Effects of chlorine and other water quality parameters on the release of silver nanoparticles from a ceramic surface

A quartz crystal microbalance was used to determine the effects of different water quality parameters on the detachment of silver nanoparticles from surfaces representative of ceramic pot filters (CPFs). Silver nanoparticles stabilized with casein were used in the experiments. The average hydrodynamic diameter of the nanoparticles ranged from 20 nm to 100 nm over a pH range of 6.5-10.5. The isoelectric point was about 3.5 and the zeta potential was -45 mV from pH 4.5 to 9.5. The silver nanoparticles were deposited onto silica surfaces and a quartz crystal microbalance was used to monitor silver release from the surface. At environmentally relevant ranges of pH (4.8-9.3), ionic strength (0 and 150 mol/m(3) NaNO3 or 150 mol/m(3) Ca(NO3)2), and turbidity (0 and 51.5 NTU kaolin clay), the rates of silver release were similar. A high concentration of sodium chloride and bacteria (Echerichia 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 h. The results suggest that contact between CPFs and prechlorinated water or bleach CPF cleaning should be avoided.