled jacket (TPJ) foundations may experience tilting and rotational failures, and even the shutdown. However, there is still a notable gap in the research on the dynamic response of the TPJ system in this condition, especially in the multilayered clay deposits. This study conducts advanced three-dimensional finite element simulation to investigate the seismic response of TPJ systems in soft-over-stiff clay deposit under the combined influence of wind and wave loadings. The results indicate that with a minor strength ratio between two layers, especially for strength ratios < 0.28, the peak values of the pile bending moment envelopes increases obviously, which is located near the soil layer interface. Near the soil layer interface, a sudden expansion in the soil plastic strain can be observed at this location. When the top layer thickness is substantial, surpassing 0.75 times the pile length, the restraining effect of the bottom stiff layer on the pile results in the peak value of the acceleration response envelopes and a significant reduction in bending moment near the pile end.

An SPH framework for drained and undrained loading over large deformations

AbstractWe propose a new approach for performing drained and undrained loading of elastoplastic geomaterials over large deformations using smoothed particle hydrodynamics (SPH), a meshfree continuum particle method, combined with the modified Cam Clay (MCC) model of critical state soil mechanics. The numerical approach draws upon a novel one‐particle two‐phase penalty‐method based formulation for handling undrained loading in saturated soils, which allows tracking of the buildup of pore‐water pressures under combined shearing and compression. Large‐scale parallelized simulations are employed to accommodate a significant number of degrees of freedom in a three‐dimensional setting. After verification and benchmark testing, the SPH based formulation is used to analyze the propagation of reverse faults through fluid‐saturated clay deposits and the rupture of strike‐slip faults across earthen embankments. The computational methodology tests the robustness of the meshfree approach in situations where the soil tends to dilate on the ‘dry’ side of the critical state line and to compact on the ‘wet’ side, but cannot, because of the incompressibility constraint imposed by undrained loading. Our results extend the current understanding of fault rupture modeling and further demonstrate the potential of our framework together with the SPH method for large deformation analyses of complex problems in geotechnics.

Cyclic behavior of port-said soft clay in cyclic direct simple shear tests

A thick deposit of soft clay, known as “Port-Said Clay” (PSC), is commonly encountered in the northern formations close to the Mediterranean shores of Egypt. The growing level of development, including transportation corridors like highways and tunnels, in areas rich with PSC necessitated an in-depth study to characterize its dynamic behavior. This study presents a first comprehensive experimental investigation of the dynamic behavior of the soft PSC using Cyclic Direct Simple Shear Tests. The effects of plasticity index (PI), loading frequency (f), and cyclic stress ratio on the cyclic resistance, shear modulus, shear modulus reduction ratio, pore water pressure generation, and damping ratio was investigated. The results showed that all the investigated behavior parameters are primarily sensitive to PI and f. The conclusions drawn from this study on PSC open the way to further laboratory-based investigations of the dynamic behavior of PSC, in addition to numerical modelling of the seismic interaction between PSC and different types of structures.

Effect of Vehicle Cyclic Loading on the Failure of Canal Embankment on Soft Clay Deposit

Road embankments along irrigation canals, constructed on soft Bangkok clay, have always been unstable. Numerous studies have shown that rapid drawdown of water level may be one of the main causes, while vehicle cyclic loading may also contribute to embankment failure. This study aims to investigate the impact of vehicle loading on the failure of embankments built on Bangkok soft clay. The behavior of soft Bangkok clay under vehicle load has been investigated by employing conventional and dynamic triaxial techniques, and finite element method (FEM). This study also examined the effects of soft clay thickness and cyclic loading with different magnitudes and frequencies. The laboratory testing results indicate that the threshold stress of the soft clay is estimated to be approximately three-fourths of the undrained shear strength of the soil. The reduction in effective stress in the soft clay is caused by varied frequencies and thicknesses of the clay. Based on the analysis results, it has been proven that the cyclic loads exerted by vehicles solely are insufficient to cause the embankment to collapse. Nevertheless, the repetitive loading of vehicles may result in a one-quarter decrease in the embankment’s factor of safety.

Estimating Shear Strength of Marine Soft Clay Sediment: Experimental Research and Hybrid Ensemble Artificial Intelligence Modeling

In the design of offshore engineering foundations, a critical consideration involves determining the peak shear strength of marine soft clay sediment. To enhance the accuracy of estimating this value, a database containing 729 direct shear tests on marine soft clay sediment was established. Employing a machine learning approach, the Particle Swarm Optimization algorithm (PSO) was integrated with the Adaptive Boosting Algorithm (ADA) and Back Propagation Artificial Neural Network (BPANN). This novel methodology represents the initial effort to employ such a model for predicting the peak shear strength of the soil. To validate the proposed approach, four conventional machine learning algorithms were also developed as references, including PSO-optimized BPANN, Support Vector Machine (SVM), BPANN, and ADA-BPANN. The study results show that the PSO-BPANN model, which has undergone optimization via Particle Swarm Optimization (PSO), has prediction accuracy and efficiency in determining the peak shear performance of marine soft clay sediments that surpass that offered by traditional machine learning models. Additionally, a sensitivity analysis conducted with this innovative model highlights the notable impact of factors such as normal stress, initial soil density, the number of drying–wetting cycles, and average soil particle size on the peak shear strength of this type of sediment, while the impact of initial soil moisture content and temperature is comparatively minor. Finally, an analytical formula derived from the novel algorithm allows for precise estimation of the peak shear strength of marine soft clay sediment, catering to individuals lacking a background in machine learning.

Mineralogical investigation of asbestos contamination of soil near old vermiculite processing plant in Honolulu, Hawaiʻi

From 1954 to 1983, a vermiculite processing facility operated near the Honolulu airport and processed raw material from the Libby, Montana mine, which is now well known for the high asbestos content of its clay deposits. The factory was closed in 1983 due to health hazard concerns, and remediation was performed in 2001 as part of the Libby mine superfund project. However, because of close proximity of the closed-down facility to residential areas of metropolitan Honolulu, some concerns remain regarding the possible environmental persistence of the harmful contaminant. To assess the dispersion of asbestos-contaminated vermiculite and explore the impact of trade winds on its distribution, air samples, and soil samples were collected from multiple locations near the former vermiculite plant. Polarized light microscopy was employed to identify elongated minerals, including potential asbestos. Quantitative mineralogical analysis utilizing X-ray powder diffraction and Rietveld refinement revealed an average content of approximately 7% vermiculite and 4% tremolite at the site. The asbestiform nature of tremolite was confirmed through X-ray micro-diffraction. Detailed analysis of airborne samples using transmission electron microscopy revealed no detectable levels of asbestos fibers in the vicinity of the former processing facilities, but the possibility of asbestos fibers becoming airborne due to mechanical disturbance during dry weather cannot be ruled out.

Enigmatic mixture of magnetite magnetofossils and diagenetic greigite as the magnetic carriers of the Early Miocene lacustrine sediments from the Most Basin in Central Europe

The Early Miocene lacustrine sediments of the Most Basin in the Czech Republic preserve a European continental paleoenvironmental archive. A number of paleoenvironmental and magnetostratigraphic studies have been carried out on sediment cores from boreholes due to ongoing coal mining in the basin. However, the magnetic carriers of the studied sediments have not been identified clearly. Here, we present a detailed paleo-rock magnetic study from the Burdigalian sediments near the Bilina mining area, Most Basin. The studied clay sediments cover the period of local lakes and a basin-wide lake above the main coal seam. Our results suggest that the magnetic carriers of the studied section in the Most Basin are mixtures of authigenic greigite and magnetite magnetofossils with overlapping magnetic signatures. Greigite is formed by migration of pore water through the sediment column, where iron from siderite grains reacts with these fluids with limited H2S, which then favors greigite precipitation. The co-existence of greigite and magnetite indicates a partial dissolution of magnetofossils due to H2S deficiency. Diagenetic greigite has been problematic in paleomagnetic studies due to an unknown time lag between the depositional remanence and the chemical remanent magnetization (CRM). A ghost polarity interval reveals that greigite acquired at least ∼45 kyr delayed CRM. The revealed timing of remanence acquisition brings a new perspective to the chronostratigraphic structure of the Most Basin.

Archaeometric Studies on Bricks from the Stratonikeia Ancient City in Caria

The ancient city of Stratonikeia is located within the territory of Eskihisar Neighbourhood in Yatağan District of Muğla Province. Excavations have been undertaken at the site since 1977. Settlement at the site of the ancient city is understood to go back to the second millennium BCE. At the site it is possible to see structures from a wide time span ranging from Classical Period through the twentieth century. Within the scope of the present study, a total of 25 samples were taken from seven structures within the ancient city of Stratonikeia. This study aims to cast light onto the archaeometric characters of the brick samples, to retrieve information on their production technologies, obtain data regarding their firing temperatures and their production sites as local or imports. The samples were investigated using stereomicroscope, optical microscope, color analysis, XRF, XRD, statistical and SEM-EDS methods. Various analyses led to compatible results and the brick samples were categorized into three main groups and one subgroup. It was noted that most of the samples were fired at 750-850oC and all of them were produced with clay taken from similar clay deposits.

Assessment of Liquefaction Potential by Comparing Semi-Empirical Methods Based on the CPT Test

Abstract Liquefaction is a dangerous and temporary phenomenon whereby water-saturated soil loses all or part of its strength. Undrained conditions associated with cyclic loading increase water pressure in soil pores, thereby reducing effective stress. The aim of this study is, on the one hand, to report on the phenomenon of liquefaction of sand, clay and silt deposits in more or less water-saturated zones in the section located at the heart of the central alluvial plain of the Oued Sebou in the mio-plioquaternary Gharb basin and, on the other hand, to study the ability of semi-empirical methods to correctly assess liquefaction potential, while specifying the most appropriate method for the area studied. The study is based on data from experimental results of static penetrometer tests between the Mnasra - Ouelad Salama zone in the Oued Sebou alluvial plain of Morocco's mio-plio-quaternary Gharb basin, made up of sandy, sandy-clay, sandy-silt and silty-sandy formations, which are more sensitive to liquefaction due to their saturation and grain size. We present and discuss the results of Olsen's method, Juang's method and Robertson's method, which are based on the CPT static penetrometer test, as well as looking at the impact of dynamic loading and soil structure on liquefaction probability index values.

Classification of rare earths mineral resources using the Jequié/BA complex rock weathering chemical index

The most common economic mineral deposits of Rare Earths are associated to magmatic calc-alkaline to alkaline rocks and their products. This work presents data from drilling carried out in rocks of the Jequié/BA Complex, mineralized in rare earths, which were subjected to an intense weathering process, similar to what occurred in the Ion Adsorption Clays deposits in southern China. The interpretation of the survey data allowed the classification of rare earths mineral resources with similar, sometimes higher, levels than those of Chinese deposits, contained in the lateritic regolithic profile studied. The chemical index of rock alteration (CIA) was adopted as a classification tool, horizontally separating the mineralized weather profile into six zones. The data indicate that there was supergenic enrichment REO in the lower portions of the profile and sometimes in the upper zones. The average levels ranged between 0.09% and 0.22% REO, with maximum values of 1.6%. A model section representing the deposit of rare earths minerals of supergenic origin in rocks of the Jequié/BA Complex was developed.

How Was the Late Neogene Red Clay Formed in the Ordos Plateau (Northwest China)?

Eolian sediments are extensively distributed across the Earth’s surface, and their formation is intricately linked to climate change, tectonic activity, and topographic features. Consequently, the investigation of eolian sediments bears great geological significance. The northwest region of China is renowned for hosting the most extensive and thickest Late Miocene–Pliocene red clay deposits globally. Nonetheless, scholars have yet to reach a consensus regarding the precise formation processes of these red clays. The identification of the source region of the red clays is crucial for comprehending their formation mechanism. The correlation of zircon U-Pb age spectra is a frequently utilized method for determining the provenance of eolian sediments. In this study, we compared the previously published zircon U-Pb ages (n = 12,918) of the Late Miocene–Pliocene red clays in the Ordos Plateau with those from the potential provenance regions (n = 24,280). The analysis, supported by the tectonic and climatic background of the region, revealed that the Late Miocene–Pliocene red clay in the Ordos Plateau originates predominantly from the Yellow and Wei rivers, with a minor contribution from the weathering of bedrock in the western North China Craton. The transport of these detrital materials by the East Asian winter monsoon is impeded by the presence of the Qinling and Taihang Shan, resulting in their deposition on the flat surface of the Ordos Plateau. This development of red clay is consistent with the proximal accumulation model, illustrating how the hydrosphere, atmosphere, and lithosphere interacted to shape the red clay deposits during the Late Miocene and Pliocene periods in the Ordos Plateau.

Fingerprinting enhanced floodplain reworking during the Paleocene–Eocene Thermal Maximum in the Southern Pyrenees (Spain): Implications for channel dynamics and carbon burial

Abstract The sedimentary record of the Paleocene–Eocene Thermal Maximum (PETM, ca. 56 Ma) allows the study of feedback mechanisms over the entire duration of a climatic event, from carbon release to the subsequent recovery phase. Clay sedimentation increase in the oceans during the PETM is linked to enhanced terrestrial erosion. Fluvial channel mobility has been invoked to explain this increase in fine sediment export based on more frequent transitional avulsions. In this study, we test whether the reworking of Microcodium (prismatic calcite concretions) from the floodplain to marine environments can serve to fingerprint floodplain reworking due to channel mobility. We quantified the abundance of floodplain-sourced Microcodium grains reworked in fluvial to marine sandstones pre-dating and coeval to the PETM in the Southern Pyrenees (Tremp Basin, Spain). Laser ablation–inductively coupled plasma–mass spectrometry U-Pb ages on calcite confirm the Thanetian age of the Microcodium grains. Our data show a four-fold increase in the export of floodplain sediments to the marine domain during the PETM. Moreover, we show that this is predominantly due to enhanced channel mobility, reworking channel banks and interfluves, with increased erosion in the hinterland as a secondary factor. This increase in floodplain reworking would correspond to an increase in biospheric carbon burial flux by a factor of 2.2. Therefore, enhanced channel mobility and fine-grain sediment transport to the oceans during a climatic perturbation such as the PETM may constitute an important negative feedback mechanism.

Migration characteristics and geohazards risk analysis of swelling clay in clayey silt hydrate sediments

The safe and long-term hydrate production in loose clayey silt sediments with high clay content is one of the research priorities, in which the fines migration is one of the key factors. The characteristics of montmorillonite swelling and dispersion make its migration behavior more challenging, which causes the evolution of reservoir seepage properties and potential geohazards risk cannot be predict. The migration behavior of montmorillonite induced by pore water was investigated, and discusses its potential impact on the geomechanical properties of the reservoir. The results show that the combined effects of montmorillonite swelling, which creates favorable conditions for blockage, and migration, which exacerbates permeability decline, make montmorillonite have a much greater effect on seepage characteristics in clayey silt sediments than illite. Higher montmorillonite content and low salinity increase the particle concentration in the pore water, which creates a source of particles for blockage. The low reynolds number indicates that the particles mainly detach from the pore wall with rolling in laminar flow and the lifting force can be neglected. As a result of this combined effect, the montmorillonite is more likely to readsorb and block the pore throat with bridging. This work will help to understand the migration behavior of montmorillonite in clayey silt formations with low permeability, which needs to be paid attention to when formulating gas production schemes and safety control strategies.

Perhitungan Volume Stockpile dan Pengoptimalan Waktu Pengolahan Stockpile 3, 5 dan 6 Terhadap Produksi Alat Gali muat dan Alat Angkut pada TB Primer Batubesi PT Timah Tbk

PT Timah Tbk's Batubesi Primary Large Mine has experienced a significant decline in production in recent years, causing a change in the mining process to stockpile management that is still economical with a grade of 0.2%. This study aims to determine the volume and production of stockpiles 3, 5 and 6, the type of sediment and Sn content of stockpile material and the time required to spend stockpile material 3, 5 and 6 in order to get the optimal time. The method used is a quantitative method by taking cycle time data as much as 30 data and analyzing sample levels using XRF on each stockpile. The results of this study obtained the volume of stockpile 3 material is 132,648.42 m3,, stockpile 5 is 162,570.25 m3, and stockpile 6 is 33,090.19 m3. The calculated machine productivity at stockpile 3 is 42.17 tons/hour, stockpile 5 is 48.11 tons/hour and stockpile 6 is 39.53 tons/hour. The highest Sn content is found in stockpile 6 which is 0.33% with the type of skarn sediment. While the lowest Sn content is found in stockpile 3 which is 0.2% with oxide clay sediment type. In stockpile 5, the Sn content is 0.31% with the type of oxide clay sediment. The remaining volume of stockpile material in stockpiles 3, 5 and 6 can be spent with a time of 2.78 years using 1 unit of excavation equipment and 1 unit of transportation equipment. Optimization is carried out so that the remaining stockpile reserves can be spent within 1.74 years using 1 unit of excavation equipment and 2 units of transport equipment.

Mid-Holocene marine faunas from the Bangkok Clay deposits in Nakhon Nayok, the Central Plain of Thailand.

Based on several field investigations, many molluscan shells and chondrichthyan teeth, together with other invertebrate and actinopterygian remains were found from the marine Bangkok Clay deposits in Ongkharak, Nakhon Nayok, at a depth of ~ 5-7 m below the topsoil surface. Animal macrofossils recovered from these Holocene marine deposits were identified and their chronological context was investigated in order to reconstruct the paleoenvironments of the area at that time. The majority of marine fossils recovered from the site consist of molluscs, with a total of 63 species identified. Other invertebrate species include a stony coral, a mud lobster, barnacles, and a sea urchin. The vertebrates are represented by fish remains, including carcharhinid shark teeth from at least nine species, stingray and trichiurid teeth, and one sciaenid otolith. The molluscan fauna indicates that the paleoenvironments of the area corresponded to intertidal to sublittoral zones, where some areas were mangrove forests and intertidal mudflats. The fish fauna is dominated by the river shark Glyphis, indicating freshwater influences and possibly occasional brackish conditions. The carbon-14 analysis of mollusc and charcoal remains shows that deposition of the marine sediment sequence began during the mid-Holocene, spanning approximately from 8,800 to 5,300 cal yr BP. This study provides in-depth insights into the diversity of fishes, marine molluscs, and other invertebrates from the Bangkok Clay deposits, supporting the existence of a marine transgression onto the Lower Central Plain of Thailand during the mid-Holocene.

Rare-earth element (REE) remobilization and fractionation in bauxite zones from sedimentary kaolin deposits, western Georgia (USA), Upper Coastal Plain

Rare-earth elements (REE) are critical minerals that are indispensable for high-tech products and technologies. Significant efforts have been focused on the exploration and identification of new and domestic reserves of REE. This study reports geochemical and mineralogical occurrences of accumulated REE with significant fractions of ion-adsorption clays (IAC) within bauxite-kaolin ore, hosted within sedimentary strata. This deposit type can be found throughout portions of Georgia and eastern Alabama (USA) in the Southeast Upper Coastal Plain. These deposits were developed by high degrees of chemical weathering of older, kaolinite-rich sedimentary strata. Several major changes in whole rock mineralogy and geochemistry occurred, leading to the development of zones of REE depletion, fractionation, and accumulation. Depletions of REE in the bauxite zone were significant, with whole rock contents of ∼50% ΣREE relative to average upper continental crust (UCC). Fractionated REE were observed by low La/YbN values (La/YbN = 0.2) due to depletion in LREE (<40% UCC) with concomitant HREE retention (∼1.1–1.3 times UCC). Strongly positive Ce/Ce* anomalies (Ce/Ce* = 1.3), very low ion-exchangeable Ce contents (Ce/LREE = 0.1), and low solubility of Ce (0.9–1.2%) under reducing conditions compared to all other LREE (4.5–9.9%) were further observed. These characteristics were strong indications of REE fractionation that occurred during formation of the bauxite zone. Underlying the bauxite zone, accumulations of the remobilized REE were substantial. At the base of the lower kaolin zone, elevated ion-exchangeable REE contents were notable (11–33% for total REE), and more specifically 11–12% for LREE, ∼28% for ΣTb-Lu, and ∼ 33% for Y. The elevated ion-exchangeable contents coincided with whole rock contents that were ∼ 250% ΣREE relative to UCC. These REE accumulations occurred within organic-rich strata at the base of the section. This setting represents a significant difference relative to the REE accumulations in profiles for the granite-regolith deposit type. These findings highlighted the movement of dissolved REE, accumulation as sorbed species, as well as the potential role that organic ligands play during REE precipitation and sorption processes. These results permit consideration for further research into REE occurrences in clay deposits of sedimentary origin, which have been underexplored compared to granite-regolith REE deposits.

Viability and life cycle assessment of Fuller's Earth as a low-cost adsorbent for zinc removal from aqueous solutions: Operating parameters, removal mechanisms and environmental impacts

Zinc is a heavy metal that has several health risks and must be removed from wastewater effluents before discharge to water bodies or reuse. Fuller's earth is a sedimentary clay and characterized by its low cost and availability. In this research, Fuller's earth (FE) was investigated as an adsorbent for the Zinc (Zn) removal from aqueous solutions to understand its performance, the mechanism of removal, and the potential environmental impacts. Life cycle assessment (LCA) was conducted using ReCiPe 2016 midpoint method. Zn adsorption studies on FE were conducted at various pH (2.5–9), temperatures (10°C, 25°C, and 40°C), initial concentrations of Zn (25, - 150 mg/L) and adsorbent doses of (0.25–4 g/ 50 ml). The Zn removal efficiency reached 99% at pH = 9 at an initial Zn concentration = 100 mg/L and the adsorbent dose = 0.25 g/ 50 ml. The experimental data fit into the Temkin isotherm, while kinetics were best expressed by pseudo-second order. The controlling step of the adsorption process was the film diffusion according to Boyd model. Thermodynamic experiments showed that adsorption is endothermic with an accompanying rise in randomness in the system. The adsorption capacity was 3.56 mg/g. Images by SEM confirmed the occurrence of adsorption. The desorption was successful at different concentrations of HCl. LCA results showed that the maximum negative and positive environmental impacts were associated with mineral resource scarcity (7.5*10–5 kg Cu eq) and human non-carcinogenic toxicity (−0.821 kg 1,4-DCB), respectively.