Article
Chemistry, Physical
D. A. Dixon, J. Stone, K. Birch, C. S. Kim
Summary: The NWMO is evaluating Sedimentary and Crystalline geosphere media for a potential Deep Geological Repository (DGR) for nuclear waste. They tested bentonite-aggregate mixtures with different compositions and observed the effect of compaction efforts on densification. The results showed that the materials met the required performance goals for swelling pressure and hydraulic conductivity.
APPLIED CLAY SCIENCE
(2023)
Article
Engineering, Geological
Chandra Bhanu Gupt, Sanandam Bordoloi, Metta Niranjan Bhatlu, Sreedeep Sekharan
Summary: This study determined the upper and lower bounds of equilibrium hydraulic conductivity of amended B under extended flow duration. The results showed significant differences between constant-volume and free-swelling conditions due to geomaterial interaction and mineralization. The study also proposed empirical relationships for estimating long-term hydraulic conductivity based on short-term results, plasticity, and geomaterial type. Overall, this study highlights the potential use of alternative amendment materials and the importance of considering free-swelling conditions in liner design.
CANADIAN GEOTECHNICAL JOURNAL
(2022)
Article
Engineering, Geological
Juan Hou, Rui Sun, Craig H. Benson
Summary: A hydrodynamic model was used to simulate the flow in an idealized geosynthetic clay liner (GCL) containing bentonite, and the results suggest that the hydraulic conductivity of GCLs decreases as the bentonite granules hydrate and swell, forming smaller intergranular flow paths. The model also indicates that greater granule swelling is required to achieve low hydraulic conductivity when the bentonite is comprised of larger granules or has a lower density. Furthermore, the model predicts that intergranular pores become extremely small as the hydraulic conductivity approaches 10-11 m/s.
GEOTEXTILES AND GEOMEMBRANES
(2023)
Article
Engineering, Geological
D. A. Dixon, J. Stone, K. Birch, C. S. Kim
Summary: Several countries plan to safely store used nuclear fuel underground in deep geologic repositories. Canada's NWMO suggests using corrosion-resistant containers and bentonite-based sealing systems to ensure low hydraulic conductivity and swelling ability when in contact with groundwater. Data from studies on bentonite behavior are evaluated to determine the best-fit relationships between density, swelling pressure, and hydraulic conductivity under different pore fluid conditions.
CANADIAN GEOTECHNICAL JOURNAL
(2023)
Article
Engineering, Geological
D. A. Dixon, J. Stone, K. Birch, C. S. Kim
Summary: Several countries, including Canada's NWMO, are planning to safely isolate used nuclear fuel deep underground. The sealing systems, using bentonite-based materials, need to have low hydraulic conductivity and the ability to swell when in contact with groundwater. Data and ongoing studies show the relationship between dry density, swelling pressure, and hydraulic conductivity under different porefluid compositions.
CANADIAN GEOTECHNICAL JOURNAL
(2023)
Article
Engineering, Geological
Yong-Gui Chen, Ye-Qing Cai, Kan Pan, Wei-Min Ye, Qiong Wang
Summary: The study found that for mixtures with low sand content, swelling pressure is only related to bentonite dry density, while hydraulic conductivity is influenced by the presence of sand particles. Exponential relationships exist among final swelling pressure, saturated hydraulic conductivity, and bentonite dry density, with infiltrating salt solutions leading to higher swelling pressure and lower hydraulic conductivity. High swelling pressure and low hydraulic conductivity in specimens infiltrated with calcium chloride solutions are attributed to cation exchange reactions and competition between calcium ions in smectite interlayers and electrolyte solutions.
Article
Environmental Sciences
Aysa Hedayati-Azar, Hamed Sadeghi
Summary: Clay liners play a vital role in controlling solute transport and preventing leakage. Existing models cannot predict the hydraulic conductivity of clayey soils permeated with saline solutions. This study aims to develop semi-empirical models to simulate the hydraulic conductivity of clayey soils with different solute concentrations and deionized water. The proposed models have been validated using experimental data.
JOURNAL OF CONTAMINANT HYDROLOGY
(2022)
Article
Engineering, Environmental
Hui Li, Yunzhi Tan, Ziyang Xie, De'an Sun
Summary: The effects of temperature and water saturation have little influence on the swelling pressure and hydraulic conductivity of bentonite, but a high-temperature history can significantly deteriorate the swelling pressure and increase hydraulic conductivity due to the loss of exchangeable cations and the cementation formed between clay particles.
BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT
(2022)
Article
Engineering, Geological
Zhixiong Zeng, Yu-Jun Cui, Jean Talandier
Summary: The effects of synthetic site solution and cement solution on the hydro-mechanical behavior of compacted mixtures of claystone and bentonite were investigated. The results showed that the solutions influenced the swelling capacity, hydraulic conductivity, and water flow of the mixtures. The cations in the synthetic site solution reduced the diffuse double layer thickness and increased the large-pore volume, enhancing water flow. The hydroxide in the cement solution dissolved the montmorillonite, reducing swelling pressure and increasing large-pore volume, facilitating water flow.
JOURNAL OF ROCK MECHANICS AND GEOTECHNICAL ENGINEERING
(2022)
Article
Engineering, Geological
Zhixiong Zeng, Yu-Jun Cui, Jean Talandier
Summary: This study investigates the effects of water chemistry and technological gaps on the hydro-mechanical property of the Callovo-Oxfordian claystone/MX80 bentonite mixture through hydration tests. The results indicate that the synthetic site solution did not impact the swelling pressure and hydraulic conductivity in the short term, but reduced swelling pressure and increased hydraulic conductivity in the long term.
ENGINEERING GEOLOGY
(2021)
Article
Engineering, Geological
Yu Tan, Huyuan Zhang, Tongwei Zhang, Guochao Zhang, Dongjin He, Zhinan Ding
Summary: Investigated the anisotropic hydro-mechanical behavior of full-scale compacted bentonite-sand blocks, finding that the blocks exhibited varying engineering performance in different directions, influenced by horizontally oriented smectite plates and bentonite aggregations.
ENGINEERING GEOLOGY
(2021)
Article
Chemistry, Physical
Jongmuk Won, Jang-Un Kim, Hyunwook Choo
Summary: In this study, the electrical conductivity of compacted bentonite was measured under different conditions to investigate its predictability for swelling strain or swelling pressure. The results showed that monitoring electrical conductivity could detect the initiation and termination of swelling process and internal changes. Relationships between normalized swelling parameters and electrical conductivity were established and verified. The limitations and possibilities of using electrical conductivity for estimating swelling parameters and monitoring swelling process were discussed.
APPLIED CLAY SCIENCE
(2023)
Article
Engineering, Geological
Jiri Svoboda, David Masin, Jan Najser, Radek Vasicek, Irena Hanusova, Lucie Hausmannova
Summary: This paper mainly introduces the use of clay materials such as bentonites as a buffer and backfill for high-level radioactive waste disposal. The design is based on mathematical models that are validated using laboratory data. The laboratory research aims to determine the hydromechanical properties and stress path behavior of BCV bentonite. The results show that the behavior is influenced by stress path and water introduction method, and that micro- and macrostructures have a significant impact on material properties and mathematical models. A hypoplastic model is implemented and validated to predict the behavior of bentonite in nuclear waste repositories.
Article
Chemistry, Physical
Kao-fei Zhu, Ke-neng Zhang, Yong He
Summary: This study investigates the effects of bentonite content on the hydro-mechanical behavior of red clay-bentonite backfills through consolidation and hydraulic conductivity tests. The microstructure evolution of the backfills under vertical loading is evaluated using mercury intrusion porosimetry tests and field emission scanning electron microscope observations. The results show that the void ratio and hydraulic conductivity decrease linearly with the increase of effective consolidation stresses, while the compression index decreases with the increase of bentonite content. The montmorillonite aggregates in the backfill form a tortuous network structure which increases the tortuosity of flow paths.
APPLIED CLAY SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Masanori Kohno, Tsuyoshi Nishimura
Summary: Chemical factors significantly affect the swelling characteristics and permeability of bentonite-based materials, with the presence of K+, Fe3+, and Mg2+ leading to a decrease in swelling-pressure and an increase in hydraulic conductivity.
MATERIALS TRANSACTIONS
(2022)
Article
Engineering, Civil
Saswati Ray, Anil Kumar Mishra, Ajay S. Kalamdhad
Summary: The present study investigates the change in surface morphology, hydraulic behaviour, and sorption capability of two locally available Indian bentonites in the presence of different lead concentrations. The results reveal that the adsorption capability of the bentonites is influenced by their cation exchange capacity, swelling behaviour, and specific surface area.
EUROPEAN JOURNAL OF ENVIRONMENTAL AND CIVIL ENGINEERING
(2022)
Article
Environmental Sciences
Saswati Ray, Anil Kumar Mishra, Ajay S. Kalamdhad
Summary: This study investigates the changes in index properties, swelling, swelling potential, swelling pressure, hydraulic conductivity, consolidation parameters, and shear strength properties of two Indian bentonites of different mineralogical compositions in the presence of fly ash, sewage sludge, and paper mill leachates. The outcomes indicate that the presence of leachates leads to a decrease in certain properties such as liquid limit, free swell, compression index, and shear strength, while increasing properties like hydraulic conductivity and coefficient of consolidation. The quality of bentonite significantly affects its behavior when interacting with leachates, with higher quality bentonite experiencing greater changes in various properties when infused with different leachates.
JOURNAL OF ENVIRONMENTAL MANAGEMENT
(2022)
Article
Environmental Sciences
Badr A. Mohamed, Loretta Y. Li, Hanna Hamid, Matthew Jeronimo
Summary: This study explores the possibility of recovering resources and energy from sewage sludge through the production of sludge-based activated carbon (SBAC) based on circular economy principles. The results show that SBAC is an effective sorbent for removing various contaminants, and it can be produced at a lower cost compared to commercial activated carbon.
Article
Environmental Sciences
Nina Ricci Nicomel, Loretta Y. Li, Gijs Du Laing
Summary: In this study, the effects of citric acid on the removal of Cu(II) by seven biosolids-based adsorbents were assessed. The results showed that only SBAC exhibited an increased Cu(II) removal efficiency in the presence of citric acid. Further investigation revealed that SBAC could effectively adsorb Cu(II) and reduce it to levels below the discharge limit.
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH
(2022)
Review
Chemistry, Multidisciplinary
Badr A. Mohamed, Loretta Y. Li
Summary: Improper management of sewage sludge causes environmental and economic issues. However, sewage sludge can be used as a promising feedstock for biofuel production. Challenges include poor chemical stability, high water content, viscosity, nitrogen concentrations, and the presence of oxygen in the produced biofuels. Additionally, the resulting biochars contain high levels of toxic metals, limiting their use in agricultural soils. Co-pyrolysis of sewage sludge with other materials has been shown to improve bio-oil quality by reducing water, oxygen, and nitrogen contents, activation energy, and increasing calorific value.
ENVIRONMENTAL CHEMISTRY LETTERS
(2023)
Article
Engineering, Environmental
Carol Huang, Badr A. Mohamed, Loretta Y. Li
Summary: This study investigated the feasibility of co-pyrolysis as a sewage sludge treatment process. The results showed that mixing co-feed biomass with sewage sludge reduced the overall environmental burden by 58-83%. Co-pyrolysis of wheat straw/SS performed better than sawdust/SS in terms of environmental impact. All examined scenarios achieved a net positive energy balance and reduced global warming potential. Sensitivity analysis indicated that transportation of feedstock and pyrolysis products should be prioritized to limit environmental burden. Co-pyrolysis is an eco-friendly and economically viable method for sewage sludge treatment.
CHEMICAL ENGINEERING JOURNAL
(2023)
Article
Green & Sustainable Science & Technology
Badr A. Mohamed, Hanna Hamid, Claudia V. Montoya-Bautista, Loretta Y. Li
Summary: This study investigates the occurrence and removal of CECs including PAHs, PBDEs, and PFASs in the effluent of a Canadian wastewater treatment plant. Activated carbon samples synthesized from sludge were used for the removal of these contaminants, and the results showed high removal rates for PAHs, PBDEs, and some PFASs. The findings suggest that producing efficient adsorbents from sewage sludge is a sustainable solution for improving the quality of wastewater effluents.
JOURNAL OF CLEANER PRODUCTION
(2023)
Review
Chemistry, Multidisciplinary
Hong Huang, Badr A. Mohamed, Loretta Y. Li
Summary: The recent global concern about the presence of microplastics in most ecosystems has raised health concerns, but their fate in terrestrial environments remains largely unknown. In this review, we examine the impact of land applications of biosolids on microplastic contamination in agricultural soils. We focus on techniques for separation and identification, distribution in wastewater, and retention, migration, and degradation in soils. We also discuss the uptake of microplastics by microorganisms. The number of microplastic particles in biosolids ranges from 506 to 15,385 per kg, and after application to land, the number of microplastics in soil ranges from 18 to 6.9 x 10(5) particles per kg, depending on soil composition. Microplastic retention in soils increases with organic carbon concentration, Fe and Al oxide concentrations, and soil ionic strength. Biodegradation of microplastics results in mass loss, changes in chemical composition, reduction in molecular weight and mechanical strength, and the production of carbon dioxide and methane gas.
ENVIRONMENTAL CHEMISTRY LETTERS
(2023)
Article
Engineering, Environmental
Badr A. Mohamed, Carol Huang, Nico Mok, Omar Swei, Chris Johnston, Loretta Y. Li
Summary: The study compares the feasibility and environmental impacts of incorporating biofilters with sludge-based activated carbon (SBAC) versus commercial activated carbon (CAC) for stormwater treatment. Results show that incorporating biofilters with SBAC can significantly reduce negative environmental impacts and increase profits. It suggests that SBAC is an economically and environmentally sustainable solution for managing sewage sludge and stormwater effluent.
JOURNAL OF HAZARDOUS MATERIALS
(2023)
Article
Engineering, Civil
N. Mahesh Babu, Anil Kumar Mishra
Summary: Due to limited bentonite availability, this study investigated the use of black cotton soil mixed with waste tire fibers as a liner. Testing the soil's swelling and strength with different concentrations of NaCl and CaCl2 salts, the results showed a reduction in both properties with the addition of tire fibers, especially at higher salt concentrations. The soil's swelling time was also reduced due to increased concentrations. Additionally, the unconfined compressive strength test demonstrated increased ductility with higher fiber content. Therefore, a tire fiber content of up to 10% is suitable for liner applications, even with the presence of different salt effects.
KSCE JOURNAL OF CIVIL ENGINEERING
(2023)
Article
Engineering, Environmental
Amirah Syafika Mohd Nasir, Badr Mohamed, Loretta Y. Li
Summary: This study compared the life cycle assessment, global warming potential, energy recovery, and economic feasibility of biofuel production via pyrolysis of sewage sludge and microalgae alone or at different ratios. The co-pyrolysis scenarios showed 36-44% lower global warming potential compared to sewage sludge alone. Gas turbine was found to be more effective for energy recovery from pyrolysis gases, compensating for up to 28% of the energy requirement. The drying process accounted for the majority of energy consumption, highlighting the need for improved dewatering process for sustainability and profitability.
RESOURCES CONSERVATION AND RECYCLING
(2023)
Article
Environmental Sciences
Badr A. Mohamed, Nina Ricci Nicomel, Hanna Hamid, Loretta Y. Li
Summary: Resource recovery from sewage sludge via optimised production of sludge-based activated carbon (SBAC) can efficiently remove poly- and perfluoroalkyl substances (PFASs), while reducing production costs and environmental impacts. Economic analysis and life-cycle assessment (LCA) demonstrate the feasibility of the process and its potential role in the circular economy.
SCIENCE OF THE TOTAL ENVIRONMENT
(2023)
Article
Energy & Fuels
Badr A. Mohamed, Marnie O'Boyle, Loretta Y. Li
Summary: This study examines the environmental sustainability and economic feasibility of using co-pyrolysed sewage sludge (SS) with lignocellulosic and algal biomass for the production of liquid and gaseous fuels. The results show that co-pyrolysis of SS with biomass can reduce environmental burden, with sawdust outperforming wheat straw and microalgae. The co-pyrolysis of SS with sawdust demonstrates the highest net present worth and emission reduction, making it a sustainable and economically feasible method for producing biofuels.
Review
Agricultural Engineering
Hui Zhu, Qing An, Amirah Syafika Mohd Nasir, Alexandre Babin, Sofia Lucero Saucedo, Amzy Vallenas, Loretta Li, Susan Anne Baldwin, Anthony Lau, Xiaotao Bi
Summary: This article reviewed the emerging applications of biochar in removing contaminants and mine remediation, and proposed methods to increase biochar production and improve its surface properties through customized pyrolysis treatments.
BIORESOURCE TECHNOLOGY
(2023)
Article
Engineering, Geological
D. Barman, A. K. Mishra
Summary: The influence of salt and initial condition of drying on the shrinkage limit of bentonite was analyzed in this study. It was found that the shrinkage limit is affected by the pore water chemistry and initial condition of drying. With an increase in salt concentration, the shrinkage limit also increased. Different methods showed slight variations in the values of shrinkage limit obtained.
INTERNATIONAL JOURNAL OF GEOTECHNICAL ENGINEERING
(2022)