Swelling Behavior and Permeability of Polymerized Bentonite with Due Monomers

Abstract

To improve the anti-cationic solution capability of geosynthetic clay liners (GCLs), new polymerized bentonites (PBs) were produced for potential use as cores of GCLs. PBs were produced using free radical polymerization method with due monomers, acrylic acid (M1) and acrylamide (M2), and potassium persulfate as initiator (I). The natural bentonite (UB) used was a sodium type one. The adopted pH was 6, I/(M1 + M2) ratio of 0.005, and (M1 + M2)/UB ratio of 0.05 (0.05 PB) and 0.1 (0.1 PB). The results of the X-ray diffraction (XRD) indicate that PBs produced in this study can be classified as micro-composite. The swelling capacity of the PBs was investigated by free swelling index (FSI) tests. In deionized water, 0.1 M to 0.6 M NaCl and 0.03 to 0.06 M CaCl2 solutions, the values of FSI of PBs are higher than that of UB. For PBs, FSI increased with increase of polymer/bentonite ratio. In deionized water, FSI of 0.1 PB was more than 5 times that of the UB. The values of permeability of the PBs and UB with 0.6 M NaCl solution were deduced from oedometer test results. At the same void ratio, the permeability of 0.1 PB was more than one order lower than that of the UB. For the 0.1 PB, for void ratio up to 7.5, the value of k was less than 10–10 m/s. Therefore, 0.1 PB can be used as core material of GCLs to be used under higher concentration of Na+ environment.