Hydraulic conductivity of bentonite-polymer geosynthetic clay liners to aggressive solid waste leachates

• Published in: Geotextiles and geomembranes Vol. 52; no. 5; pp. 900 - 911
• Main Authors: Li, Dong, Zhao, Hanrui, Tian, Kuo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2024
• Subjects: Bentonite-polymer (B–P); CCR leachate; Geosynthetic clay liners (GCLs); MSWI leachates; MW leachate; Polymer type; MW leachate; Bentonite-polymer (B–P); CCR leachate; MSWI leachates; Geosynthetic clay liners (GCLs); Polymer type
• ISSN: 0266-1144
• DOI: 10.1016/j.geotexmem.2024.05.006

Hydraulic conductivity of conventional mock sodium bentonite (Na–B) and bentonite-polymer (B–P) geosynthetic clay liners (GCLs) were evaluated with three synthetic leachates that are chemically representative of aggressive leachates from coal combustion product (CCR) (I = 3179 mM), mining waste (MW) (I = 2127 mM, pH = 2.0), and municipal solid waste incineration ash landfill (MSWI) (I = 2590 mM). The mock B–P GCLs were created by dry mixing bentonite with branched, linear, or crosslinked polymer. The polymer loading of mock B–P GCLs ranged from 3 to 15%. Comparative tests were also conducted with Na–B GCLs. The mock Na–B GCLs cannot maintain low hydraulic conductivity to aggressive CCR, MW, and MSWI leachates. Mock B–P GCLs with 10% branched polymer had low hydraulic conductivity (< 1.0 × 10−10 m/s) to synthetic MW and MSWI leachates at 20 kPa effective confining stress, whereas the hydraulic conductivity of mock B–P GCLs with 10% linear or crosslinked polymer ranged from 1.5 × 10−9 to 1.4 × 10−7 m/s. As the effective stress increased, the B–P GCLs branched polymer showed a faster decreasing trend than that of Na–B and B–P GCLs with linear or crosslinked polymer. •Hydraulic conductivity tests were conducted up to 4 years to test long-term hydraulic conductivity of B-P GCLs.•The ratios of KL/K6766 for B-P GCLs to synthetic CCP leachate were higher than that of Na-B GCLs (e.g., 3.5 to 14.7 vs. 1.7).•Polymer elution from B-P GCLs affects the long-term hydraulic conductivity of B-P GCLs.•The polymer elution should be measured and considered as an additional termination criterion in ASTM D6766.