Sodium polyacrylate modification method to improve the permeant performance of bentonite in chemical resistance

Abstract

Bentonite, an important geotechnical material in the fields of environmental geotechnical engineering, can effectively adsorb harmful substances from the environment and fuel oil. This study investigated the formulation of sodium polyacrylate-modified bentonite that improves the permeant performance in the context of chemical resistance. The optimum material mix ratio and synthesis process were determined through multiple experiments. To better understand the sodium polyacrylate/bentonite interaction, the swelling index, filtrate loss, cation exchange capacity (CEC) and hydraulic conductivity performance in solutions of Pb(NO3)2 and acid were compared. The microstructures of raw bentonite and sodium polyacrylate bentonite were analyzed using scanning electron microscopy and infrared spectroscopy. The results showed that the microstructure of modified bentonite was characterized by isolated cavities, whereas the original configuration comprised a stacked layer, and the free swell index (FSI) increased from 25 to 50 mL/2 g. The modified bentonite showed a significant improvement in terms of chemical resistance through FSI testing and filtrate loss experiments, particularly in hydraulic conductivity tested in acidic and saline solutions. The permeability decreased by an order of magnitude through the modification process under the deionized water condition, and the chemical resistance increased to more than 40 mM in the Pb(NO3)2 solution. In addition, the CEC increased from 62.06 to 96.1 meq./100 g as a result of sodium polyacrylate modification.