Silver
Dissolution and Release from Ceramic Water
Filters
- Publication date
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Abstract
Application of silver
nanoparticles (nAg) or silver nitrate (AgNO<sub>3</sub>) has been
shown to improve the microbiological efficacy of
ceramic water filters used for household water treatment. Silver release,
however, can lead to undesirable health effects and reduced filter
effectiveness over time. The objectives of this study were to evaluate
the contribution of nanoparticle detachment, dissolution, and cation
exchange to silver elution, and to estimate silver retention under
different influent water chemistries. Dissolved silver (Ag<sup>+</sup>) and nAg release from filter disks painted with 0.03 mg/g casein-coated
nAg or AgNO<sub>3</sub> were measured as a function of pH (5–9),
ionic strength (1–50 mM), and cation species (Na<sup>+</sup>, Ca<sup>2+</sup>, Mg<sup>2+</sup>). Silver elution was controlled
by dissolution as Ag<sup>+</sup> and subsequent cation exchange reactions
regardless of the applied silver form. Effluent silver levels fell
below the drinking water standard (0.1 mg/L) after flushing with 30–42
pore volumes of pH 7, 10 mM NaNO<sub>3</sub> at pH 7. When the influent
water was at pH 5, contained divalent cations or 50 mM NaNO<sub>3</sub>, silver concentrations were 5–10 times above the standard.
Our findings support regular filter replacement and indicate that
saline, hard, or acidic waters should be avoided to minimize effluent
silver concentrations and preserve silver treatment integrity