Lead in drinking water is a persistent public health issue, and there is increasing evidence that it occurs in colloidal and nanoparticulate forms. Since remedial actions for dissolved lead may differ from those used to target colloids and nanoparticles, physicochemical characterization can make treatment strategies more effective. Here we review the evidence for colloidal/nanoparticulate lead in drinking water, with a focus on four factors that promote it: natural organic matter; colloidal/nanoparticulate iron and manganese; orthophosphate; and polyphosphate- or sodium silicate-based sequestrants. We also present new data on sequestrant interactions with iron corrosion scale that result in nanoparticles. Specifically, we characterized the colloidal iron oxide suspensions that resulted from corroding cast iron coupons in solutions containing either sodium hexametaphosphate (3 mg P L-1) or sodium silicate (100 mg SiO2 L-1). We determined the elemental composition and size distribution of these suspensions using flow field-flow fractionation with ultraviolet absorbance, multielement, and multiangle light scattering detection (FFF-UV-MALS-ICP-MS). We used light scattering data to estimate the radius of gyration, rg, via the Zimm model, with r2 ranging from 0.983–0.999. Polyphosphate and sodium silicate suspensions yielded particles in two distinct size fractions. The smaller particles had rg equaling 29–34 and 25–38 nm, respectively, and the larger particles had rg equaling 73–83 and 72–94 nm. Lead associated preferentially with these particles over free hexametaphosphate, suggesting that sequestrants may interact with iron corrosion scale to yield highly effective transport vectors for lead—and perhaps other heavy metals—in drinking water systems.

Colloids and nanoparticles in drinking water: a review of occurrence and new data on the role of sequestrants

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.