Ion exchange in amorphous alkali-activated aluminosilicates: Potassium based geopolymers

Abstract Ion exchange properties of pure potassium-based geopolymer ( pure K-GP) formulated with Si/Al = 2.1 and K/Al = 1.0 ± 0.02 atomic ratios have been studied. For pure K-GP, the maximum ion-exchange level of K + with respect to Na + and Cs + is 77 and 61%, respectively, as determined by exhausted exchange with 1 M solutions of appropriate nitrates at 22 ± 2 °C. The geopolymer shows a slight preference for K + over Cs + as indicated by the normalized Cs/K-GP isotherm obtained under noncompetitive exchange. Parent geopolymer yields a pure geopolymer when it is extensively washed with deionized water until neutral pH is obtained and equilibrated with aqueous solution of KNO 3 resulting in changing in composition and textural properties. As calculated from N 2 sorption–desorption isotherms, surface specific area and cumulative pore volume for parent K-GP are 5.5 m 2 g − 1 and 0.01 cm 3 g − 1 , respectively, whereas for pure K-GP surface specific area and cumulative pore volume are 270 m 2 g − 1 and 0.4 cm 3 g − 1 , respectively.