Cation interception and permeability characteristics of bentonite barriers exposed to NaCl and NH₄Cl solutions

High concentrations of Na⁺ and NH₄⁺ in landfill leachate lead to deterioration of bentonite barrier and pose a threat to the environment. This study focused on the pollution interception and permeability characteristics of the bentonite barrier exposed to NaCl and NH₄Cl solutions. Based on previous findings, salt solution concentrations were established at 74.80, 37.40, 18.70, and 9.4 mmol/L. The bentonite contents in the mixture were set at 0, 5, 10, and 15%. The results indicate that the samples exhibit better interception of NH₄⁺ compared to Na⁺. This difference arises from the cation exchange sequence, the size of the hydration radius, and the hydrogen bonding of the two cations. Additionally, the difference in hydration enthalpy between the two cations leads to variations in the swelling of bentonite, resulting in a higher hydraulic conductivity coefficient in NH₄Cl solution. This study shows that although bentonite barriers have better interception for NH₄⁺, they exhibit greater hydraulic conductivity in NH₄Cl solution, increasing the risk of leachate carrying other contaminants.