A quartz crystal microbalance was used to determine the effects of different water quality parameters on the desorption of silver nanoparticles from surfaces representative of ceramic water filters (CWFs). Silver nanoparticles stabilized with 25-30% casein were used in the experiments. The average hydrodynamic diameter of the nanoparticles ranged from 20 to 100 nm over pH 6.5 to 10.5. The isoelectric point was ca. 3.5 and the zeta potential was -45 mV from pH 4.5 to 9.5. The silver nanoparticles were adsorbed onto silica surfaces and then a quartz crystal microbalance was used to monitor silver release from the surface. At environmentally relevant ranges of pH (4.8 to 9.3), ionic strength (0 and 150 mM NaNO3 or 150 mM Ca(NO3)2), and turbidity (0 and 51.5 NTU kaolin clay), the rates of silver release were very similar. A high concentration of organics and bacteria (E. coli in 10% tryptic soy broth) caused rapid silver release. Water containing sodium hypochlorite removed 85% of the silver from the silica surface within 3 hours. The results suggest that contact between CWFs and prechlorinated water or bleach should be avoided.
Citation: Water Research
Pub Type: Journals
silver release, quartz crystal microbalance, pH, ionic strength