Adsorptive property of Cu2+-ZnO/cetylpyridinium-montmorillonite complexes for pathogenic bacterium in vitro

Cu(2+)-ZnO/cetylpyridinium-montmorillonite (Cu(2+)-ZnO/CP-MMT) complexes were prepared using montmorillonite (MMT), Cu(2+), Zn(2+), and cetylpyridinium (CP). The goal was to assess comparatively the adsorption properties of Cu(2+)-ZnO/CP-MMT in vitro using pathogenic Escherichia coli. The results showed that Cu(2+)-ZnO/CP-MMT adsorbed significantly (P<0.05) more E. coli compared with the parent clay. The adsorption process of bacterial cells occurring on the modified MMT surface reached equilibrium after 90 min. The percentages of E. coli adsorbed onto the surfaces of Cu(2+)-ZnO/CP-MMT and MMT in adsorption equilibrium were 84.66% and 47.01%, respectively. Adsorption data from the bacteria-clay systems followed the Langmuir and Freundlich isotherms, but not the BET isotherm. Adsorption of E. coli in acidic medium was higher than in alkaline medium. The extent of bacteria adsorption onto the modified MMT increased with decreasing ionic strength, and with increasing temperature. The processes of E. coli adsorption onto the tested adsorbents were endothermic and spontaneous at the experimental temperature. The mechanism of adsorption of bacteria on Cu(2+)-ZnO/CP-MMT may involve enhanced hydrophobicity and the reversal of surface charge from negative to positive.