Kinetics of hydrogen-sodium ion exchange in acid zirconium phosphate

Proton diffusion in NaHZr(PO4)(2)-5H(2)O and Na2Zr(PO4)(2)-3H(2)O phases wa s examined by studying the kinetics of hydrogen-sodium ion exchange. Three regions characterized by an almost linear dependence of the apparent diffus ion coefficients of the hydrogen ion on the pH values were obtained at pH < 7, 7 < pH < 9 and 9 < pH < 11. The phenomenon was explained by different m echanisms of defect formation in the pH ranges investigated. The distributi on of the proton defect concentration in the grains was estimated for diffe rent pH values, The influence of the anion nature in the contacting solutio ns on the diffusion coefficients was also discussed. The rate of ion exchan ge increases in the series: I- < Br- < Cl-, ClO4- <NO3- <SO42-. (C) 1999 El sevier Science B.V. All rights reserved.