A review of barrier properties of polymer-modified bentonite applied to vertical cutoff walls under dry-wet cycling and chemical erosion

Polymer-modified bentonite has been widely used in vertical cutoff walls due to its good barrier properties. This paper illustrates the changes in fissure development and permeability properties of bentonite due to microstructural changes under wet and dry cycling and chemical erosion; the modification mechanism of polymermodified bentonite is described; The applicable environment of three types of polymer-modified bentonite under the coupling of wet and dry cycles with different chemical erosion is discussed. The main conclusions are as follows: The polymers improve the barrier properties of bentonite mainly through clogging mechanism and cation scavenging effect; In the case of multiple coupling of wet and dry cycles with inorganic salt, heavy metal and organic matter contamination, nonionic and anionic polymers can effectively prevent the fissure development of bentonite due to their similar modification effects in mixed modification; Although the cationic polymer modified bentonite has a good modification effect in the adsorption of organic matter and heavy metal ions, the modification effect is not stable under the long-term effect of such as dry and wet cycles and salt intrusion. The study aims to synthesize the barrier properties of polymer-modified bentonite under wet and dry cycling with different chemical erosion. The significance is to provide a certain reference basis for bentonite-based vertical cutoff wall materials in the application of treatment in different coupling environment.