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Effects of hydration fluid on moisture-suction relationships for geosynthetic clay liners
Published in N. Khalili, A.R. Russell, A. Khoshghalb, Unsaturated Soils: Research & Applications, 2020
N. Yesiller, J.L. Risken, J.L. Hanson, J.B. Darius
Geosynthetic Clay Liners (GCLs) are manufactured barrier materials that consist of a thin layer of bentonite clay (with montmorillonite as the predominant mineral) contained between two geotextiles or a geotextile and a geotextile with an attached geofilm. GCLs increasingly are used to replace compacted clay liners in containment systems due to various perceived advantages including low thickness, low hydraulic conductivity, self-healing capability, resistance to environmental factors (e.g., cyclic freeze-thaw or wetting-drying), and ease of installation.
Landfill cap designs using geosynthetic clay liners
Published in R. M. Koerner, E. Gartung, H. Zanzinger, Geosynthetic Clay Liners, 2020
Compacted clay liners (CCLs) are required for the barrier layer portion of the new final cover systems. Because of the high costs and long time needed to construct a CCL, geosynthetic clay liners (GCLs) often represent a cost-effective alternative. GCLs also provide several performance advantages.
Design of Subtitle D and Subtitle C Landfill Containment Systems
Published in Robert E. Landreth, Paul A. Rebers, Municipal Solid Wastes, 2020
There is a large and ever growing body of technical information on geosynthetics; for example, see Koerner.2 For geosynthetics used in the liner of a solid waste landfill, the most important types are described as follows: Geomembranes (GM) are very low permeability, polymeric membrane liners or barriers used to contain the generated leachate and to control fluid migration.Geotextiles (GT) are planar, permeable, polymeric materials comprised solely of textiles used for filtration, drainage, separation, or reinforcement.Geosynthetic clay liners (GCL) are factory-manufactured hydraulic barriers consisting of a layer of bentonite clay or other very low permeability material, supported by geotextiles and/or geomembranes, being mechanically held together by adhesives, needling, or stitching.Geonets (GN) are net-like sets of interconnected polymer ribs used for the transmission of liquids in the plane of the structure.Geogrids (GG) are grid-like sets of interconnected polymer ribs used for reinforcement of soils or solid waste.
Modified geosynthetic clay liners bentonite for barriers of Cr (VI) in contaminated soil
Published in Environmental Technology, 2023
Shao-Qiu Zhang, Wei Yang, Ren-Peng Chen, Xin Kang, Meng-Jian Ren
Over the past decades, geosynthetic clay liners (GCLs) have been widely used in waste containment facilities as landfill leachate barriers in place of bulky compacted clay liners (CCLs) because of their low hydraulic conductivity, self-healing, metal retention, and easily controlled construction quality [19–21]. GCLs contain a thin layer of Na-bent sandwiched by two layers of geotextile, while Na-bent is mainly composed of Na-montmorillonite clay minerals [22–24]. Therefore, GCLs with Na-bent as the main component have the dual functions of a chemical barrier to adsorb cationic pollutants and a mechanical barrier to prevent from entering the groundwater [25]. Hexavalent chromium always exits in the form of acid radical anions including HCrO4−, CrO42− and Cr2O72− in the presence of landfill leachate due to its relatively high positive charge, a small ion radius (0.52 Å), and a strong force to oxygen [26]. Thus, the traditional GCLs with the active ingredient of Na-bent cannot be ion-exchanged with acid radical ions to effectively adsorb hexavalent chrome. In order to improve the adsorption efficiency of Cr (VI) on GCLs, a large member of researchers have conducted a lot of research on the adsorption performance of modified bentonite, such as inorganic pillar modification, organic modification and composite modification. Organic modification makes the bentonite mineral have a larger interlayer spacing, which is beneficial to the exchange and adsorption of hexavalent chromium anion groups into the interlayer. At the same time, surfactants are introduced to make the surface of bentonite positive, which can effectively adsorb hexavalent chromium anion groups [327]. Inorganic pillar modification can significantly increase the pore volume and specific area of bentonite, and inorganic modified bentonite has strong tolerance to changes in pH and inorganic ions [28]. Composite modified bentonite is considered to combine the advantages of the above two, so it not only has mechanical structure and stability of inorganic bentonite, but also has hydrophobicity, larger pore volume and specific surface area of organic bentonite [2,2930]. To date, previous studies have carried out a lot of work on different modifiers to improve the capacity of bentonite to adsorb Cr (VI). These studies mainly focused on a certain modifier to determine the modification effect and modification mechanism. However, the results from different studies might be inconsistent or even contradictory due to different preparation, which made it confusing to understand the modification mechanism obtained by comparing these results.