Zn2+-exchange kinetics and antimicrobial properties of synthetic zirconium umbite (K2ZrSi3O9•H2O)

Zirconium umbite, K2ZrSi3O9 center dot H2O, is a microporous framework ion exchanger whose potential as a carrier for Zn2+ ions in antimicrobial formulations has not yet been investigated. Accordingly, batch Zn2+-exchange kinetics of synthetic zirconium umbite (K-UM) and the subsequent antimicrobial action of the zinc-bearing phase (Zn-UM) against Staphylococcus aureus and Escherichia coli are reported. Nonstoicheiometric over-exchange of Zn2+ for K+ was observed and attributed to hydrolysis and complexation reactions of Zn2+ within the umbite framework. The exchange process, which was described by a simple pseudo-first-order model (k (1) = 2.69 x 10(-4) min(-1), R (2) = 0.992), did not achieve equilibrium within 120 h at 25 A degrees C, by which time the uptake of zinc was found to be 1.04 mmol g(-1). The minimal bactericidal concentrations of Zn-UM for E. coli and S. aureus were found to be > 10 g cm(3) and < 1.0 g cm(3), respectively.