Preparation of elution-resistant Ca-bentonite/polymer nanocomposite for effectively containing high-salinity leachate

Le résumé fourni par la source

Geosynthetic clay liners (GCLs) consisting of dry-mixed bentonite-polymer composites (BPCs) were developed for the containment of landfill leachate. However, the weak interface bonding between the bentonite and polymer can lead to serious polymer elution, deteriorating the containment efficacy of BPCs. Herein, a salt-resistant polymer, P(acrylic acid-2-acryl amido-2-methyl propane sulfonic acid-vinyltriethoxysilane) (denoted as P-AAV) is proposed to covalently graft onto Calcium-bentonite (CaB) by in situ polymerization and interface crosslinking. As a silane coupling agent, the vinyltriethoxysilane (VTES) repeating units form an interface crosslinking structure with the silanol groups at the CaB surface, resulting in the formation of interface-crosslinked CaB/P-AAV nanocomposite. The interface crosslinking structure enhances the CaB/polymer interface bonding, thereby improving the CaB/P-AAV nanocomposite’s resistance to polymer elution. After permeation tests with trona ash leachate (ionic strength I as high as 746 mmol/L), the polymer elution of CaB/P-AAV is only 22% that of the dry-mixed control sample and substantially lower than that reported in the literature, and the bound water content of CaB/P-AAV is 3.9 times higher than that of natural CaB and thus its effective porosity is 37.5% lower. Consequently, the hydraulic conductivity of CaB/P-AAV to trona ash leachate is as low as 2.8✕10 -12 m/s, which is only 5.6% of the required hydraulic conductivity for GCLs (5✕10 -11 m/s).

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