Hydraulic conductivity and swelling of nonprehydrated GCLs permeated with single-species salt solutions

The influence of single-species salt solutions of various concentration, ca tion valence, and pH on swelling and hydraulic conductivity of nonprehydrat ed GCLs was examined. At similar concentration, swell was largest with NaCl , KCl, and LiCl solutions (monovalent cations Na+, K+, and Li+) and smalles t with LaCl3 solutions (trivalent cation La3+). Intermediate swell volumes were obtained with divalent solutions (CaCl2, MgCl2, ZnCl2, and CuCl2). Ana logous results were obtained from hydraulic conductivity tests. GCL specime ns permeated with solutions containing divalent or trivalent cations had hi gher hydraulic conductivity than GCLs permeated with monovalent solutions o r deionized water, unless the divalent or trivalent solutions were very dil ute (less than or equal to0.01 M). Hydraulic conductivity increased as the concentration increased, and at high concentration (1 M) only small differe nces existed between hydraulic conductivities measured with all solutions. Swelling and hydraulic conductivity were related to size of the hydrated ca tion for monovalent cations, but no relationship was observed for different species of divalent and trivalent cations provided that the valence was th e same. However, pH only influenced swelling and hydraulic conductivity whe n the pH was very low (<3) or very high (> 12).