GC/Na⁺-bentonite retained more COC than PC/Na⁺-bentonite at high I salt solutions.

CO groups of COC interact with the interlayer cations through water at low I.

GC was more effective in linking directly to interlayer Na⁺ compared to PC at high I.

GC OH H-bonded with surface oxygens of Mt.

GC/Na⁺-bentonite was found to be a more stable material than PC/Na⁺-bentonite.